Adhesive sheet for printed wiring board, metal clad laminate, printed wiring board, and electronic apparatus

Abstract

To provide an adhesive sheet for printed wiring boards, which realizes printed wiring stable in impedance characteristics, is free from generation of puddling, is excellent in thermal cycle resistance, can form an opening excellent in appearance when laser processing or drilling, and has high adhesion to a substrate during lamination.SOLUTION: A problem is solved by an adhesive sheet for printed wiring board characterized by containing an adhesive sheet with a release film laminated on at least one side (side A) of an adhesive layer, wherein the adhesive layer contains 5 to 15,000 ppm of toluene and is used as an interlayer adhesive material for printed wiring boards.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an adhesive sheet for printed wiring boards, a metal-clad laminate, a printed wiring board, and an electronic device.

Background Art

[0002] In recent years, the development of the electronics field has been remarkable, and there has been a need to process a large amount of information at high speed. The frequency band of signals used in printed wiring boards used in electronic devices, communication devices, etc. has shifted from the MHz band to the GHz band, and it is assumed that appropriate materials will be required in a wide high-frequency band in the future. Generally, the transmission loss of an electrical signal is considered to consist of dielectric loss caused by the dielectric properties of the insulating layer around the wiring and conductor loss caused by the shape of the conductor, skin resistance, characteristic impedance, etc. However, in the case of a high-frequency circuit, the influence of dielectric loss is large, and since dielectric loss increases in proportion to the product of the square root of the relative permittivity of the material and the dielectric tangent of the material, a material with both low relative permittivity and low dielectric tangent is required.

[0003] Furthermore, in the case of a high-frequency circuit, it is important to match the impedance of the transmission line and the circuit to suppress transmission delay. When the impedance between the transmission line and the connected circuit is different, the signal is reflected at the interface between the transmission line and the circuit, generating a wave in the reverse direction. This reflected wave causes signal loss and distortion, leading to a decrease in the performance of the circuit. Therefore, it is necessary to match the impedance of each component in the circuit. A printed wiring board forms a signal line pattern by etching a metal-clad laminate in which a metal plate, a resin layer, and an adhesive layer are laminated. For example, Patent Document 1 discloses a metal-clad laminate having an insulating resin layer, an adhesive layer, and a metal layer. The adhesive layer contains a tetracarboxylic acid residue and a diamine residue, and contains 50 mol parts or more of a diamine residue derived from a dimer acid type diamine in which two terminal carboxylic acid groups of the dimer acid are substituted with a primary aminomethyl group or an amino group with respect to 100 mol parts of the diamine residue, and has a polyimide. A metal-clad laminate is disclosed.

Prior Art Documents

Patent Document

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A printed wiring board forms signal lines in a pattern by etching a metal-clad laminate in which a metal plate, a resin layer, and an adhesive layer are laminated together. In a multilayer printed wiring board, in order to provide a laminated structure on one signal line, an adhesive layer that is a dielectric may be laminated. The impedance characteristics of the signal lines can vary depending on the dielectric properties and thickness of the neighboring dielectric. When manufacturing this multilayer printed wiring board, the adhesive layer and other layers are adhered by a hot press process. However, if the adhesive layer contains a large amount of low molecular components such as residual solvents, their heating and evaporation cause a change in the thickness of the adhesive layer, resulting in a variation in the impedance characteristics of the signal lines from the design value and posing a problem that hinders circuit design.

[0006] Also, in the process of manufacturing the above-mentioned multilayer printed wiring board, it is common to laminate (temporarily attach) an adhesive sheet for printed wiring boards to the adherend and then go through a hot press process. However, in this lamination process, air enters between the adhesive sheet for printed wiring boards and the adherend (air entrapment), causing a problem of poor appearance (padding).

[0007] In recent years, with the worldwide spread of electronic devices such as smartphones and tablets, reliability in a wide temperature range from low to high temperatures is required. Conventional printed wiring boards have a problem that when exposed to extreme temperature changes, peeling occurs between the adhesive layer and the adjacent layer, and the adhesive layer has been required to have high cold and heat cycle resistance.

[0008] In recent years, due to space-saving and new concepts in circuit design, there is a demand that processing methods such as lasers and drills used for forming vias and through-holes in printed wiring boards do not cause peeling of the adhesive layer or appearance defects such as burrs. (Hereinafter referred to as processability)

[0009] The present invention has been made in view of the above background, and aims to provide an adhesive sheet for a printed wiring board that realizes printed wiring with stable impedance characteristics, has no generation of padding, is excellent in thermal cycle resistance, can form an opening with good appearance during laser processing or drill processing, and has high substrate adhesion during lamination.

