Material for printed wiring board and method for manufacturing printed wiring board

Abstract

The material (10) for a printed wiring board is obtained by sequentially laminating, on at least one surface (11a) of a metal foil (11), at least a catalyst layer (12) and an adhesive layer (13) containing a polyimide resin, wherein the polyimide resin is obtained by copolymerizing an acid dianhydride containing a bisphenol diether acid dianhydride and a diamine compound.

Description

Technical Field

[0001] This disclosure relates to a material for printed circuit boards and a method for manufacturing a printed circuit board made from the material. Background Technology

[0002] Commercially available printed circuit boards (PCBs) typically use rigid substrates, multilayer substrates, or flexible PCBs. These boards typically have a catalyst layer on the surface of a resin-based substrate and a copper-plated layer with circuit patterns on its surface. With the increasing speed of processing electronic components such as semiconductor chips, there is a growing demand for finer lines in PCBs, requiring high manufacturing efficiency for PCBs with such fine line structures.

[0003] For example, Patent Document 1 discloses a method in which a catalyst material is supported on the surface of a metal foil, the side of the metal foil supporting the catalyst material is bonded to a substrate of a circuit board, and then the metal foil is removed to allow the catalyst material to be laminated onto the substrate. By further plating copper on the catalyst material laminated on the substrate and performing patterning, a printed circuit board with a circuit pattern can be obtained efficiently. However, in this method, if the adhesion between the copper plating layer and the substrate is weak during the patterning process for forming the circuit, the copper plating layer may peel off during processing, resulting in a lower yield. In Patent Document 1, the embossing provided on the metal foil is transferred to the surface of the substrate, and the anchoring effect of this embossing improves the adhesion between the copper plating layer and the substrate.

[0004] Existing technical documents Patent documents Patent Document 1: International Publication No. 2021 / 163440 Summary of the Invention -The technical problem the invention aims to solve- However, in applications requiring high-frequency characteristics, the skin effect occurs, where the electrical signals passing through the circuit are more concentrated near the surface. Therefore, a high degree of smoothness is required at the interface between the copper plating layer forming the circuit and the substrate. In other words, in the technology of Patent Document 1, to improve adhesion, unevenness must be provided at the interface; on the other hand, to improve high-frequency characteristics, a high degree of smoothness at the interface must be ensured. These two aspects are contradictory, and this is the problem.

[0005] Therefore, the object of this disclosure is to provide a material for printed circuit boards and a method for manufacturing a printed circuit board made from the material, wherein the material can provide a printed circuit board that has sufficient adhesive strength at the interface even without forming unevenness at the interface between the copper plating layer and the substrate.

[0006] - Technical solutions used to solve technical problems - The inventors of this application have discovered through in-depth research that when manufacturing printed circuit boards using materials for printed circuit boards, if an adhesive layer containing a specific polyimide resin is applied to the interface between the copper plating layer and the substrate, sufficient adhesion can be ensured even without creating unevenness at the interface.

[0007] In other words, one aspect of the printed circuit board material disclosed herein is made by sequentially laminating a catalyst layer and an adhesive layer containing a polyimide resin on at least one side of a metal foil, said polyimide resin being made by copolymerizing an acid dianhydride containing bisphenol diether type acid dianhydride (sometimes referred to as "specific acid dianhydride" in this specification) and a diamine compound.

[0008] -The effects of the invention- If the adhesive layer of the printed circuit board material of this disclosure is bonded together with the substrate and the metal foil is removed, the exposed catalyst layer is copper-plated and patterned, a printed circuit board can be obtained. In the obtained printed circuit board, an adhesive layer containing the aforementioned polyimide resin is formed at the interface between the copper plating layer and the substrate. Moreover, since chemical bonds are formed between the polyimide resin in the copper plating layer and the adhesive layer, and between the polyimide resin and the substrate, the copper plating layer adheres to the substrate with strong adhesive strength. In other words, if the printed circuit board material of this disclosure is used, it is not necessary to form unevenness at the interface between the copper plating layer and the substrate to obtain an anchoring effect, and a printed circuit board with both high smoothness and high adhesion at the interface can be obtained. Attached Figure Description

[0009] Figure 1 A schematic cross-sectional view of the materials used in printed circuit boards.

[0010] Figure 2 A flowchart illustrating one example of a method for manufacturing a printed circuit board. Detailed Implementation

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following description of preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0012] <Materials for Printed Circuit Boards and Printed Circuit Boards> like Figure 1As shown, the printed circuit board material 10 of this embodiment includes a metal foil 11, a catalyst layer 12, and an adhesive layer 13. Specifically, the printed circuit board material 10 is formed by sequentially laminating a catalyst layer 12 and an adhesive layer 13 containing polyimide resin onto at least one side 11a of the metal foil 11. It should be noted that the catalyst layer 12 and the adhesive layer 13 may also be disposed on the other side 11b of the metal foil 11. The printed circuit board material 10 may also include, for example, a substrate 21, which is further laminated on the side of the adhesive layer 13 where the catalyst layer 12 is not present (see reference...). Figure 2 (c)).

[0013] Material 10 for printed circuit boards is used to manufacture printed circuit boards 20 (see reference). Figure 2 (f) The material used in this process. The adhesive layer 13 and the substrate 21 for the printed circuit board are bonded together, and the metal foil 11 is removed. The exposed catalyst layer 12 is then copper-plated and processed into a circuit pattern shape, thereby obtaining the printed circuit board 20, as detailed later. In other words, in this disclosure, the material 10 for the printed circuit board can also be described as the material used to transfer the catalyst layer 12 and the adhesive layer 13 onto the substrate 21 for the printed circuit board.

[0014] The following is a detailed description of the printed circuit board material 10 and the printed circuit board 20 and their constituent materials.

[0015] [Metal foil] The metal foil 11 serves as a support material for holding the catalyst layer 12 and the adhesive layer 13. The metal foil 11 is to be removed during the manufacturing process of the printed circuit board 20 and is not included in the printed circuit board 20 as the final product. Therefore, the metal foil 11 is also referred to as sacrificial transfer foil.

