JP2011096984A - Multilayer flexible wiring board - Google Patents

Abstract

Provided is a multilayer flexible wiring board that can be simplified in structure, simplified in manufacturing process, excellent in bending resistance and refraction resistance, and easy to be thinned.
A multilayer flexible wiring board according to the present invention includes an insulating substrate, a pair of conductive layers provided on both sides of the insulating substrate, and a pair provided on the pair of conductive layers. The insulating layers 17 and 19 are provided on the pair of insulating layers 17 and 19, respectively, and are electrically connected to the pair of conductive layers without covering via the coverlay by plating and / or conductive paste. The outer layer circuits L3 (18) and L4 (20) are provided.
[Selection] Figure 1

Description

  The present invention relates to a multilayer flexible wiring board in which a plurality of conductive layers can be connected within a wiring board without using a coverlay.

  In recent years, multi-layer flexible wiring boards and rigid flex wiring boards have been adopted in mobile phone terminals and the like. Multilayer flexible wiring boards and rigid flex wiring boards have a rigid part that requires component mounting and a flexible part that requires bending or bendability. As an example of these, Patent Documents 1 and 2 disclose the structure and manufacturing method of a multilayer flexible wiring board, and Patent Documents 3, 4, and 5 disclose the structure and manufacturing method of a rigid flex wiring board.

  Conventionally, a manufacturing process of a four-layer board using a multilayer flexible wiring board or a rigid flex wiring board is manufactured through complicated processes. In particular, in a multilayer flexible wiring board, a process of forming a hollow structure necessary for forming a flexible part, and in a rigid flex wiring board, an outer layer peeling process for forming a flexible part is a very complicated process. For this reason, many man-hours and materials are required, which is a major factor in cost increase and quality instability.

  FIG. 6A to FIG. 6E are diagrams showing an outline of the manufacturing process of the multilayer flexible wiring board. Multilayer flexible wiring boards have several types of structures, and the manufacturing process differs slightly depending on the structure. Here, the manufacturing process of the multilayer flexible wiring board which has the structure which laminated | stacked two most typical double-sided flexible wiring boards (henceforth double-sided FPC) is demonstrated.

  As shown in FIG. 6A, first, two double-sided FPC substrates (substrate A and substrate B) in which conductive layers 102 and 103 are formed on both surfaces of an insulating substrate 101 are prepared. Next, as shown in FIG. 6B, inner layer circuits L1 (substrate A) and L2 (substrate B) are formed on the conductive layer 102 of the substrate A and the conductive layer 103 of the substrate B by a subtractive method or the like. . Next, as shown in FIG. 6 (c), insulation is performed by laminating cover lays 104 and 105 using polyimide film on the inner layer circuit L1 formation surface of the substrate A and the inner layer circuit L2 formation surface of the substrate B. Do. Next, as shown in FIG. 6 (d), an interlayer adhesive 106 (which may be a prepreg made of glass epoxy) is used, and the cover layer 104 of the substrate A is placed so that the inner layer circuit L1, L2 formation surface is on the inner side. And the cover lay 105 of the substrate B are laminated and bonded. Here, when the cover lay 104 and the cover lay 105 are bonded, they are bonded so that a hollow portion R1 (a portion to be a flexible portion) without the interlayer adhesive 106 can be formed using a mold or the like. Therefore, the accuracy of alignment of the interlayer adhesive 106 is required at the time of lamination bonding.

  Next, after drilling through-hole 107 (generally drilling) and forming blind via holes 108 and 109 (typically laser processing by a conformal mask method), inner layer circuit L1 is formed by copper plating. , L2 or each layer is electrically connected. At this time, due to the influence of the interlayer adhesive 106, the reliability of electrical connection between layers by copper plating may be impaired.

  Next, as shown in FIG. 6E, outer layer circuits L3 and L4 are formed by a subtractive method or the like. Here, the conductive layer 103 of the substrate A is formed in the outer layer circuit L3, and the conductive layer 102 of the substrate B is formed in the outer layer circuit L4. Next, the cover coat 110 (or cover lay) performs insulation treatment of the outer layer circuits L3 and L4, and plating treatment and rust prevention treatment on the exposed surface of the outer layer serving as component mounting and electrical contact. Finally, after drilling and outline processing, electrical inspection and appearance inspection are performed, the finished product is obtained.

  7A to 7E are diagrams showing an outline of a method for manufacturing a rigid flex wiring board. Rigid-flex wiring boards have several types of structures and manufacturing processes similar to multilayer flexible wiring boards. Here, the manufacturing process of the rigid flex wiring board by the build-up method which is the latest mass production technology will be described.

  As shown in FIG. 7A, first, using a double-sided substrate in which conductive layers 112 and 113 are formed on both sides of an insulating substrate 111, through-hole plating or blind via plating (not shown) is performed to form the conductive layer 112, 113 is connected. Next, as shown in FIG. 7B, inner layer circuits (L1, L2) are formed on both sides of the double-sided substrate by a subtractive method. Next, as shown in FIG. 7C, a double-sided FPC obtained by laminating cover lays 114 and 115 and performing insulation treatment is used as a core substrate.

  Next, as illustrated in FIG. 7D, uncured interlayer adhesives 116 and 117 are temporarily fixed to the upper surface of the cover lay 114 and the lower surface of the cover lay 115 of the core substrate, respectively. Here, it is necessary to remove the interlayer adhesives 116 and 117 in advance from the portions to be the flexible portions R2 and R3 using a mold or the like. Therefore, the alignment accuracy of the interlayer adhesives 116 and 117 is also required at the time of lamination.

  Next, an insulating resin 118 such as a glass epoxy resin and a single-sided copper-clad substrate having a copper foil 119 on one surface of the insulating resin 118 are laminated on the upper surface of the interlayer adhesive 116, and are heated and cured by pressure. Next, similarly, an insulating resin 118 such as a glass epoxy resin and a single-sided copper-clad substrate having a copper foil 81 on one surface of the insulating resin 120 are laminated on the lower surface of the interlayer adhesive 117 and cured by pressure and heating. The copper foils 119 and 121 become the outer layer circuits L3 and L4, respectively. Next, after drilling through-hole 82 (generally drilling) and forming blind via holes 123 and 124 (generally laser machining), inner layer circuit L1, L2-copper foils 119 and 121 are formed by copper plating. In addition, the inner layer circuit L1 and the inner layer circuit L2 and the copper foil 119 and the copper foil 121 are electrically connected. At this time, due to the influence of the interlayer adhesives 116 and 117, reliability of electrical connection between the layers by copper plating may be impaired.

  Next, as shown in FIG. 7E, copper foils 119 and 121 are formed on the outer layer circuits L3 and L4 by a subtractive method or the like. Next, the cover coat 125 (or cover lay) performs insulation treatment of the outer layer circuits L3 and L4, and plating treatment and rust prevention treatment on the conductor exposed surfaces of the outer layer circuits L3 and L4 that become component mounting and electrical contacts. Next, drilling and outline processing are performed. Next, the outer layer circuits L3 and L4 in the flexible portions R2 and R3 are cut to the interlayer adhesive by router processing or the like, and the outer layer is peeled off using a jig or the like. Finally, after conducting electrical inspection and appearance inspection, it becomes a finished product.

  In conventional multilayer flexible wiring boards and rigid flex wiring boards, examples in which a negative photosensitive resin is used as a base film as an interlayer adhesive for a substrate are disclosed (Patent Documents 6, 7, and 8). In addition, the flexible part of the conventional multilayer flexible wiring board and rigid flex wiring board is a wiring on only one side, and the wiring density is increased. However, with such an insulating material, the dielectric constant (@ 1 MHz) is 3.7 to 4 .2 and it was difficult to speed up signal transmission.

  Patent Document 9 discloses a rigid flex wiring board in which a copper foil with resin (RCC) in which an adhesive and a copper foil are laminated in advance is laminated on both sides of a double-sided FPC. This rigid flex wiring board has moderate resilience and can be easily bent, but has the following drawbacks.

  In parts where bending resistance (sliding flexibility / IPC test) is required, such as a hinge part of a cellular phone, the flexible part needs to be a single-sided wiring and a single-sided coverlay structure (symmetrical structure with the conductor at the center). . Even if the rigid-flex wiring board disclosed in Patent Document 9 can be used for single-sided wiring, it is difficult to form a single-sided coverlay structure, and the bending resistance is insufficient.

  In addition, in a portion where the flexible wiring board is bent and attached, folding resistance is required so as not to be disconnected by bending the flexible wiring board several times. However, in a flexible wiring board having a structure of six layers or more, the peeling process of the outermost layer portion is performed. It becomes necessary, the process becomes complicated, and productivity decreases.

JP 2006-299209 A JP 2006-179679 A Japanese Patent No. 4237726 Japanese Patent No. 4021472 Japanese Patent No. 4024846 JP 2002-198623 A Japanese Patent No. 2900785 JP 63-34937 A JP 2009-1111033 A

  By the way, in a multilayer flexible wiring board, in order to form a flexible part, when using an interlayer adhesive, it is necessary to ensure and laminate | stack a hollow part with a metal mold | die etc. previously. In terms of quality, the interlayer adhesive may adversely affect the reliability during through-hole plating or blind via-hole plating. Further, in order to obtain flexibility, it is necessary to use a coverlay layer in order to ensure insulation of the inner layer circuit in the hollow portion, which causes an increase in cost.

  Further, in each layer of the rigid flex wiring board, in order to improve the flexibility of the flexible portion, it is necessary to secure a hollow portion to be a flexible portion with a mold or the like in advance when using an interlayer adhesive. In terms of quality, the interlayer adhesive may adversely affect the reliability during through-hole plating or blind via-hole plating. Further, after the circuit formation of the outer layer, cover coating, and surface treatment are completed, a process of peeling the outer layer by router processing or the like is necessary, which is a cause of cost increase.

  As described above, both of the multilayer flexible wiring board and the rigid flex wiring board are complicated in manufacturing process and complicated in structure, so that cost reduction is difficult. There was also a problem in quality stability.

  The present invention has been made in view of the above points, and it is possible to simplify a configuration, simplify a manufacturing process, and provide a multilayer flexible wiring board that is excellent in bending resistance and refraction resistance and can be easily thinned. The purpose is to provide.

  In order to overcome the above problems, the present inventors have intensively studied. As a result, it has been found that the above-mentioned problems can be solved by plating and / or conductive paste connecting the inner layer circuit and the outer layer circuit without using a coverlay, and the present invention has been completed. That is, the present invention is as follows.

  The multilayer flexible wiring board of the present invention includes an insulating substrate, a pair of conductive layers provided on both surfaces of the insulating substrate, a pair of insulating layers provided on the pair of conductive layers, and the pair of insulating layers, respectively. And at least one outer layer circuit that is provided on each of the layers and is electrically connected to the pair of conductive layers without passing through a cover lay by plating and / or conductive paste.

  The multilayer flexible wiring board of the present invention includes an insulating substrate, a conductive layer provided on one side of the insulating substrate, an insulating layer provided on the conductive layer, and provided on the insulating layer, and / or plating and / or It is characterized by comprising at least one outer layer circuit electrically connected by the conductive paste without passing through the cover layer and the cover layer.

  The multilayer flexible wiring board of the present invention includes an insulating substrate, a multilayer flexible substrate provided on the insulating substrate, and at least three conductive layers disposed via the insulating layer, on both surfaces of the multilayer flexible substrate. A pair of insulating layers provided, and at least one layer provided on the pair of insulating layers and electrically connected to the at least three conductive layers without a coverlay by plating and / or conductive paste And an outer layer circuit.

  The multilayer flexible wiring board of the present invention preferably has a structure in which the insulating layer is partially removed in the insulating layer.

  In the multilayer flexible wiring board of the present invention, the insulating layer preferably contains a positive photosensitive resin composition.

  In the multilayer flexible wiring board of the present invention, in the insulating layer, the insulating layer that is partially removed is only on one side, and at least the insulating layer that is partially removed is a positive photosensitive resin composition. It was preferable that it was obtained using.

  In the multilayer flexible wiring board of the present invention, it is preferable that the positive photosensitive resin composition comprises at least an alkali-soluble resin and a quinonediazide compound.

  In the multilayer flexible wiring board of the present invention, the alkali-soluble resin preferably has at least a polyamic acid structure.

  In the multilayer flexible wiring board of the present invention, the alkali-soluble resin preferably has a polyamic acid structure and a polyimide structure.

  In the multilayer flexible wiring board of the present invention, the alkali-soluble resin preferably has a polyalkylene ether structure and / or a siloxane structure.

  In the multilayer flexible wiring board of the present invention, it is preferable that the positive photosensitive resin composition further contains a dissolution inhibitor.

  In the multilayer flexible wiring board of the present invention, the dissolution inhibitor is preferably an amide compound or a urea compound.

  In the multilayer flexible wiring board of the present invention, it is preferable that the positive photosensitive resin composition further contains a phosphorus compound.

  In the multilayer flexible wiring board of the present invention, the phosphorus compound is preferably a phosphate ester compound and / or a phosphazene compound.

In the multilayer flexible wiring board of the present invention, the insulating layer is obtained from the positive photosensitive resin composition containing the alkali-soluble resin, and the dissolution rate of the alkali-soluble resin in an aqueous sodium carbonate solution is 0.00. The positive photosensitive resin composition was applied to a substrate and irradiated with actinic rays of 1000 mJ / cm ² or less on a 30 μm-thick photosensitive layer obtained after solvent removal by heating. In this case, the dissolution rate of the actinic ray-irradiated portion of the photosensitive layer composed of the photosensitive resin composition in the sodium carbonate aqueous solution is 0.22 μm / sec or more, and the remaining film ratio of the actinic ray-irradiated portion is 90% or more. Furthermore, the elastic modulus of the insulating layer obtained by heating the photosensitive layer not irradiated with actinic rays at 200 ° C. is 0.2 to 1.5 GPa and the dielectric constant is 3.5 or less. And are preferred.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to simplify a structure and a manufacturing process, it is excellent in bending resistance and refraction resistance, and can provide the multilayer flexible wiring board which is easy to make thin.

