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

Abstract

This material 10 for printed wiring boards is obtained by superposing at least a catalyst layer 12 and an adhesive layer 13, which contains a polyimide resin, in this order on at least one surface 11a of a metal foil 11. The imide group concentration of the polyimide resin is 8% to 26% inclusive.

Description

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

[0001] The present disclosure relates to a material for a printed wiring board and a method for manufacturing a printed wiring board using the same.

[0002] Generally available printed wiring boards, such as rigid boards, build-up boards, and flexible printed circuit boards, have a catalyst layer on the surface of a base material made of, for example, a resin, and further have a copper plating layer in the shape of a circuit pattern on the surface of the catalyst layer. As the speed of electronic components such as semiconductor chips increases, thinner lines are also required for printed wiring boards, and efficient manufacturing of printed wiring boards with such fine line structures is required.

[0003] For example, Patent Document 1 discloses a method in which the catalytic material-supported surface of a metal foil is bonded to a substrate of a circuit board, and then the metal foil is removed and the catalytic material is laminated onto the substrate. Copper plating is then applied to the catalytic material laminated on the substrate, followed by pattern processing, to efficiently obtain a printed wiring board with a circuit pattern. In this method, if the adhesion between the copper plating layer and the substrate is weak during pattern processing to form the circuit, peeling of the copper plating layer occurs during processing, leading to a decrease in yield. In Patent Document 1, irregularities provided on the metal foil are transferred to the surface of the substrate, and the anchoring effect of the irregularities improves the adhesion between the copper plating layer and the substrate.

[0004] International Publication No. 2021 / 163440

[0005] However, in applications requiring high-frequency characteristics, there is a skin effect, in which electrical signals passing through the circuit are concentrated near the surface. This requires high smoothness at the interface between the copper plating layer that forms the circuit and the substrate. In other words, the technology of Patent Document 1 requires unevenness at the interface to improve adhesion, while ensuring high smoothness at the interface to improve high-frequency characteristics, resulting in a trade-off between the two.

[0006] Therefore, an object of the present disclosure is to provide a material for printed wiring boards that can provide printed wiring boards having sufficient adhesive strength at the interface between a copper plating layer and a substrate without forming irregularities at the interface, and a method for manufacturing a printed wiring board using the material for printed wiring boards.

[0007] Through extensive research, the inventors of the present application have discovered that when a printed wiring board is manufactured using a material for printed wiring boards, sufficient adhesion can be ensured without providing unevenness at the interface between the copper plating layer and the substrate by providing an adhesive layer containing a polyimide resin having an imide group concentration within a specific range at the interface.

[0008] That is, one embodiment of the material for printed wiring boards disclosed herein comprises at least a catalyst layer and an adhesive layer containing a polyimide resin laminated in this order on at least one surface of a metal foil, and the imide group concentration of the polyimide resin is 8% or more and 26% or less.

[0009] A printed wiring board can be obtained by bonding the adhesive layer of the material for printed wiring boards of the present disclosure to a substrate, removing the metal foil, and then copper plating and patterning the exposed catalyst layer. In the resulting printed wiring board, an adhesive layer containing the above-mentioned polyimide resin is formed at the interface between the copper plating layer and the substrate. Chemical bonds are then formed between the copper plating layer and the polyimide resin of the adhesive layer, and between the polyimide resin and the substrate, resulting in strong adhesion between the copper plating layer and the substrate. In other words, by using the material for printed wiring boards of the present disclosure, it is not necessary to form irregularities at the interface between the copper plating layer and the substrate to achieve an anchoring effect, and a printed wiring board can be obtained that combines high smoothness and high adhesion at the interface.

[0010] 1 is a schematic cross-sectional view of a material for a printed wiring board. FIG. 2 is a flow chart showing an example of a method for producing a printed wiring board.

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

[0012] <Printed Wiring Board Material and Printed Wiring Board> As shown in Figure 1, the printed wiring board material 10 according to this embodiment includes a metal foil 11, a catalyst layer 12, and an adhesive layer 13. Specifically, the printed wiring board material 10 is formed by laminating at least the catalyst layer 12 and an adhesive layer 13 containing a polyimide resin in this order on at least one surface 11a of the metal foil 11. The catalyst layer 12 and the adhesive layer 13 may also be provided on the other surface 11b of the metal foil 11. The printed wiring board material 10 may further include a substrate 21 laminated on the surface of the adhesive layer 13 on which the catalyst layer 12 is not present (see Figure 2(c)).

[0013] The printed wiring board material 10 is a material used when manufacturing a printed wiring board 20 (see FIG. 2( f)). As will be described in detail below, the printed wiring board 20 is obtained by bonding the adhesive layer 13 and a substrate 21 for the printed wiring board, removing the metal foil 11, and copper plating the exposed catalyst layer 12 and processing it into a circuit pattern shape. That is, in the present disclosure, the printed wiring board material 10 can also be described as a material for transferring the catalyst layer 12 and the adhesive layer 13 to the substrate 21 for the printed wiring board.

[0014] The printed wiring board material 10, the printed wiring board 20, and each of the constituent materials will be described in detail below.