[0016] The type of metal foil 11 is not particularly limited, for example, aluminum foil, aluminum alloy foil, copper foil and tin foil with a thickness of 5μm or more and 200μm or less can be used appropriately.

[0017] One surface 11a of the metal foil 11 can be provided with concave and convex features to improve the adhesion strength between the copper plating layer 22 and the substrate 21, but it can also be left unprovided with concave and convex features.

[0018] From the viewpoint of ensuring that the printed circuit board, as the final product, has excellent high-frequency characteristics, the smoothness of one surface 11a of the metal foil 11 can be very high. In this case, the surface roughness Ra of the metal foil 11 can be, for example, 0.4 μm or less, preferably 0.2 μm or less. There is no particular limitation on the lower limit of the surface roughness Ra of the metal foil 11, and for example, a metal foil with a surface roughness Ra of 6 nm or more can be appropriately used.

[0019] In this specification, "surface roughness Ra" refers to the arithmetic mean roughness Ra defined in Japanese Industrial Standard JIS B0601 (1982 edition). It should be noted that when aluminum foil is used as the metal foil 11, the "surface roughness Ra" of the aluminum foil can also be expressed as a value calculated by three-dimensionally expanding the arithmetic mean roughness Ra defined in Japanese Industrial Standard JIS B0601 (1982 edition) in a manner applicable to the surface.

[0020] When using aluminum foil as metal foil 11, the following aluminum foil can be used: the proportion of the total surface area of ​​the crystals present in the predetermined surface area is less than 2%, and the average surface area of ​​each crystal is 2 μm. 2 Hereinafter, the surface roughness Rz in the direction perpendicular to the rolling direction is 40 nm or less, and the surface roughness Ra is 10 nm or less (refer to WO2015 / 019960). Because this aluminum foil has high smoothness, the catalyst layer can be transferred to the substrate in a highly smooth state. That is, by stacking a copper plating layer on this catalyst layer, a printed circuit board with a highly smooth interface between the copper plating layer and the substrate can be manufactured. It should be noted that the surface roughness Ra and Rz of the aluminum foil can be determined, for example, using the same method as described in paragraph 0049 of WO2015 / 019960. That is, the surface shape of the aluminum foil can be observed using an atomic force microscope (e.g., a Nanopics 1000 scanning probe microscope manufactured by Nippon Seiko Instruments Co., Ltd.), using a damped (non-contact) method within a rectangular field of view of a specified size, such as 80 μm × 80 μm. Based on the observed results, the tilt of the sample was corrected using a cubic surface automatic tilt correction method that utilizes the least squares approximation to calculate and fit the surface. The surface roughness Ra and the surface roughness Rz in the width (TD) direction perpendicular to the rolling direction were measured. The surface roughness Ra was calculated by three-dimensionally expanding the arithmetic mean roughness Ra defined in Japanese Industrial Standard JIS B0601 (1982 edition) in a manner applicable to the entire observed surface, as described above. The surface roughness Rz in the width (TD) direction was measured using the evaluation method based on Japanese Industrial Standard JIS B0601 (1982 edition) to measure the two-dimensional Rz value of a cross-section in any width (TD) direction within the same field of view.

[0021] The surface of the metal foil 11 can be very smooth, but it is not excluded that the surface may have irregularities. In this case, the surface roughness Ra of the metal foil 11 can exceed 0.4 μm. There are no particular limitations on the method of creating irregularities on the surface of the metal foil 11, and generally known methods can be used.

[0022] [Catalyst layer] Catalyst layer 12 is a layer containing the catalyst for electroless copper plating, which will be described later.

[0023] The catalyst used for catalyst layer 12 is not particularly limited; any generally known catalyst can be used as long as it can form a copper plating layer on the surface. Specifically, as a catalyst, at least one selected from the group consisting of palladium, platinum, gold, and copper can be used. More preferably, palladium is used as the catalyst because if palladium is used, surface oxidation is less likely to occur, the catalytic activity is high, and a plating layer can be formed even in small amounts.

[0024] There is no particular limitation on the thickness (layer thickness) of the catalyst layer; a thickness range of more than 1 nm and less than 1 μm can be appropriately selected.

[0025] [Adhesive layer] The adhesive layer 13 is used to improve the adhesion between the copper plating layer 22 and the substrate 21 in the printed circuit board 20, which is the final product.

[0026] The adhesive layer 13 contains polyimide resin and any additives.

[0027] (Polyimide resin) Polyimide resins contain building blocks derived from dianhydrides of specific acids.

[0028] In other words, polyimide resin is made by copolymerizing (A) acid dianhydride and (B) diamine compound, where (A) acid dianhydride contains (A1) specific acid dianhydride and any acid dianhydride other than (A2) specific acid dianhydride.

[0029] (A) Acid dianhydride Acid dianhydrides only need to contain a specific acid dianhydride (A1), there are no special restrictions.

[0030] Acid dianhydrides can be formed from only a specific acid dianhydride (A1), or from acid dianhydrides other than a specific acid dianhydride (A1) and a specific acid dianhydride (A2).

[0031] (A1) Specific acid dianhydrides The specific acid dianhydride is a bisphenol diether type acid dianhydride. As a bisphenol diether type acid dianhydride, there are no particular restrictions as long as it has a bisphenol diether structure. Examples include: 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (hereinafter also called BisDA), 4,4'-(4,4'-methylenediphenoxy)bis(phthalic anhydride), 4,4'-(4,4'-hexafluoroisopropylidenediphenoxy)bis(phthalic anhydride), etc.

[0032] [Chemical Formula 1]

[0033] By incorporating ether groups in the bisphenol diether dianhydride, the flexibility of the polyimide resin is improved. Even with a high degree of smoothness at the interface between the copper plating layer 22 and the substrate 21 (and a low surface roughness Ra of the metal foil 11), an improved adhesion due to the anchoring effect can be expected. Furthermore, the presence of bisphenol groups enhances toughness, thus enabling good adhesion even in thin films. The presence of both a framework and a flexible, resilient coating film allows for further improvement in interfacial adhesion.

