JP2009028993A - Laminate for wiring board - Google Patents

Abstract

The present invention provides a wiring board laminate having a low coefficient of linear expansion and excellent heat resistance, particularly a wiring board laminate useful for applications such as FPC and HDD suspension boards.
In a laminate having a metal layer on one or both sides of a polyimide resin layer, the polyimide resin layer has two or more different resin layers, and at least one of the resin layers has a specific structural unit of 10 to 85. It is a polyimide resin layer (i) containing mol%, and at least one layer is composed of a polyimide resin layer (ii) having a glass transition temperature lower than that of the polyimide resin layer (i), and the polyimide resin layer (i) has a thickness of polyimide resin A laminate for a wiring board that is 50% or more of the total thickness of the layer.
[Selection figure] None

Description

  The present invention relates to a laminate for a wiring board used for a flexible printed board, an HDD suspension and the like.

  In recent years, the performance and functionality of electronic devices have been rapidly increasing, and with this, electronic components used in electronic devices and the boards on which they are mounted have become higher density and higher performance. The demand is growing. On the other hand, electronic devices are becoming increasingly lighter, smaller, and thinner, and the space for housing electronic components is becoming narrower.

  In general, polyimide resins having excellent characteristics such as heat resistance, electrical characteristics, and moisture resistance are widely used for insulating layers of flexible printed boards (hereinafter referred to as FPC) used in electronic devices. Conventional polyimide resin has a rigid structure and high elastic modulus.For example, when used in LCD modules, mounting failure such as peeling or disconnection due to repulsive force occurs, and the radius at the time of bending becomes extra. There was a problem of needing space. In recent years, electronic devices have been rapidly increasing in performance, functionality, and miniaturization. As a result, electronic components used in electronic devices and the boards on which they are mounted have higher density and higher performance. The demand for performance is increasing. With regard to FPC, fine wire processing, multilayer formation, etc. have been performed, and thinning and dimensional stability have also been strictly demanded for wiring board laminates used for manufacturing FPC. .

In order to solve such a problem, recently, it is required that the polyimide resin also has low elasticity. In order to obtain a low-elasticity polyimide, as shown in Patent Document 1 below, a method of blending a low-elasticity filler with a conventional polyimide resin, a method using polyimidesiloxane (Patent Documents 2 and 3), an epoxy resin, etc. are mixed. The method (Patent Document 4) is well known. This makes it possible to easily obtain a polyimide film having an arbitrary modulus of elasticity from 1 × 10 ⁵ to 1 × 10 ¹⁰ Pa, but on the other hand, a decrease in heat resistance, an increase in linear expansion coefficient (CTE), and a glass transition temperature Various problems such as lowering of the frequency occurred and it was unsuitable for use as an FPC application.

  Recently, a method of directly forming a polyimide resin layer on a metal foil without forming an adhesive layer has been adopted. Patent Document 5 discloses a method for providing a laminate for a wiring board having excellent adhesion and thermal dimensional stability by multilayering a polyimide resin layer with a plurality of polyimide resins having different linear expansion coefficients. Yes. However, since the polyimide resin used therein has a high hygroscopic property, it is swollen when immersed in a solder bath, poor connection due to dimensional changes after moisture absorption during thin wire processing, and warpage of the laminate due to dimensional changes after moisture absorption. There was a concern that it would cause problems.

  Against this background, in recent years, there has been an increasing demand for polyimide resins having excellent low hygroscopicity and dimensional stability after moisture absorption, and various studies have been conducted on such demands. For example, a polyimide resin that improves hydrophobicity and exhibits low hygroscopicity by introducing a fluorine-based resin has been proposed, but has disadvantages such as increased manufacturing costs and poor adhesion to metal materials. . In addition, polyimides exhibiting good characteristics such as low hygroscopicity and low linear expansion coefficient are also known, but other characteristics such as high heat resistance are inferior.

  In Non-Patent Document 1 and Non-Patent Document 2, there are reports on a polyimide resin using a diamine having a fluorene skeleton. However, the polyimide resins described in these documents do not satisfy the performance for use in materials for precision electrical and electronic equipment.

  By the way, in general, a dry etching method using an ultraviolet laser processing method or a plasma processing method is performed for drilling a laminated body for a wiring board used for a flexible printed wiring board. Is expensive, has a high running cost such as a gas cost to be used, and has a problem of low mass productivity. As an alternative to the dry etching method, a material capable of wet etching with an organic alkali or an alkaline aqueous solution has been demanded. However, generally, when the polyimide resin etching rate is high, the moisture absorption rate increases, so the etching rate is high. At the same time, development of materials with low moisture absorption has been desired.