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

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

[0017] Furthermore, the surface 11a of the metal foil 11 may have irregularities to improve the adhesive strength between the copper plating layer 22 and the substrate 21, but this is not essential.

[0018] The surface 11a of the metal foil 11 may be highly smooth in order to ensure excellent high-frequency characteristics in the final product, a printed wiring board. In this case, the surface roughness Ra of the metal foil 11 may be, for example, 0.4 μm or less, and preferably 0.2 μm or less. There is no particular lower limit to the surface roughness Ra of the metal foil 11, but a surface roughness of, for example, 6 nm or more can be preferably used.

[0019] In this specification, "surface roughness Ra" refers to the arithmetic mean roughness Ra defined in JIS B0601 (1982 edition). When an aluminum foil is used as the metal foil 11, the "surface roughness Ra" of the aluminum foil may be expressed as a value calculated by expanding the arithmetic mean roughness Ra defined in JIS B0601 (1982 edition) into three dimensions so that it can be applied to a surface.

[0020] When an aluminum foil is used as the metal foil 11, the ratio of the total surface area of ​​the crystallized particles present in a predetermined surface area is 2% or less, and the average surface area per crystallized particle is 2 μm ２It is also possible to use an aluminum foil having a surface roughness Rz of 40 nm or less in the direction perpendicular to the rolling direction and a surface roughness Ra of 10 nm or less (see WO 2015 / 019960). Because this aluminum foil has high smoothness, a catalyst layer can be transferred to the substrate in a highly smooth state. That is, by laminating a copper plating layer on this catalyst layer, a printed wiring board having high smoothness at the interface between the copper plating layer and the substrate can be manufactured. The surface roughness Ra and Rz of the aluminum foil can be determined, for example, by a method similar to that described in paragraph 0049 of WO 2015 / 019960. That is, the surface shape of the aluminum foil can be observed using an atomic force microscope (e.g., a scanning probe microscope Nanopics 1000 manufactured by Seiko Instruments Inc.) using a damping method (non-contact) in a rectangular field of view of a predetermined size, such as 80 μm x 80 μm. The tilt of the sample is corrected using a cubic surface automatic tilt correction method, which calculates and fits a curved surface using least-squares approximation, to the obtained observation results, and the surface roughness Ra and the surface roughness Rz in the transverse (TD) direction perpendicular to the rolling direction are measured. As described above, the surface roughness Ra is a value calculated by expanding the arithmetic mean roughness Ra defined in JIS B0601 (1982 edition) into three dimensions so that it can be applied to the entire observed surface. The surface roughness Rz in the transverse (TD) direction can be measured by the two-dimensional Rz value of any cross section in the transverse (TD) direction within the same field of view using an evaluation method based on JIS B0601 (1982 edition).

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

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

[0023] The catalyst used in the catalyst layer 12 is not particularly limited, and any commonly known catalyst can be used as long as it can form a copper plating layer on the surface. Specifically, at least one selected from the group consisting of palladium, platinum, gold, and copper can be suitably used as the catalyst. Palladium is more preferably used as the catalyst because it is less susceptible to surface oxidation, has high catalytic activity, and can form plating even with a small amount.

[0024] The thickness (layer amount) of the catalyst layer is not particularly limited, and can be appropriately selected from the range of 1 nm to 1 μm.

[0025] [Adhesive Layer] The adhesive layer 13 is a layer for improving the adhesion at the interface between the copper plating layer 22 and the substrate 21 in the printed wiring board 20, which is the final product.

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

[0027] (Polyimide Resin) The polyimide resin is obtained by copolymerizing (A) an acid dianhydride and (B) a diamine compound, and has an imide group concentration in the range of 8% to 26%. The acid dianhydride (A) and the diamine compound (B) are not particularly limited as long as the imide group concentration of the resulting polyimide resin is within the above range. The method for calculating the imide group concentration will be described later.

[0028] (A) Acid Dianhydride The acid dianhydride is preferably a tetracarboxylic acid dianhydride, more preferably an aromatic tetracarboxylic acid dianhydride.

[0029] Specific examples of the acid dianhydride include 3,4,3',4'-biphenyltetracarboxylic dianhydride (BPDA), 1,1'-bicyclohexane-3,3',4,4'-tetracarboxylic-3,4:3',4'-dianhydride (H-BPDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic dianhydride (ODPA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 5-(2, 5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, 5-(2,5-dioxotetrahydrofurfuryl)-3-cyclohexene-1,2-dicarboxylic dianhydride, ethylene glycol bistrimellitic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, perylene-3,4 ,9,10-tetracarboxylic dianhydride, ethylene tetracarboxylic dianhydride, 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride (BisDA), 4,4'-(4,4'-methylenediphenoxy)bis(phthalic anhydride), 4,4'-(4,4'-hexafluoroisopropylidenediphenoxy)bis(phthalic anhydride), etc. (Structural formulas of some of these compounds are shown below.) Among these, bisphenol diether type acid dianhydrides are preferred. Examples of bisphenol diether acid dianhydrides include 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride, 4,4'-(4,4'-methylenediphenoxy)bis(phthalic anhydride), 4,4'-(4,4'-hexafluoroisopropylidenediphenoxy)bis(phthalic anhydride), etc. These acid dianhydrides may be used alone or in combination of two or more.