[0034] In order to obtain a soft and tough coating with improved adhesion, the content of the specific dianhydride in the total dianhydride is preferably 30% by mass or more, more preferably 40% by mass or more, and particularly preferably 50% by mass or more.

[0035] A specific acid dianhydride can be used alone or in combination with two or more.

[0036] (A2) Acid dianhydrides other than specific acid dianhydrides There are no particular limitations on the acid dianhydrides other than the specific acid dianhydrides mentioned above, as long as they are not among the specific acid dianhydrides mentioned above, preferably tetracarboxylic dianhydrides.

[0037] Other dianhydrides besides specific acid dianhydrides include, for example: 3,4,3',4'-biphenyltetracarboxylic dianhydride (BPDA), 1,1'-dicyclohexane-3,3',4,4'-tetracarboxylic acid-3,4:3',4'-dianhydride (H-BPDA), pyromellitic dianhydride (PMDA), 4,4'-oxodiphthalic dianhydride (ODPA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride, 5-(2,5-dioxotetrahydrofurfuryl)- 3-Cyclohexene-1,2-dicarboxylic acid dianhydride, ethylene glycol bis(triphenyl) dianhydride, 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, thiophene-2,3,4,5-tetracarboxylic acid dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 2,3,3',4-biphenyltetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, perylene-3,4,9,10-tetracarboxylic acid dianhydride, ethylenetetracarboxylic acid dianhydride, etc. (The structural formulas of some compounds are shown below). It should be noted that only one of the above-mentioned dianhydrides can be used, or two or more can be used in combination.

[0038] [Chemical Formula 2]

[0039] (B) Diamine compounds Diamine compounds are amine compounds that have two amino groups within a single molecule. Aromatic compounds and aliphatic compounds can be listed as diamine compounds, but from the viewpoint of obtaining polyimide films with high mechanical strength, aromatic diamine compounds are preferred.

[0040] Examples of aromatic diamine compounds include: p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4'-diaminobiphenyl, and 5-amino-1-(4'-aminophenyl)-1,3,3-trimethylindene. 6-Amino-1-(4'-aminophenyl)-1,3,3-trimethylindene, 4,4′-diaminobenzoylaniline, 3,5-diamino-3'-trifluoromethylbenzoylaniline, 3,5-diamino-4'-trifluoromethylbenzoylaniline, 3,4′-diaminodiphenyl ether, 2,7-diaminofluorene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4′-methylene-bis(2-chloroaniline), 2,2′,5,5′-tetrafluoroethylene Chloro-4,4'-diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5'-dimethoxybiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,4-bis(4-aminophenoxy) Examples of biphenyls include 4,4-bis(4-aminophenoxy)-biphenyl, 1,3-bis(3-aminophenoxy)benzene (APBN), 9,9-bis(4-aminophenyl)fluorene, 4,4'-(p-phenyleneisopropylidene)bis(aniline), 4,4'-(m-phenyleneisopropylidene)bis(aniline) (Bisaniline M), 4,4'-(p-phenyleneisopropylidene)bis(aniline) (Bisaniline P), 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, and 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]octafluorobiphenyl, etc.

[0041] Preferably, the above-mentioned substances are aromatic diamine compounds having at least one of an ether group and a bisphenol skeleton within their molecules. Specifically, examples of such aromatic diamine compounds include: 4,4′-(m-phenyleneisopropylidene)bis(aniline) (Bisaniline M), 4,4′-(p-phenyleneisopropylidene)bis(aniline) (Bisaniline P), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 1,4-bis(4-aminophenoxy)benzene, and 1,3′-bis(3-aminophenoxy)benzene (APBN), etc. Aromatic diamine compounds that simultaneously possess ether groups and bisphenol skeletons within the molecule are more preferred. Specifically, examples include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

[0042] It should be noted that the above-mentioned aromatic diamine compounds can be used alone or in combination of two or more.

[0043] Preferably, the polyimide resin is a polyurethane-modified polyimide resin (also referred to as "specific polyimide resin" in this specification). More specifically, it is preferably a polyurethane-modified polyimide resin obtained by copolymerizing an acid dianhydride and a diamine compound with an NCO-terminated polyurethane prepolymer. By using the specific polyimide resin in the adhesive layer, a higher adhesive strength can be obtained at the interface between the copper plating layer 22 and the substrate 21. It should be noted that the polyimide resin may also be a mixture of the specific polyimide resin and polyimide resins other than the specific polyimide resin. In this case, the content of the specific polyimide resin in the polyimide resin is not particularly limited, for example, it can be set to 50% by mass or more.

[0044] The adhesive layer 13 may be formed solely of polyimide resin, or it may contain additives other than polyimide resin. Specifically, examples of additives include at least one adhesion-improving additive selected from the group consisting of aminosilanes, epoxysilanes, and triazines. By adding such an additive to the polyimide resin, a higher adhesive strength at the interface between the copper plating layer 22 and the substrate 21 can be obtained. The amount of additive in the adhesive layer 13 is not particularly limited, but is preferably 0.1 parts by weight or more and 10 parts by weight or less, more preferably 0.5 parts by weight or more and 2 parts by weight or less, relative to 100 parts by weight of the polyimide resin. By setting the amount of additive within the above range, a high adhesive strength between the copper plating layer and the substrate can be obtained.

[0045] The content of polyimide resin in the adhesive layer 13 is preferably 90% by mass or more, and more preferably 98% by mass or more.

[0046] There are no particular limitations on the manufacturing method of polyimide resin, and existing known manufacturing methods can be used. Specifically, examples include thermal imidization methods that dehydrate the resin by heating and cause a ring-closing reaction, and chemical imidization methods that use a dehydrating agent.

[0047] (Imide group concentration) The concentration of imide groups in the polyimide resin is preferably 8% or more and 26% or less, more preferably 8.8% or more and 21.1% or less. If the concentration of imide groups is less than 8%, the inherent heat resistance of the polyimide may deteriorate. In addition, if the concentration of imide groups exceeds 26%, the adhesion strength between the copper plating layer and the substrate is low, and the copper plating layer may peel off.

