TWI840435B - Multilayer body and manufacturing method thereof, and manufacturing method of printed wiring board - Google Patents

Abstract

The first main surface of the rigid support (30) of the laminate (100) of the present invention has a release sheet (21) and a flexible film-like substrate (11) laminated in sequence. The film-like substrate may include a flexible insulating resin film, and a metal conductor layer is provided on the main surface of the insulating resin film. The outer periphery of the support protrudes further outward than the outer periphery of the release sheet, and the outer periphery of the film-like substrate protrudes further outward than the outer periphery of the release sheet. The support and the film-like substrate are in contact in a region (8) further outward than the outer periphery of the release sheet.

Description

Multilayer body and manufacturing method thereof, and manufacturing method of printed wiring board

The present invention relates to a multilayer body and a method for manufacturing the multilayer body, and a method for manufacturing a printed wiring board using the multilayer body.

Printed wiring boards with circuits containing metal conductors on an insulating substrate are generally divided into rigid printed wiring boards and flexible printed wiring boards. Flexible printed wiring boards are mainly used to fully utilize their flexibility to miniaturize and bend the substrate and store it inside electronic equipment.

In the manufacturing process of printed wiring boards, various chemical solutions are used in the formation of metal conductor layers by wet plating, patterning of metal conductor layers by wet etching, development of anti-corrosive agents, and slag removal. In the manufacturing process of rigid printed wiring boards, sheet-shaped rigid substrates are used for batch processing. Since flexible printed wiring boards use flexible substrates, their manufacturing process is often implemented by a so-called roll-to-roll film conveying process, and their processing accuracy is lower than that of rigid printed wiring boards that are processed in batches using rigid substrates. For example, in semiconductor package substrates classified as rigid printed wiring boards, the circuit wiring pitch is gradually becoming narrower, and printed wiring boards with a circuit width (line/pitch) of less than 10μm can be mass-produced. In contrast, the circuit width of flexible printed wiring boards is small, but it is still around 20μm.

As electronic devices become more multifunctional and miniaturized, printed wiring boards are required to have narrower pitches, and rigid-flex composites are required to be accommodated in miniaturized electronic devices. In order to manufacture a narrow-pitch rigid-flex composite substrate, it is necessary to form a narrow-pitch circuit on a flexible film substrate to the same degree as a rigid printed wiring board.

As a method for performing high-precision processing on a flexible film substrate, the following process is disclosed: a flexible film substrate is bonded to a rigid support such as a glass plate to form a rigid laminate, and after printing or forming elements on the flexible film substrate of the laminate, the flexible film substrate is peeled off from the support (for example, Patent Document 1).

[Prior Art Literature] [Patent Literature]

[Patent document 1] Japanese Patent Publication No. 2015-193101

As disclosed in Patent Document 1, since a laminate having a flexible film substrate bonded to a rigid support can be applied to a batch process using a rigid substrate, it is believed that a printed wiring board having a narrow pitch circuit comparable to that of a rigid printed wiring board can be formed on the flexible film substrate. However, since various chemical solutions are used in the manufacturing steps of the printed wiring board, there is a possibility that the chemical solution penetrates into the laminate interface between the support and the flexible film substrate and causes unexpected peeling. In addition, if the adhesive or bonding agent disposed at the laminate interface dissolves in the chemical solution, it may cause contamination.

In order to prevent contamination caused by poor bonding or dissolution in the chemical solution, consider using photocurable or thermosetting bonding materials to more firmly bond the support and the flexible film substrate to prevent the chemical solution from penetrating the layer interface or the bonding material from dissolving in the chemical solution. However, if a hardening bonding material is used, it is difficult to peel the processed flexible film substrate from the support, and there may be residual bonding materials on the surface of the flexible film, causing contamination.

In view of the above, the purpose of the present invention is to provide a laminate that can be applied to a manufacturing device for a rigid printed wiring board, and a method for manufacturing a printed wiring board using the laminate.

The first main surface of the rigid support of the laminate of the present invention has a release sheet and a flexible film substrate laminated in sequence. The film substrate includes a flexible insulating resin film such as a polyimide film. The film substrate can be composed of an insulating resin film, and can also have a metal conductor layer on at least one main surface of the insulating resin film.

In the laminate of the present invention, the periphery of the support and the periphery of the film-like substrate protrude further outward than the periphery of the release sheet, and the support protruding further outward than the periphery of the release sheet is in contact with the film-like substrate.

The outer periphery of the film-like substrate may also protrude further outward than the outer periphery of the support. An opening may be provided on the release sheet, and the first main surface of the support and the second main surface of the film-like substrate may be connected at the portion of the release sheet where the opening is provided.

The above-mentioned laminate is obtained, for example, by heat-pressing a laminate having a release sheet and a film-like substrate arranged in sequence on the first main surface of the support. By heat-pressing, the support protruding outward from the outer periphery of the release sheet is bonded to the film-like substrate. For example, when the support is a prepreg, the impregnated resin of the prepreg exhibits adhesion by heat curing.

The above-mentioned laminate can be applied to the manufacture of printed wiring boards. In the manufacture of printed wiring boards, a first circuit is formed on the first main surface of the insulating resin film of the laminate. For example, the first circuit is formed by etching a metal conductor layer provided on the first main surface of the insulating resin film. The first circuit can also be formed by pattern plating. Before forming the first circuit, a metal conductor layer can be formed on the first main surface of the insulating resin film by wet or dry electroless plating.

After forming the first circuit on the first main surface of the insulating resin film, the insulating resin film is separated from the support and the release sheet. For example, the insulating resin film is separated from the laminate by cutting off the outer peripheral portion where the support and the film-like substrate are connected.