[0030]

[0031] (B) Diamine Compound The diamine compound is an amine compound having two amino groups in the molecule. Examples of the diamine compound include aromatic compounds and aliphatic compounds, but from the viewpoint of obtaining a polyimide film having high mechanical strength, the diamine compound is preferably an aromatic diamine compound.

[0032] Examples of the aromatic diamine compound 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, 5-amino-1-(4'-aminophenyl)-1,3,3-trimethylindane, 6-amino-1-(4'-aminophenyl)-1 , 3,3-trimethylindane, 4,4'-diaminobenzanilide, 3,5-diamino-3'-trifluoromethylbenzanilide, 3,5-diamino-4'-trifluoromethylbenzanilide, 3,4'-diaminodiphenyl ether, 2,7-diaminofluorene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-methylene-bis(2-chloroaniline), 2,2',5,5'-tetrachloro-4,4'-diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5'-di Methoxybiphenyl, 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)benzene, 4,4'-bis(4-aminophenoxy)-biphenyl, 1,3'-bis(3-aminophenoxy)benzene (APBN), 9,9-bis(4-aminophenoxy) aminophenyl)fluorene, 4,4'-(p-phenyleneisopropylidene)bisaniline, 4,4'-(m-phenyleneisopropylidene)bisaniline (Bisaniline-M), 4,4'-(p-phenylenediisopropylidene)bisaniline (Bisaniline-P), 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[4-(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl, and the like.Among these, it is preferable to use an aromatic diamine compound having at least one of an ether bond group and a bisphenol skeleton in the molecule. An aromatic diamine compound having both an ether bond group and a bisphenol skeleton in the molecule is more preferable. These aromatic diamine compounds may be used alone or in combination of two or more.

[0033] The polyimide resin is preferably a urethane-modified polyimide resin (also referred to as a "specific polyimide resin" in this specification). More specifically, it is preferably a urethane-modified polyimide resin obtained by copolymerizing an NCO-terminated urethane prepolymer with an acid dianhydride and a diamine compound. By using the specific polyimide resin in the adhesive layer, higher adhesive strength can be obtained at the interface between the copper plating layer 22 and the substrate 21. The polyimide resin may also be a mixture of the specific polyimide resin and a polyimide resin other than the specific polyimide resin. In this case, the content of the specific polyimide resin in the polyimide resin is not particularly limited, but can be, for example, 50% by mass or more.

[0034] The adhesive layer 13 may be composed solely of polyimide resin, or may contain additives other than polyimide resin. Specific examples of additives include at least one adhesion-imparting additive selected from the group consisting of aminosilanes, epoxysilanes, and triazines. Adding such an additive to the polyimide resin can achieve even higher adhesive strength at the interface between the copper plating layer 22 and the substrate 21. The content of the additive in the adhesive layer 13 is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 2 parts by weight, per 100 parts by weight of the polyimide resin. By setting the additive amount within the above range, high adhesive strength can be achieved between the copper plating layer and the substrate.

[0035] The content of the polyimide resin in the adhesive layer 13 is preferably 90% by mass or more, and more preferably 98% by mass or more.

[0036] The method for producing the polyimide resin is not particularly limited, and any conventionally known production method can be used, such as a thermal imidization method in which the polyimide resin is thermally dehydrated and cyclized, or a chemical imidization method in which a dehydrating agent is used.

[0037] (Imide group concentration) The imide group concentration of the polyimide resin is within the above-mentioned range, preferably 8.8% or more and 21.1% or less. If the imide group concentration is less than 8%, the inherent heat resistance of polyimide may be deteriorated. If the imide group concentration is more than 26%, the adhesive strength between the copper plating layer and the substrate may be low, and the copper plating layer may peel off.

[0038] The imide group concentration here is defined by the following formula (1).

[0039] Imide group concentration = (molecular weight of imide group portion: 70.03) ÷ (molecular weight of polyimide repeating unit) × 100 (1) In formula (1), the molecular weight of the imide group portion is the molecular weight of the (-CO-N-CO-) portion contained in the polyimide repeating unit. The molecular weight per imide group is 70.03.

[0040] The molecular weight of a repeating unit of a polyimide is the molecular weight of the portion derived from the acid dianhydride and diamine compound that constitute one repeating unit.

[0041] When a polyimide contains a plurality of repeating units, the imide group concentration of each repeating unit is determined, and the values ​​obtained by multiplying the values ​​by the content ratio of each repeating unit are summed to obtain the imide group concentration of the polyimide.

[0042] (Weight-average molecular weight) The weight-average molecular weight of the polyimide resin is not intended to be limited, but can be, for example, 5,000 to 1,000,000, and preferably 10,000 to 500,000. If the weight-average molecular weight is below the above-mentioned lower limit, the adhesive layer tends to become brittle, and sufficient adhesive strength between the copper plating layer and the substrate may not be ensured. On the other hand, if the weight-average molecular weight exceeds the above-mentioned upper limit, the solubility in solvents may decrease, and the coatability may be reduced.