[0048] It should be noted that the concentration of imide groups here is defined by the following formula (1).

[0049] Imide group concentration = (molecular weight of imide group portion: 70.03) ÷ (molecular weight of polyimide repeating unit) x 100···(1) In formula (1), the molecular weight of the imide group is the molecular weight of the (-CO-N-CO-) portion contained in the repeating unit of the polyimide. The molecular weight of each imide group is 70.03.

[0050] The molecular weight of a repeating unit in polyimide is derived from the molecular weight of the acid dianhydride and diamine compounds that make up a repeating unit.

[0051] When there are multiple repeating units in a polyimide, after determining the concentration of imide groups in each repeating unit, the determined concentration of imide groups is multiplied by the proportion of each repeating unit to obtain multiple values. The sum of these multiple values ​​is taken as the concentration of imide groups in the polyimide.

[0052] (weight-average molecular weight) While there is no intention to limit the weight-average molecular weight of the polyimide resin, it is possible, for example, to have a weight-average molecular weight of 5,000 to 1,000,000, preferably 10,000 to 500,000. If the weight-average molecular weight is below the lower limit mentioned above, there is a tendency for the adhesive layer to become brittle, which may prevent sufficient adhesion strength between the copper plating layer and the substrate. On the other hand, if the weight-average molecular weight exceeds the upper limit mentioned above, the solubility in the solvent decreases, and the coatability may decrease.

[0053] It should be noted that the weight-average molecular weight of polyimide resins can be measured using generally known methods such as gel permeation chromatography (GPC).

[0054] [Substrate] The substrate 21 serves as the base of the printed circuit board 20 and is a supporting material that holds the copper plating layer 22 and imparts hardness and strength to the printed circuit board 20.

[0055] The substrate 21 may or may not be included in the printed circuit board material 10. That is, the printed circuit board material 10 can be distributed without the substrate 21. In this case, the printed circuit board manufacturer can bond the printed circuit board material 10 and the desired substrate 21 together, remove the metal foil 11, and laminate the copper plating layer 22 to manufacture the printed circuit board 20. Alternatively, the printed circuit board material 10 can also be distributed with the substrate 21 included. In this case, the printed circuit board manufacturer can remove the metal foil 11 and laminate the copper plating layer 22 to manufacture the printed circuit board 20.

[0056] The substrate 21 can be appropriately selected depending on the type of semiconductor to be mounted and the intended use of the printed circuit board 20 as the final product; its material and size are not limited. Specifically, the material of the substrate 21 can be at least one selected from the group consisting of ceramics, resin, glass, paper, and metals with an insulating layer on the surface. From the viewpoints of strength, insulation, and processability, resin is more preferred, and glass epoxy resin is particularly preferred. Furthermore, the thickness of the substrate 21 is not particularly limited; for example, a substrate with a thickness of 10 μm or more and 10 mm or less can be appropriately used.

[0057] [Copper plating] The copper plating layer 22 acts as a conductor in the printed circuit board 20, serving as a wiring element during semiconductor mounting. In other words, it routes the semiconductor leads (terminals) in a manner that allows them to connect to external wiring or terminals. Since the copper plating layer 22 is formed on the catalyst layer 12, it is stacked over the entire surface of the catalyst layer 12, but is processed into a circuit pattern shape through etching or similar processes. In other words, the copper plating layer 22 is either the entire surface of the catalyst layer 12 or a portion of the catalyst layer 12, formed into a circuit pattern and stacked on the catalyst layer 12.

[0058] The copper plating layer 22 can be formed using generally known methods, but preferably, firstly, the copper plating layer formed by electroless copper plating is further thickened by electrolytic copper plating to obtain a copper plating layer 22 of the desired thickness.

[0059] The thickness of the copper plating layer 22 is not particularly limited, for example, it can be in the range of 10nm or more and 100,000nm or less.

[0060] [Adhesion between the copper plating layer and the substrate] In the printed circuit board 20, the peel strength measured by the method described later is preferably 1.00 lbf / in or more, more preferably 2.00 lbf / in or more, and particularly preferably 5.00 lbf / in or more.

[0061] <Printed Circuit Board Manufacturing Method> The method for manufacturing a printed circuit board 20 using printed circuit board material 10 will be described. It should be noted that the following description takes the case where the printed circuit board material 10 does not contain the substrate 21 as an example, but it is not intended to be limiting.

[0062] like Figure 2 As shown, the method for manufacturing a printed circuit board disclosed herein sequentially includes: a step of preparing a material 10 for a printed circuit board; a step of bonding the adhesive layer 13 of the material 10 for the printed circuit board and a substrate 21 together; a step of removing the metal foil 11 of the material 10 for the printed circuit board to expose the surface 12b of the catalyst layer 12 where the adhesive layer 13 is not provided; a step of laminating a copper plating layer 22 onto the surface 12b; and a step of, although not in Figure 2 The diagram shows the process of shaping the copper plating layer 22 into a circuit pattern shape as needed.

[0063] [Process for preparing materials for printed circuit boards] like Figure 2 (a) and Figure 2 As shown in (b), in the process of preparing the material 10 for the printed circuit board, a catalyst layer 12 and an adhesive layer 13 containing polyimide resin are sequentially formed on at least one side 11a of the metal foil 11.

[0064] The formation of the catalyst layer 12 is not particularly limited and can be carried out using generally known methods such as wet methods (e.g., catalyst-accelerator method), dry methods (e.g., sputtering method), and vapor deposition method. Specifically, for example, in the case of a wet method, the catalyst solution is coated onto at least one side 11a of the metal foil 11 using methods such as doctor blade coating, gravure coating, slot die coating, inkjet printing, spin coating, screen printing, or dip coating, and the catalyst layer 12 is obtained through the required post-treatment. In the case of a dry method, the catalyst layer 12 is obtained by directly forming a layer of catalyst metal on the metal foil 11.