An insulating layer covering the first main surface of the insulating resin film and the first circuit formed thereon may be provided, and a second circuit may be formed on the insulating layer to perform multilayering. The multilayering may be performed before the insulating resin film is separated from the laminate, or after the insulating resin film is separated from the laminate. The third circuit may be formed on the second main surface of the insulating resin film after the insulating resin film is separated from the laminate.

Since the laminated body having a film-like substrate laminated on a rigid support with a release sheet interposed therebetween has rigidity, it can be applied to equipment for processing rigid substrates such as manufacturing equipment for rigid printed wiring boards. Therefore, printed wiring boards using film-like substrates such as flexible and rigid composite wiring boards as bases can be manufactured.

The support body is connected to the film substrate at the outer periphery of the laminate, so that the chemical solution can be prevented from penetrating into the laminate interface of the release sheet during the manufacturing process of the printed wiring board. Therefore, the peeling of the film substrate during the circuit formation process or the contamination of the manufacturing step can be prevented. At any stage after the circuit is formed, the film substrate can be easily separated from the laminate by cutting off the outer periphery of the laminate.

1: Peripheral end

2: Peripheral end

3: Peripheral end

5: Open mouth

7: Region

8: Peripheral area

9: Region

11: Film substrate

12: Film substrate

21: Release film

22: Release film

30: Support body

42: Protective film

100: Layered body

101: Laminated body

102: Laminated body

103: Laminated body

C1, C2, C3, C4: lines

Figure 1 is a schematic cross-sectional view of a laminated body in one embodiment.

Figure 2 is a top view of a model of a multilayer structure in an implementation form.

Figure 3 is a schematic cross-sectional view of a laminated body in one implementation form.

Figure 4 is a schematic cross-sectional view of a laminated body in one embodiment.

Figure 5 is a schematic cross-sectional view of a laminated body in one implementation form.

[Composition of laminated bodies]

FIG1 is a cross-sectional view of a laminate 100 in an implementation form, and FIG2 is a top view thereof. On one main surface of a support 30 in the laminate 100, a release sheet 21 and a film-like substrate 11 are sequentially laminated. The size of the release sheet 21 is smaller than that of the support 30 and the film-like substrate 11, and the outer peripheral end 3 of the support 30 and the outer peripheral end 1 of the film-like substrate 11 protrude further outward than the outer peripheral end 2 of the release sheet 21.

In the central area 7 within the surface of the laminate, a film-like substrate 11 is laminated on the support 30 via a release sheet 21. In the area 8 outside the outer peripheral end 2 of the release sheet 21, the support 30 and the film-like substrate 11 are in contact with each other and are in contact with each other.

<Support>

The support 30 has rigidity that can be processed by a manufacturing device for a rigid printed wiring board. In addition, the support 30 is required to have heat resistance and chemical resistance for use in the manufacturing steps of a printed wiring board. Specific examples of the support 30 include: a glass plate, a resin sheet, and a prepreg. A prepreg refers to a fibrous reinforcing material such as a non-woven fabric or cloth including glass fiber, carbon fiber, synthetic fiber, etc., which is impregnated with a thermosetting resin, a thermoplastic resin, etc. and has rigidity. As long as the support 30 has rigidity, its thickness is not particularly limited. When the support 30 is a prepreg, in order to have sufficient rigidity, the thickness is preferably 30μm or more, and more preferably 80μm or more.

The support 30 needs to have the function of bonding with the film substrate 11 in the peripheral area 8. When using a substrate material without bonding function such as a glass plate or a resin sheet, a suitable bonding agent layer can be formed on the entire surface or the peripheral area of the substrate to make the substrate have bonding properties to the film substrate 11.

Because it has a proven track record of being widely used in the manufacture of printed wiring boards and has advantages in terms of durability, availability, price, etc. during the process, a prepreg is preferably used as the support 30. As the prepreg, a semi-cured prepreg can be used. The semi-cured prepreg cures the resin component by heating, so by laminating under heating conditions such as hot pressing, it exhibits adhesion to the film-like substrate 11.

<Film-like substrate>

The film-like substrate 11 is flexible and includes a flexible insulating resin film that serves as a substrate material for a printed wiring board. The film-like substrate 11 may be a single insulating resin film, or may have a metal conductor layer for circuit formation on one or both sides of the insulating resin film. After laminating the insulating resin film on the support 30 via the release sheet 21, the metal conductor layer may be formed on the insulating resin film by electroless plating or the like.

(Insulating resin film)

As an insulating resin film, it is preferred to have a high degree of adhesion with the conductor layer used to form the circuit, and have excellent heat resistance and chemical resistance. Examples of resin materials for insulating resin films include: polyimide, liquid crystal polymer, polyamide, polyethylene terephthalate (PET), polyphenylene sulfide (PPS), etc. Since polyimide film has excellent heat resistance and chemical resistance and a small thermal expansion coefficient, it is suitable to use it as an insulating resin film.

The insulating resin film may have a bonding layer for improving the bonding with a conductive layer such as a metal foil or a coating layer. For example, a thermoplastic resin layer may be provided as a bonding layer on one or both sides of a high heat-resistant (non-thermoplastic) resin layer serving as a core.

As long as the insulating resin film is flexible, its thickness is not particularly limited. The thickness of the insulating resin film is, for example, about 3 to 150 μm, 5 to 100 μm, or less than 75 μm, less than 50 μm, less than 30 μm, or less than 20 μm. The thinner the thickness of the flexible film, the more difficult it is to handle as a single body. However, by laminating the film substrate 11 with the rigid support 30 and the release sheet 21 to form the laminate 100, the laminate 100 is made rigid. Therefore, when the thickness of the insulating resin film of the film substrate 11 is relatively small, it is also easy to handle.