(A) is typical sectional drawing which shows the one aspect | mode of the structure of the multilayer flexible wiring board which concerns on embodiment of this invention, (b) is in the multilayer flexible wiring board which concerns on embodiment of this invention. It is a figure which shows an example of a reinforcement board. (A)-(g) is a figure which shows the outline of the manufacturing process of the multilayer flexible wiring board which concerns on embodiment of this invention. (A)-(e) is a figure which shows the outline of the manufacturing process in the case of using a metal paste in the multilayer flexible wiring board which concerns on embodiment of this invention. (A), (b) is a figure which shows the other structural example of the multilayer flexible wiring board which concerns on embodiment of this invention. (A)-(g) is a figure which shows an example of a structure of the multilayer flexible wiring board of 6 layer structure in the multilayer flexible wiring board which concerns on embodiment of this invention. (A)-(e) is a figure which shows the outline of the manufacturing process of the conventional multilayer flexible wiring board. (A)-(e) is a figure which shows the laminated structure of the conventional rigid flex wiring board.

  In multilayer flexible wiring boards and rigid flex wiring boards, in order to reduce costs, it is desirable to simplify the manufacturing process and stabilize the quality. In general multilayer flexible wiring boards and rigid flex wiring boards, a coverlay is provided between the inner layer circuit and the outer layer circuit. The coverlay is used to ensure insulation between the inner layer circuit and the outer layer circuit, and the inner layer circuit and the outer layer circuit are electrically connected by a through hole and a blind peer hole.

  In addition, in multilayer flexible wiring boards and rigid flex wiring boards, in order to connect the inner layer circuit and the outer layer circuit through the cover lay, the interlayer adhesion for bonding the cover lay and the cover lay or between the cover lay and the external circuit. An agent is needed. As such an interlayer adhesive, a negative photosensitive resin that is cured by exposure is mainly used.

  In the field of cellular phones and the like in which multilayer flexible wiring boards and rigid flex wiring boards are used, the flexibility of multilayer flexible wiring boards and rigid flex wiring boards is required. In general multilayer flexible wiring boards and rigid flex wiring boards, it is necessary to remove the interlayer adhesive in the flexible portion in order to ensure flexibility.

  The inventors focused on the structure of a multilayer flexible wiring board or a rigid flex wiring board, and conducted intensive research on simplification of the structure and simplification of the manufacturing process. First, focusing on the coverlay provided between the inner layer circuit and the outer layer circuit, various studies were made on simplification of the structure of the multilayer flexible wiring board. As a result, a multilayer flexible wiring board can be constructed without using a coverlay, and a multilayer flexible wiring board can be constructed without using an interlayer adhesive by not using a coverlay. It has been found that the manufacturing process can be greatly simplified.

  Furthermore, the inventors of the present invention, in the configuration of the multilayer flexible wiring board that does not use a cover lay, have an insulating layer used between the inner layer circuit and the outer layer circuit having a predetermined composition, so that the outer layer circuit and the insulating layer It has been found that the adhesive strength can be improved and can also be used as an interlayer adhesive layer. Furthermore, by using a structure that does not use the cover lay described above, and using a positive photosensitive resin as a predetermined ratio as an insulating layer, the insulating layer can be easily removed by exposure and development, and a flexible portion can be easily formed. The headline and the present invention have been completed.

  That is, according to the present invention, the inner layer circuit and the outer layer circuit sequentially provided on the flexible substrate can be connected without going through the cover lay, thereby simplifying the configuration, simplifying the manufacturing process, bending resistance, A multilayer flexible wiring board having excellent refraction resistance is realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the structure of a flexible printed wiring board according to an embodiment of the present invention. As shown in FIG. 1, the multilayer flexible substrate according to the present embodiment includes two rigid portions 11a and 11b including inner layer circuits L1 and L2 and outer layer circuits L3 and L4, and a rigid portion 11a and a rigid portion 11b. And a flexible portion 12 formed therebetween. The rigid portions 11a and 11b and the flexible portion 12 are integrally formed on a double-sided flexible substrate 13 as a core layer.

  The rigid parts 11a and 11b have a conductive layer 15 formed on one surface of the insulating substrate 14 of the double-sided flexible substrate 13 and a conductive layer 16 formed on the other surface. The conductive layer 15 and the conductive layer 16 are patterned by etching or the like to form inner layer circuits L1 and L2. A conductive layer 18 is formed on the conductive layer 15 on one surface side of the insulating substrate 14 with an insulating layer 17 interposed therebetween. On the other hand, a conductive layer 20 is formed on the conductive layer 16 on the other surface side of the insulating substrate 14 via an insulating layer 19. The conductive layer 18 and the conductive layer 20 are patterned by etching or the like, so that the conductive layer 18 becomes the outer layer circuit L3 and the conductive layer 20 becomes the outer layer circuit L4.

  That is, the rigid portions 11a and 11b are formed with a laminated structure including the inner layer circuit L1 / insulating layer 17 / outer layer circuit L3 on one surface side of the insulating substrate 14 without the cover lay, On the surface side, a laminated structure including the inner layer circuit L2 / insulating layer 19 / outer layer circuit L4 is formed. As described above, since the laminated structure including the inner layer circuits L1, L2 and the outer layer circuits L3, 4 can be formed without using the coverlay, the configuration of the multilayer flexible substrate can be simplified and the manufacturing process can be simplified. Can do. Moreover, since a multilayer flexible wiring board can be comprised without using a coverlay, a multilayer flexible wiring board can be reduced in thickness. For this reason, a multilayer flexible wiring board capable of higher density wiring can be realized. The outer layer circuit L3 is covered with the cover coat 21, and the outer layer circuit L4 is covered with the cover coat 22.

  The flexible portion 12 is formed by partially removing the insulating layer 17 or the insulating layer 19 of the multilayer flexible substrate. By forming the flexible portion 12, flexibility and / or flexibility is improved.

  The insulating layers 17 and 19 mainly include a positive photosensitive resin composition, insulate the inner layer circuits L1 and L2 from the outer layer circuits L3 and L4, and adhere the outer layer circuits L3 and L4. . As described above, in the present embodiment, the insulating layers 17 and 19 function as a cover lay that insulates the inner layer circuits L1 and L2 from the outer layer circuits L3 and L4, and the layers that bond the outer layer circuits L3 and L4. Since it has both functions as an adhesive, there is no need to use coverlay and other interlayer adhesives. Thereby, while being able to simplify a structure, the manufacturing process mentioned later can be simplified. In addition, since at least the flexible part 12 of the insulating layers 17 and 19 on one surface side of the multilayer flexible wiring board partially contains the positive photosensitive resin composition, the insulating of the flexible part 12 is performed in the etching process described later. This is preferable because a part of the layers 17 and 19 can be easily removed.

  In the present invention, the insulating layers 17 and 19 also function as interlayer adhesives. For this reason, the characteristic which can develop and remove the exposed part is required, and it is preferable to have positive photosensitivity.

  In the present invention, the positive photosensitive resin content of the insulating layers 17 and 19 is preferably in the range of 40 parts by mass to 99 parts by mass with respect to the mass of the insulating layers 17 and 19 as a whole. If the content of the positive photosensitive resin is 40 parts by mass or more, it is preferable from the viewpoints of insulation, adhesiveness, and elastic modulus, and if it is 99 parts by mass or less, it is preferable from the viewpoint of developability.

  In the manufacturing process of the multilayer flexible wiring board, the insulating layers 17 and 19 are required to have resistance to a copper layer etching process and a desmear process at the time of forming a blind via hole.

  In addition, the insulating layers 17 and 19 preferably have a low elastic modulus in order to provide flexibility at the flexible portion of the multilayer flexible wiring board. The elastic modulus is preferably in the range of 0.2 to 1.5.

More preferably, in the present invention, the insulating layers 17 and 19 are obtained from a positive photosensitive resin composition containing an alkali-soluble resin, and the dissolution rate of the alkali-soluble resin in an aqueous sodium carbonate solution is 0.04 μm / When the positive photosensitive resin composition is applied onto a substrate and irradiated with an actinic ray of 1000 mJ / cm ² or less on a 30 μm-thick photosensitive layer obtained after solvent removal by heating, The rate of dissolution of the actinic ray irradiated part of the photosensitive layer composed of the photosensitive resin composition in the aqueous sodium carbonate solution is 0.22 μm / sec or more, and the remaining film ratio of the actinic ray non-irradiated part is 90% or more. Furthermore, the elastic modulus of the insulating layer obtained by heating the photosensitive layer in the actinic ray non-irradiated part at 200 ° C. is 0.2 to 1.5 GPa, and the dielectric constant (@ 1 MHz) is 3.5 to 2. 5 . By adopting such a composition, it is preferable in the step of exposing and removing the insulating layer because the photosensitivity is high, the productivity is high, and the interface between the exposed portion and the unexposed portion becomes sharp.

  The dissolution rate of the alkali-soluble resin in the sodium carbonate aqueous solution is 0.04 μm / sec or more, and the dissolution rate in the aqueous solution of the actinic ray of the photosensitive layer composed of the photosensitive resin composition is 0.00. If it is 22 μm / sec or more and the remaining film rate of the actinic ray non-irradiated part is 90% or more, the elution of the insulating layer in the unexposed part is more preferably suppressed during development. If the elastic modulus is 0.2 GPa to 1.5 GPa, there is no warping of the substrate and excellent flexibility. When the dielectric constant (@ 1 MHz) is 3.5 to 2.5, preferably 3.2 to 2.5, the wiring signal transmission is excellent in reliability.

  As a material for the insulating layers 17 and 19, a positive photosensitive resin composition is used. The insulating layers 17 and 19 may be formed by applying a positive photosensitive resin composition to a substrate, or once forming a film on a film and then laminating it on the substrate. The obtained semi-cured insulating layer is exposed and developed as necessary, and further heated and cured to form the insulating layer.

  In the present invention, the positive photosensitive resin composition comprises at least an alkali-soluble resin and a quinonediazide compound. Examples of the alkali-soluble resin include novolak resins, acrylic resins, copolymers of styrene and acrylic acid, polymers of hydroxystyrene, polyvinylphenol, poly α-methylvinylphenol, polyimide resins, polybenzoxazole resins, and the like. Can be mentioned.

  In the present invention, the content of the alkali-soluble resin in the insulating layers 17 and 19 is preferably in the range of 40 parts by mass to 99 parts by mass with respect to the total mass of the insulating layers 17 and 19. If content of alkali-soluble resin is 40 mass parts or more, it is preferable from a viewpoint of insulation, adhesiveness, and an elasticity modulus, and if it is 99 mass parts or less, it is preferable from a developability viewpoint.

  The alkali-soluble resin is preferably a resin having a carboxyl group in the molecular chain in order to have alkali solubility. Furthermore, from the viewpoint of heat resistance and flexibility of the insulating layer obtained after heating at 200 ° C. or less, polyimide having a carboxyl group in the molecule (hereinafter referred to as carboxyl group-containing), polyimide precursor, and having a carboxyl group in the molecule (hereinafter referred to as “lower”) , Carboxyl group-containing) polybenzoxazole, and polybenzoxazole precursor having a carboxyl group in the molecule (hereinafter, carboxyl group-containing) are preferred. In addition, for the purpose of dissolving and removing the insulating layer in the exposed portion after solvent removal, a polyimide precursor is more preferable from the viewpoint of sodium carbonate development, and the polyamic acid represented by the following general formula (1) has a carboxyl group in the molecule. A polymer having a polyamic acid ester structure (hereinafter containing a carboxyl group) is more preferred.

（Ｒ１は４価の有機基である。Ｒ２、Ｒ３は水素又は炭素数１〜炭素数２０の有機基であり、それぞれ同一でも異なっていてもよい。Ｒ４は２価〜４価の有機基である。Ｒ５、Ｒ６は水素又は炭素数１〜炭素数２０の有機基であり、それぞれ同一でも異なっていてもよい。ただし、Ｒ２及びＲ３が水素でないとき、ｍ＋ｎ＞０かつｎ＞０であり、Ｒ５は水素又は炭素数１〜炭素数２０の有機基、Ｒ６は水素である。Ｒ２、Ｒ３の少なくとも一方が水素のときｍ＋ｎ≧０であり、かつＲ５、Ｒ６は水素又は炭素数１〜炭素数２０の有機基であって、それぞれ同一でも異なっていてもよい。）

(R1 is a tetravalent organic group. R2 and R3 are hydrogen or an organic group having 1 to 20 carbon atoms, which may be the same or different. R4 is a divalent to tetravalent organic group. R5 and R6 are hydrogen or an organic group having 1 to 20 carbon atoms, and may be the same or different, provided that when R2 and R3 are not hydrogen, m + n> 0 and n>0; R5 is hydrogen or an organic group having 1 to 20 carbon atoms, R6 is hydrogen, m + n ≧ 0 when at least one of R2 and R3 is hydrogen, and R5 and R6 are hydrogen or 1 to carbon atoms. 20 organic groups, each of which may be the same or different.)

  As the alkali-soluble resin according to the present invention, a polyamic acid represented by the following general formula (2) is more preferable.