  Briefly explaining the FPC manufacturing method, a circuit layer is formed after laminating a conductor layer such as copper foil directly on one or both sides of a polyimide resin layer or via an adhesive such as an epoxy resin to form a laminate for a wiring board. It is common to do. This polyimide resin layer is obtained by dehydrating and cyclizing (imidizing) a polyimide precursor resin (polyamic acid) produced from a tetracarboxylic acid component and a diamine component by heating to a high temperature. In this way, the laminate for a wiring board used for FPC is applied by directly applying a polyamic acid solution to a thin metal foil and heat-cured, so if the difference in CTE between the metal foil and the polyimide resin is greatly different, Resin contraction sometimes occurs, resulting in problems such as warping and curling of the board, and changes in dimensions when mounting electronic components, making accurate mounting impossible. The impact of was serious.

  So far, low-elasticity and low-CTE polyimide resins have been studied, but low-elasticity and low-CTE are inherently contradictory properties, so polyimide resins with physical properties that satisfy both of these two properties. Development was not easy. Actually, studies have been made on a combination of a plurality of tetracarboxylic acid components and diamine components, but a polyimide resin having sufficient performance has not yet been obtained.

JP-A-2005-23183 JP 2000-103848 A JP 2003-20404 A JP 2005-36136 A JP-A-8-250860 The Chemical Society of Japan, 1977, (5), 701-705 Journal of Polymer Science Part B, 33, 1907-1915 (1995)

  The present invention has a polyimide resin layer having excellent heat resistance, a low coefficient of linear expansion and excellent dimensional stability, good adhesion between the polyimide resin layer and the metal layer, and no warpage or solder heat expansion It aims at providing the laminated body for use. Another object of the present invention is to provide a laminate for a wiring board in which the polyimide resin layer has a low hygroscopic property and a low humidity expansion coefficient in addition to the above characteristics. An object of the present invention is to provide a laminate for a wiring board in which the layer exhibits low elasticity. Furthermore, this invention aims at providing the laminated body for wiring boards with the favorable etching characteristic of a polyimide resin layer.

  As a result of repeated studies to solve the above-mentioned problems, the present inventors have added a specific polyimide resin to one of the resin layers constituting the polyimide resin layer of the laminate for a wiring board having a plurality of polyimide resin layers. It was used, and it discovered that the said subject could be solved by providing another resin layer, and came to complete this invention.

（式中、Ar₁は芳香環を1個以上有する4価の有機基であり、Ar₂は下記式(a)又は(b)で示される含酸素環と縮合した構造を有する芳香族基である。）

That is, according to the present invention, in a laminate having a metal layer on one or both sides of a polyimide resin layer, the polyimide resin layer has two or more different resin layers, and at least one of the resin layers is represented by the following general formula (1 ) Is a polyimide resin layer (i) containing 10 to 85 mol% of a structural unit represented by formula (ii), and at least one of the resin layers has a glass transition temperature lower than that of the polyimide resin layer (i) (ii) And the thickness of the polyimide resin layer (i) is 50% or more of the total thickness of the polyimide resin layer.

(In the formula, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and Ar ₂ is an aromatic group having a structure condensed with an oxygen-containing ring represented by the following formula (a) or (b): is there.)

A preferred embodiment of the present invention is shown below.
The laminate for a wiring board as described above, wherein the thickness of the polyimide resin layer (i) is 70 to 95% of the total thickness of the polyimide resin layer.
The laminate for a wiring board as described above, wherein the linear expansion coefficient of the polyimide resin layer is 30 ppm / K or less, the moisture absorption is 1.0 wt% or less, and the peel strength between the polyimide resin layer and the metal layer is 0.8 kN / m or more.
The laminate for a wiring board as described above, wherein the polyimide resin layer has a linear expansion coefficient of 30 ppm / K or less, an elastic modulus of 4 GPa or less, and a peel strength between the polyimide resin layer and the metal layer of 0.8 kN / m or more.
The above wiring wherein the etching rate of the polyimide resin layer is 10 μm / min or more when etched at 80 ° C. using an alkaline aqueous solution consisting of 11 wt% ethylene diamine, 22 wt% ethylene glycol and 33.5 wt% potassium hydroxide as an etching solution. Laminate for substrate.

Below, the laminated body for wiring boards of this invention is demonstrated.
The laminate for a wiring board of the present invention has a metal layer on one or both sides of a polyimide resin layer, and the polyimide resin layer is composed of a plurality of layers. As the metal layer, a copper foil with a thickness of 5 to 50 μm, preferably 9 to 30 μm is suitable when used for flexible printed wiring boards, and a thickness when used as a substrate for an HDD suspension. A stainless steel foil of 5 to 70 μm, preferably 10 to 30 μm is suitable.