(Conductor layer)

The conductor layer disposed on the surface of the insulating resin film is used to form a circuit by patterning. The material of the conductor layer includes metals such as Ni, Cr, Ti, Al, Zn, Sn, Cu, Ag, Cu, and alloys containing these metals. Among them, copper or copper alloy is preferred. As a film-like substrate having a copper layer (or copper alloy layer) as a conductive layer on the surface of an insulating resin film, there can be listed: a three-layer flexible copper foil laminate, a laminated two-layer flexible copper foil laminate, a cast two-layer flexible copper foil laminate, a PVD (Physical Vapor Deposition) type flexible copper foil laminate, etc.

The thickness of the conductor layer is not particularly limited and can be appropriately selected according to the specifications of the printed wiring board to be manufactured. When forming a fine circuit, it is preferred that the thickness of the conductor layer is thinner. When forming a circuit by an additive method (including a semi-additive method), the conductor layer on the insulating resin film can function as a feed layer during electrolytic plating, and the thickness of the conductor layer is preferably less than 5μm. When forming a circuit by a subtractive method, the thickness of the conductor layer is generally about 10~100μm.

The conductive layer is formed, for example, by wet or dry electroless plating. Furthermore, in this specification, unless otherwise stated, not only wet electroless plating (chemical reduction plating and substitution plating) but also dry plating such as physical vapor deposition (PVD) and chemical vapor deposition (CVD (Chemical Vapor Deposition)) are considered "electroless plating". The type of electroless plating can be appropriately selected based on the compatibility with the insulating resin film (e.g., adhesion), the specifications of the printed wiring board, etc. For example, in a PVD-type flexible copper foil laminate, a copper layer is formed on an insulating resin film by the PVD method. As PVD methods, sputtering, evaporation, ion plating, etc. can be listed. The conductive layer formed by electroless plating can be used as a feeding layer, and a conductive layer can be formed thereon by electrolytic plating. The conductive layer can be a metal foil such as copper foil. When copper foil is used as the conductive layer, either rolled copper foil or electrolytic copper foil can be used.

<Release sheet>

As the release sheet 21 disposed between the support 30 and the film substrate 11, the following types can be adopted: when forming a laminate and in the manufacturing step of a printed wiring board using the laminate, it has heat resistance, can be easily peeled off from the film substrate 11, and does not contaminate the contact surface with the film substrate 11. As long as the release sheet 21 does not contaminate the contact surface with the film substrate 11, it can also have close adhesion to the support 30 and/or the film substrate 11.

The thickness of the release sheet 21 is not particularly limited. When the thickness is too large, the step difference at the outer peripheral end 1 of the release sheet 21 becomes larger, which may lead to reduced adhesion between the support 30 and the film substrate 11 in the peripheral area 8, or separation due to the mixing of air bubbles. Therefore, the thickness of the release sheet 21 is preferably less than 200μm, more preferably less than 100μm, and further preferably less than 50μm. The thickness of the release sheet can also be more than 5μm or more than 10μm.

The heat-resistant resin material constituting the release sheet 21 includes: polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyamide (PA), heat-resistant polyolefins such as polymethylpentene, polyarylate, fluorine resins (polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), perfluoroalkoxy fluorine resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), etc.), polyimide, etc.

The release sheet 21 may also be a heat-resistant film having a heat-resistant adhesive layer on one or both sides. Examples of adhesives for the heat-resistant adhesive layer include silicone resin adhesives, acrylic resin adhesives, etc.

As the release sheet 21, a commercially available release sheet for stamping of printed wiring boards can be used. Commercially available release sheets that do not have an adhesive layer including a heat-resistant film include: "TPX" manufactured by Mitsui Chemicals (product name of the release sheet: "Opulent"), "Aflex" manufactured by Asahi Glass, etc. A release sheet without an adhesive layer on the surface has the advantage that it is not easy to cause contamination on the contact surface with the film substrate 11. In particular, fluorine-based resin films are suitable for use as materials for release sheets because of their excellent heat resistance and release properties, and their close adhesion (micro-adhesion) to resin films or conductive layers.

Commercially available release sheets with heat-resistant adhesive layers include: "LIOELM" series (LE951, LE957, etc.) manufactured by TOYOCHEM, "KT" series (polyester base materials such as KT508ZZ) and "KY" series (polyimide base materials such as KY5010) manufactured by Kawamura Sangyo, polyimide film adhesive tapes (1030, 1030S, etc.) and polyester film adhesive tapes (2034, 2230GX) manufactured by Okamoto, etc.

<Formation of laminated bodies>

On one main surface of the support 30, a release sheet 21 and a film-like substrate 11 are arranged and the laminate is integrated to form a laminate 100. When the insulating resin film surface of the film-like substrate 11 has a conductive layer, the conductive layer is arranged on the outer side (the side opposite to the release sheet 21).

The outer peripheral end 3 of the support 30 and the outer peripheral end 1 of the film-like substrate 11 both protrude further outward than the outer peripheral end 2 of the release sheet 21. To achieve this state, the release sheet 21 is cut into a size that is one circle smaller than the support 30, and the film-like substrate 11 is cut into a size that is one circle larger than the release sheet 21, and the outer peripheral area 8 of the frame is aligned so that the support 30 and the film-like substrate 11 are connected.

The shape of the support 30 is not limited to a rectangle, and may be a rhombus, a polygon, a circle, etc., depending on the shape of the printed wiring board. The area of the support 30 is, for example, about 50 to 10,000 ^cm2 , and may be set according to the specifications of the step or the size of the printed wiring board.

The size of the release sheet 21 only needs to be smaller than the support 30. Since the peripheral area 8 will not eventually become a product, from the perspective of area efficiency, it is preferred that the width of the peripheral area 8 is as small as possible. The width of the peripheral area 8 is preferably 50 mm or less, more preferably 30 mm or less, and further preferably 20 mm or less. On the other hand, from the perspective of using the peripheral area 8 to ensure the adhesion between the support 30 and the film-like substrate 11, the width of the peripheral area 8 is preferably 1 mm or more, more preferably 3 mm or more, and further preferably 5 mm or more. The area of the release sheet 21 is preferably 0.6 times or more of the area of the support 30, more preferably 0.8 times or more, and further preferably 0.9 times or more.