[0065] The adhesive layer 13 can be formed, for example, by means of a resin solution prepared by dissolving polyimide resin in a solvent using methods such as doctor blade coating, gravure printing, slot die coating, inkjet printing, spin coating, screen printing, or dip coating, which is then coated onto the metal foil 11 after the catalyst layer 12 has been formed. Then, the solvent is removed by heat treatment at a temperature suitable for the solvent used, under atmospheric conditions.

[0066] It should be noted that the surface of the metal foil 11 may not be provided with unevenness, but if unevenness is provided, it can be addressed by roughening the surface of the metal foil 11 before forming the catalyst layer 12.

[0067] [The process of bonding the adhesive layer and the substrate together] Next, as Figure 2 As shown in (c), the adhesive layer 13 and the substrate 21 are bonded together. This results in a structure made by sequentially stacking the catalyst layer 12, the adhesive layer 13, and the substrate 21 on the metal foil 11.

[0068] There is no particular limitation on the method for bonding the adhesive layer 13 and the substrate 21, and generally known methods can be used. Specifically, for example, when bonding the adhesive layer 13 and the substrate 21, a heating process or pressure (tension) can be applied.

[0069] For example, by heating the adhesive layer 13 and the substrate 21 within a temperature range of 120°C to 300°C while bonding them together, a tighter bond can be achieved. More specifically, the fluidity of the adhesive layer 13 and the substrate 21 is increased by heating, and the shapes of the adhesive layer 13 and the substrate 21 change in a way that fills the gaps by conforming to the surface shapes of the contacting metal foil 11 and catalyst layer 12. Then, if the fluidity is lost due to cooling, the surface shapes of the metal foil 11 and catalyst layer 12 are transferred onto the substrate 21.

[0070] When bonding the adhesive layer 13 and the substrate 21, by applying a pressure of 0.2 MPa to 10 MPa depending on the type of substrate 21, the two can be bonded together more tightly.

[0071] Heating and pressurization can be performed individually, or both. For example, a known hot press can be used to perform the above process. Furthermore, hot pressing can also be performed under a reduced pressure atmosphere.

[0072] It should be noted that polyimide resin has higher heat resistance compared to other thermosetting resins such as epoxy resin, thus enabling high-temperature hot pressing. If a resin with low heat resistance is used, the catalyst in the catalyst layer may diffuse into the resin layer due to resin flow. However, by using polyimide resin with high heat resistance, the catalyst layer and adhesive layer can be kept consistent with the design. Furthermore, while other thermosetting resins such as epoxy resin can cause adhesion, polyimide resin exhibits high resistance to adhesion, allowing for the manufacture of printed circuit boards that conform to the design.

[0073] [The process of removing the metal foil to expose the surface of the catalyst layer] Then, as Figure 2As shown in (d), the metal foil 11 is removed from the structure obtained as described above. This exposes the surface 12b of the catalyst layer 12 where the adhesive layer 13 is not disposed (the side of the catalyst layer 12 opposite to the side where the adhesive layer 13 is stacked). This yields a first intermediate product 20A of a printed circuit board 20 made by sequentially stacking the catalyst layer 12, the adhesive layer 13, and the substrate 21.

[0074] There is no particular limitation on the method for removing the metal foil 11, and generally known methods can be used. Specifically, for example, it is preferable to use a method of coating with an etching solution or etching the metal foil 11 by allowing the etching solution to penetrate. When the metal foil 11 is an aluminum foil or an aluminum alloy foil, for example, hydrochloric acid or an aqueous solution of sodium hydroxide can be used as the etching solution.

[0075] [The process of stacking copper plating layers] like Figure 2 (e) Figure 2 As shown in (f), copper plating is performed on the exposed surface 12b of the catalyst layer 12, and a copper plating layer 22 is stacked. Specifically, for example, a copper plating layer with a thickness of less than 1 μm is stacked on the catalyst layer 12 using chemical copper plating, and then an electrolytic copper plating layer with a thickness of more than 5 μm and less than 100 μm is formed to achieve thick film formation. As a result, a uniform, smooth, and conductive layer with good electrical conductivity is formed. That is, a conductive layer with low resistance and excellent high-frequency characteristics is formed. In this way, a second intermediate product 20B of a printed circuit board with a copper plating layer 22, a catalyst layer 12, an adhesive layer 13, and a substrate 21 stacked in sequence is obtained.

[0076] [The process of shaping the copper plating layer into a circuit pattern] Next, although in Figure 2 Not shown in the diagram, but the copper plating layer 22, which is stacked on the entire surface 12b of the catalyst layer 12, is processed into a circuit pattern shape. This results in the printed circuit board 20 as the final product.

[0077] There are no particular limitations on the method for processing the copper plating layer 22 into a circuit pattern shape, and generally known methods such as photolithography can be used. For example, in photolithography, after applying resist ink into a circuit pattern shape on the surface of the copper plating layer 22 on the side where the catalyst layer 12 is not provided, an etching solution is applied or the etching solution is allowed to penetrate, thereby dissolving the copper plating layer 22 in the area where the resist ink is not applied, leaving the copper plating layer 22 in the circuit pattern shape.

[0078] There are no particular limitations on the shape of the circuit pattern; it can be designed appropriately based on the shape or number of semiconductor terminals, or the number or shape of external terminals.

[0079] Regarding the printed circuit board 20 manufactured through the above processes, chemical bonds are formed between the polyimide resin of the copper plating layer 22 and the adhesive layer 13, as well as between the polyimide resin and the substrate 21. Therefore, the copper plating layer 22 and the substrate 21 adhere with strong adhesive strength. In other words, if the printed circuit board material 10 of this disclosure is used, it is not necessary to form unevenness at the interface between the copper plating layer 22 and the substrate 21 to obtain a printed circuit board with both high smoothness and high adhesion at that interface.

[0080] Example Next, specific implementation examples will be described.

[0081] Polyimide resin solutions A to E of Manufacturing Examples 1 to 5 as shown in Table 1 were prepared, and printed circuit board samples of Examples 1 to 14 and Comparative Examples 1 to 4 were made.