[0043] The weight average molecular weight of the polyimide resin can be measured by a commonly known method such as gel permeation chromatography (GPC).

[0044] [Substrate] The substrate 21 is a support material that serves as the base of the printed wiring board 20, holds the copper plating layer 22, and provides stiffness and strength to the printed wiring board 20.

[0045] The substrate 21 may or may not be included in the printed wiring board material 10. That is, the printed wiring board material 10 can be distributed without the substrate 21. In this case, the printed wiring board manufacturer can manufacture the printed wiring board 20 by bonding the printed wiring board material 10 and a desired substrate 21 together, removing the metal foil 11, and laminating the copper plating layer 22. The printed wiring board material 10 may also be distributed in a state including the substrate 21. In this case, the printed wiring board manufacturer can manufacture the printed wiring board by removing the metal foil 11 and laminating the copper plating layer 22.

[0046] The substrate 21 can be appropriately selected depending on the type of semiconductor to be mounted and the intended use of the printed wiring board 20 as a final product, and 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 metal with an insulating layer on its surface. Resin is more preferable, and glass epoxy resin is particularly preferable from the viewpoints of strength, insulation, and processability. The thickness of the substrate 21 is also not particularly limited, and a substrate having a thickness of 10 μm to 10 mm can be suitably used, for example.

[0047] [Copper Plating Layer] The copper plating layer 22 serves as a conductor in the printed wiring board 20, and serves as wiring that connects pins (terminals) of the semiconductor to external connection wiring or terminals when the semiconductor is mounted. Since the copper plating layer 22 is formed on the catalyst layer 12, it is laminated over the entire surface of the copper plating layer 22, but is processed into a circuit pattern shape by etching or the like. In other words, the copper plating layer can be said to be a layer that covers the entire surface or part of the catalyst layer, is formed into a circuit pattern shape, and is laminated on the catalyst layer 12.

[0048] A generally known method can be used to form the copper plating layer 22, but it is preferable to first form a copper plating layer by electroless copper plating, and then further thicken the copper plating layer by electrolytic copper plating to obtain a copper plating layer 22 of the desired thickness.

[0049] The thickness of the copper plating layer 22 is not particularly limited, and can be, for example, in the range of 10 nm to 100,000 nm.

[0050] [Adhesion at the interface between the copper plating layer and the substrate] In the printed wiring board 20, the peel strength measured by the method described below 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.

[0051] <Method for manufacturing printed wiring board> A method for manufacturing a printed wiring board 20 using the printed wiring board material 10 will be described. Note that, although the following description will be given taking as an example a case where the printed wiring board material 10 does not include a base material 21, this is not intended to be limiting.

[0052] As shown in FIG. 2 , the method for manufacturing a printed wiring board according to the present disclosure includes, in this order, a step of preparing a material for printed wiring boards 10, a step of bonding an adhesive layer 13 of the material for printed wiring boards 10 and a base material 21 together so that they face each other, a step of removing metal foil 11 from the material for printed wiring boards 10 to expose a surface 12 b of catalyst layer 12 on which the adhesive layer 13 is not provided, a step of laminating a copper plating layer 22 on surface 12 b, and, although not shown in FIG. 2 , a step of processing the copper plating layer 22 into a circuit pattern shape as necessary.

[0053] [Process for preparing a material for a printed wiring board] As shown in (a) and (b) of Figures 2, in the process for preparing a material for a printed wiring board 10, a catalyst layer 12 and an adhesive layer 13 containing a polyimide resin are formed in this order on at least one surface 11a of a metal foil 11.

[0054] The formation of the catalyst layer 12 is not particularly limited, and can be performed by a generally known method, such as a wet method such as a catalyst-accelerator method, or a dry method such as a sputtering method or a vapor deposition method. Specifically, for example, in the case of a wet method, a catalyst solution is applied to at least one surface 11a of the metal foil 11 using a bar coater, gravure, slot die, inkjet, spin coating, screen printing, dip coating, or the like, and the catalyst layer 12 is obtained after necessary post-treatment. In the dry method, a layer of catalyst metal is directly formed on the metal foil 11 to obtain the catalyst layer 12.

[0055] The adhesive layer 13 can be formed, for example, by the following method: A resin solution prepared by dissolving a polyimide resin in a solvent is applied to the metal foil 11 after the formation of the catalyst layer 12 using a bar coater, gravure, slot die, inkjet, spin coating, screen printing, dip coating, or the like. The solvent is then removed by heat treatment in the air at a temperature appropriate for the solvent used.

[0056] It is not necessary to provide the surface of the metal foil 11 with irregularities. However, if irregularities are to be provided, they can be achieved by subjecting the surface of the metal foil 11 to a roughening treatment or the like before forming the catalyst layer 12.

[0057] 2(c), the adhesive layer 13 and the substrate 21 are bonded together so as to face each other, thereby obtaining a structure in which the catalyst layer 12, the adhesive layer 13, and the substrate 21 are laminated in this order on the metal foil 11.

[0058] There are no particular limitations on the method for bonding the adhesive layer 13 and the substrate 21, and any commonly known method may be used. Specifically, for example, when bonding the adhesive layer 13 and the substrate 21, heating may be performed or pressure (tension) may be applied.