The size of the film substrate 11 only needs to be larger than the release sheet 21. From the perspective of improving the area utilization efficiency of the film substrate 11 and suppressing material loss, the area of the film substrate 11 is preferably 1.8 times or less, more preferably 1.4 times or less, and further preferably 1.1 times or less of the area of the release sheet 21. On the other hand, as described above, from the perspective of improving the adhesion between the support 30 and the film substrate 11 at the periphery of the release sheet 21, it is preferred to ensure the width of the peripheral area 8 on the outer side of the peripheral end where the support 30 and the film substrate 11 protrude from the release sheet 21. The protrusion amount of the film substrate 11 from the outer peripheral end of the release sheet 21 is preferably 1 mm or more, more preferably 3 mm or more, and further preferably 5 mm or more.

As long as both the support 30 and the film-like substrate 11 protrude further outward than the outer peripheral end of the release sheet 21, the size of either the support 30 or the film-like substrate 11 may be larger or the sizes of both may be the same. When forming a laminate (e.g., hot pressing) or in the manufacturing step of a printed wiring board, the bonding layer or resin material of the support 30 (e.g., the melt or softened product of the impregnated resin of the prepreg) flows back to the surface of the laminate 100 (the surface of the film-like substrate 11), which may contaminate the printed wiring board or the step as a product. From the perspective of preventing contamination from the support 30, as shown in FIG1 , it is preferred that the outer peripheral end 1 of the film-like substrate 11 protrude further outward than the outer peripheral end 3 of the support 30.

The width of the area 9 where the film substrate 11 protrudes from the outer peripheral end 3 of the support 30 is preferably 1 mm or more, more preferably 3 mm or more, and further preferably 5 mm or more. On the other hand, when the protrusion of the film substrate 11 from the outer periphery of the support 30 (the width of the area 9) is too large, the material loss of the film substrate will increase, which will become a factor of cost increase. In addition, when the protrusion of the film substrate is large, it may sometimes hinder the operation of the laminate. Therefore, the protrusion of the film substrate 11 is preferably 50 mm or less, more preferably 30 mm or less, and further preferably 15 mm or less. The area of the film substrate 11 is preferably 1.3 times or less, 1.2 times or less, and further preferably 1.1 times or less of the area of the support 30.

As described above, a support 30 and a film-like substrate having a larger size than the release sheet 21 are prepared, and the support 30 and the film-like substrate 11 are arranged in a manner of being connected to each other in a region 8 outside the outer peripheral end of the release sheet to be laminated and integrated. Alignment holes can be pre-formed on the support 30, the release sheet 21, and the film-like substrate 11, respectively, and positioning can be performed by pins or the like.

The support 30, release sheet 21 and film substrate 11 can be subjected to surface treatment such as plasma treatment or corona treatment on one or both sides before lamination. By performing surface treatment, the adhesion between the layers can be improved.

In the lamination integration of the support 30, the release sheet 21 and the film-like substrate 11, methods such as heat pressing, vacuum pressing, roll pressing, and vacuum lamination can be applied. During lamination, it is preferred to adopt a method that can connect the support 30 and the film-like substrate 11 in the peripheral area 8. The lamination method or conditions can be selected according to the bonding material of the support 30. For example, when the support 30 is a prepreg commonly used in the manufacture of printed wiring boards, the support 30 and the film-like substrate 11 are firmly bonded (fused) in the peripheral area 8 by performing heat pressing at about 200°C for about 1 hour.

In the laminate 100, since the film substrate 11 is fixed to the outer peripheral region 8 of the rigid support 30, the operability is excellent when processing such as patterning (circuit formation) of the conductive layer provided on the surface of the film substrate 11 (the surface not in contact with the release sheet 21) or forming an insulating layer.

In the manufacturing process of the printed wiring board, the treatment with the chemical solution is performed in the process of removing slag, forming the conductive layer by wet plating, patterning the conductive layer by etching, developing the insulating layer such as the resist, etc. In the laminate 100, since the support 30 and the film-like substrate 11 are fixed in contact at the peripheral region 8, when the chemical solution treatment is performed by spraying or dipping, the infiltration of the chemical solution from the side surface of the laminate 100 to the region 7 of the inner center portion of the surface can be suppressed. Therefore, the peeling of the release sheet 21 and the film-like substrate 11 at the laminate interface caused by the infiltration of the chemical solution can be suppressed. Furthermore, since the chemical solution is prevented from contacting the release sheet 21, the heat-resistant film or adhesive layer constituting the release sheet 21 can be prevented from being corroded by the chemical solution. Therefore, in addition to suppressing the peeling at the lamination interface, it can also prevent the chemical solution from being contaminated by the dissolution of the constituent material of the release sheet 21.

Since the release sheet 21 is disposed between the support 30 and the film substrate 11 in the central region 7 of the laminate 100, even when the bonding material of the support 30 is melted or softened by heat pressing, it will not adhere to the film substrate. Therefore, after the laminate is processed such as forming a circuit or forming an insulating layer, the release sheet 21 can be easily peeled off from the film substrate 11.

From the perspective of improving the operability in steps such as forming a circuit or forming an insulating layer, in the laminate 100, in addition to making the support 30 and the film-like substrate 11 contact each other in the peripheral area 8, it is preferred that the film-like substrate 11 is closely laminated on the support 30 in the area 7 where the release sheet 21 is provided. For example, if the release sheet 21 has close contact with the support 30 and the film-like substrate 11, the film-like substrate 11 is closely laminated on the support 30 via the release sheet 21 in the area 7.