（Ｒ７は炭素数２以上である４価の有機基を示し、Ｒ８は炭素数２以上の２価の有機基を示す。）

(R7 represents a tetravalent organic group having 2 or more carbon atoms, and R8 represents a divalent organic group having 2 or more carbon atoms.)

  The polyimide precursor used in the present invention is preferably produced by polymerizing tetracarboxylic dianhydride and diamine. Examples of the tetracarboxylic dianhydride and diamine used are as follows: There is something to show.

  Specific examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-. Biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2 ′, 3 , 3′-benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane Anhydride, bis (2 3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 3,3′-oxydiphthalic dianhydride, 4,4′-oxydiphthalic dianhydride, 2, 2-bis (4- (4-aminophenoxy) phenyl) propane, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1,4-phenylene ester, 4- (2,5-di Oxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6, 7-naphthalene tetracarboxylic dianhydride, 2,3,5,6-pyridinetetracarboxylic dianhydride, 3,4,9,10-perylene tetracarboxylic dianhydride, 2,2-bi (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 2,2-bis (4- (3,4-dicarboxyphenoxy) phenyl) hexafluoropropane dianhydride, 2,2-bis (4- (3,4-Dicarboxybenzoyloxy) phenyl) hexafluoropropane dianhydride, 2,2′-bis (trifluoromethyl) -4,4′-bis (3,4-dicarboxyphenoxy) biphenyl dianhydride Etc.

  Aliphatic tetracarboxylic dianhydrides include cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5,6-cyclohexanetetracarboxylic dianhydride 5- (2,5-dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene-1,2-dicarboxylicsan dianhydride, ethylene glycol-bis-trimellitic anhydride, bicyclo [2 , 2,2] oct-7-ene-2,3,5,6 tetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride and the like. These may be used alone or in combination of two or more.

  Among these tetracarboxylic dianhydrides, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid dihydrate is used from the viewpoint of increasing the flexibility of the insulating layer formed through the heat treatment. Anhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone Tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis ( 2,3-dicarboxyphenyl) propane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride Bis (3,4-di Ruboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 3,3′-oxydiphthalic acid dianhydride, 4,4′-oxydiphthalic dianhydride, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid-1, 4-phenylene ester, ethylene glycol-bis-trimellitic anhydride ester is preferred. These may be used alone or in combination of two or more.

  Specific examples of the diamine include 1,4-diaminobenzene, 1,3-diaminobenzene, 2,4-diaminotoluene, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 3,4 ′. -Diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis (trifluoromethyl) -4,4 ' -Diaminobiphenyl, 3,7-diamino-dimethylbenzothiophene-5,5-dioxide, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-bis (4-aminophenyl) sulfide, 4,4′-diaminodiphenylsulfone, 4,4′-diaminobenzanilide, 1, n-bis (4-aminophenyl) Noxy) alkane, 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane, 1,2-bis [2- (4-aminophenoxy) ethoxy] ethane, 9,9-bis (4-amino) Phenyl) fluorene, 5 (6) -amino-1- (4-aminomethyl) -1,3,3-trimethylindane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4- Aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 2,2- Bis (4-aminophenoxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, , 2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 3,3′-dicarboxy-4,4′-diaminodiphenylmethane, 4,6-dihydroxy-1,3-phenylenediamine, 3, 3′-dihydroxy-4,4′-diaminobiphenyl, 1,4-bis (4-aminophenoxy) pentane, 1,5-bis (4′-aminophenoxy) pentane, bis (γ-aminopropyl) tetramethyldi Siloxane, 1,4-bis (γ-aminopropyldimethylsilyl) benzene, bis (4-aminobutyl) tetramethyldisiloxane, bis (γ-aminopropyl) tetraphenyldisiloxane, represented by the following general formula (3) And diaminosiloxane compounds. These may be used alone or in combination of two or more.

（式中、Ｒ９は炭素数１以上３０以下の炭化水素基を表し、それぞれ同じであっても異なっていても良い。Ｒ１０は、炭素数１以上３０以下である２価の有機基を表し、それぞれ同じであっても異なっても良い。ａは、２以上３０以下の整数である。）

(In the formula, R9 represents a hydrocarbon group having 1 to 30 carbon atoms, which may be the same or different. R10 represents a divalent organic group having 1 to 30 carbon atoms, Each may be the same or different, and a is an integer of 2 to 30.)

  Moreover, it is also preferable to use the diamine which has chain | strand-shaped polyether in molecular structure for the diamine used by this invention, and using the compound represented by the following general formula (4) or the following general formula (5). preferable.

（式中、ｂは１〜５０の整数を表し、Ｒ１１はそれぞれ独立に炭素数２〜１０のアルキレン基を表す。)

(In the formula, b represents an integer of 1 to 50, and R11 each independently represents an alkylene group having 2 to 10 carbon atoms.)

（式中、Ｒ１２、Ｒ１３、Ｒ１４、Ｒ１５、Ｒ１６はそれぞれ独立して炭素数１〜炭素数２０のアルキレン基を表し、それぞれ独立して炭素数１〜炭素数５のアルキル基を1個以上、有していても良い。ｃ、ｄ、ｅはそれぞれ独立して０以上の整数を表す。）

(Wherein R12, R13, R14, R15 and R16 each independently represents an alkylene group having 1 to 20 carbon atoms, and each independently represents one or more alkyl groups having 1 to 5 carbon atoms, (C, d, and e each independently represent an integer of 0 or more.)

  Specific examples of the diamine represented by the general formula (4) include, for example, polytetramethylene oxide-di-o-aminobenzoate, polytetramethylene oxide-di-m-aminobenzoate, polytetramethylene oxide-di-p. Examples include, but are not limited to, aminobenzoates, polytrimethylene oxide-di-o-aminobenzoates, polytrimethylene oxide-di-m-aminobenzoates, polytrimethylene oxide-di-p-aminobenzoates and the like. Among them, those having both ends at the p-aminobenzoic acid ester group are preferable, and among them, polytetramethylene oxide-di-p-aminobenzoate is preferably used. Two or more diamines may be used. The diamine represented by the general formula (4) contains 25 mol% to 55 mol% of the diamine represented by the general formula (4) with respect to the total diamine. Preferably they are 25 mol%-50 mol%, More preferably, they are 30 mol%-50 mol%. If it is 25 mol% or more, flexibility is shown, and if it is 55 mol% or less, it is excellent in solvent resistance and heat resistance.

  Specific examples of the diamine represented by the general formula (5) include polyoxyethylene diamine such as 1,8-diamino-3,6-dioxyoctane, polyoxypropylene diamine, and other oxyalkylenes having different lengths. And polyoxyalkylene diamines such as those containing a group. As polyoxyalkylene diamines, polyoxyethylene diamines such as Jeffamine EDR-148 and EDR-176 by Huntsman, Inc., polyoxypropylene diamines such as Jeffamine D-230, D-400, D-2000 and D-4000, Commercial products such as those having different oxyalkylene groups such as HK-511, ED-600, ED-900, ED-2003, XTJ-542 are listed as examples of use. In particular, since EDR-148, D-230, D-400, HK-511, etc., which have relatively low molecular weights, can be polymers having a relatively high glass transition temperature, they are used in applications that require heat resistance and chemical resistance. can do. On the other hand, D-2000 having a relatively high molecular weight is excellent in flexibility, low boiling point solvent solubility and the like. In addition, it is easier to obtain a high molecular weight polyamic acid when the one having high purity is used, preferably 95% or more, more preferably 97% or more, and further preferably 98.5% or more.

  It is preferable that the diamine represented by the said General formula (5) is 25 mol%-60 mol% with respect to all the diamines. More preferably, it is 25 mol%-50 mol%, More preferably, it is 30 mol%-50 mol%. If it is 25 mol% or more, flexibility is shown, and if it is 60 mol% or less, it is excellent in solvent resistance and heat resistance.

  Among these diamines, 1,4-diaminobenzene, 1,3-diaminobenzene, 2,4-diaminotoluene, 4,4′-diamino are used from the viewpoint of enhancing the flexibility of the insulating layer formed through the heat treatment. Diphenylmethane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′-dimethyl-4,4′-dianobiphenyl, 2,2′-dimethyl-4,4′-diaminobiphenyl, 3, , 7-diamino-dimethylbenzothiophene-5,5-dioxide, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-bis (4-aminophenyl) sulfide, 4,4′- Diaminodiphenylsulfone, 4,4′-diaminobenzanilide, 1, n-bis (4-aminophenoxy) alkane, 1 3-bis (4-aminophenoxy) -2,2-dimethylpropane, 1,2-bis [2- (4-aminophenoxy) ethoxy] ethane, 9,9-bis (4-aminophenyl) fluorene, 5 ( 6) -Amino-1- (4-aminomethyl) -1,3,3-trimethylindane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, , 3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 2,2-bis (4-aminophenoxy) Phenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 4,6-dihydroxy- , 3-phenylenediamine, 3,3′-dihydroxy-4,4′-diaminobiphenyl, 1,4-bis (4-aminophenoxy) pentane, 1,5-bis (4′-aminophenoxy) pentane, bis ( γ-aminopropyl) tetramethyldisiloxane, 1,4-bis (γ-aminopropyldimethylsilyl) benzene, bis (4-aminobutyl) tetramethyldisiloxane, bis (γ-aminopropyl) tetraphenyldisiloxane, formula The diaminosiloxane compound represented by (3) and the compound represented by the general formula (4) or the general formula (5) having a chain polyether in the molecular structure are preferred. These may be used alone or in combination of two or more.

  The polyimide precursor in the present invention preferably has a polyimide structure in addition to the polyamic acid structure. The imide ratio is preferably in the range of 0% to 99.9%, more preferably in the range of 0% to 90%, and still more preferably in the range of 0% to 80%.

  Next, a method for producing a polyimide precursor will be described. The polyimide precursor can be easily synthesized by a known method described in the latest polyimide, basics and applications, edited by Japan Polyimide Research Group, pp4 to pp49. Specifically, a method of reacting a tetracarboxylic dianhydride and a diamine at a low temperature to 100 ° C. or lower, a tetracarboxylic dianhydride and an alcohol are reacted to synthesize a diester, and then a diamine in the presence of a condensing agent. And a method of reacting tetracarboxylic dianhydride with an alcohol to synthesize a diester, and then converting the remaining dicarboxylic acid into an acid chloride and then reacting with a diamine. A method in which tetracarboxylic dianhydride and diamine are reacted at a low temperature to 100 ° C. or less is preferred.

  The reaction is preferably performed in an organic solvent. As a solvent used in such a reaction, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 1,3 -Dioxane, 1,4-dioxane, dimethyl sulfoxide, benzene, toluene, xylene, mesitylene, phenol, cresol and the like. These may be used alone or in combination of two or more.

The density | concentration of the reaction raw material in this reaction is 2 mass%-60 mass% normally, Preferably it is 5 mass%-50 mass%, More preferably, it is 10 mass%-45 mass%.

  The molar ratio of the acid dianhydride to be polymerized and the diamine is in the range of 0.8 to 1.2. Within this range, the molecular weight can be increased, and the elongation and the like are excellent. Preferably it is 0.9-1.1, More preferably, it is 0.95-1.05.

  The weight average molecular weight of the polyimide precursor is preferably 5000 or more and 100,000 or less. Here, the weight average molecular weight refers to a molecular weight measured by gel permeation chromatography using polystyrene having a known number average molecular weight as a standard. The weight average molecular weight is more preferably from 10,000 to 60,000, and most preferably from 20,000 to 50,000. When the weight average molecular weight is 5,000 or more and 100,000 or less, the warp of the insulating layer obtained using the resin composition is improved, and the flexibility and heat resistance are excellent.

  In order to introduce an imide structure, the polyimide precursor obtained above is preferably heated to 100 ° C. to 400 ° C. to thermally imidize, or chemically imidized using an imidizing agent such as acetic anhydride. Thus, a polyimide having a repeating unit structure corresponding to the polyamic acid structure is obtained. In the case of imidization by heating, in order to remove by-product water, dehydration is carried out under reflux using a Dean-Stark type dehydrator in the presence of an azeotropic agent (preferably toluene or xylene). Is also preferable.

  Moreover, it is also preferable to obtain a polyimide by carrying out the reaction at 80 ° C. to 220 ° C. to advance both the generation of the polyimide precursor and the thermal imidization reaction. That is, the diamine component and the acid dianhydride component are suspended or dissolved in an organic solvent and reacted under heating at 80 ° C. to 220 ° C. to cause both generation of a polyimide precursor and dehydration imidization. It is also preferable to obtain polyimide.

  Further, as one method for introducing an imide structure, in order to produce a polyamic acid-polyimide block body, there is a method in which an acid dianhydride-terminated oligomer is first synthesized and then the oligomer and the monomer are polymerized.

  In the synthesis of the first acid dianhydride-terminated oligomer, the acid dianhydride and the diamine compound are reacted in an organic polar solvent to synthesize the acid dianhydride-terminated polyamic acid. The number of equivalents in this case is acid dianhydride> diamine compound. The addition polymerization reaction is carried out at a reaction temperature of 80 ° C. or lower, preferably 50 ° C. or lower for 1 to 12 hours to obtain a polyamic acid as an acid dianhydride-terminated oligomer. The number of equivalents in this case is acid dianhydride> diamine compound, and the ratio of acid dianhydride / diamine compound is preferably more than 1 and preferably 10 or less, more preferably 1.1 or more and 5 or less. It is particularly preferably 3 or more and 3 or less.