[0059] For example, by laminating the adhesive layer 13 and the substrate 21 while heating them in the range of 120°C to 300°C, the two can be bonded more closely. More specifically, the fluidity of the adhesive layer 13 and the substrate 21 increases as they are heated, and their shapes change to fill gaps in accordance with the surface shapes of the metal foil 11 and catalyst layer 12 that are in contact with them. When the fluidity is subsequently lost as the temperature drops, the surface shapes of the metal foil 11 and catalyst layer 12 are transferred to the substrate 21.

[0060] Furthermore, when bonding the adhesive layer 13 and the substrate 21 together, applying a pressure of 0.2 MPa to 10 MPa depending on the type of substrate 21 allows the two to be bonded together more closely.

[0061] Either heating or pressure application may be performed, or both may be performed. These treatments may be performed using, for example, a known heat press device. Furthermore, the heat press may be performed in a reduced pressure atmosphere.

[0062] Furthermore, polyimide resin has higher heat resistance than other thermosetting resins such as epoxy resin, allowing it to be subjected to high-temperature heat pressing. Using a resin with low heat resistance can cause the resin layer to flow, potentially leading to the catalyst in the catalyst layer diffusing into the resin layer. However, using a polyimide resin with high heat resistance allows the catalyst layer and adhesive layer to remain as designed. Furthermore, while other thermosetting resins such as epoxy resins can cause blocking, polyimide resin has high blocking resistance, allowing printed wiring boards to be manufactured as designed.

[0063] 2(d), the metal foil 11 is removed from the structure obtained as described above. This exposes the surface 12b of the catalyst layer 12 on which the adhesive layer 13 is not provided (the surface of the catalyst layer 12 opposite to the surface on which the adhesive layer 13 is laminated). This results in a first intermediate product 20A of the printed wiring board 20, which is formed by laminating the catalyst layer 12, the adhesive layer 13, and the base material 21 in this order.

[0064] The method for removing the metal foil 11 is not particularly limited, and a generally known method can be used. Specifically, for example, a method in which an etching solution is applied to or impregnated into the metal foil 11, and the metal foil 11 is etched and removed is preferably used. 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.

[0065] 2(e) and 2(f), copper plating is applied to the exposed surface 12b of the catalyst layer 12 to form a copper plating layer 22. Specifically, for example, a copper plating layer of 1 μm or less is deposited on the catalyst layer 12 by electroless copper plating, and then an electrolytic copper plating layer of 5 μm to 100 μm in thickness is formed by electrolytic copper plating to increase the thickness. This results in a conductor layer that is uniform, smooth, and highly conductive, i.e., has low electrical resistance and excellent high-frequency characteristics. In this way, a second intermediate product 20B of a printed wiring board is obtained, in which the copper plating layer 22, catalyst layer 12, adhesive layer 13, and substrate 21 are sequentially deposited.

[0066] [Step of Processing the Copper Plating Layer into a Circuit Pattern] Next, although not shown in Fig. 2, the copper plating layer 22 laminated on the entire surface 12b of the catalyst layer 12 is processed into a circuit pattern, thereby obtaining the final product, the printed wiring board 20.

[0067] The method for processing the copper plating layer 22 into a circuit pattern shape is not particularly limited, and a commonly known method such as lithography can be used. For example, in the lithography method, a resist ink is applied in the shape of a circuit pattern to the surface of the copper plating layer 22 on the side where the catalyst layer 12 is not provided, and then an etching solution is applied or impregnated therein, thereby dissolving the copper plating layer 22 in the areas where the resist ink is not applied, and leaving the copper plating layer 22 in the shape of a circuit pattern.

[0068] The shape of the circuit pattern is not particularly limited, and a shape designed appropriately according to the shape of the semiconductor, the number of terminals, and the number and shape of the external terminals can be adopted.

[0069] In the printed wiring board 20 manufactured by the above steps, chemical bonds are formed between the copper plating layer 22 and the polyimide resin of the adhesive layer 13, and between the polyimide resin and the substrate 21. As a result, the copper plating layer 22 and the substrate 21 are adhered to each other with strong adhesive strength. In other words, by using the printed wiring board material 10 of the present disclosure, it is not necessary to form irregularities at the interface between the copper plating layer 22 and the substrate 21, and a printed wiring board can be obtained that has both high smoothness and high adhesion at the interface.

[0070] Next, specific examples will be described.

[0071] Polyimide resin solutions A to E of Production Examples 1 to 5 shown in Table 1 were prepared, and printed wiring board samples of Examples 1 to 14 and Comparative Examples 1 to 4 were fabricated.

[0072]

[0073] <Production Examples of Polyimide Resins> (Production Example 1) A 500 mL separable four-neck flask equipped with a stainless steel anchor stirrer, a nitrogen inlet tube, and a Dean-Stark apparatus was charged with 0.08 mol of 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic 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. The reaction system was then purged with nitrogen, and the reaction was carried out under a nitrogen stream at 180°C for 6 hours. Water produced by the reaction was distilled off from the reaction system. After the reaction was completed, the mixture was cooled to 120° C., and 250.00 g of NMP was added to obtain a 20% by mass concentration polyimide resin solution A. The imide group concentration of the polyimide resin contained in polyimide resin solution A, calculated by the above-mentioned method, was 21.1%.