As shown in FIG3 , an opening 5 is provided on the release sheet 21, and the support 30 and the film-like substrate 11 can be in contact with each other in the area where the opening 5 is provided. In the area where the opening 5 is provided, the support 30 and the film-like substrate 11 are in contact with each other as in the peripheral area 8, so the film-like substrate 11 is also fixed on the support 30 in the area 7, thereby improving the operability during processing. In particular, when the area of the laminate 101 (area of the release sheet) is large, or when the adhesion of the release sheet 21 to the film-like substrate 11 is low, it is more effective to make the support 30 and the film-like substrate in contact with each other through the opening 5 provided on the release sheet 21.

When the opening 5 is provided on the release sheet 21, the shape and size of the opening, the number of the openings, etc. are not particularly limited. When the size of the opening 5 is relatively large, since the contact area between the support 30 and the film-like substrate 11 is relatively large, it is sometimes difficult to separate the film-like substrate 11 from the laminate after processing such as circuit formation. Therefore, the area of one opening is preferably ¹⁰⁰⁰ mm2 or less, more preferably ⁵⁰⁰ mm2 or less, further preferably ³⁰⁰ mm2 or less, and may also be 100 ^mm2 or less or ⁵⁰ mm2 or less. On the other hand, from the viewpoint of fixing the film-like substrate 11 on the support 30 at the opening forming portion, the area of one opening is preferably 1 ^mm2 or more, and more preferably 5 ^mm2 or more. The area ratio (opening ratio) of the opening forming portion in the release sheet 21 is preferably 10% or less, more preferably 5% or less, and further preferably 3% or less. The opening ratio may also be 0.1% or more, 0.3% or more, or 0.5% or more.

As shown in FIG. 4 , the laminate 102 can laminate the release sheet 21 and the film substrate 11 on one main surface of the support 30, and laminate the release sheet 22 and the film substrate 12 on the other main surface of the support 30. Since the release sheet and the film substrate are laminated on both surfaces of one support, the processing of two film substrates 11 and 12 can be performed using one laminate 102, so it can be expected that the material utilization efficiency and production efficiency will be improved. In addition, since the two main surfaces of the support 30 are covered with the film substrate, when the support uses a material with adhesive properties such as a prepreg, contamination of the step can also be prevented.

As shown in FIG. 5 , a release sheet 21 and a film-like substrate 11 may be laminated on one main surface of a support 30, and a protective sheet 42 may be laminated on the other surface so as to cover the entire surface of the support 30. The protective sheet 42 may protrude further outward than the outer peripheral end of the support 30. In the laminate 103, since one main surface of the support 30 is covered by the film-like substrate 11 and the other main surface is covered by the protective sheet 42, contamination of the step can be prevented even when the support uses a material having adhesive properties such as a prepreg.

As the protective sheet 42, a material having excellent heat resistance and chemical resistance and capable of being bonded to the support 30 is used. The protective sheet 42 may be rigid or flexible. As the material of the protective sheet 42, glass or resin material may be listed. As the resin material, the material exemplified as the insulating resin film of the film-like substrate 11 or the material of the heat-resistant resin film of the release sheet 21 is suitable.

[Manufacturing of printed wiring boards]

The above-mentioned multilayer body can be applied to the manufacture of the following printed wiring boards, in which a circuit including a patterned metal conductor is provided on one or both main surfaces of an insulating resin film included in a film-like substrate of the printed wiring board. Examples of printed wiring boards having a circuit provided on the main surface of an insulating resin film include: multi-layer printed wiring boards, rigid-flex composite wiring boards, single-sided flexible printed circuit boards, double-sided flexible printed circuit boards, etc.

In the manufacturing step of a printed wiring board using a laminate, a circuit is formed on an insulating resin film of a film-like substrate (first circuit forming step). In the laminate, since the film-like substrate 11 is laminated on the rigid support 30 via the release sheet 21, the circuit can be formed using an apparatus for processing a rigid substrate. Therefore, a narrow pitch circuit equivalent to that of a rigid printed wiring board can be formed on the main surface of the flexible insulating resin film. After the circuit is formed on the insulating resin film, the film-like substrate 11 (insulating resin film provided with the circuit) is separated from the support 30 and the release sheet 21 (separation step).

When a conductive layer is provided on the insulating resin film of the film-like substrate 11, a circuit is formed by using the conductive layer of the film-like substrate by a subtractive method, an additive method, etc. On the conductive layer pre-set on the film-like substrate 11, a conductive layer is further formed by electrolytic plating, etc. When the film-like substrate 11 includes an insulating resin film and has a conductive layer, a conductive layer is formed on the main surface of the insulating resin film, and a circuit is formed by a subtractive method, an additive method, etc.

Below, we will provide an overview of each step in the manufacture of printed wiring boards.

<Conductor layer formation step>

When no conductive layer is provided on the first main surface (the main surface on the opposite side of the release sheet 21) of the film-like substrate 11, a conductive layer is formed on the insulating resin film by electroless plating. A conductive layer can also be provided by laminating a metal foil such as copper foil on the insulating resin film. When the film-like substrate 11 has a conductive layer, it is not necessary to form a conductive layer, but a conductive layer can be formed on the conductive layer previously provided on the insulating resin film by electrolytic plating. When a hole is provided on the film-like substrate 11, in addition to the first main surface of the film-like substrate 11, metal can also be precipitated on the wall surface of the hole to make it conductive. After the film-like substrate is opened, a slag removal treatment can be performed as needed.

As electroless plating, there are: wet electroless plating, sputtering, evaporation, ion plating, CVD, etc. The type of electroless plating can be appropriately selected according to the compatibility with the film substrate, the specifications of the printed wiring board, etc. If the general printed wiring board manufacturing steps and equipment are considered, wet electroless copper plating is preferred. As the metal types deposited by electrolytic plating, there are: copper, gold, silver, zinc, nickel, chromium, various alloys (for example, solder, tin-silver, tin-zinc, etc.), etc. In the manufacture of printed wiring boards, copper is generally preferred. The thickness of the conductor layer is not particularly limited and can be set according to the specifications of the printed wiring board, etc.