  Next, the obtained polyamic acid is dehydrated and cyclized into an acid dianhydride-terminated oligomer. As a method for dehydrating cyclization, a known method can be used. For example, a thermal cyclization method by refluxing such as toluene and xylene, or a chemical cyclization method using acetic anhydride and an aromatic tertiary amine such as pyridine can be used.

  Subsequently, the acid dianhydride terminal oligomer synthesized by the above method and a diamine forming a polyamic acid structure are subjected to an addition polymerization reaction. Specifically, the acid dianhydride terminal oligomer and diamine are subjected to an addition polymerization reaction in an organic solvent for 0.5 hours to 12 hours. The reaction temperature at this time is preferably 100 ° C. or lower, and more preferably 50 ° C. or lower. In addition, it is also preferable to add an acid anhydride with a diamine at the process of adding a diamine. The molar ratio of the acid dianhydride and diamine in the final composition is adjusted to be in the range of 0.8 to 1.2.

  Furthermore, as a polyamic acid-polyimide block body, a diamine having a chain siloxane structure represented by the above general formula (3) in the molecular structure and / or the above general formula (4) or the above general formula ( The storage stability of the positive photosensitive resin composition of the present invention can also be obtained by introducing a diamine having a chain polyether represented by 5) in the molecular structure and converting the terminal of these diamines to an imide structure. Can be improved.

  It is also preferable that the terminal of the polymer main chain of the polyimide precursor is end-capped with a terminal capping agent made of a monoamine derivative or a carboxylic acid derivative. It is excellent in storage stability because the end of the polymer main chain of the polyimide precursor is sealed.

  Examples of the end capping agent comprising a monoamine derivative include aniline, o-toluidine, m-toluidine, p-toluidine, 2,3-xylidine, 2,6-xylidine, 3,4-xylidine, and 3,5-xylidine. O-chloroaniline, m-chloroaniline, p-chloroaniline, o-bromoaniline, m-bromoaniline, p-bromoaniline, o-nitroaniline, m-nitroaniline, p-nitroaniline, o-aminophenol M-aminophenol, p-aminophenol, o-anisidine, m-anisidine, p-anisidine, o-phenetidine, m-phenetidine, p-phenetidine, o-aminobenzaldehyde, p-aminobenzaldehyde, m-aminobenzaldehyde, o-aminobenzonitrile, p-aminobenzonitrile Lyl, m-aminobenzonitrile, 2-aminobiphenyl, 3-aminobiphenyl, 4-aminobiphenyl, 2-aminophenylphenyl ether, 3-aminophenylphenyl ether, 4-aminophenylphenyl ether, 2-aminobenzophenone, 3 -Aminobenzophenone, 4-aminobenzophenone, 2-aminophenyl phenyl sulfide, 3-aminophenyl phenyl sulfide, 4-aminophenyl phenyl sulfide, 2-aminophenyl phenyl sulfone, 3-aminophenyl phenyl sulfone, 4-aminophenyl phenyl sulfone , Α-naphthylamine, β-naphthylamine, 1-amino-2-naphthol, 5-amino-1-naphthol, 2-amino-1-naphthol, 4-amino-1-naphthol, 5-amino Aromatic monoamines such as 2-naphthol, 7-amino-2-naphthol, 8-amino-1-naphthol, 8-amino-2-naphthol, 1-aminoanthracene, 2-aminoanthracene, 9-aminoanthracene Of these, derivatives of aniline are preferably used. These may be used alone or in combination of two or more.

  Examples of the terminal blocking agent comprising a carboxylic acid derivative include carboxylic anhydride derivatives, such as phthalic anhydride, 2,3-benzophenone dicarboxylic anhydride, 3,4-benzophenone dicarboxylic anhydride, 2,3- Dicarboxyphenyl phenyl ether anhydride, 3,4-dicarboxyphenyl phenyl ether anhydride, 2,3-biphenyl dicarboxylic acid anhydride, 3,4-biphenyl dicarboxylic acid anhydride, 2,3-dicarboxyphenyl phenyl sulfone anhydride 3,4-dicarboxyphenyl phenyl sulfone anhydride, 2,3-dicarboxyphenyl phenyl sulfide anhydride, 3,4-dicarboxyphenyl phenyl sulfide anhydride, 1,2-naphthalenedicarboxylic acid anhydride, 2, 3-Naphthalenedicarboxylic anhydride, 1,8-naphthalene Carboxylic acid anhydride, 1,2-anthracene dicarboxylic acid anhydride, 2,3-anthracene dicarboxylic acid anhydride, 1,9-aromatic dicarboxylic acid anhydrides such as anthracene dicarboxylic acid anhydride. Of these aromatic dicarboxylic acid anhydrides, phthalic anhydride is preferably used. These may be used alone or in combination of two or more.

  In the present invention, the polyimide precursor preferably has a functional group selected from a carboxyl group, an aromatic hydroxyl group, and a sulfonic acid group in addition to the polyamic acid structure in the main chain. For example, a diamine having a carboxyl group, an aromatic hydroxyl group or a sulfonic acid group may be copolymerized, or a diamine-terminated polyimide precursor and an acid having a carboxyl group, an aromatic hydroxyl group or a sulfonic acid group in the molecular structure. It can also be obtained by reacting with an anhydride or by reacting an acid anhydride-terminated polyimide precursor with an amine compound having a carboxyl group, an aromatic hydroxyl group or a sulfonic acid group.

  Examples of the acid anhydride having a carboxyl group, an aromatic hydroxyl group, or a sulfonic acid group in the molecular structure include carboxyl group-containing acid anhydrides such as trimellitic acid anhydride.

  Examples of the amine compound having a carboxyl group, an aromatic hydroxyl group, or a sulfonic acid group in the molecular structure include 2-aminobenzoic acid, 3-aminobenzoic acid, and 4-aminobenzoic acid.

  With respect to the introduction rate of a site derived from a functional group selected from a carboxyl group, an aromatic hydroxyl group and a sulfonic acid group at the end of the polymer main chain, the flexibility of the resulting insulating layer is not impaired for the purpose of improving developability. Determined by range. Preferably, it is 0.5 mol% or more and 10 mol% or less.

Next, the quinonediazide compound of the present invention will be described.
The quinonediazide compound is a compound containing a quinonediazide structure. Examples of the compound containing a quinonediazide structure include 1,2-benzoquinonediazidesulfonic acid esters, 1,2-benzoquinonediazidesulfonic acid amides, and 1,2-naphtho. Examples thereof include quinonediazidesulfonic acid esters and 1,2-naphthoquinonediazidesulfonic acid amides. Specifically, for example, 2,3,4-trihydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 2,3,4-trihydroxybenzophenone-1,2-naphthoquinonediazide-5-sulfone Acid esters, 2,4,6-trihydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 2,4,6-trihydroxybenzophenone-1,2-naphthoquinonediazide-5-sulfonic acid ester, etc. 1,2-naphthoquinone diazide sulfonic acid esters of trihydroxybenzophenones; 2,2 ′, 4,4′-tetrahydroxybenzophenone-1,2-naphthoquinone diazide-4-sulfonic acid ester, 2,2 ′, 4, 4'-tetrahydroxybenzophenone-1,2-naphthoquinonedia Dido-5-sulfonic acid ester, 2,2 ′, 3 ′, 4-tetrahydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 2,2 ′, 3 ′, 4-tetrahydroxybenzophenone-1 , 2-Naphthoquinonediazide-5-sulfonic acid ester, 2,3,4,4′-tetrahydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 2,3,4,4′-tetrahydroxybenzophenone -1,2-naphthoquinonediazide-5-sulfonic acid ester, 2,2 ′, 3,4-tetrahydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 2,2 ′, 3,4-tetra Hydroxybenzophenone-1,2-naphthoquinonediazide-5-sulfonic acid ester, 2,3,4,4′-te Lahydroxy-3′-methoxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 2,3,4,4′-tetrahydroxy-3′-methoxybenzophenone-1,2-naphthoquinonediazide-5-sulfone 1,2-naphthoquinone diazide sulfonic acid esters of tetrahydroxybenzophenones such as acid esters; 2,2 ′, 3,4,6′-pentahydroxybenzophenone-1,2-naphthoquinone diazide-4-sulfonic acid esters, 2 1,2-naphthoquinone diazide sulfonic acid esters of pentahydroxybenzophenones such as 2,2 ', 3,4,6'-pentahydroxybenzophenone-1,2-naphthoquinonediazide-5-sulfonic acid ester; 4,4 ′, 5 ′, 6-hexahydroxybenzophenone-1 2-naphthoquinonediazide-4-sulfonic acid ester, 2,3 ′, 4,4 ′, 5 ′, 6-hexahydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 3,3 ′, 4, 4 ', 5,5'-Hexahydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid ester, 3,3', 4,4 ', 5,5'-hexahydroxybenzophenone-1,2-naphthoquinonediazide 1,2-naphthoquinone diazide sulfonic acid esters of hexahydroxybenzophenones such as -5-sulfonic acid ester; bis (2,4-dihydroxyphenyl) methane-1,2-naphthoquinone diazide-4-sulfonic acid ester, bis ( 2,4-Dihydroxyphenyl) methane-1,2-naphthoquinonediazide-5-sulfonic acid ester Bis (p-hydroxyphenyl) methane-1,2-naphthoquinonediazide-4-sulfonic acid ester, bis (p-hydroxyphenyl) methane-1,2-naphthoquinonediazide-5-sulfonic acid ester, 1,1, 1-tri (p-hydroxyphenyl) ethane-1,2-naphthoquinonediazide-4-sulfonic acid ester, 1,1,1-tri (p-hydroxyphenyl) ethane-1,2-naphthoquinonediazide-5-sulfonic acid Ester, bis (2,3,4-trihydroxyphenyl) methane-1,2-naphthoquinonediazide-4-sulfonic acid ester, bis (2,3,4-trihydroxyphenyl) methane-1,2-naphthoquinonediazide- 5-sulfonic acid ester, 2,2′-bis (2,3,4-trihydroxyphenyl) propane- , 2-Naphthoquinonediazide-4-sulfonic acid ester, 2,2′-bis (2,3,4-trihydroxyphenyl) propane-1,2-naphthoquinonediazide-5-sulfonic acid ester, 1,1,3- Tris (2,5-dimethyl-4-hydroxyphenyl) -3-phenylpropane-1,2-naphthoquinonediazide-4-sulfonic acid ester, 1,1,3-tris (2,5-dimethyl-4-hydroxyphenyl) ) -3-Phenylpropane-1,2-naphthoquinonediazide-5-sulfonic acid ester, 4,4 ′-[1- [4- [1- [4-hydroxyphenyl] -1-methylethyl] phenyl] ethylidene] Bisphenol-1,2-naphthoquinonediazide-5-sulfonic acid ester, 4,4 ′-[1- [4- [1- [4-hydroxyphenyl]- 1-methylethyl] phenyl] ethylidene] bisphenol-1,2-naphthoquinonediazide-4-sulfonic acid ester, bis (2,5-dimethyl-4-hydroxyphenyl) -2-hydroxyphenylmethane-1,2-naphthoquinonediazide -4-sulfonic acid ester, bis (2,5-dimethyl-4-hydroxyphenyl) -2-hydroxyphenylmethane-1,2-naphthoquinonediazide-5-sulfonic acid ester, 3,3,3 ', 3'- Tetramethyl-1,1′-spirobiindene-5,6,7,5 ′, 6 ′, 7′-hexanol-1,2-naphthoquinonediazide-4-sulfonic acid ester, 3,3,3 ′, 3 '-Tetramethyl-1,1'-spirobiindene-5,5', 6,6 ', 7,7'-hexanol-1,2-naphthoquinonediazide-5-sulf Acid ester, 2,2,4-trimethyl-2 ′, 4 ′, 7-trihydroxyflavan-1,2-naphthoquinonediazide-4-sulfonic acid ester, 2,2,4-trimethyl-2 ′, 4 ′ 1,2-naphthoquinone diazide sulfonic acid esters of (polyhydroxyphenyl) alkanes such as 7,7-trihydroxyflavan-1,2-naphthoquinone diazide-5-sulfonic acid ester. From the viewpoint of dissolution inhibiting ability, 1,2-naphthoquinone diazide sulfonic acid esters are preferable, 1,2-naphthoquinone diazide-4-sulfonic acid esters, and 1,2-naphthoquinone diazide-5-sulfonic acid esters are photosensitive. More preferable from the viewpoint of contrast. Of these, the quinonediazide compound (A) represented by the following general formula (6) (Q is a structure or a hydrogen atom represented by the following formula (7)) is particularly preferable.

  As a photosensitive agent in the photosensitive resin composition according to the present invention, the quinonediazide compound (A) has an average of 2.9 out of the three Qs in the general formula (6) represented by the general formula (7). Refers to those that have a structure.

  The amount of the photosensitive agent in the photosensitive resin composition according to the present invention is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 100 parts by mass or less from the viewpoint of photosensitive contrast, with respect to 100 parts by mass of the polyimide precursor according to the present invention. Is 5 parts by mass or more and 30 parts by mass or less. If it is 1 mass part or more, since there exists a tendency for dissolution suppression of an unexposed part to be enough, it is preferable. Less than 50 parts by mass is preferred because the sensitivity tends to be sufficiently high.

  The photosensitive resin composition according to the present invention contains a dissolution inhibitor for the purpose of suppressing the solubility of an alkali-soluble resin in an alkaline developer. The dissolution inhibitor according to the present invention refers to a compound that hydrogen bonds with a carboxyl group of an alkali-soluble resin containing a carboxyl group. When the carboxyl group of the alkali-soluble resin is hydrogen-bonded with the dissolution inhibitor, it is shielded from the developer, and dissolution can be suppressed.