[0074] (Production Example 2) Except for changing the acid dianhydride to 0.15 mol of 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride (BisDA) and the diamine to 0.15 mol of 4,4'-(p-phenylenediisopropylidene)bisaniline (BisanilineP), synthesis was carried out in the same manner as in Production Example 1 to obtain a 20 mass% polyimide resin solution B. The imide group concentration of the polyimide resin contained in polyimide resin solution B, calculated by the above-mentioned method, was 16.9%.

[0075] (Production Example 3) The same synthesis as in Production Example 1 was carried out, except that the acid dianhydride was changed to 0.11 mol of 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride (BisDA), the diamine was changed to 0.11 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and the solvent was changed to methyl benzoate, to obtain a 20 mass% polyimide resin solution C. The imide group concentration of the polyimide resin contained in polyimide resin solution C, calculated by the above-mentioned method, was 15.6%.

[0076] (Production Example 4) To the same apparatus as in Production Example 1, 0.02 mol of an NCO-terminated urethane prepolymer composed of polycarbonate diol (PCD) and diphenylmethane diisocyanate (MDI), 0.06 mol of 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic dianhydride (BisDA), and 156.54 g of methyl benzoate were added, and the mixture was reacted for 1.5 hours while being heated and stirred at 140°C.

[0077] Thereafter, 0.04 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) and 76.32 g of methyl benzoate were added, and the mixture was reacted for 5 hours with heating and stirring at 180°C. Water produced by the reaction was distilled out of the reaction system. After the reaction was completed, the mixture was cooled to 120°C, and 166.33 g of methyl benzoate was added to obtain a 20% by mass polyimide resin solution D. The imide group concentration of the polyimide resin contained in polyimide resin solution D, calculated by the above method, was 8.8%.

[0078] (Production Example 5) Into the same apparatus as in Production Example 1, 0.18 mol of 4,4'-oxydiphthalic dianhydride (ODPA), 0.13 mol of diethyltoluenediamine (DETDA), 138.90 g of NMP, 4.26 g of pyridine, and 50 g of toluene were charged, and after the atmosphere in the reaction system was replaced with nitrogen, the reaction was carried out at 180°C for 2 hours under a nitrogen stream.

[0079] Next, 0.09 mol of 1,1'-bicyclohexane-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 gamma-butyrolactone (GBL) were added, and the mixture was reacted at 180°C for 6 hours. After the reaction was completed, the mixture was cooled to 120°C, and 83.33 g of GBL was added to obtain a polyimide resin solution E with a concentration of 25% by mass. The imide group concentration of the polyimide resin contained in polyimide resin solution E, calculated by the above method, was 30.3%.

[0080] Examples and Comparative Examples Example 1 A palladium-containing solution (LMI, manufactured by Averatek) was coated on the surface of an aluminum foil (1N30, manufactured by Toyo Aluminum K.K., thickness 35 μm, surface roughness Ra 0.2 μm) and heated to form a palladium-based catalyst layer on the aluminum foil. Polyimide resin solution A of Production Example 1 was applied to the palladium-based catalyst layer at a dry mass of 0.5 g / m. ２ The solvent was then removed by heat treatment at 180°C for 3 minutes, yielding a material for printed wiring boards having a polyimide resin-containing adhesive layer, a palladium-based catalyst layer, and an aluminum foil.

[0081] The adhesive layer surface of this printed wiring board material and a glass epoxy resin substrate (manufactured by ISOLA, 0.2 μm thick) were bonded using a heat press under conditions of 180°C for 80 minutes at 0.35 MPa to produce a laminate of "substrate / adhesive layer containing polyimide resin / palladium-based catalyst layer / aluminum foil." This laminate was then immersed in a hydrogen chloride solution to dissolve and remove the aluminum foil, resulting in a laminate of "substrate / adhesive layer containing polyimide resin / palladium-based catalyst layer" (intermediate product 20A). This laminate was then subjected to electroless copper plating to produce a laminate of "substrate / adhesive layer containing polyimide resin / palladium-based catalyst layer / copper plating layer (thickness 1 μm or less)." Further copper electroplating was performed to obtain a laminate of "substrate / adhesive layer containing polyimide resin / palladium-based catalyst layer / copper plating layer (thickness 35 μm)" (intermediate product 20B).

[0082] For convenience, the copper plating layer was not processed into a circuit pattern shape, but was used as a printed wiring board sample as is.

[0083] The obtained samples were heat-treated at 80°C for 12 hours, then cut into 1 cm widths, and the peel strength of the interface between the copper plating layer and the substrate was measured. Peel strength was measured by modifying 8.1 of JIS C 5012 (1993 edition) with the following modifications: the sample was peeled 10 mm at a speed of 100 mm / min, and the convex average load per unit width (lbf / inch) during this process was extracted. Peel strength was measured using a Strograph and a 90° peeling jig manufactured by Toyo Seiki Seisakusho. The peel strength of the sample of Example 1 was 1.36 lbf / in.