<Circuit formation steps>

A circuit is formed on the insulating resin film using a conductive layer pre-set on the film substrate 11 or a conductive layer formed in the conductive layer forming step. For example, a predetermined portion of the circuit is selectively coated with an anti-etching agent, and the conductive layer in the area not coated with the anti-etching agent is dissolved with a chemical solution (etching liquid) to form a circuit (subtractive method). It is also possible to selectively coat the predetermined portion that will become the non-circuit forming portion (the distance between circuits) with an anti-plating agent, perform pattern plating by electrolytic plating with a conductive layer as a feeding layer, then peel off the anti-etching agent, and remove the exposed feeding layer by etching to form a circuit (semi-additive method). The circuit formation method can be appropriately selected according to the specifications of the printed wiring board to be manufactured.

In the formation of circuits, various chemical solutions are used in the formation of conductive layers using wet methods such as wet electroless plating or electrolytic plating, development during patterning with an anti-etchant, patterning of conductive layers using etching, stripping of anti-etchants, and etching of feed layers after patterning. If these chemical solutions penetrate into the laminated interface between the film substrate and the release sheet, there is a possibility that the film substrate will be peeled off from the laminated body. In addition, when an adhesive layer is provided on the release sheet, there is concern about the contamination of the chemical solution due to the mixing of adhesive dissolved in the chemical solution.

In the above-mentioned laminate, the support 30 is in contact with the film substrate 11 at the periphery of the release sheet 21, and the peripheral end (end face) 2 of the release sheet 21 is not exposed. Therefore, the infiltration of the chemical solution into the end face of the release sheet 21 and the laminated interface between the release sheet 21 and the film substrate 11 can be suppressed, and the peeling of the film substrate or the contamination of the steps in the process of circuit formation can be prevented.

<Separation steps>

After forming the circuit on the first main surface of the insulating resin film, the film substrate 11 (insulating resin film with the circuit) is separated from the laminate. The film substrate 11 and the support 30 can be separated by cutting off the peripheral area 8 where the two are connected. For example, the peripheral part is cut off by cutting the laminate along the C1 line, C2 line, C3 line and C4 line in Figure 2. The cutting method can be appropriately selected according to the material of the support 30 and the film substrate 11, and can be applied to milling processing, mold processing (pressing), etc.

When separating, it is not necessary to completely cut off the outer peripheral portion. For example, the film substrate can be cut in half along the outer peripheral portion. Alternatively, the film substrate 11 can be separated from the portion where the film substrate 11 is connected to the support.

Since the adhesion between the film substrate 11 and the release sheet 21 at the interface is relatively small, it is easy for the laminated interface between the two to peel off, and it is difficult for the second main surface (the main surface opposite to the circuit forming surface) of the film substrate 11 to be contaminated by the release sheet 21.

According to the above process, a printed wiring board having a first circuit formed on the first main surface of the insulating resin film is obtained. Another insulating layer can be further laminated on the first main surface of the insulating resin film having the first circuit formed thereon, and a second circuit can be formed, thereby achieving multi-layering. Furthermore, after separating the film substrate from the laminate, a third circuit can also be formed on the second main surface of the film substrate (insulating resin film).

<Multi-layered>

Multi-layering can be performed according to the common process of printed wiring boards. For example, an insulating layer is formed on the first main surface of the insulating resin film provided with the first circuit, a hole is formed through the insulating layer, and then a second circuit is formed on the insulating layer. Multi-layering of more than three layers can be performed by repeatedly forming an insulating layer on the circuit, forming a hole, and forming a circuit.

(Formation of insulating layer)

Materials for the insulating layer include: prepregs, bonding sheets containing thermosetting resins, ink materials of thermosetting or photosetting resins, thermosetting build-up films, laminates with a bonding layer provided on the non-forming surface of the copper layer of a single-sided copper foil laminate, etc. Prepregs, sheets, and film-like materials can be laminated by heat pressing, roll pressing, vacuum lamination, etc. Ink-like materials can form an insulating layer by printing, curtain coating, etc. Metal foil can also be laminated when forming the insulating layer.

(Opening holes and conducting)

The holes in the insulating layer can be formed by laser drilling, mechanical drilling, etc. The holes in the insulating layer can also be opened by plasma irradiation, chemical etching, etc. In addition to the insulating layer, the holes can also be opened by penetrating the film substrate, and the holes can also be opened by penetrating more than two insulating layers.

After the hole is formed, the wall surface of the hole is made conductive. Conductivity is performed, for example, by electroless plating. Electroless plating can be wet plating or dry plating (PVD or CVD), and can be appropriately selected according to the material or thickness of the insulating layer, the specifications of the printed wiring board, etc. If the general printed wiring board manufacturing steps and equipment are considered, wet electroless copper plating is preferred. Conductive paste can also be printed in the hole to make it conductive.

(Formation of conductive layer)

The method for providing the conductor layer for forming the second circuit on the insulating layer is not particularly limited, and may be appropriately selected from electroless plating, electrolytic plating, or a combination of electroless plating and electrolytic plating. Considering the steps and equipment for manufacturing a general printed wiring board, wet electroless copper plating is preferred. When forming the conductor layer on the insulating layer, metal may be deposited on the wall surface of the hole provided in the insulating layer to make it conductive. When a laminate having a conductive layer on the surface of an insulating layer is used, for example, a laminate having a metal foil laminated thereon via a single-sided copper foil laminate, a prepreg, or a bonding sheet, the conductive layer of the laminate can be used to form a second circuit.