  In the present invention, at least one of the polyimide resin layers is a polyimide resin layer (i) containing 10 to 85 mol% of the structural unit represented by the general formula (1).

式(a1)及び(b1)において、Ar₁は芳香環を1個以上有する4価の有機基である。 Specific examples of the structural unit represented by the general formula (1) include those represented by the following formulas (a1) and (b1).

In the formulas (a1) and (b1), Ar ₁ is a tetravalent organic group having one or more aromatic rings.

  The polyimide resin layer (i) contains 10 to 85 mol% or more of either or both of the structural units represented by the formulas (a1) and (b1).

The method for producing a polyimide resin is generally a method in which a diamine and an aromatic acid dianhydride are reacted in a solvent. Therefore, the method for producing the polyimide resin used in the present invention is described as a representative example. It is not limited to this. In the structural unit represented by the general formula (1) or the formulas (a1) and (b1), Ar ₁ is a tetravalent organic group having one or more aromatic rings and is a residue derived from an aromatic dianhydride. It can be said. Thus, Ar ₁ is understood by describing the aromatic dianhydride used. Preferred Ar ₁ is described below using an aromatic dianhydride.

  It does not specifically limit as said aromatic acid dianhydride, A well-known thing can be used. Specific examples include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 2 , 3,3 ', 4'-benzophenone tetracarboxylic dianhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride , Naphthalene-1,4,5,8-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6 , 7-Hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-2,3,6, 7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid Anhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8- Tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic Acid dianhydride, 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride, 3,3``, 4,4' '-p-terphenyltetracarboxylic dianhydride, 2,2' ', 3,3' '-p-terphenyltetracarboxylic dianhydride, 2,3,3``, 4' '-p-terphenyltetracarboxylic dianhydride, 2,2-bis (2, 3-Dicarboxyphenyl) -propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2 , 3-dicarboxyphenyl) methane dianhydride, bis (3.4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) Sulfone dianhydride, 1,1-bis (2,3-dicarbo Xylphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9 , 10-tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2, 7,8-tetracarboxylic dianhydride, phenanthrene-1, 2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1, 2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2 , 3,4,5-tetracarboxylic dianhydride, 4,4′-oxydiphthalic dianhydride, and the like. Moreover, these may be used independently or can also be used together 2 or more types.

  In selecting aromatic dianhydrides, specifically, the characteristics required for the purpose of use such as CTE and thermal decomposition temperature, glass transition temperature (Tg), humidity expansion coefficient of polyimide obtained by polymerization and heating are expressed. It is preferable to select so as to. Among these, pyromellitic dianhydride (PMDA) is preferably used from the viewpoint of low elasticity and low CTE, and it is preferable to use this as the main component of aromatic dianhydride. This is effective for a polyimide resin containing 10 mol% or more of the structural unit represented by the formula (b1).

  From the viewpoint of low humidity expansion coefficient, pyromellitic dianhydride (PMDA), 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), naphthalene-2,3,6,7- Tetracarboxylic dianhydride (NTCDA), naphthalene-1,4,5,8-tetracarboxylic dianhydride, 3,3 ", 4,4" -p-terphenyltetracarboxylic dianhydride, 4, At least one aromatic tetra selected from 4'-oxydiphthalic dianhydride, 3,3'4,4'-benzophenone tetracarboxylic dianhydride and bis (2,3-dicarboxyphenyl) sulfone dianhydride Carboxylic acids are preferred, and among them, those selected from PMDA, NTCDA and BPDA are particularly preferred. This is effective for a polyimide resin containing 10 mol% or more of the structural unit represented by the formula (a1).

  The diamine used as an essential component in the synthesis of the polyimide resin constituting the polyimide resin layer (i) is represented by the aromatic diamine represented by the following formula (2) (hereinafter also referred to as ABPN) or the formula (3). Aromatic diamine (hereinafter also referred to as ABF). ABPN gives the structural unit represented by the formula (a1), and ABF gives the structural unit represented by the formula (b1). Hereinafter, the polyimide resin constituting the polyimide resin layer (i) is also referred to as polyimide resin (i).

  The aromatic diamine represented by the formula (2) comprises a step of synthesizing 3,8-dinitrodibenzopyranone by oxidizing the ketone portion of 1,5-dinitrofluorenone to an ester group with a peracid, and two nitro It can be obtained from the step of reducing the group to give diamine and obtaining 3,8-diaminodibenzopyranone as the desired aromatic diamine.