[0084] Example 2 A sample was prepared and the peel strength was measured in the same manner as in Example 1, except that polyimide resin solution A was replaced with polyimide resin solution B. The peel strength of the sample was 2.86 lbf / in.

[0085] Example 3 A sample was prepared and the peel strength was measured in the same manner as in Example 1, except that polyimide resin solution A was replaced with polyimide resin solution C. The peel strength of the sample was 2.63 lbf / in.

[0086] Example 4 A sample was prepared in the same manner as in Example 3, except that 1 part by mass of an aminosilane adhesion promoter (KBE903 manufactured by Shin-Etsu Chemical Co., Ltd., represented by formula (2)) was added to 100 parts by mass of the polyimide resin in the polyimide resin solution C used in Example 3, and the peel strength was measured. The peel strength of the sample was 4.10 lbf / in.

[0087]

[0088] Example 5 A sample was prepared in the same manner as in Example 3, except that 1 part by mass of an epoxy silane adhesion promoter (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd., represented by formula (3)) was added to 100 parts by mass of the polyimide resin in the polyimide resin solution C used in Example 3, and the peel strength was measured. The peel strength of the sample was 3.32 lbf / in.

[0089]

[0090] Example 6 A sample was prepared in the same manner as in Example 3, except that 1 part by mass of an epoxy silane adhesion promoter (KBM4803 manufactured by Shin-Etsu Chemical Co., Ltd., represented by formula (4)) was added to 100 parts by mass of the polyimide resin in the polyimide resin solution C used in Example 3, and the peel strength was measured. The peel strength of the sample was 2.87 lbf / in.

[0091]

[0092] Example 7 A sample was prepared in the same manner as in Example 3, except that 1 part by mass of a triazine-based adhesion-imparting additive (Starfine F-10, manufactured by Nissan Chemical Industries, Ltd., represented by formula (5)) was added to 100 parts by mass of the polyimide resin in the polyimide resin solution C used in Example 3, and the peel strength was measured. The peel strength of the sample was 2.86 lbf / in.

[0093]

[0094] Example 8 A sample was prepared in the same manner as in Example 3, except that 1 part by mass of a triazine-containing adhesion-imparting additive (VD-3, formula (6), manufactured by Shikoku Chemical Industry Co., Ltd.) was added to 100 parts by mass of the polyimide resin in the polyimide resin solution C used in Example 3, and the peel strength was measured. The peel strength of the sample was 3.79 lbf / in.

[0095]

[0096] Example 9 A sample was prepared in the same manner as in Example 3, except that 1 part by mass of a triazine-containing adhesion-imparting additive (VD-5, formula (7), manufactured by Shikoku Chemical Industry Co., Ltd.) was added to 100 parts by mass of the polyimide resin in the polyimide resin solution C used in Example 3, and the peel strength was measured. The peel strength of the sample was 5.34 lbf / in.

[0097]

[0098] Example 10 A sample was prepared and the peel strength was measured in the same manner as in Example 1, except that polyimide resin solution A was replaced with polyimide resin solution D. The peel strength of the sample was 3.86 lbf / in.

[0099] Example 11 A sample was prepared in the same manner as in Example 10, except that 1 part by mass of an epoxy silane adhesion promoter (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd., represented by formula (3) in Example 5) was added to 100 parts by mass of the polyimide resin in modified polyimide resin solution D used in Example 10, and the peel strength was measured. The peel strength of the sample was 5.33 lbf / in.

[0100] Example 12 A sample was prepared in the same manner as in Example 10, except that 1 part by mass of a triazine-based adhesion-imparting additive (VD-5 manufactured by Shikoku Chemical Industry Co., Ltd., formula (7) in Example 9) was added to 100 parts by mass of the polyimide resin in Polyimide Resin Solution D used in Example 10, and the peel strength was measured. The peel strength of the sample was 5.43 lbf / in.

[0101] (Example 13) The aluminum foil is subjected to a test in which the ratio of the total surface area of ​​the crystallized particles present in a predetermined surface area is 2% or less, and the average surface area per crystallized particle is 2 μm ２ A sample was prepared in the same manner as in Example 1, except that the aluminum foil (manufactured by Toyo Aluminum, thickness 11 μm, trade name "Laxal", surface roughness Ra 7 nm) having a surface roughness Rz of 40 nm or less in the direction perpendicular to the rolling direction and a surface roughness Ra of 10 nm or less was used, and further polyimide resin solution A was replaced with polyimide resin solution C, and the peel strength of the sample was measured. The peel strength of the sample was 1.15 lbf / in.

[0102] (Example 14) The aluminum foil is subjected to a test in which the ratio of the total surface area of ​​the crystallized particles present in a predetermined surface area is 2% or less, and the average surface area per crystallized particle is 2 μm ２ A sample was prepared in the same manner as in Example 1, except that the aluminum foil (manufactured by Toyo Aluminum, thickness 11 μm, trade name "Laxal", surface roughness Ra 7 nm) having a surface roughness Rz of 40 nm or less in the direction perpendicular to the rolling direction and a surface roughness Ra of 10 nm or less was used, and further polyimide resin solution A was replaced with polyimide resin solution D, and the peel strength of the sample was measured. The peel strength of the sample was 2.58 lbf / in.