(Formation of the second circuit)

A second circuit is formed on the insulating layer using a conductive layer disposed on the insulating layer. The method for forming the second circuit is not particularly limited, and can be formed in the same manner as the first circuit, using a subtractive method, a semi-additive method, etc.

The multi-layering on the first main surface of the film-like substrate can be implemented before or after the above-mentioned separation step. In the case of multi-layering before the separation step, the second circuit can be formed using an apparatus for processing a rigid substrate in the same manner as the first circuit forming step. In the case of using a rigid material as an insulating layer, since the substrate has rigidity after separation from the support 30, even after the separation step, the second circuit can be formed using an apparatus for processing a rigid substrate in the same manner as the first circuit forming step. The support 30 and the release sheet 21 can be separated in the middle of the multi-layering. For example, a rigid insulating layer may be provided behind the first main surface of the film-like substrate 11 to ensure rigidity, and then the separation step may be performed before opening holes or forming circuits.

<Third circuit formation step>

After the release sheet 21 is peeled off from the second main surface of the film-like substrate 11 by the separation step, a third circuit can be formed on the second main surface of the film-like substrate 11. The method for forming the third circuit can be implemented by an appropriate method in the same manner as the formation of the first circuit and the second circuit described above. For example, a conductive layer is formed on the second main surface of the insulating resin film, and the conductive layer is patterned to form a circuit. The conductive layer can also be used as a feed layer to form a circuit by pattern coating. When a conductive layer is pre-set on the second main surface of the film-like substrate 11, the conductive layer can be used to form the third circuit.

A hole penetrating the film substrate 11 (insulating resin film) can be formed before or after the formation of the third circuit. When an insulating layer is formed on the first main surface of the insulating resin film to form a multilayer, a hole can be opened in a manner that penetrates the insulating layer in addition to the film substrate 11. After the hole is opened, the conductor is made by electroless plating or printing of conductive paste.

Before forming the third circuit, when an insulating layer is formed on the first main surface of the insulating resin film to form a multilayer structure, since the substrate has rigidity, the third circuit can be formed using a device for processing a rigid substrate in the same manner as the above-mentioned first circuit formation step.

After the film substrate 11 (insulating resin film) after the first circuit is formed is separated from the support 30 and the release sheet 21, a rigid support can be laminated on the first main surface (first circuit forming surface) of the film substrate 11 to form a laminate. By using this laminate, the device for processing a rigid substrate can be applied to the formation of the third circuit on the second main surface in the same way as the formation of the first circuit on the first main surface, so it is easier to narrow the pitch of the circuit.

Similar to the formation of the above-mentioned laminate 100, a release sheet may be arranged between the film substrate and the support, and the laminate may be formed by heat pressing or the like in a state where the film substrate and the support protrude outward from the outer peripheral end of the release sheet. By forming such a laminate, in the formation of the third circuit, similar to the formation of the first circuit, it is possible to prevent peeling caused by the infiltration of the chemical solution into the laminate interface or contamination of the chemical solution by dissolved substances.

If a laminate 100 in which the second main surface of the film-like substrate is laminated is used as the support side, a first circuit is formed on the first main surface, and after the separation step, a laminate is formed in which the first main surface of the film-like substrate is formed as the support side, and a third circuit is formed on the second main surface, a double-sided flexible printed circuit board having circuits on both sides of the insulating resin film can be formed.

[Implementation example]

The following are examples and comparative examples to explain the present invention in more detail, but the present invention is not limited to the following examples.

[Implementation Example 1]

A FR-4 prepreg "GEA-67N" (thickness 150μm) manufactured by Hitachi Chemical was used as a support, a heat-resistant micro-adhesive film ("LIOELM LE951" manufactured by TOYOCHEM) having a 10μm thick acrylic micro-adhesive layer provided on one side of a 50μm thick polyethylene terephthalate (PET) film was used as a release sheet, and the following double-sided copper foil laminate was used as a film substrate. The double-sided copper foil laminate was formed by hot laminating an electrolytic copper foil "HD2" manufactured by Fukuda Metal on a polyimide film ("Pixeo FRS25" manufactured by Kaneka) having a total thickness of 25μm and a thermoplastic polyimide bonding layer provided on both sides of a polyimide core layer. The support is cut into a size of 120mm×120mm, the release sheet is cut into a size of 100mm×100mm, the film substrate is cut into a size of 140mm×140mm, the support protrudes from the outer periphery of the release sheet by 10mm, and the film substrate protrudes from the outer periphery of the release sheet by 20mm. The positional relationship is adjusted, and the support, release sheet, and film substrate are overlapped in this order. The release sheet is arranged in a manner such that the adhesive layer forming surface is in contact with the film substrate.

The laminate is obtained by laminating using a hot press at 180°C/3MPa/60 minutes. The laminate has sufficient rigidity for operation in a rigid printed wiring board manufacturing device, wherein the release sheet is in close contact with the film substrate in the area where the release sheet is arranged, and the film substrate is fixed on the support body via the release sheet. In the 10mm wide frame-shaped area outside the outer periphery of the release sheet, the support body and the film substrate are firmly connected.

The above-mentioned laminate was used for slag removal under the conditions shown in Table 1 and for wet electroless copper plating under the conditions shown in Table 2. A copper plating film was formed on the copper foil of the film-like substrate. In addition, there was no chemical solution infiltration around the laminate, and no abnormalities such as peeling between layers were observed.

<Deslagging treatment>

<Wet electroless copper plating treatment>

After using scissors to cut off the frame-shaped connecting part on the periphery of the laminate, it was found that the interface between the release sheet and the film substrate could be peeled off well, and no abnormalities such as contamination were found on the contact surface between the film substrate and the release sheet.