  Examples of the compound having a group capable of hydrogen bonding with a carboxyl group include a carboxylic acid compound, a carboxylic acid ester compound, an amide compound, and a urea compound. An amide compound and a urea compound are preferable from the viewpoint of the effect of inhibiting dissolution in an alkaline aqueous solution and storage stability.

  Examples of the amide compound include N, N-diethylacetamide, N, N-diisopropylformamide, N, N-dimethylbutyramide, N, N-dibutylacetamide, N, N-dipropylacetamide, N, N-dibutylformamide. N, N-diethylpropionamide, N, N-dimethylpropionamide, N, N′-dimethoxy-N, N′-dimethyloxamide, N-methyl-ε-caprolactam, 4-hydroxyphenylbenzamide, salicylamide, salicylanilide , Acetanilide, 2′-hydroxyphenylacetanilide, 3′-hydroxyphenylacetanilide, 4′-hydroxyphenylacetanilide.

  Among these, from the viewpoint of lowering the Tg of the insulating layer after heat curing, an amide compound containing an aromatic hydroxyl group is more preferable. Specific examples include 4-hydroxyphenylbenzamide, 3'-hydroxyphenylacetanilide, and 4'-hydroxyphenylacetanilide. These may be used alone or in combination of two or more.

  Examples of the urea compound include 1,3-dimethylurea, tetramethylurea, tetraethylurea, 1,3-diphenylurea, and 3-hydroxyphenylurea. Among these, from the viewpoint of lowering the Tg of the insulating layer after heat curing, a urea compound containing an aromatic hydroxyl group is more preferable. Specific examples include 3-hydroxyphenylurea. These may be used alone or in combination of two or more.

  In the case of using an amide compound, the dissolution inhibitor according to the present invention is preferably blended in an amount of 0.1 mol to 1.5 mol or less with respect to 1 mol of the carboxylic acid of the alkali-soluble resin in terms of the dissolution inhibitory effect. It is more preferable to blend 15 to 1.0 mol.

  In the case of using a urea compound, the dissolution inhibitor used in the present invention is preferably 0.1 mol to 1.5 mol or less from the viewpoint of the dissolution inhibition effect with respect to 1 mol of the carboxyl group of the alkali-soluble resin. From the viewpoint of the dissolution inhibiting effect and the mechanical properties of the polyimide obtained by curing after alkali development, it is more preferable to add 0.15 mol to 0.5 mol.

  Moreover, when using both an amide compound and a urea compound, the total amount of an amide compound and a urea compound is 0.1 mol-1.5 mol with respect to 1 mol of carboxylic acids of alkali-soluble resin from a viewpoint of a dissolution inhibitory effect. The range of is preferable.

  The photosensitive resin composition according to the present invention preferably contains a phosphorus compound in order to improve developability. A phosphorus compound will not be limited if it is a compound which contains a phosphorus atom in a structure. Examples of such compounds include phosphate ester compounds and phosphazene compounds.

  Examples of the phosphoric acid ester compound include trimethyl phosphate, triethyl phosphate, tributyl phosphate, triisobutyl phosphate, tris (2-ethylhexyl) phosphate, phosphate ester having tris (2-ethylhexyl) phosphate as a substituent, tris (butoxyethyl) phosphate ( Aromatics such as phosphate esters, triphenyl phosphates, tricresyl phosphates, trixylenyl phosphates, resorcinol bis (diphenyl phosphates) substituted with aliphatic organic groups containing oxygen atoms such as TBXP) Examples thereof include phosphate ester compounds having an organic group as a substituent. Among these, TBXP and triisobutyl phosphate are preferable from the viewpoint of developability.

  Examples of the phosphazene compound include structures represented by the following general formula (8) and the following general formula (9).

  R17, R18, R19, and R20 in the phosphazene compound represented by the general formula (8) and the general formula (9) are not limited as long as they are organic groups having 1 to 20 carbon atoms. A carbon number of 1 or more is preferable because flame retardancy tends to be exhibited. A carbon number of 20 or less is preferred because it tends to be compatible with the polyimide precursor. Among these, a functional group derived from an aromatic compound having 6 to 18 carbon atoms is particularly preferable from the viewpoint of flame retardancy. As such a functional group, phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 2-hydroxyphenyl group, 3-hydroxyphenyl group, 4-hydroxyphenyl group, 2-cyanophenyl Group, functional group having a phenyl group such as 3-cyanophenyl group and 4-cyanophenyl group, functional group having a naphthyl group such as 1-naphthyl group and 2-naphthyl group, pyridine, imidazole, triazole, tetrazole and the like. And functional groups derived from nitrogen heterocyclic compounds. These compounds may be used alone or in combination of two or more as required. Among these, a compound having a phenyl group, a 4-hydroxyphenyl group, and a 4-cyanophenyl group is preferable because of availability.

  X in the phosphazene compound represented by the general formula (8) is not limited as long as it is an integer of 3 or more and 25 or less. When it is 3 or more, flame retardancy is exhibited, and when it is 25 or less, the solubility in an organic solvent is high. Among these, it is particularly preferably 3 or more and 10 or less in view of availability.

  Y in the phosphazene compound represented by the general formula (9) is not limited as long as it is an integer of 3 or more and 10,000 or less. When it is 3 or more, flame retardancy is exhibited, and when it is 10,000 or less, the solubility in organic solvents is high. Among these, 3 or more and 100 or less are preferable in view of availability.

A and B in the phosphazene compound represented by the general formula (9) are not limited as long as they are organic groups having 3 to 30 carbon atoms. In this, A is _{-N = P (OC 6 H 5} ) 3, -N = P (OC 6 H 5) 2, (OC 6 H 4 OH), - N = P (OC 6 H 5) (OC _{6 H 4 OH) 2, -N} = P (OC 6 H 4 OH) 3, -N = P (O) (OC 6 H 5), - N = P (O) (OC 6 H 4 OH) is preferred . B is _{-P (OC 6 H 5) 4} , -P (OC 6 H 5) 3 (OC 6 H 4 OH), - P (OC 6 H 5) 2 (OC 6 H 4 OH) 2, -P ( _{OC 6 H 5) (OC 6} H 4 OH) 3, -P (OC 6 H 4 OH) 4, -P (O) (OC 6 H 5) 2, -P (O) (OC 6 H 4 OH) _2, such as _{-P (O) (OC 6 H} 5) (OC 6 H 4 OH) are preferred. A phosphorus compound may be used alone or in combination of two or more.

  In the photosensitive resin composition of the present invention, the addition amount of the phosphorus compound is preferably 50 parts by mass or less from the viewpoint of photosensitivity with respect to 100 parts by mass of the polyimide precursor. From the viewpoint of flame retardancy of the cured product, 45 parts by mass or less is preferable, and 40 parts by mass or less is more preferable.

  The photosensitive resin composition of the present invention may contain a solvent in which the polyimide precursor, the photosensitive agent, and / or the phosphorus compound can be uniformly dissolved and / or dispersed as necessary. As a solvent, the solvent used for the synthesis | combination of the above-mentioned polyimide precursor can be used.

  The solvent constituting the resin composition containing the polyimide precursor according to the present invention is not limited as long as it can uniformly dissolve and / or disperse the polyimide precursor according to the present invention. Examples of the solvent include ether compounds having 2 to 9 carbon atoms such as dimethyl ether, diethyl ether, methyl ethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether; carbons such as acetone and methyl ethyl ketone. A ketone compound having 2 to 6 carbon atoms; a saturated hydrocarbon compound having 5 to 10 carbon atoms such as normal pentane, cyclopentane, normal hexane, cyclohexane, methylcyclohexane, and decalin; such as benzene, toluene, xylene, mesitylene, and tetralin An aromatic hydrocarbon compound having 6 to 10 carbon atoms; 3 or more carbon atoms such as methyl acetate, ethyl acetate, γ-butyrolactone, methyl benzoate 9 or less ester compounds; halogen-containing compounds having 1 to 10 carbon atoms such as chloroform, methylene chloride and 1,2-dichloroethane; acetonitrile, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl- Examples thereof include nitrogen-containing compounds having 2 to 10 carbon atoms such as 2-pyrrolidone; sulfur-containing compounds such as dimethyl sulfoxide. These may be one kind or a mixture of two or more kinds as necessary. Particularly preferable solvents include ether compounds having 2 to 9 carbon atoms, ester compounds having 3 to 9 carbon atoms, aromatic hydrocarbon compounds having 6 to 10 carbon atoms, and nitrogen-containing compounds having 2 to 10 carbon atoms. Can be mentioned. Moreover, 1 type or 2 or more types of mixtures may be sufficient as needed. From the viewpoint of solubility of the polyimide precursor, triethylene glycol dimethyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, N, N-dimethylformamide, and N, N-dimethylacetamide are preferable.

  If the density | concentration of the polyimide precursor in the resin composition which consists of the polyimide precursor and solvent which concerns on this invention is a density | concentration with which a resin molding is manufactured, it will not restrict | limit in particular. The concentration of the polyimide precursor is preferably 1% by mass or more from the viewpoint of the film thickness of the resin molded body to be produced, and the concentration of the polyimide precursor is preferably 90% by mass or less from the uniformity of the film thickness of the resin molded body. From the viewpoint of the film thickness of the obtained insulating layer, it is more preferably 2% by mass or more and 80% by mass or less.

  It is also preferable to add a crosslinking agent to the positive photosensitive resin composition of the present invention. This makes it possible to increase the molecular weight of the alkali-soluble resin during curing. As a crosslinking agent, what has the carbonate protecting group and carbamate protecting group of the said diamine compound is preferable, for example. It is preferable to add 0.1 mass part-10 mass parts of compounding quantities of a crosslinking agent with respect to 100 mass parts of polyimide precursors.

  The photosensitive resin composition according to the present invention can contain other compounds as long as the performance is not adversely affected. Specific examples include heterocyclic compounds for improving adhesion.

  The heterocyclic compound in the present invention is not limited as long as it is a cyclic compound containing a hetero atom. Here, the hetero atom in the present invention includes oxygen, sulfur, nitrogen, and phosphorus.

  The heterocyclic compound in the present invention means 2-methylimidazole, 2-undecylimidazole, 2-ethyl-4-methylimidazole, imidazole such as 2-phenylimidazole, and N-alkyl such as 1,2-dimethylimidazole. Aromatic group-containing imidazole such as group-substituted imidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole , Cyano group-containing imidazole such as 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, imidazole compounds such as silicon-containing imidazole such as imidazolesilane, 5-methylbenzotriazole, 1- ( ', 2'-dicarboxyethylbenzotriazole), triazole compounds such as 1- (2-ethylhexylaminomethylbenzotriazole), tetrazole compounds such as 5-phenyltetrazole, and oxazoles such as 2-methyl-5-phenylbenzoxazole Compound etc. are mentioned.

  The addition amount of the other compound in the present invention is not limited as long as it is 0.01 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polyimide precursor. If it is 0.01 mass part or more, there exists a tendency for adhesiveness to fully improve, and if it is 30 mass parts or less, there is no bad influence on photosensitivity.

  Other specific additives include adhesion improvers, surfactants, antioxidants, UV inhibitors, light stabilizers, plasticizers, waxes, fillers, pigments, dyes, foaming agents, extinguishing agents. Examples include foaming agents, dehydrating agents, antistatic agents, antibacterial agents, antifungal agents, leveling agents, dispersants, and ethylenically unsaturated compounds.

  In the present invention, the positive photosensitive resin composition can be prepared by mixing the above components by a conventional method. Specifically, for example, a laika machine equipped with a stirring device and a heating device, a three-roll, a ball mill, a planetary mixer, and the like can be used. Moreover, you may use these mixing apparatuses in combination of 2 or more types suitably.

  The positive photosensitive resin composition according to the present invention is applied to the entire surface of a substrate having wiring by screen printing, curtain coating, spray coating, roll coating, spin coating, etc., dried, exposed and developed. Pattern formation, thermosetting, and used as an insulating layer having excellent heat resistance and electrical insulation.

  Moreover, when using the dry film comprised with the positive photosensitive resin composition which concerns on this invention, the solution of the photosensitive resin composition is used on arbitrary carrier films, such as a polyethylene terephthalate film and a metal film, by arbitrary methods. After being applied, the film is dried and formed into a dry film to obtain a laminated film having a carrier film and a dry film. Further, at least one arbitrary antifouling film such as a low-density polyethylene film or a protective film may be provided on the dry film to form a laminated film. This dry film is laminated on a substrate having wiring by any method such as a thermal laminating method, a hot pressing method, a thermal vacuum laminating method, or a thermal vacuum pressing method. In this way, a base material having wiring, and an insulating layer formed on the base material so as to cover the wiring, and composed of a substance obtained by exposing and developing the photosensitive resin composition according to the present invention, , A multilayer flexible printed wiring board can be produced.

  As described above, in this embodiment, since the multilayer flexible wiring board can be configured without using the coverlay and the interlayer adhesive, the multilayer flexible wiring board can be significantly thinned. As a result, flexibility can be improved.

  In addition, when using the multilayer flexible wiring board reduced in thickness in this way, it is effective to use a reinforcing plate as needed as shown in FIG. In the example shown in FIG. 1B, the reinforcing plate 24 is joined via the reinforcing plate adhesive 23 on the cover coat 22 which is one rigid portion of the multilayer flexible wiring board. Thus, by adhering the reinforcing plate 24, the rigidity of the rigid portion can be maintained, and the mountability of electronic components and the like can be improved.