[0082] [Table 1]

[0083] <Examples of the manufacture of polyimide resins> (Manufacturing Example 1) A 500 mL separable four-necked flask equipped with an anchor-type stainless steel stirrer, a nitrogen inlet pipe, and a Dean-Stark apparatus was filled with 0.08 mol of 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]phthalic dianhydride (BisDA), 0.08 mol of 3,4,3',4'-biphenyltetracarboxylic dianhydride (BPDA), 0.16 mol of 1,3'-bis(3-aminophenoxy)benzene (APBN), 150.00 g of N-methyl-2-pyrrolidone (NMP), 2.38 g of pyridine, and 50 g of toluene. After purging the reaction system with nitrogen, the reaction was carried out at 180 °C for 6 hours under a nitrogen atmosphere. The water generated during the reaction was removed from the reaction system. After the reaction was completed, the solution was cooled to 120°C, and then 250.00 g of NMP was added to obtain a 20% (w / w) polyimide resin solution A. The concentration of imide groups in polyimide resin in polyimide resin solution A, calculated using the above method, was 21.1%.

[0084] (Manufacturing Example 2) Except for replacing the acid dianhydride with 0.15 moles of 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride (BisDA) and the diamine with 0.15 moles of 4,4'-(p-phenylene diisopropylidene)bisaniline (Bisaniline P), the synthesis was carried out in the same manner as in Manufacturing Example 1, yielding a 20% by mass polyimide resin solution B. The concentration of imide groups in the polyimide resin in polyimide resin solution B, calculated by the above method, was 16.9%.

[0085] (Manufacturing Example 3) Except that 0.11 mol of 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride (BisDA) was used instead of the acid dianhydride, 0.11 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was used instead of the diamine, and methyl benzoate was used instead of the solvent, the synthesis was carried out in the same manner as in Manufacturing Example 1, yielding a 20% by mass polyimide resin solution C. The concentration of imide groups in the polyimide resin in polyimide resin solution C, calculated by the above method, was 15.6%.

[0086] (Manufacturing Example 4) 0.02 mol of an NCO-terminated polyurethane prepolymer composed of polycarbonate diol (PCD) and diphenylmethane diisocyanate (MDI), 0.06 mol of 4,4'-[propane-2,2-dimethylbis(1,4-phenyleneoxy)]phthalic dianhydride (BisDA), and 156.54 g of methyl benzoate were added to an apparatus identical to that used in Manufacturing Example 1, and the reaction was carried out at 140°C with stirring for 1.5 hours.

[0087] Then, 0.04 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) and 76.32 g of methyl benzoate were added, and the reaction was carried out at 180 °C with stirring for 5 hours. The water generated during the reaction was removed from the reaction system. After the reaction was complete, the mixture was cooled to 120 °C, and then 166.33 g of methyl benzoate was added, thus obtaining a 20% by mass polyimide resin solution D. The concentration of imide groups in the polyimide resin in polyimide resin solution D, calculated by the above method, was 8.8%.

[0088] (Manufacturing Example 5) 0.18 mol of 4,4'-oxophthalic dianhydride (ODPA), 0.13 mol of diethyltoluene diamine (DETDA), 138.90 g of NMP, 4.26 g of pyridine, and 50 g of toluene were added to an apparatus identical to that used in Manufacturing Example 1. After purging the reaction system with nitrogen, the reaction was carried out at 180°C for 2 hours under a nitrogen atmosphere.

[0089] Next, 0.09 mol of 1,1'-dicyclohexane-3,3',4,4'-tetracarboxylic acid-3,4:3',4'-dianhydride (H-BPDA), 0.13 mol of p-(m-aminophenoxy)aniline (mDADE), and 152.77 g of γ-butyrolactone (GBL) were added, and the reaction was carried out at 180 °C for 6 hours. After the reaction was completed, the mixture was cooled to 120 °C, and then 83.33 g of GBL was added, thereby obtaining a 25% by mass polyimide resin solution E. The concentration of imide groups in the polyimide resin in polyimide resin solution E, calculated by the above method, was 30.3%.

[0090] <Examples and Comparative Examples> (Example 1) A palladium-containing liquid (manufactured by Averatek, USA, LMI) was coated onto the surface of aluminum foil (manufactured by Toyo Aluminum Co., Ltd., 1N30, 35μm thick, surface roughness Ra0.2μm), and then heated to deposit a palladium catalyst layer onto the aluminum foil. A doctor blade coater was used to achieve a dry weight of 0.5g / m³. 2 The polyimide resin solution A of Manufacturing Example 1 was coated onto the palladium catalyst layer in the manner described in Example 1. Then, the solvent was removed by heat treatment at 180°C for 3 minutes, resulting in a printed circuit board material consisting of "an adhesive layer containing polyimide resin / a palladium catalyst layer / an aluminum foil".

[0091] Using a hot press at 180°C for 80 minutes and 0.35 MPa, the adhesive layer of the printed circuit board material was bonded to a glass epoxy resin substrate (manufactured by ISOLA, 0.2 μm thick) to create a laminate consisting of "substrate / adhesive layer containing polyimide resin / palladium catalyst layer / aluminum foil". Next, the laminate was immersed in an aqueous hydrogen chloride solution to dissolve and remove the aluminum foil, resulting in a laminate consisting of "substrate / adhesive layer containing polyimide resin / palladium catalyst layer" (intermediate product 20A). Then, the laminate was chemically copper-plated to create a laminate consisting of "substrate / adhesive layer containing polyimide resin / palladium catalyst layer / copper plating layer (thickness less than 1 μm)". Further copper electroplating yielded a laminate consisting of "substrate / adhesive layer containing polyimide resin / palladium catalyst layer / copper plating layer (thickness 35 μm)" (intermediate product 20B).

[0092] For simplicity, the copper plating layer is used directly as a sample of the printed circuit board, without processing the copper plating layer into a circuit pattern shape.