[Example 2]

In Example 1, except that the release sheet was changed to a 25μm thick fluorine resin film ("Aflex 25N NT" manufactured by Asahi Glass), a laminate was formed, and a slag removal treatment and a wet electroless copper plating treatment were performed. In Example 2, a copper plating film was formed on the copper foil of the film substrate in the same manner as in Example 1. There was no chemical solution infiltration on the periphery of the laminate, and no abnormalities such as peeling between layers were observed. After the frame-shaped connecting part on the periphery of the laminate was cut off with scissors, it was found that the interface between the release sheet and the film substrate could be well peeled, and no abnormalities such as contamination were observed on the contact surface between the film substrate and the release sheet.

[Comparison Example 1]

The laminate was formed in the same manner as in Example 1 except that the size of the release sheet was changed to 120 mm × 120 mm (the same size as the support) and the release sheet was arranged to cover the entire surface of the support. In the obtained laminate, the release sheet was firmly attached to the entire surface of the support, and the release sheet was in close contact with the film-like substrate. The laminate was used to perform the deslagging treatment and wet electroless copper plating treatment in the same manner as in Example 1, and it was found that the chemical solution infiltrated the adhesive of the release sheet at the periphery and near the periphery of the release sheet, and the film-like substrate was peeled off from the release sheet. In this case, it is believed that the contamination of the chemical solution was caused by the adhesive infiltrated by the chemical solution being mixed into the chemical solution.

[Comparison Example 2]

The laminate was formed in the same manner as in Example 2 except that the size of the release sheet was changed to 120 mm × 120 mm (the same size as the support) and the release sheet was arranged to cover the entire surface of the support. Regarding the obtained laminate, the release sheet was firmly attached to the entire surface of the support, but the adhesion between the release sheet and the copper foil of the film-like substrate was not sufficient. Using the laminate, after the deslagging treatment and wet electroless copper plating treatment were carried out in the same manner as in Examples 1 and 2, it was found that peeling occurred from the periphery. It is believed that the reason is that the chemical solution penetrated into the interface between the release sheet and the film-like substrate.

According to the results of the above-mentioned embodiments and comparative examples, it can be seen that by using a laminate in which the size of the support (prepreg) and the film substrate (copper foil laminate) is larger than the size of the release sheet, and the support and the film substrate are connected in the peripheral frame-shaped area, the infiltration of the chemical solution into the laminate interface during the manufacturing step of the printed wiring board can be blocked, thereby preventing the interface from peeling off or the contamination of the chemical solution.

1: Peripheral end

2: Peripheral end

3: Peripheral end

7: Region

8: Peripheral area

9: Region

11: Film substrate

21: Release film

30: Support body

100: Layered body

Claims (13)

A method for manufacturing a laminate, wherein the laminate is sequentially laminated with: a rigid support body, which includes a prepreg having a first main surface and a second main surface; a release sheet, which has a first main surface and a second main surface; and a flexible film-like substrate, which has a first main surface and a second main surface; the film-like substrate includes a flexible insulating resin film, and the method for manufacturing the laminate comprises: preparing a laminate, wherein the release sheet and the film-like substrate are sequentially arranged on the first main surface of a semi-hardened prepreg, and the prepreg is The first main surface of the prepreg is in contact with the second main surface of the release sheet, the first main surface of the release sheet is in contact with the second main surface of the film-like substrate, the outer periphery of the prepreg protrudes outwards more than the outer periphery of the release sheet, and the outer periphery of the film-like substrate protrudes outwards more than the outer periphery of the release sheet; by heat pressing the laminate, the impregnated resin of the prepreg is heated and hardened, and the first main surface of the prepreg is in contact with the second main surface of the film-like substrate in a region outside the outer periphery of the release sheet. The method for manufacturing a laminate as claimed in claim 1, wherein an opening is provided on the release sheet, and the first main surface of the support and the second main surface of the film-like substrate are bonded to each other by heat pressing, except for the area outside the periphery of the release sheet, at the portion where the opening is provided on the release sheet. A method for manufacturing a laminate as claimed in claim 1 or 2, wherein the outer periphery of the film-like substrate protrudes further outward than the outer periphery of the support. A method for manufacturing a laminate as claimed in claim 1 or 2, wherein the insulating resin film is a polyimide film. A method for manufacturing a laminate as claimed in claim 1 or 2, wherein the film-like substrate comprises the insulating resin film. A method for manufacturing a laminate as claimed in claim 1 or 2, wherein a metal conductor layer is provided on at least one main surface of the insulating resin film of the film-like substrate. A method for manufacturing a printed wiring board, which has a circuit including a metal conductor on an insulating resin film, the method comprising: a first circuit forming step, which is to form a first circuit on the first main surface of the insulating resin film of a laminated body manufactured by the method of any one of claims 1 to 6; and a separation step, which is to separate the insulating resin film provided with the first circuit from the support and the release sheet. The method for manufacturing a printed wiring board as claimed in claim 7 has a multi-layering step, wherein an insulating layer covering the first main surface of the insulating resin film and the first circuit is provided, and a second circuit is formed on the insulating layer. The method for manufacturing a printed wiring board as claimed in claim 7 or 8 has a third circuit forming step, wherein the third circuit forming step is to form a third circuit on the second main surface of the insulating resin film after the separation step. A method for manufacturing a printed wiring board as claimed in claim 7 or 8, wherein in the first circuit forming step, the circuit is formed by etching the metal conductor layer on the first main surface of the insulating resin film. A method for manufacturing a printed wiring board as claimed in claim 7 or 8, wherein in the first circuit forming step, a circuit is formed by coating a pattern on the first main surface of the insulating resin film. A method for manufacturing a printed wiring board as claimed in claim 7 or 8, wherein before the first circuit formation step, a metal conductor layer is formed by performing wet or dry electroless plating on the first main surface of the insulating resin film. A method for manufacturing a printed wiring board as claimed in claim 7 or 8, wherein in the above separation step, the outer peripheral portion where the above support and the above film-like substrate are connected is cut off from the above laminate.