  Next, a method for manufacturing a multilayer flexible wiring board according to the embodiment of the present invention will be described with reference to FIGS. 2 (a) to 2 (g). A double-sided flexible board (double-sided FPC) that does not have a cover layer as a core layer is a conventional method such as a subtractive method in which a conductor pattern is formed by selectively removing unnecessary portions of a conductor such as a copper foil. Formed by technology. First, as shown in FIG. 2A, a circuit pattern (inner layer circuits L1, L2) is formed on the copper foil (conductive layers 15, 16) on the insulating substrate 14 by using a subtractive method. Subsequently, the inner layer circuits L1 and L2 on both surfaces of the insulating substrate 14 are electrically joined by through-hole plating or blind via plating with a hole diameter of about 0.1 mm to 0.3 mm. Here, through-hole plating is a method in which a conductor is formed inside a hole by plating with respect to a hole (through-hole) drilled vertically through all the layers of the insulating substrate 14 to connect each layer of the wiring board. is there. A blind via is a via that connects only specific layers. These are formed by drilling, laser processing, etching, or laser processing after etching the copper foil. The plating is performed by a method of forming a metal layer such as copper by electroplating after performing electroless plating on the wall surface of the hole. This double-sided FPC often avoids wiring on one side in a portion that becomes a flexible part as a multilayer board in order to remove the interlayer adhesive in a subsequent process.

  Next, as shown in FIG. 2 (b), insulating layers 17 and 19 (interlayer adhesive) are stacked on the upper and lower inner layer circuits L1 and L2, and further copper foils for forming outer layer circuits L3 and L4 (see FIG. Conductive layers 18, 20) are laminated. The conductive layers 18 and 20 may be laminated by a hot press method or a laminate method. As the conductive layers 18 and 20, electrolytic copper foil or rolled copper foil having a thickness of 12 μm to 35 μm is usually used. Here, insulating layers 17 and 19 (interlayer adhesive) and copper foil (pre-laminated conductive layers 18 and 20 (RCC) may also be used. Here, insulating layers 17 and 19 (interlayer adhesive) The thickness is preferably 10 μm to 20 μm thicker than the thickness of the conductor on which the circuit is formed, and preferably 28 μm to 38 μm when the conductor is 18 μm, and at this stage, the adhesive is not completely cured. Usually, laminating is performed at a temperature of 150 ° C. or lower, preferably 120 ° C. or lower, more preferably 100 ° C. or lower, after drying or heating.

Next, as shown in FIG. 2 (c), the blind vias for connecting the outer layer circuits L3 and L4 and the inner layer circuits L1 and L2 are partially removed by removing the interlayer adhesive resin by laser processing using the conformal method. Form. In general, a CO ₂ laser or a YAG laser is used. After that, blind vias are formed by performing copper plating, and the outer layer circuits L3, L4 and the inner layer circuits L1, L2 are electrically connected. The hole diameter formed by laser processing is suitably about 0.07 mm to 0.3 mm.

  Next, as shown in FIG. 2D, the conductive layer 20 on the surface side (the side where no wiring is provided on the double-sided FPC) of the portion to be the flexible portion is removed by the same etching method as in the circuit formation. As the etching solution, a ferric chloride aqueous solution or a cupric chloride aqueous solution is usually used.

Next, as shown in FIG. 2 (e), using the conductive layer 20 as a mask, the portion of the conductive layer 20 removed by etching is irradiated with ultraviolet rays, and then the interlayer adhesive in the flexible portion is removed by development and dissolution with an alkaline solution. To do. The amount of ultraviolet irradiation is 500 mJ / cm ² or more, preferably 800 mJ / cm ² or more, more preferably 1000 mJ / cm ² or more. As the alkaline solution, caustic soda or sodium carbonate aqueous solution is preferable, and about 1% sodium carbonate aqueous solution is more preferable. Thereafter, the interlayer adhesive (the part where the copper foil has not been etched and is not developed because it has not been exposed) is heated and cured to obtain a coverlay layer made of the interlayer adhesive. The heating temperature is 150 ° C or higher, preferably 180 ° C or higher and 200 ° C or lower.

  Next, as shown in FIG. 2F, after the circuit pattern is printed using the subtractive method and the photolithography technique, the conductive layers 18 and 20 are etched to form outer layer circuits L3 and L4.

  Next, as shown in FIG. 2 (g), an epoxy resin was coated on the circuit surfaces of the outer layer circuits L3 and L4 with a thickness of 10 μm to 30 μm, and then a portion requiring exposure of the conductor was opened by photolithography. A cover coat or a polyimide film with a thickness of 12 μm to 25 μm coated with an adhesive with a thickness of 20 μm to 40 μm is punched and removed in advance using a mold, and then adhesively pressed to the circuit surface to cover coat 21 and 22 are formed. With the cover coats 21 and 22, the outer layer circuits L3 and L4 are insulated. Here, it is also preferable to use the positive photosensitive resin used for the insulating layers 17 and 19 as the cover coat.

  Next, plating treatment such as electrolytic gold plating, electroless gold plating, electrolytic solder plating, or imidazole film is formed on the exposed conductor surface of the outer layer that will be used for component mounting and electrical contact. Rust prevention treatment with antirust effect is performed. Next, generally, a die or an NC drill is used to perform drilling or outline processing that is necessary when the product is used. Finally, after conducting electrical inspection and appearance inspection, it becomes a finished product.

  In the configuration and manufacturing method of the multilayer flexible wiring board described above, the outer layer circuits L3 and L4 are bonded to each other by an interlayer connection structure by copper plating through a through hole or a blind via. For the interlayer connection, for example, a conductive paste is used. May be. FIG. 3A to FIG. 3E are diagrams showing an outline of a manufacturing process when a conductive paste is filled in a conductive layer (interlayer adhesive). Here, differences from the manufacturing process shown in FIGS. 2A to 2G will be described, and description of other processes will be omitted.

  First, as shown in FIG. 3A, inner layer circuits L1 and L2 are formed using a double-sided flexible substrate having conductive layers 15 and 16 on both sides of an insulating substrate. Next, the inner layer circuits L1 and L2 are connected by through holes or blind vias. Next, insulating layers (interlayer adhesives) 17 and 19 are stacked on the conductive layers 15 and 16 on the insulating substrate 14. Here, in this example, when the insulating layers (interlayer adhesives) 17 and 19 are laminated, the conductive paste 23 is used at positions corresponding to the inner layer circuits L1 and L2 of the insulating layers 17 and 19. Next, copper foils 18 and 20 are laminated on the insulating layers 17 and 19. Thus, by laminating the conductive layers 18 and 20 with the inner layer circuits L1 and L2 via the conductive paste 23, the inner layer circuit L1 and the copper foil 18 that becomes the outer layer circuit L3, and the inner layer circuit L3 and the outer layer circuit L4. An electrical connection with the copper foil 20 can be obtained. As described above, in this example, the inner layer circuits L and L2 and the outer layer circuits L3 and L4 are stacked without going through the coverlay, so that the inner layer circuit L1 and the outer layer circuit L3 can be formed without forming a through hole or a blind via. And electrical connection between the inner layer circuit L2 and the outer layer circuit L4. For this reason, while being able to simplify a structure more, a manufacturing process can be simplified.

  In the above-described example, the example in which the multilayer flexible substrate is configured by using the double-sided flexible substrate 13 as the core layer has been described. However, in the present invention, the multilayer flexible substrate can be configured by using a flexible substrate having another configuration. can do. As an example, a single-sided flexible wiring board having a circuit conductor pattern only on one side, a multilayer flexible wiring board having a circuit conductor pattern having a multilayer structure of three or more layers, and the like can be used.

  FIG. 4A is a diagram showing an example of a multilayer flexible wiring board formed using a single-sided flexible substrate as a core layer. As shown in FIG. 4A, in this example, the insulating substrate 43 is formed using a single-sided flexible substrate having a conductive layer 44 on one side. A conductive layer 46 is laminated on the conductive layer 44 of the single-sided flexible board via an insulating layer 45, the conductive layer 44 is formed in the inner layer circuit L1, and the conductive layer 46 is formed in the outer layer circuit L3. The outer layer circuit L3 and the inner layer circuit L1 are electrically connected by plating or conductor paste. Thus, it can be set as the multilayer flexible printed wiring board by which the outer layer circuit of one layer or more was provided in the single side | surface of the single-sided flexible substrate. By configuring a multilayer flexible wiring board using a single-sided flexible board in this way, the thickness of the flexible part 42 can be particularly reduced with respect to the rigid parts 41a and 41b, and a highly flexible multilayer flexible wiring board can be obtained. Can be configured.

  FIG. 4B is a diagram illustrating an example of a multilayer flexible wiring board formed using a flexible substrate having a circuit conductor pattern having a multilayer structure of three or more layers as a core layer. In this example, a flexible substrate is used in which conductive layer 54 / insulating layer 55 / conductive layer 56 are stacked in this order on one surface of insulating substrate 53, and conductive layer 57 is stacked on the other surface. Using this flexible substrate, the insulating layer 58 and the conductive layer 59 are stacked in this order on the conductive layer 56 on one surface side of the insulating substrate 53, and the insulating layer 60 and the conductive layer 61 are sequentially stacked on the conductive layer 57 on the other surface side. Laminate. The conductive layers 54, 56, and 59 on one surface side of the insulating substrate 53 are the inner layer circuit L1, the outer layer circuit L3, and the outermost layer circuit L5 from the insulating substrate 53 side, respectively, and a three-layer conductive pattern is formed. Further, the conductive layers 57 and 61 on the other surface side of the insulating substrate 53 become the inner layer circuit L2 and the outer layer circuit L4 from the insulating substrate 53 side, and a two-layer conductive pattern is formed. Inner layer circuits L1, L2, outer layer circuits L3, L4, and outermost layer circuit L5 are electrically connected by plating or conductor paste. In this way, a multilayer flexible printed wiring board having one or more outer layer circuits on both surfaces of the multilayer flexible substrate can be obtained.

  Moreover, in this invention, it is not limited to the multilayer flexible wiring board which consists of the four conductive layers mentioned above, The multilayer flexible wiring board by which the conductive layer of 6 layers or more was laminated | stacked can also be manufactured. FIGS. 5A to 5G are diagrams illustrating an example of a manufacturing process of a multilayer flexible wiring board including six conductive layers L1 to L6. In this case, as shown in FIGS. 5A and 5B, the multilayer flexible wiring board including the four conductive layers L1 to L4 is manufactured in the same process as in FIGS. 2A to 2G. .

  Next, as shown in FIG. 5C, an insulating layer 71 is stacked on the inner layer circuit L <b> 3 on one surface side of the insulating substrate 14, and a conductive layer 72 is stacked on the insulating layer 71. This conductive layer 72 becomes the outermost layer circuit L5. Next, the insulating layer 73 is stacked on the inner layer circuit L4 on the other surface side of the insulating substrate 14, and the conductive layer 74 is stacked on the insulating layer 73. This conductive layer 74 becomes the outermost layer circuit L6.

  Next, as shown in FIG.5 (d), the conductive layers 72 and 74 copper foil of the part used as the flexible part of a multilayer flexible substrate are removed by an etching. Next, as shown in FIG. 5E, the insulating layers 71 and 73 are removed by etching to form a flexible portion.

  Next, as shown in FIG. 5F, the rigid conductive layers 72 and 74 are patterned by etching to form outermost layer circuits L5 and L6. Finally, as shown in FIG. 5G, cover coats 75 and 76 are formed on the outermost layer circuits L5 and L6 to manufacture a multilayer flexible wiring board having six conductive layers.

  As described above, at the portion where the flexible wiring board is bent and attached, folding resistance to the extent that it does not break even when bent multiple times is required. In the multilayer flexible wiring board according to the present embodiment, as shown in FIG. 5G, the flexible part can also have a double-sided wiring structure. Further, since the insulating layers 71 and 73 can be easily removed by etching, the folding resistance of the flexible portion can be further improved.

  As described above, according to the present embodiment, by using an insulating layer (interlayer adhesive) containing a resin having the same insulating performance as that of the coverlay and having positive photosensitivity, the coverlay and interlayer adhesion can be achieved. A multilayer flexible wiring board can be constructed without using an agent. Thereby, the process of forming the hollow structure in the conventional multilayer flexible wiring board and the process of peeling the outer layer of the rigid flex wiring board can be simplified or omitted. Moreover, since a coverlay or an interlayer adhesive is not used, the multilayer flexible wiring board can be thinned, and the bending resistance and folding resistance can be improved.

  Further, according to the present embodiment, by using a positive photosensitive resin as the insulating layer (interlayer adhesive), an appropriate adhesive strength that allows the outer layer to be peeled off as necessary in the manufacturing process. Can be obtained. In other words, it is possible to remove the adhesive layer by exposing and developing the adhesive layer using the remaining copper foil part as a mask after removing the copper foil part of the outer layer in the etching process as in the circuit formation. It became. For this reason, alignment at the time of exposure becomes unnecessary, and productivity can be further improved.

  Furthermore, according to the present embodiment, since there is no use of a coverlay and an interlayer adhesive in a layer portion without a multilayer flexible wiring board, the reliability of interlayer connection during through-hole plating or blind via plating can be improved. Can do.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, it is not limited at all by these examples.

[Alkali dissolution test of alkali-soluble resin]
Evaluation of the solubility characteristics of the alkali-soluble resin was carried out according to the following procedure.
A coating table (manufactured by MATSUKI SCIENCE CO., LTD.) That can be vacuum-adsorbed and heated is preliminarily heated to 60 ° C., and a polyester film (R-310-25, manufactured by Mitsubishi Polyester Co., Ltd.) is laid thereon and vacuum-adsorbed. A polyester film was pasted. An alkali-soluble resin was applied onto the polyester film using an applicator (manufactured by Matsuki Scientific Co., Ltd.) having a gap of 250 μm. After removing the solvent at 60 ° C. for 30 minutes, the solvent was removed at 95 ° C. for 20 minutes with a dryer (SPH-201, manufactured by Espec Corp.).