  The polyimide resin (i) can be obtained by reacting an aromatic dianhydride and a diamine containing 10 to 85 mol% of the aromatic diamine represented by the formula (2) or (3). In the present invention, together with the aromatic diamine represented by the above formula (2) or (3), other diamines other than the aromatic diamine are used in a proportion of 15 to 90 mol% to obtain a copolymer type polyimide resin.

  In the diamine used to obtain the polyimide resin (i), when the amount of ABPN or ABF is less than 10 mol%, it is difficult to obtain a polyimide resin satisfying heat resistance and low CTE, while 85 mol If it exceeds 50%, bubbles are likely to be formed when the polyimide resin layer is multilayered, and it is difficult to multilayer. Here, when ABPN is used as the diamine, it is difficult to obtain a polyimide resin satisfying low hygroscopicity and low CTE when the amount is less than 10 mol%, and when the amount of ABPN exceeds 85 mol%, the polyimide There arises a problem that the adhesion between the resin layer and the metal layer or another polyimide resin layer is deteriorated. In this respect, 50 to 85 mol% is preferable. Also, when using ABF, it is difficult to obtain a polyimide resin satisfying low elasticity and low CTE if the amount is less than 10 mol%, but if the amount of ABF exceeds 85 mol%, the elastic modulus Therefore, it is not suitable for wiring board applications that require flexibility and bending resistance. From this viewpoint, the amount of ABF and ABPN (the total amount when both are used) is preferably in the range of 30 to 70 mol%.

  In addition to the aromatic diamine represented by the formula (2) or (3), the diamine used for the copolymerization is not particularly limited, but for example, 4,6-dimethyl-m- Phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,5,3 ', 5'-tetramethyl-4 , 4'-diaminodiphenylmethane, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis [4- (4 -Aminophenoxy) phenyl] propane, 4,4'-diaminodiphenyls Rufide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl -4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4 "-diamino-p-terphenyl, 3,3" -diamino-p-terphenyl, bis (p-aminocyclohexyl) methane, Bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1 , 1-Dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diamino Naphthalene, 2,4-bis (β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine , P-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine and the like. These can be used alone or in combination of two or more.

  Among these, when used in combination with ABPN, 1,3-bis (3-aminophenoxy) benzene (APB), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,4-bis (4-aminophenoxy) benzene (TPE-Q), diaminodiphenyl ether (DAPE), 2,7-bis (4-aminophenoxy) naphthalene (NBOA), 2,2-bis [4- (4-aminophenoxy) phenyl Propane (BAPP) or the like is preferably used. Moreover, when using these diamines, the preferable usage rate is 15-60 mol% of all the diamine, More preferably, it is the range of 15-50 mol%.

  When used in combination with ABF, 4,4'-diaminodiphenyl ether (DAPE), paraphenylenediamine (PDA), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 4,4'- Diaminodiphenylmethane (MDA) is preferably used. Moreover, when using these diamines, the use ratio is preferably in the range of 30 to 70 mol% of the total diamines. By mixing and using these diamine components, the CTE can be adjusted to the same level as that of the metal foil, and can be adjusted to a practically required value of 30 ppm / ° C. or less. Thereby, it is possible to suppress the occurrence of warping, curling, and the like of the laminated body.

  The polyimide resin layer in the laminate for a wiring board of the present invention has at least one polyimide resin layer (ii) in addition to the polyimide resin layer (i). The polyimide resin layer (ii) is a polyimide resin layer different from the polyimide resin layer (i) and does not have the structural unit represented by the general formula (1) or is in the range of 10 to 85 mol%. Does not have. Advantageously, it does not have or does not have more than 5 mol%.

  The polyimide resin layer (ii) needs to have a glass transition temperature (Tg) lower than that of the polyimide resin layer (i), but a thermoplastic resin having a Tg of 200 ° C. or higher is preferable. More preferably, it is a thermoplastic resin having a Tg in the range of 200 to 350 ° C. The polyimide resin (ii) constituting the polyimide resin layer (ii) can be a known polyimide resin as long as the above physical properties are satisfied, and can be obtained from the acid dianhydride component and the diamine component described above.

  Preferred acid dianhydride components used for producing the polyimide resin (ii) constituting the polyimide resin layer (ii) include pyromellitic dianhydride (PMDA), 3,3 ', 4,4'- Biphenyltetracarboxylic dianhydride (BPDA), 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride Aromatic acid dianhydrides such as (DSDA), 4,4′-oxydiphthalic dianhydride (ODPA) are exemplified.