[0093] The obtained samples were heat-treated at 80°C for 12 hours, then cut into 1 cm wide pieces, and the peel strength of the copper plating layer at the substrate interface was measured. The peel strength was measured by modifying section 8.1 of Japanese Industrial Standard JIS C 5012 (1993 edition) to: peeling the sample 10 mm at a speed of 100 mm / min, and extracting the average load (lbf / inch) per unit width during the peeling process. The peel strength was measured using a Strograph manufactured by Toyo Seiki Co., Ltd., and a 90° peel fixture. The peel strength of the sample in Example 1 was 1.36 lbf / in.

[0094] (Example 2) Except for replacing polyimide resin solution A with polyimide resin solution B, everything else remained the same, and a sample was prepared according to the same method as in Example 1. The peel strength of the sample was measured. The peel strength of the sample was 2.86 lbf / in.

[0095] (Example 3) Except for replacing polyimide resin solution A with polyimide resin solution C, everything else remained the same, and a sample was prepared according to the same method as in Example 1. The peel strength of the sample was measured. The peel strength of the sample was 2.63 lbf / in.

[0096] (Example 4) In the polyimide resin solution C used in Example 3, 1 part by mass of an aminosilane adhesion promoter (manufactured by Shin-Etsu Chemical Industry Co., Ltd., KBE903, formula (2)) was added to 100 parts by mass of the polyimide resin to obtain a solution. Except for using the solution, everything else remained the same, and a sample was prepared in the same manner as in Example 3, and the peel strength was measured. The peel strength of the sample was 4.10 lbf / in.

[0097] [Chemical Formula 3]

[0098] (Example 5) In the polyimide resin solution C used in Example 3, 1 part by mass of an epoxy silane adhesion promoter (manufactured by Shin-Etsu Chemical Industry Co., Ltd., KBM403, formula (3)) was added to 100 parts by mass of the polyimide resin to obtain a solution. Except for using the solution, everything else remained the same, and a sample was prepared in the same manner as in Example 3, and the peel strength was measured. The peel strength of the sample was 3.32 lbf / in.

[0099] [Chemical Formula 4]

[0100] (Example 6) In the polyimide resin solution C used in Example 3, 1 part by weight of an epoxy silane adhesion promoter (manufactured by Shin-Etsu Chemical Industry Co., Ltd., KBM4803, formula (4)) was added relative to 100 parts by weight of the polyimide resin to obtain a solution. Except for using this solution, everything else remained the same, and a sample was prepared in the same manner as in Example 3, and the peel strength was measured. The peel strength of this sample was 2.87 lbf / in.

[0101] [Chemical Formula 5]

[0102] (Example 7) In the polyimide resin solution C used in Example 3, 1 part by mass of a triazine adhesion-improving additive (manufactured by Nissan Chemical Co., Ltd., STARFINE F-10, formula (5)) was added relative to 100 parts by mass of the polyimide resin to obtain a solution. Except for using the solution, everything else remained the same, and a sample was prepared in the same manner as in Example 3, and the peel strength was measured. The peel strength of the sample was 2.86 lbf / in.

[0103] [Chemical Formula 6]

[0104] (Example 8) In the polyimide resin solution C used in Example 3, 1 part by mass of an adhesion-improving additive containing triazine (manufactured by Shikoku Chemical Industry Co., Ltd., VD-3, formula (6)) was added relative to 100 parts by mass of the polyimide resin to obtain a solution. Except for using the solution, everything else remained the same, and a sample was prepared in the same manner as in Example 3, and the peel strength was measured. The peel strength of the sample was 3.79 lbf / in.

[0105] [Chemical Formula 7]

[0106] (Example 9) In the polyimide resin solution C used in Example 3, 1 part by mass of an adhesion-improving additive containing triazine (manufactured by Shikoku Chemical Industry Co., Ltd., VD-5, formula (7)) was added relative to 100 parts by mass of the polyimide resin to obtain a solution. Except for using the solution, everything else remained the same, and a sample was prepared in the same manner as in Example 3, and the peel strength was measured. The peel strength of the sample was 5.34 lbf / in.

[0107] [Chemical Formula 8]

[0108] (Example 10) Except for replacing polyimide resin solution A with polyimide resin solution D, everything else remained the same, and samples were prepared and their peel strength measured in the same manner as in Example 1. The peel strength of this sample was 3.86 lbf / in.

[0109] (Example 11) In the polyimide resin solution D used in Example 10, 1 part by mass of an epoxy silane adhesion promoter (manufactured by Shin-Etsu Chemical Industry Co., Ltd., KBM403, formula (3) of Example 5) was added relative to 100 parts by mass of the polyimide resin to obtain a solution. Except for using the solution, everything else remained the same, and a sample was prepared in the same manner as in Example 10, and the peel strength was measured. The peel strength of the sample was 5.33 lbf / in.

[0110] (Example 12) In the polyimide resin solution D used in Example 10, 1 part by mass of a triazine adhesion-improving additive (manufactured by Shikoku Chemical Industry Co., Ltd., VD-5, formula (7) of Example 9) was added relative to 100 parts by mass of the polyimide resin to obtain a solution. Except for using the solution, everything else remained unchanged, and a sample was prepared in the same manner as in Example 10, and the peel strength was measured. The peel strength of the sample was 5.43 lbf / in.

[0111] (Example 13) The aluminum foil was replaced with the following aluminum foil (manufactured by Toyo Aluminum Co., Ltd., 11μm thick, trade name "LUXAL", surface roughness Ra7nm), which has the following characteristics: the proportion of the total surface area of ​​the crystals present in the predetermined surface area is less than 2%, and the average surface area of ​​each crystal is 2μm. 2 The following aluminum foil, with a surface roughness Rz of less than 40 nm and a surface roughness Ra of less than 10 nm in the direction perpendicular to the rolling direction, and polyimide resin solution C instead of polyimide resin solution A, was prepared in the same manner as in Example 1, and the peel strength was measured. The peel strength of this sample was 1.15 lbf / in.