  The obtained film was immersed in a 1 wt% aqueous sodium carbonate solution heated to 40 ° C. and rocked at a rate of 1 degree every 30 seconds for 10 seconds. The time required for the film to completely dissolve is defined as the dissolution time, and the dissolution rate of the alkali-soluble resin in the sodium carbonate aqueous solution is divided by the film thickness (μm) before dissolution by the dissolution time (sec) and multiplied by 100. Calculated.

[Alkali solubility test of positive photosensitive resin composition]
Production of the photosensitive layer obtained from the positive photosensitive resin composition and measurement of the remaining film ratio were carried out according to the following procedure.

  The surface of a glass epoxy substrate laminated with copper (thickness: 0.4 mm, manufactured by Matsushita Electric Works Co., Ltd.) was scrubbed by abrasive scrub-in (produced by Ishii Notation Co., Ltd.) (abrasive: Sac Random RF220, manufactured by Nippon Grinding Co., Ltd.). . The photosensitive polyamic acid composition was dropped onto the obtained substrate and coated using a YBA type baker applicator (manufactured by Yoshimitsu Seiki Co., Ltd.) whose height was adjusted so that the film thickness after solvent removal was 30 μm. After coating, a sample was placed on a hot plate (Charman hot plate HHP-412, manufactured by ASONE), and the solvent was removed at 95 ° C. for 10 minutes.

After removing the solvent, using a mask aligner (MA-10, manufactured by Mikasa) equipped with a pattern mask (manufactured by Tokyo Process Service Co., Ltd.) having a hole pattern of 100 μm in diameter, an exposure amount of 1000 mJ / cm ² (UV 350 nm calibration) Ultraviolet irradiation was performed under conditions.

  The obtained film was immersed in a 1 wt% aqueous sodium carbonate solution heated to 40 ° C. and rocked at a rate of 1 degree every 30 seconds for 10 seconds. The time required for the photosensitive layer of the exposed portion to completely dissolve is taken as the dissolution time, the dissolution rate in the aqueous solution of sodium carbonate in the exposed portion is divided by the dissolution time (sec) of the film thickness (μm) before dissolution, and 100 Calculated by multiplying.

  Using a stylus type surface shape measuring instrument (DEKTAK, ULVAC, Inc.), the film thickness of the unexposed area before development and the film thickness after development were measured. The film thickness after development was divided by the film thickness before development and multiplied by 100 to calculate the remaining film ratio.

[Elastic modulus]
It formed into a film on copper foil so that it might become a film thickness of about 30 micrometers using the photosensitive resin composition. Then 1 hour at 120 ° C., and heat-treated for 1 hour at 180 ° C., followed FeCl ₂ solution by dissolving the copper foil part, washed with water with tap water to obtain a film was dried at room temperature for 1 day. The obtained film was cut out into 5 mm x 100 mm, and it was set as the test piece. The obtained test piece was measured with a tensile tester (RTG-1210 / A & D).

[Dielectric constant]
The dielectric constant was measured using a 126096W type impedance measuring device manufactured by Solartron.

〔reagent〕
The reagents used are listed. Silicone diamine (KF-8010) (manufactured by Shin-Etsu Chemical Co., Ltd.), ethylene glycol-bis-trimellitic anhydride ester (TMEG) (manufactured by Shin Nippon Chemical Co., Ltd.), 1,3-bis (3-aminophenoxy) benzene (APB) -N) (manufactured by Mitsui Chemicals), tris (butoxyethyl) phosphate (TBXP) (manufactured by Daihachi Chemical Co., Ltd.), phosphazene compound (FP-100) (manufactured by Fushimi Pharmaceutical Co., Ltd.), toluene (manufactured by Wako Pure Chemical Industries, Ltd.) , For organic synthesis), γ-butyrolactone (manufactured by Wako Pure Chemical Industries), triethylene glycol dimethyl ether (manufactured by Wako Pure Chemical Industries), N, N-dimethylacetamide (DMAc) (manufactured by Wako Pure Chemical Industries), carbonic acid Sodium (manufactured by Wako Pure Chemical Industries, Ltd.) was used for the reaction without any special purification.

[Preparation Example 1]
1,3-bis (3-aminophenoxy) benzene (APB-N) (20 g) and γ-butyrolactone (220 g) were placed in a three-necked separable flask and stirred until a homogeneous solution was obtained. Next, ethylene glycol-bis-trimellitic anhydride (TMEG) (28 g) was added, and the polyamic acid solution (i) was obtained by stirring for 1 hour while cooling with ice and then for 24 hours at room temperature. This polyamic acid solution was used after pressure filtration with a Teflon (registered trademark) filter having an opening diameter of 5 μm. The alkali dissolution rate of this resin was 0.13 μm / sec.

  Polyamic acid solution (i) (10 g), 0.5 equivalent of 3′-hydroxyphenylacetanilide (0.26 g) with respect to the carboxylic acid of the polyamic acid, and 20 parts by weight of the quinonediazide compound (A) with respect to the polyamic acid (A) ( 0.42 g) was placed in a 50 ml glass bottle and stirred with a mix rotor (MR-5, manufactured by AS ONE) until uniform to obtain a positive photosensitive resin composition (I). Regarding the physical properties of the film obtained from the obtained positive photosensitive resin composition (I), the alkali dissolution rate of the exposed area is 0.31 μm / sec, the residual film rate is 98%, the elastic modulus is 1.5 GPa, and the dielectric constant (@ 1 MHz) was 3.2. The results are shown in Table 1 below.

[Preparation Example 2]
In a separable flask under a nitrogen atmosphere, γ-butyrolactone (42.0 g), triethylene glycol dimethyl ether (18.0 g), toluene (20.0 g), silicone diamine (KF-8010, 21.36 g (17.09 mmol)) ), TMEG (40.00 mmol) was added, a Dean-Stark apparatus and a reflux were attached, and the mixture was heated and stirred at 180 ° C. for 30 minutes. After removing toluene as an azeotropic solvent, the mixture was cooled to 25 ° C., APB-N (18.64 mmol) was added, and the mixture was stirred at 25 ° C. for 5 hours. After stirring, a mixed solvent of γ-butyrolactone / triethylene glycol dimethyl ether was added so that the polymer solid content concentration was 30% by mass to obtain a polyamic acid solution (ii). This polyamic acid solution was used after being pressure-filtered with a Teflon (registered trademark) filter having an opening diameter of 5 μm. The alkali dissolution rate of this resin was 0.15 μm / sec.

  Quinonediazide compound A (20 parts by mass), tris (butoxyethyl) phosphate (TBXP) (10 parts by mass), phosphazene compound (FP-100) (7 parts by mass) with respect to the polyimide precursor solution (ii) (100 parts by mass). Part) was mixed to prepare a positive photosensitive resin composition (II). Regarding the physical properties of the film obtained from the obtained positive photosensitive resin composition (II), the alkali dissolution rate in the exposed area is 0.22 μm / sec, the residual film rate is 96%, the elastic modulus is 0.9 GPa, and the dielectric constant (@ 1 MHz) was 2.9. The results are shown in Table 1 below.

[Preparation Example 3]
In a 1 L separable flask, thionyl chloride (75.0 g) was added to a solution of 4,4′-diphenyl ether dicarboxylic acid (72.4 g) and N, N-dimethylaminopyridine (3.7 g) in DMAc (600 g) at room temperature. Dropped and stirred for 1 hour. To a 1 L separable flask, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (109.9 g) dissolved in DMAc (300 g) was added at 0 ° C. Stir for hours. This was diluted with DMAc (1000 g) and then added dropwise to water with stirring. The precipitated polymer was filtered and then vacuum dried at 40 ° C. to obtain a polybenzoxazole precursor. 10 g of this polymer was added to γ-butyrolactone (4.6 g) and stirred using a mixed rotor until uniform, thereby obtaining a polybenzoxazole precursor resin solution (iii) using γ-butyrolactone as a solvent. This alkali-soluble resin solution was used after pressure filtration with a Teflon (registered trademark) filter having an opening diameter of 5 μm. The alkali dissolution rate of this resin was 0.03 μm / sec.

  Using the obtained polybenzoxazole precursor resin solution (iii), a positive photosensitive resin composition (III) was obtained in the same manner as in Preparation Example 2. Regarding the physical properties of the film obtained from the obtained positive photosensitive resin composition (III), the alkali dissolution rate of the exposed area is 0.10 μm / sec, the residual film rate is 96%, the elastic modulus is 2.2 GPa, and the dielectric constant (@ 1 MHz) was 3.3. The results are shown in Table 1 below.

[Example 1]
An example in which a four-layer multilayer flexible wiring board having a component mounting portion and a bent portion used for a mobile phone or the like is manufactured will be described below. The processing of the double-sided FPC (L1 and L2 layers) was completed up to the circuit formation step by a subtractive method. Electrical bonding of the conductive layers L1 and L2 of the double-sided FPB was performed by through-hole plating or blind via plating with a hole diameter of about 0.1 mm to 0.3 mm. This double-sided FPC was formed so as to avoid wiring on one side in order to remove the interlayer adhesive in a later step in a portion that becomes a flexible portion as a multilayer board.

  Next, an insulating layer (interlayer adhesive) was laminated on the upper and lower circuit surfaces, and a copper foil for forming outer layer circuits (L3 and L4 layers) was further laminated. Here, an electrolytic copper foil having a thickness of 12 μm to 35 μm is used as the copper foil, a rolled copper foil may be used, and an insulating layer (interlayer adhesive) and a copper foil laminated in advance (RCC) are also available. It may be used. Here, the thickness of the insulating layer (interlayer adhesive) is desirably about 10 μm to 20 μm thicker than the thickness of the conductor formed with the circuit. (When the conductor is 18 μm, 28 μm to 38 μm) At this stage, the interlayer adhesive is not completely cured. In the conventional multilayer flexible printed wiring board, the cover adhesive is stacked on the upper and lower circuit surfaces, and then the interlayer adhesive is stacked. In this embodiment, the interlayer adhesive functions as a cover lay (Table 2 below). Therefore, it was possible to omit the coverlay lamination press step (twice in the case of a four-layer flexible wiring board and once in the case of a four-layer rigid flex wiring board). As shown in Table 2 below, the interlayer adhesive according to this example showed the same performance as the conventional coverlay.

Next, blind vias for connecting the outer layer circuits (L3, L4) and the inner layer circuits (L1, L2) were formed by partially removing the resin of the interlayer adhesive by laser processing by a conformal method. As the laser, a CO ₂ laser or a YAG laser is usually used. After that, blind vias were formed by performing copper plating, and electrical connections were made. The hole diameter formed by laser processing is suitably about 0.07 mm to 0.3 mm.

Next, the copper foil on one side (the side without the double-sided FPC wiring) of the portion to be the flexible portion was removed by the same etching method as that for circuit formation. Next, using the copper foil as a mask on the same surface side, the etched portion of the copper foil was irradiated with 1000 mJ / cm ² of ultraviolet light, and then the interlayer adhesive of the flexible part was developed with an alkaline liquid such as 1% by mass of sodium carbonate. Removed by dissolution. After that, the interlayer adhesive (the part where the copper foil is not etched and the part which has not been developed because it is unexposed) is heat-cured at 180 ° C. for 1 hour to form a coverlay layer made of the interlayer adhesive. Was made. At this stage, since the flexible portion functions as an interlayer adhesive as a coverlay, it has a thin single-sided flexible wiring board structure that does not have an adhesive layer like a conventional coverlay, and exhibits excellent bending resistance.

  Next, after printing a circuit pattern using a photolithography technique by a subtractive method, the copper foils on the front and back sides were etched to form outer layer circuits (L3, L4). Next, an epoxy resin is coated on the circuit surface of the outer layer circuit (L3, L4) with a thickness of 10 μm to 30 μm, and then a cover coat or an adhesive in which a portion where conductor exposure is required is opened by photolithography technology. A polyimide film having a thickness of 12 μm to 25 μm applied to a thickness of 20 μm to 40 μm was previously punched and removed by a mold, and then the outer layer was insulated with a coverlay that was adhesively pressed to the circuit surface. .

  Rust-proofing effect is achieved by plating plating such as electrolytic gold plating, electroless gold plating, and electrolytic solder plating on the outer conductor exposed surface that is used for component mounting and electrical contact, and by forming an imidazole film on the exposed conductor surface. Rust prevention treatment with Next, generally, a die or an NC drill is used to perform drilling or outline processing that is necessary when the product is used. Finally, after conducting an electrical inspection and an appearance inspection, a four-layer flexible wiring board was obtained.

  In the multilayer flexible wiring board according to the present example, since the coverlay layer was removed, as shown in Table 3 below, it was found that the layer thickness was small, and a great effect was obtained in reducing the thickness of the electronic device. The thickness of each layer is shown in Table 3 below. As shown in Table 3, the thickness of the general multilayer flexible wiring board was 273 μm, whereas the thickness of the multilayer flexible wiring board obtained in this example does not use a coverlay or the like. It was possible to reduce the thickness significantly to 168 μm.

  Table 4 below shows the results of folding resistance and bending resistance. It can be seen that a single-sided wiring board having no single-sided interlayer adhesive layer is superior in folding resistance and bending resistance as compared to a double-sided wiring board. Here, the single-sided wiring board having no single-sided interlayer adhesive layer refers to a wiring board from which the interlayer adhesive layer on the side where there is no wiring in the flexible part is removed in order to increase flexibility or flexibility. The term “wiring board” refers to a wiring board having an interlayer adhesive layer on both sides without removing the interlayer adhesive layer.