  Examples of the diamine component include 2,2-bis (4-aminophenoxyphenyl) propane (BAPP), bis [4- (4-aminophenoxy) phenyl] sulfone (BAPS), 3,4′-diaminodiphenyl ether (3,4 '-DAPE), 4,4'-diaminodiphenyl ether (4,4'-DAPE), 1,4-bis (4-aminophenoxy) benzene (TPE-Q), 4,4'-bis (4-aminophenoxy) ) Biphenyl (BAPB), 1,3-bis (3-aminophenoxy) benzene (APB), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,3-bis (4-aminophenoxy) Aromatic diamines such as -2,2-dimethylpropane (DANPG) are preferred.

  The polyamic acid for forming the polyimide resin layer is a known method in which the aromatic diamine component and the aromatic tetracarboxylic dianhydride component shown above are used in substantially equimolar amounts and polymerized in an organic polar solvent. Can be manufactured by. That is, it can be obtained by dissolving the diamine in an organic polar solvent such as N, N-dimethylacetamide under a nitrogen stream and then adding the aromatic tetracarboxylic dianhydride and reacting at room temperature for about 3 hours.

  The laminate for a wiring board of the present invention, for example, applies the polyamic acid solution obtained by the above reaction onto a metal foil serving as a support or a resin layer formed on the metal foil using an applicator or the like. Then, after preliminary drying at a temperature of 150 ° C. or lower for 2 to 20 minutes, it is usually obtained by heat treatment at a temperature of about 130 to 360 ° C. for about 2 to 30 minutes to remove the solvent and imidize. Since the laminate for a wiring board of the present invention has a plurality of polyimide resin layers, after repeating the operation of applying a polyamic acid solution and drying, heat treatment is performed to remove the solvent, and this is further heat treated at a high temperature to obtain an imide. By forming, a polyimide resin layer can be formed. At this time, the total thickness of the formed polyimide resin layer is preferably in the range of 3 to 75 μm. In the present invention, the thickness range of the polyimide resin layer (i) with respect to the total thickness of the polyimide resin layer needs to be 50% or more, preferably 70% or more and 95% or less. The thickness range of the polyimide resin layer (ii) needs to be less than 50%, but is preferably in the range of 5 to 30%.

  The degree of polymerization of the polyamic acid and the polyimide used for forming the polyimide resin layer is preferably in the range of 500 cP to 200,000 cP when the polyamic acid solution is expressed in the viscosity range of the polyamic acid solution. The solution viscosity can be measured with a cone plate viscometer with a thermostatic water bath.

Moreover, when manufacturing the laminated body for wiring boards which has metal foil on both surfaces, after forming a metal foil directly or after forming an adhesive layer on the polyimide resin layer of the laminated body for single-sided wiring boards obtained by the said method, It is obtained by thermocompression bonding. The hot pressing temperature at the time of the thermocompression bonding is not particularly limited, but it is desirable to be not lower than the glass transition temperature of the polyimide resin used. The hot press pressure is preferably in the range of 1 to 500 kg / cm ² , although it depends on the type of press equipment used. Furthermore, the preferable metal foil used at this time can use the thing similar to the above-mentioned metal foil, The preferable thickness is also 50 micrometers or less, More preferably, it is the range of 5-40 micrometers.

  The polyimide resin layer (i) constituting the laminate for a wiring board of the present invention comprises an aromatic diamine represented by the formula (2) or (3) and other aromatic diamines used in combination with the aromatic diamine. The properties can be controlled by various combinations with the group tetracarboxylic acids or their acid dianhydrides.

  When a polyimide resin layer having a structural unit represented by the formula (a1) is used, a polyimide resin layer having a linear expansion coefficient of 30 ppm / K or less, preferably 25 ppm / K or less and a moisture absorption of 1.1 or less, In addition, by providing the polyimide resin layer (ii), a laminate for a wiring board having a peel strength of 0.8 kN / m or more between the polyimide resin layer and the metal layer can be obtained. Here, when the linear expansion coefficient of the polyimide resin layer exceeds 30 ppm / K, various problems such as curling or the polyimide resin layer shrinkage being too large to be processed well, and the moisture absorption rate are likely to occur. If it exceeds 1.1, solder heat bulge tends to occur.

  Further, when a polyimide resin layer having a structural unit represented by the formula (b1) is used, the linear expansion coefficient is 30 ppm / K or less, preferably 25 ppm / K or less, and the elastic modulus at 25 ° C. is 4 GPa or less. Preferably, it can be a polyimide resin layer of 1 to 3 GPa, and by providing the polyimide resin layer (ii), a laminate for a wiring board having a peel strength between the polyimide resin layer and the metal layer of 0.8 kN / m or more. Can be obtained. If the elastic modulus of the polyimide resin layer exceeds 4 GPa, mounting defects such as peeling or disconnection due to repulsive force may occur, or the radius at the time of bending may be increased, which hinders high performance and high functionality of the wiring board. In addition, it is difficult to obtain sufficient bending characteristics when a laminated body for a wiring board is obtained.