[0112] (Example 14) The aluminum foil was replaced with the following aluminum foil (manufactured by Toyo Aluminum Co., Ltd., 11μm thick, trade name "LUXAL", surface roughness Ra7nm), which has the following characteristics: the proportion of the total surface area of ​​the crystals present in the predetermined surface area is less than 2%, and the average surface area of ​​each crystal is 2μm. 2Hereinafter, the surface roughness Rz in the direction perpendicular to the rolling direction is 40 nm or less, and the surface roughness Ra is 10 nm or less. Polyurethane-modified polyimide resin solution D is used instead of polyimide resin solution A. All other aspects remain unchanged. Samples were prepared in the same manner as in Example 1, and the peel strength was measured. The peel strength of this sample was 2.58 lbf / in.

[0113] (Comparative Example 1) A palladium-containing liquid was coated onto the surface of an aluminum foil (manufactured by Toyo Aluminum Co., Ltd., 1N30, 11μm thick), and heated to deposit a palladium catalyst layer on the aluminum foil, thus obtaining a material for printed circuit boards.

[0114] Using a hot press at 180°C for 80 minutes and 0.35 MPa, the catalyst layer of the printed circuit board material was bonded to a glass epoxy resin substrate (manufactured by ISOLA, 0.2 μm thick) to create a laminate of "substrate / palladium catalyst layer / aluminum foil". Next, the laminate was immersed in an aqueous hydrogen chloride solution to dissolve and remove the aluminum foil, thus creating a laminate of "substrate / palladium catalyst layer". Then, the laminate was chemically plated with copper to create a laminate of "substrate / palladium catalyst layer / copper plating layer (less than 1 μm thick)". Further copper electroplating yielded a laminate of "substrate / palladium catalyst layer / copper plating layer (35 μm thick)".

[0115] For simplicity, the copper plating layer is used directly as a sample of the printed circuit board, without processing the copper plating layer into a circuit pattern shape.

[0116] The obtained sample was heat-treated at 80°C for 12 hours, then cut into 1 cm wide pieces. As in Example 1, the peel strength of the copper plating layer at the substrate interface was measured. The peel strength was 0.57 lbf / in.

[0117] (Comparative Example 2) Except for replacing polyimide resin solution A with polyimide resin solution E, all other aspects remained unchanged, and samples were prepared in the same manner as in Example 1, and peel strength was measured. The peel strength of this sample was 0.90 lbf / in.

[0118] (Comparative Example 3) The aluminum foil was replaced with the following aluminum foil (manufactured by Toyo Aluminum Co., Ltd., 11μm thick, trade name "LUXAL", surface roughness Ra7nm), which has the following characteristics: the proportion of the total surface area of ​​the crystals present in the predetermined surface area is less than 2%, and the average surface area of ​​each crystal is 2μm. 2Hereinafter, the surface roughness Rz in the direction perpendicular to the rolling direction is 40 nm or less, and the surface roughness Ra is 10 nm or less. Other than this, all other aspects remain unchanged. Samples were prepared in the same manner as Comparative Example 1, and the peel strength was measured. The peel strength was 0.32 lbf / in.

[0119] (Comparative Example 4) Except for the use of a commercially available plating surface conditioner (Condilizer-SP manufactured by Okuno Pharmaceutical Co., Ltd.) to form the adhesive layer, all other aspects remained unchanged, and samples were prepared in the same manner as in Example 1, and the peel strength was measured. The peel strength was 0.11 lbf / in.

[0120] Based on the peel strength results of the above embodiments and comparative examples, the evaluation results of the adhesive strength are shown in Table 1. Here, a peel strength less than 1.00 lbf / in is represented as adhesive strength ×, a peel strength of 1.00 lbf / in or more but less than 2.00 lbf / in is represented as adhesive strength △, a peel strength of 2.00 lbf / in or more but less than 5.00 lbf / in is represented as adhesive strength ○, and a peel strength of 5.00 lbf / in or more is represented as adhesive strength ◎.

[0121] As shown in the results above, the printed circuit board manufactured using the printed circuit board material 10 of this disclosure will have sufficient adhesive strength between the copper plating layer and the substrate, even if there is not necessarily a bump or depression at the interface between the copper plating layer and the substrate.

[0122] -Industry Applicability- This disclosure provides a material for printed circuit boards and a method for manufacturing a printed circuit board using the material. The material provides a printed circuit board with sufficient adhesive strength at the interface between the copper plating layer and the substrate, even without creating unevenness at the interface. Therefore, this disclosure is extremely useful.

[0123] - Symbol Explanation - 10 Materials for Printed Circuit Boards 11 metal foil 11a (one side of the metal foil) 12 Catalyst Layer 13 Adhesive Layer 20 Printed Circuit Boards 21 Substrate 22. Copper plating layer.

Claims

1. A material for printed circuit boards, characterized in that: It is made by sequentially laminating a catalyst layer and an adhesive layer containing polyimide resin on at least one side of a metal foil. The polyimide resin is made by copolymerizing an acid dianhydride containing bisphenol diether type acid dianhydride and a diamine compound.

2. The material for printed circuit boards according to claim 1, characterized in that: The adhesive layer contains, relative to 100 parts by weight of the polyimide resin, at least 0.1 parts by weight and less than 10 parts by weight of an adhesion-improving additive selected from the group consisting of aminosilanes, epoxysilanes and triazines.

3. The material for printed circuit boards according to claim 1, characterized in that: The polyimide resin comprises a polyurethane-modified polyimide resin.

4. The material for printed circuit boards according to claim 1, characterized in that: The surface roughness Ra of the metal foil is below 0.4 μm.

5. The material for printed circuit boards according to claim 1, characterized in that: The metal foil is at least one selected from the group consisting of aluminum foil, aluminum alloy foil, copper foil and tin foil.

6. The material for printed circuit boards according to claim 1, characterized in that: The catalyst layer contains at least one catalyst selected from the group consisting of palladium, platinum, gold and copper.

7. A method for manufacturing a printed circuit board, characterized in that: The method for manufacturing the printed circuit board includes, in sequence: The process of bonding the adhesive layer and the substrate in the printed circuit board material according to any one of claims 1 to 6; The process of removing the metal foil from the printed circuit board material to expose the surface of the catalyst layer where the adhesive layer is not provided; The process of laminating a copper plating layer onto the surface; and The process of processing the copper plating layer into a circuit pattern shape.

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