[0103] Comparative Example 1 A palladium-containing solution was coated on the surface of an aluminum foil (manufactured by Toyo Aluminum K.K., 1N30, thickness 11 μm), and heated to laminate a palladium-based catalyst layer on the aluminum foil, thereby obtaining a material for printed wiring boards.

[0104] The catalyst layer of this printed wiring board material and a glass epoxy resin substrate (manufactured by ISOLA, thickness 0.2 μm) were bonded using a heat press under conditions of 180°C for 80 minutes at 0.35 MPa to produce a "substrate / palladium-based catalyst layer / aluminum foil" laminate. This laminate was then immersed in a hydrogen chloride aqueous solution to dissolve and remove the aluminum foil, resulting in a "substrate / palladium-based catalyst layer" laminate. This laminate was then subjected to electroless copper plating to produce a "substrate / palladium-based catalyst layer / copper plating layer (thickness 1 μm or less)" laminate. Copper electroplating was then performed to obtain a "substrate / palladium-based catalyst layer / copper plating layer (thickness 35 μm)" laminate.

[0105] For convenience, the copper plating layer was not processed into a circuit pattern shape, but was used as a printed wiring board sample as is.

[0106] The obtained sample was subjected to a heat treatment at 80°C for 12 hours, and then cut into a piece with a width of 1 cm, and the peel strength at the interface between the copper plating layer and the substrate was measured in the same manner as in Example 1. The peel strength was 0.57 lbf / in.

[0107] Comparative Example 2 A sample was prepared and the peel strength was measured in the same manner as in Example 1, except that the polyimide solution A was replaced with the polyimide resin solution E. The peel strength of the sample was 0.90 lbf / in.

[0108] (Comparative Example 3) The aluminum foil is prepared such that the ratio of the total surface area of ​​the crystallized particles present in a predetermined surface area is 2% or less, and the average surface area per crystallized particle is 2 μm ２ A sample was prepared in the same manner as in Comparative Example 1, except that an aluminum foil (manufactured by Toyo Aluminum, thickness 11 μm, trade name "Laxal", surface roughness Ra 7 nm) having a surface roughness Rz of 40 nm or less in the direction perpendicular to the rolling direction and a surface roughness Ra of 10 nm or less was used, and the peel strength was measured. The peel strength was 0.32 lbf / in.

[0109] Comparative Example 4 A sample was prepared in the same manner as in Example 1, except that the adhesive layer was formed using a commercially available surface conditioner for plating (Condilizer SP, manufactured by Okuno Chemical Industries Co., Ltd.), and the peel strength was measured. The peel strength was 0.11 lbf / in.

[0110] Based on the peel strength results for each of the above Examples and Comparative Examples, the evaluation results for adhesive strength are shown in Table 1. Here, peel strengths of less than 1.00 lbf / in were rated as x, peel strengths of 1.00 lbf / in or more but less than 2.00 lbf / in were rated as Δ, peel strengths of 2.00 lbf / in or more but less than 5.00 lbf / in were rated as ◯, and peel strengths of 5.00 lbf / in or more were rated as ⊚.

[0111] As shown by the above results, a printed wiring board manufactured using the printed wiring board material 10 of the present disclosure has sufficient adhesive strength between the copper plating layer and the substrate, even if unevenness is not necessarily formed at the interface between the copper plating layer and the substrate.

[0112] The present disclosure is extremely useful because it can provide a material for printed wiring boards that can provide printed wiring boards having sufficient adhesive strength at the interface between a copper plating layer and a substrate without forming irregularities at the interface, and a method for manufacturing a printed wiring board using the material for printed wiring boards.

[0113] REFERENCE SIGNS LIST 10 Material for printed wiring board 11 Metal foil 11a One surface (of metal foil) 12 Catalyst layer 13 Adhesion layer 20 Printed wiring board 21 Base material 22 Copper plating layer

Claims

1. A material for printed wiring boards, comprising at least a catalyst layer and an adhesive layer containing a polyimide resin laminated in this order on at least one surface of a metal foil, the imide group concentration of the polyimide resin being 8% or more and 26% or less.

2. The material for printed wiring boards according to claim 1, wherein the adhesive layer contains 0.1 parts by mass or more and 10 parts by mass or less of at least one adhesion-imparting additive selected from the group consisting of aminosilanes, epoxysilanes, and triazines, per 100 parts by mass of the polyimide resin.

3. The material for printed wiring boards according to claim 1, wherein the polyimide resin includes a urethane-modified polyimide resin.

4. The material for printed wiring boards according to claim 1, wherein the surface roughness Ra of the metal foil is 0.4 μm or less.

5. The material for printed wiring boards according to claim 1, wherein 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 wiring boards according to claim 1, wherein 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 wiring board comprising the steps of: bonding the adhesive layer of the material for printed wiring boards according to any one of claims 1 to 6 and a base material in opposing positions; removing the metal foil of the material for printed wiring boards to expose a surface of the catalyst layer on which the adhesive layer is not provided; laminating a copper plating layer on the surface; and processing the copper plating layer into a circuit pattern shape, in this order.

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