  The polyimide resin layer of the laminate for a wiring board of the present invention satisfies the above-described requirements, and at the same time uses an alkaline aqueous solution consisting of 11 wt% ethylenediamine, 22 wt% ethylene glycol, and 33.5 wt% potassium hydroxide as an etching solution. It is preferable that the etching rate when etching is performed at a temperature of 10 μm / min or more.

  The laminate for a wiring board of the present invention has a low coefficient of linear expansion and excellent heat resistance, and is useful as a laminate for a wiring board. It is particularly useful for applications such as FPC and HDD suspension substrates. In addition, the laminate for a wiring board having a polyimide resin layer containing the structural unit represented by the formula (a1) has excellent heat resistance, low moisture absorption, and excellent dimensional stability. And has an effect of suppressing warpage due to humidity, and the etching rate of the polyimide resin layer is also excellent. Further, the polyimide resin layer containing the structural unit represented by the formula (b1) has a low linear expansion coefficient, heat resistance, and low elasticity.

  EXAMPLES Hereinafter, although the content of this invention is demonstrated concretely based on an Example, this invention is not limited to the range of these Examples.

Abbreviations used in Examples and the like are shown below.
• ABPN: 3,8-diaminodibenzopyranone • DAF: 2,7-diaminofluorene • ABF: 3,7-diaminodibenzofuran • m-TB: 2,2′-diamino-4,4′-diaminobiphenyl • 4 , 4'-DAPE: 4,4'-diaminodiphenyl ether, 3,4'-DAPE: 3,4'-diaminodiphenyl ether, TPE-Q: 1,4-bis (4-aminophenoxy) benzene, TPE-R: 1,3-bis (4-aminophenoxy) benzene, APB: 1,3-bis (3-aminophenoxy) benzene, BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane, DABA: 4,4'-Diaminobenzanilide DANPG: 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane PMDA: pyromellitic dianhydride BPDA: 3,3 ', 4,4' -Biphenyltetracarboxylic dianhydride BTDA: 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride DMAc: N, N-dimethylacetamide

  In addition, measurement methods and conditions for various physical properties in the examples are shown below.

[Measurement of linear expansion coefficient (CTE)]
Tensile test of polyimide film with a size of 3mm x 15mm in a temperature range from 30 ° C to 260 ° C at a constant heating rate (20 ° C / min) while applying a 5.0g load with a thermomechanical analysis (TMA) device The linear expansion coefficient (ppm / K) was measured from the amount of elongation of the polyimide film with respect to temperature.

[Measurement of glass transition temperature (Tg)]
The dynamic viscoelasticity of a polyimide film (10mm x 22.6mm) was measured at a rate of 5 ° C / min from 20 ° C to 500 ° C using a dynamic thermo-analyzer, and the glass transition temperature (tanδ maximum value: ° C).

[Measurement of moisture absorption rate]
After drying 4cm x 20cm polyimide films (each 3 sheets) at 120 ° C for 2 hours, leave it in a constant temperature and humidity chamber of 23 ° C / 50% RH for more than 24 hours. Asked.
Moisture absorption rate (wt%) = [(weight after moisture absorption−weight after drying) / weight after drying] × 100

[Measurement of humidity expansion coefficient (CHE)]
An etching resist layer is provided on a copper foil of a 35 cm x 35 cm polyimide / copper foil laminate, and this is arranged through a mask so that 16 points with a diameter of 1 mm are arranged at 10 cm intervals on four sides of a 30 cm square. Exposure and development were carried out to obtain a CHE measurement polyimide film having the above 16 copper foil remaining points. This film was dried at 120 ° C for 2 hours, then left in a constant temperature and humidity environment of 23 ° C / 50% RH for at least 24 hours, and the humidity expansion coefficient was determined from the dimensional change between the copper foil points measured by a two-dimensional measuring machine. (ppm /% RH) was determined.

[Measurement of etching rate (Eg ')]
The etching rate is measured using a polyimide film and using a reference etching solution (ethylene diamine 11 wt%, ethylene glycol 22 wt%, potassium hydroxide 33.5 wt%, and water 33.5%). The measurement was performed by measuring the time when the polyimide resin was completely removed by immersing in the reference etching solution at 80 ° C., and the value obtained by dividing the initial thickness by the time required for etching was taken as the etching rate.