[Example 2]
Next, an example of a 6-layer flexible wiring board will be described.
First, double-sided FPC was completed up to the circuit formation step by a subtractive method. The electrical connection of the conductive layers (inner layer circuits L1, L2) on both sides of the double-sided FPC was performed by through-hole plating or blind via plating with a hole diameter of about 0.1 mm to 0.3 mm. In this embodiment, the double-sided FPC is formed so as to be a double-sided wiring at a portion to be a flexible part of the multilayer flexible wiring board.

  Next, after laminating an insulating layer (interlayer adhesive) on the upper and lower inner layer circuits L1 and L2, and further laminating a copper foil for forming outer layer circuits (L3 and L4), generally a hot press or the like is performed. Used to heat cure the adhesive. In addition, you may use what laminated | stacked the interlayer adhesive and copper foil previously (RCC). Here, it is desirable that the thickness of the interlayer adhesive is about 10 μm to 20 μm thicker than the thickness of the conductor formed with the circuit. (When the conductor is 18 μm, 28 μm to 38 μm) The interlayer adhesive used here is not necessarily the interlayer adhesive according to the present invention, and various interlayer adhesives can be used.

Next, blind vias for connecting the outer layer circuits (L3, L4) and the inner layer circuits (L1, L2) were formed by partially removing the resin of the interlayer adhesive by laser processing by a conformal method. As the laser, a CO ₂ laser, a YAG laser, or the like is used. After that, blind vias were formed by applying copper plating to make electrical connection. In addition, about 0.07 mm-0.3 mm is suitable for the hole diameter formed by laser processing.

  Next, a circuit pattern was printed using a photolithographic technique by a subtractive method, and then the copper foils on the front and back sides were etched to form outer layer circuits (L3, L4). In the portion that becomes the flexible portion, it is necessary to remove the interlayer adhesive in a later step, so it is desirable to avoid wiring.

  Next, an interlayer adhesive according to the present invention was laminated on the circuit surfaces of the upper and lower outer layer circuits (L3, L4), and a copper foil for forming outermost layer circuits (L5, L6) was further laminated. In addition, you may use what laminated | stacked the interlayer adhesive and copper foil previously (RCC). Here, it is desirable that the thickness of the interlayer adhesive is about 10 μm to 20 μm thicker than the thickness of the conductor formed with the circuit. (When the conductor is 18 μm, 28 μm to 38 μm) At this stage, the adhesive is not completely cured.

  Next, the copper foil on both sides of the portion to be the flexible portion (the portion without the FPC wiring) was removed by the same etching method as that for circuit formation. Next, using the copper foil as a mask from both sides, the etched portion of the copper foil was irradiated with ultraviolet rays, and then the interlayer adhesive in the flexible portion was developed and dissolved with an alkaline solution such as caustic soda and removed. Thereafter, the interlayer adhesive was cured by heating, and a coverlay layer composed of the interlayer adhesive according to the present invention was completed. At this stage, the flexible part has a double-sided flexible wiring board structure that does not have an adhesive layer like a conventional cover lay, using the interlayer adhesive according to the present invention as a cover lay, and exhibits excellent folding resistance. Is also possible.

  Next, after the circuit pattern is printed using the photolithographic technique by the subtractive method, the front and back copper foils are etched to form the outermost circuit (L5, L6) on the front and back sides. Next, the outermost layer circuit (L5, L6) part is generally a cover coat in which a circuit surface is coated with an epoxy resin and then a part where conductor exposure is necessary is opened by photolithography, or generally, The polyimide film coated with an adhesive was punched and removed in advance with a die in a portion that required conductor exposure, and then the outermost layer was insulated with a coverlay that was adhesively pressed onto the circuit surface.

  Rust-proofing effect is achieved by plating plating such as electrolytic gold plating, electroless gold plating, and electrolytic solder plating on the outer conductor exposed surface that is used for component mounting and electrical contact, and by forming an imidazole film on the exposed conductor surface. Rust prevention treatment with Next, using a die or an NC drill, drilling and outline processing necessary when the product is used are performed. Finally, after conducting electrical inspection and appearance inspection, it becomes a finished product.

  Table 4 below shows the results of folding resistance and bending resistance. A single-sided wiring board having no single-sided interlayer adhesive layer is superior in folding resistance and bending resistance compared to a double-sided wiring board. Here, the single-sided wiring board having no single-sided interlayer adhesive layer refers to a wiring board from which the interlayer adhesive layer on the side where there is no wiring in the flexible part is removed in order to increase flexibility or flexibility. The term “wiring board” refers to a wiring board having an interlayer adhesive layer on both sides without removing the interlayer adhesive layer.

[Example 3]
Next, instead of interlayer connection by copper plating through through holes or blind vias, a four-layer flexible wiring board was produced by a manufacturing method (metal paste method) in which an interlayer adhesive was filled by filling a conductive paste into an interlayer adhesive. Examples will be described.

  First, the circuit formation process was implemented by the subtractive method for double-sided FPC. The electrical connection of the inner layer circuits L1 and L2 on the double-sided FPC was performed by through-hole plating or blind via plating. In this double-sided FPC, it is desirable to avoid wiring on one side in a portion that becomes a flexible portion in order to remove the interlayer adhesive in a later step.

  Next, the interlayer adhesive according to the present invention is preliminarily filled with a conductive paste at predetermined positions (L1-L3, L2-L4 connection points), and then laminated on the upper and lower circuit surfaces, and further outer layer circuits (L3, L4). A copper foil for forming a layer was laminated. Here, it is desirable that the thickness of the interlayer adhesive is 10 μm to 20 μm thicker than the thickness of the conductor on which the circuit is formed. (When the conductor is 18 μm, 28 μm to 38 μm) At this stage, the adhesive is not completely cured. The conductive paste is filled in advance at a predetermined position of the interlayer adhesive according to the present invention, generally by drilling with laser processing, and then with a screen printing method.

  Next, the copper foil on one side (the side without the double-sided FPC wiring) of the portion to be the flexible portion was removed by the same etching method as that for circuit formation. Next, using the copper foil as a mask on the same surface side, the etched portion of the copper foil was irradiated with ultraviolet rays, and then the interlayer adhesive in the flexible portion was removed by development and dissolution with an alkaline solution such as caustic soda. Thereafter, the interlayer adhesive (undeveloped portion) was heated and cured at 180 ° C. for 1 hour to produce a coverlay layer made of the interlayer adhesive.

  Next, a circuit pattern was printed using a photolithographic technique by a subtractive method, and then the copper foils on the front and back sides were etched to form outer layer circuits (L3, L4). Next, the outer layer part is generally coated with an epoxy resin on the circuit surface, and then a cover coat in which a part that needs to be exposed with a photolithographic technique is opened, or in general, a polyimide coated with an adhesive. After the film was previously punched and removed with a mold, the outer layer circuits (L3 and L4) were insulated with a coverlay that was adhesively pressed onto the circuit surface.

  Rust-proofing effect is achieved by plating plating such as electrolytic gold plating, electroless gold plating, and electrolytic solder plating on the outer conductor exposed surface that is used for component mounting and electrical contact, and by forming an imidazole film on the exposed conductor surface. Rust prevention treatment was performed. Next, using a die and an NC drill, drilling and outline processing required when the product was used were performed. Finally, after conducting an electrical inspection and an appearance inspection, a four-layer multilayer flexible wiring board was obtained.

  Table 4 below shows the results of folding resistance and bending resistance. A single-sided wiring board having no single-sided interlayer adhesive layer is superior in folding resistance and bending resistance compared to a double-sided wiring board. Here, the single-sided wiring board having no single-sided interlayer adhesive layer refers to a wiring board from which the interlayer adhesive layer on the side where there is no wiring in the flexible part is removed in order to increase flexibility or flexibility. The term “wiring board” refers to a wiring board having an interlayer adhesive layer on both sides without removing the interlayer adhesive layer.

  As described above, according to the present invention, a multilayer flexible wiring board that can omit the conventional coverlay layer and manufacturing process can be realized by using an interlayer adhesive having coverlay performance. This interlayer adhesive is mainly obtained by using a positive photosensitive resin composition. Since this interlayer adhesive is positive photosensitive, the outer layer can be easily peeled off as necessary during the manufacturing process. That is, the copper foil portion of the outer layer can be removed by an etching process in the same manner as the circuit formation, and then the adhesive layer can be removed by exposure and development using the copper foil portion as a mask. In terms of quality, in the case of a multilayer flexible wiring board, the inner coverlay layer can be removed. In addition, since the cover-lay layer is not required in the rigid flex wiring board, the reliability of interlayer connection during through-hole plating or blind via plating can be improved. For this reason, since the coverlay layer can be removed, the thickness can be greatly reduced, and higher density wiring can be realized. In addition, by attaching the reinforcing plates, adverse effects on component mounting and the like can be suppressed even when the thickness is reduced. Further, in the present invention, instead of interlayer connection by copper plating through a through hole or a blind via, a method of filling an interlayer adhesive by filling a conductive paste into an interlayer adhesive is also possible. The outer layer can be removed by taking advantage of the positive photosensitivity.

  The present invention can be used for various flexible printed wiring boards, such as rigid flex wiring boards and multilayer flexible wiring boards.

11a, 11b, 41a, 41b, 51a, 51b Rigid part 12, 42, 52 Flexible part 14, 43, 53, 101, 111 Insulating substrate 15, 16, 18, 20, 44, 46, 54, 56, 57, 59 61, 72, 74,
102, 103, 112, 113 Conductive layer 17, 19, 45, 55, 58, 60, 71, 73 Insulating layer 21, 22, 75, 76, 110 Cover coat 23 Reinforcing plate adhesive 24 Reinforcing plate 104, 105, 114 , 115 Coverlay 106, 116, 117 Interlayer adhesive 107, 122 Through hole 108, 109, 123, 124 Blind via hole 118, 120 Insulating resin 119 Copper foil L1, L2 Inner layer circuit L3, L4 Outer layer circuit L5, L6 Outer layer circuit

Claims (15)

  An insulating substrate, a pair of conductive layers provided on both surfaces of the insulating substrate, a pair of insulating layers provided on the pair of conductive layers, and a pair of insulating layers provided on the pair of insulating layers. Alternatively, a multilayer flexible wiring board comprising: a pair of conductive layers and at least one outer layer circuit electrically connected without using a cover lay with a conductive paste.   An insulating substrate; a conductive layer provided on one side of the insulating substrate; an insulating layer provided on the conductive layer; and a conductive layer and a cover provided on the insulating layer by plating and / or a conductive paste. A multilayer flexible wiring board comprising: at least one outer layer circuit electrically connected without a ray.   A multilayer flexible substrate having an insulating substrate, at least three conductive layers provided on the insulating substrate and disposed via an insulating layer, and a pair of insulating layers provided on both surfaces of the multilayer flexible substrate; And at least one outer layer circuit that is provided on the pair of insulating layers and is electrically connected to the at least three conductive layers without a coverlay by plating and / or conductive paste. A multilayer flexible wiring board characterized by   The multilayer flexible wiring board according to any one of claims 1 to 3, wherein the insulating layer has a structure in which the insulating layer is partially removed.   The multilayer flexible wiring board according to any one of claims 1 to 4, wherein the insulating layer includes a positive photosensitive resin composition.   In the insulating layer, the insulating layer that is partially removed is only on one side, and at least the insulating layer that is partially removed is obtained using a positive photosensitive resin composition. The multilayer flexible wiring board according to claim 4 or 5.   The multilayer flexible wiring board according to claim 5 or 6, wherein the positive photosensitive resin composition comprises at least an alkali-soluble resin and a quinonediazide compound.   The multilayer flexible wiring board according to claim 7, wherein the alkali-soluble resin has at least a polyamic acid structure.   The multilayer flexible wiring board according to claim 7 or 8, wherein the alkali-soluble resin has a polyamic acid structure and a polyimide structure.   The multilayer flexible wiring board according to any one of claims 7 to 9, wherein the alkali-soluble resin has a polyalkylene ether structure and / or a siloxane structure.   The multilayer flexible substrate according to claim 7, wherein the positive photosensitive resin composition further contains a dissolution inhibitor.   The multilayer flexible wiring board according to claim 11, wherein the dissolution inhibitor is an amide compound or a urea compound.   The multilayer flexible wiring board according to any one of claims 7 to 12, wherein the positive photosensitive resin composition further contains a phosphorus compound.   14. The multilayer flexible wiring board according to claim 13, wherein the phosphorus compound is a phosphate ester compound and / or a phosphazene compound. The insulating layer is obtained from the positive photosensitive resin composition containing the alkali-soluble resin, and the dissolution rate of the alkali-soluble resin in an aqueous sodium carbonate solution is 0.04 μm / sec or more. When the photosensitive resin composition is coated on a substrate and irradiated with an actinic ray of 1000 mJ / cm ² or less on a 30 μm-thick photosensitive layer obtained after solvent removal by heating, the photosensitive resin composition is composed of the photosensitive resin composition The dissolution rate of the actinic ray-irradiated portion of the photosensitive layer to be dissolved in the sodium carbonate aqueous solution is 0.22 μm / sec or more, the remaining film ratio of the actinic ray non-irradiated portion is 90% or more, and the actinic ray non-irradiated portion 15. The insulating layer obtained by heating the photosensitive layer at 200 ° C. has an elastic modulus of 0.2 to 1.5 GPa and a dielectric constant of 3.5 or less. Izu A multilayer flexible wiring board as described above.

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