[Measurement of viscosity]
The viscosity was measured at 25 ° C. with a cone plate viscometer (manufactured by Tokimec Co., Ltd.) equipped with a constant temperature water bath.

[Measurement of tensile modulus (E ')]
Using a tension tester, a polyimide film having a width of 12.4 mm and a length of 160 mm was subjected to a tensile test at 50 mm / min while applying a load of 10 kg, and the tensile elastic modulus (E ′) at 25 ° C. was obtained.

[warp]
Visually judge the warpage of the laminate (size 10cm x 10cm). A flat object is indicated by a circle, and a bent object is indicated by a cross.

[Solder heat resistance test]
The laminated body is processed in a predetermined shape and immersed in a 350 ° C. solder bath for 30 s. If there are no blisters, use ◯.

Synthesis Examples 1-12
In order to synthesize the polyamic acids A to L, the diamines shown in Table 1 were dissolved in the solvent DMAc while stirring in a 200 ml separable flask under a nitrogen stream. Subsequently, the tetracarboxylic dianhydride shown in Table 1 was added. Thereafter, the solution is stirred at room temperature for 3 hours to carry out a polymerization reaction, whereby a yellow-brown viscous solution of polyamic acids A to L to be a polyimide precursor is obtained, and a high degree of polyamic acid is produced. It was confirmed that The solid content and solution viscosity of the polyamic acid are shown in Table 1. Here, the solid content is a weight ratio of the polyamic acid to the total amount of the polyamic acid and the solvent. The solution viscosity was measured using an E-type viscometer. The results are summarized in Table 1. In addition, the numerical value of the monomer component of a raw material in a table | surface shows a compounding quantity (g).

Reference Examples 1-12
The solution of polyamic acid A to L was applied on a copper foil or SUS foil using an applicator, dried at 130 ° C. for 2 to 4 minutes, and then further 130 ° C., 160 ° C., 200 ° C., 230 ° C., 280 Stepwise heat treatment was performed at 2 ° C., 320 ° C., and 360 ° C. for 2 to 12 minutes to form a polyimide layer on the copper foil. In the case of a multilayer polyimide resin layer, the operation of applying and drying the polyamic acid solution in order was repeated, and then a stepwise heat treatment was performed at a higher temperature to form a multilayered polyimide resin layer. .

  Copper foil is etched away from the laminate using an aqueous ferric chloride solution to create polyimide films of Reference Examples 1 to 9, linear expansion coefficient (CTE), glass transition temperature (Tg), moisture absorption, humidity expansion coefficient (CHE), polyimide etching rate and tensile modulus were determined. It should be noted that the A to L polyimide films were obtained from the A to L polyamic acids, respectively.

Example 1
The solution of polyamic acid resin J obtained in Synthesis Example 10 was applied onto an electrolytic copper foil (average surface roughness Rz: 2.0 μm) having a thickness of 18 μm so that the thickness after curing was 2 μm and heated at 120 ° C. Dry and remove the solvent. Next, the solution of the polyamic acid resin A obtained in Synthesis Example 1 was applied thereon so that the thickness after curing was 22 μm, and dried by heating at 120 ° C. to remove the solvent. Further, a solution of the polyamic acid resin J was applied thereon so that the thickness after curing was 2 μm, and dried by heating at 120 ° C. to remove the solvent. After this, stepwise heat treatment is performed at 130 ° C, 160 ° C, 200 ° C, 230 ° C, 280 ° C, 320 ° C, and 360 ° C for 2 to 12 minutes each, and the wiring board is composed of three polyimide layers on the copper foil. A laminate was prepared. The thickness of the polyimide layer on the copper foil is 2/22/2 μm in the order of J / A / J. The evaluation of the polyimide resin layer was performed on a polyimide film obtained by removing the copper foil of the wiring board laminate by etching. The evaluation results of the laminate are shown in Table 3.

Example 2
Apply the solution of polyamic acid resin L obtained in Synthesis Example 12 on a stainless steel foil (Rz: 0.5 μm) with a thickness of 20 μm so that the thickness after curing is 2 μm, and heat dry at 120 ° C. to remove the solvent. did. Next, the solution of the polyamic acid resin B obtained in Synthesis Example 2 was applied thereon so that the thickness after curing was 8 μm, and dried by heating at 120 ° C. to remove the solvent. After this, heat treatment is performed stepwise at 130 ° C, 160 ° C, 200 ° C, 230 ° C, 280 ° C, 320 ° C, and 360 ° C for 2 to 12 minutes each to form a wiring board composed of two polyimide layers on a stainless steel foil. A laminate was prepared. The thickness of the polyimide layer on the stainless steel foil is 2/8 μm in the order of L / B from the stainless steel side. Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

Example 3
The configuration of the polyimide resin layer on the stainless steel foil was K / C, and the same procedure as in Example 2 was performed except that the thickness of the cured polyimide layer was 2/8 μm in the order of K / C from the stainless steel side. It was. Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

Example 4
The configuration of the polyimide resin layer on the stainless steel foil was set to D / L, and the same procedure as in Example 2 was performed except that the thickness of the cured polyimide layer was 8/2 μm in the order of D / L from the stainless steel side. It was. Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

Example 5
The same procedure as in Example 1 was performed except that a rolled copper foil (Rz: 1.0 μm) having a thickness of 18 μm was used as the copper foil, and the polyimide resin layer A was changed to E. Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

Example 6
The configuration of the polyimide resin layer on the stainless steel foil was F / J, and the same procedure as in Example 2 was performed except that the thickness of the cured polyimide layer was 8/2 μm in the order of F / J from the stainless steel side. . Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

Comparative Example 1
It carried out similarly to Example 2 except having set the structure of the polyimide resin layer on stainless steel foil to K / G. The thickness of the polyimide layer on the stainless steel foil is 2/8 μm in the order of K / G from the stainless steel side. Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

Comparative Example 2
It carried out similarly to Example 2 except having set the structure of the polyimide resin layer on stainless steel foil to L / H. The thickness of the polyimide layer on the stainless steel foil is 2/8 μm in the order of L / H from the stainless steel side. Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

Comparative Example 3
The same operation as in Example 1 was performed except that the polyimide resin layer A was changed to I. Table 3 shows the evaluation results of the polyimide resin layer (polyimide film) and the laminate.

  As shown in Table 3, the laminates for wiring boards of Examples 1 to 4 were polyimide resin layers with high heat resistance that did not generate solder heat swell with a low linear expansion coefficient. Moreover, the laminated body did not warp, and the adhesive force (peel strength) between the metal layer and the polyimide resin layer was also good. In particular, the polyimide layers of Examples 2 to 4 had a high etching rate.

  The laminates for wiring boards of Examples 5 and 6 were not only high heat resistance that did not cause solder heat expansion but also low thermal expansion, and were low-modulus polyimide resin layers. In particular, the polyimide layer of Example 6 had a high etching rate.

  The laminates for wiring boards of Comparative Examples 1 and 2 had a high moisture absorption rate and humidity expansion coefficient of the polyimide resin layer and a slow etching rate. Due to the high moisture absorption rate, swelling occurred in the solder heat resistance test.

  Comparative Example 3 was a laminate obtained from the polyamic acid I having 90 mol% of the structural unit of the formula (a1). Since a large amount of bubbles was generated, the film characteristics could not be evaluated (NG). A laminate applicable to a wiring board could not be obtained.

Claims (5)

In a laminate having a metal layer on one or both sides of a polyimide resin layer, the polyimide resin layer has two or more different resin layers, and at least one layer of the resin layer is represented by the following general formula (1) It is a polyimide resin layer (i) containing 10 to 85 mol% of units, and at least one of the resin layers is composed of a polyimide resin layer (ii) having a glass transition temperature lower than that of the polyimide resin layer (i). The laminate for a wiring board, wherein the thickness of (i) is 50% or more of the total thickness of the polyimide resin layer.

(In the formula, Ar ₁ is a tetravalent organic group having one or more aromatic rings, and Ar ₂ is an aromatic group having a structure condensed with an oxygen-containing ring represented by the following formula (a) or (b): is there.)

  The laminate for a wiring board according to claim 1, wherein the thickness of the polyimide resin layer (i) is 70 to 95% of the total thickness of the polyimide resin layer.   The wiring board according to claim 1 or 2, wherein the linear expansion coefficient of the polyimide resin layer is 30 ppm / K or less, the moisture absorption is 1.0 wt% or less, and the peel strength between the polyimide resin layer and the metal layer is 0.8 kN / m or more. Laminated body.   The linear expansion coefficient of the polyimide resin layer is 30 ppm / K or less, the elastic modulus is 4 GPa or less, and the peel strength between the polyimide resin layer and the metal layer is 0.8 kN / m or more. Laminated body for wiring board.   2. The etching rate of the polyimide resin layer when etched at 80 ° C. is 10 μm / min or more when an alkaline aqueous solution consisting of 11 wt% ethylene diamine, 22 wt% ethylene glycol and 33.5 wt% potassium hydroxide is used as an etching solution. The laminated body for wiring boards in any one of -4.