Means for Solving the Problems

[0010] As a result of intensive studies by the present inventors, it has been found that the problems of the present disclosure can be solved in the following aspects, and the present disclosure has been completed. [1]: An adhesive sheet having a release film laminated on at least one surface (A surface) of the adhesive layer, wherein the adhesive layer contains 5 to 15,000 ppm of toluene, and the adhesive layer is used as an interlayer adhesion member for a printed wiring board. An adhesive sheet for a printed wiring board, characterized in that [2]: The surface (B surface) of the adhesive layer opposite to the surface (A surface) on which the release film of the adhesive layer is laminated is The arithmetic mean roughness Sa determined in accordance with ISO 25178-2:2012 is 0.05 to 2 μm. The adhesive sheet for a printed wiring board according to [1].[[]END]] [3]: In the cured layer obtained by heating the adhesive layer, the difference |Er 25 | between the storage elastic modulus (Er 250 ) at 25°C and the storage elastic modulus (Er 25 - Er 250 | at 250°C is 0.1 to 100,000 MPa. The adhesive sheet for a printed wiring board according to [1].[[]END]] [4]: The elongation at break of the cured layer obtained by heating the adhesive layer at 180°C for 60 minutes is 50 to 1,000%. The adhesive sheet for a printed wiring board according to [1].[[]END]] [5]: The metal-clad laminate having the cured layer of the adhesive layer described in [1] to [4]. [6]: The printed wiring board having the metal-clad laminate described in [5]. [7]: The electronic device having the printed wiring board described in [6].

Advantages of the Invention

[0011] According to the present disclosure, it is possible to provide an adhesive sheet for a printed wiring board that realizes printed wiring with stable impedance characteristics, has no generation of paddling, is excellent in resistance to thermal cycling, can form an opening with good appearance during laser processing or drill processing, and has high substrate adhesion during lamination.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0013] Hereinafter, the adhesive sheet for a printed wiring board, the metal-clad laminate, the printed wiring board, and the electronic device according to the present disclosure will be described in order. Note that "~" indicating a numerical range includes the lower limit value and the upper limit value thereof unless otherwise specified. In addition, for clarity of explanation, the drawings are appropriately simplified. Also, for the purpose of explanation, the scales of the respective configurations in the drawings may be greatly different.

[0014] [Adhesive Sheet for Printed Wiring Board] The adhesive sheet for a printed wiring board of the present disclosure is an adhesive sheet in which a release film is laminated on at least one surface (A surface) of an adhesive layer, and is used as a member for interlayer adhesion of a printed wiring board.

[0015] The adhesive sheet for a printed wiring board of the present disclosure contains 5 to 15,000 ppm of toluene in the adhesive layer. When the toluene content of the adhesive layer is 5 ppm or more, the temporary adhesion strength to the base material can be increased, and transfer defects of the sheet to the base material can be suppressed. On the other hand, when the toluene content of the adhesive layer is 15,000 ppm or less, it is possible to suppress a decrease in film thickness due to heat evaporation of low molecular components during hot pressing, and the impedance characteristics are stabilized. The toluene content of the adhesive layer is preferably 10 to 10,000 ppm, and more preferably 50 to 5,000 ppm. The toluene content of the adhesive layer can be calculated, for example, from the peak area of the chart obtained by gas chromatography.

[0016] As disclosed in, for example, Japanese Patent Application Laid-Open No. 2014-114373, toluene is one of the general-purpose organic solvents widely used in the production of adhesives in the electrical field including the printed wiring board according to the present disclosure. In the above-mentioned electrical field, since it is preferable to use a highly hydrophobic organic solvent to avoid problems such as short circuits caused by moisture, toluene, which has no polar group in the molecule and has high solubility, is particularly frequently used in the process of manufacturing the adhesive layer of the adhesive resin sheet for printed wiring boards. Therefore, toluene often remains in the adhesive layer even after the adhesive layer is formed, and by controlling the toluene content, the above-described effects can be most effectively exhibited.

[0017] The toluene content of the adhesive layer is not particularly limited as long as it is a method for setting the content to a desired value. For example, it can be controlled by the solid content (non-volatile content) and viscosity of the resin composition (also referred to as the coating solution), the drying temperature and time of the coating film, and further the thickness of the coating film. Specific drying temperature and time will be described later in the method for manufacturing an adhesive resin sheet for a printed wiring board.

[0018] [Adhesive layer] The adhesive layer of the present disclosure is obtained by coating an adhesive composition on a release film and drying it, and is a solid that is non-fluid at room temperature and forms a layer with a certain thickness. From the viewpoint of achieving both embedability and thin film properties of the adhesive layer with respect to the signal lines, the thickness of the adhesive layer in the adhesive sheet for a printed wiring board is preferably 5 to 200 μm, more preferably 10 to 100 μm, and even more preferably 15 to 70 μm. The adhesive layer of the present disclosure is cured by heating to form a cured layer described later.

[0019] The adhesive layer preferably contains a binder (A), a filler (B), and other optional components.

[0020] [Binder (A)] The binder (A) serves as a base of the adhesive layer and has a function of dispersing and supporting the filler (B) and other additives. The composition of the binder (A) is not particularly limited as long as it has the above-described function, but it preferably contains a resin (a-1). The resin (a-1) in the present disclosure is usually defined as an organic material that is solid, semi-solid, or solidified, has a softening or melting range, and has a weight average molecular weight (Mw) of 5,000 or more.

[0021] [Resin (a-1)] Except for the above-described weight average molecular weight (Mw), the composition, molecular structure, etc. of the resin (a-1) are not particularly limited, but it is also possible to select a suitable one depending on the properties of the resin. From the viewpoint of applying a thermal stimulus to the adhesive layer to develop adhesiveness, the resin (a-1) is preferably a thermosetting resin or a thermoplastic resin.

[0022] [Thermosetting resin] The thermosetting resin is one of the resins (a-1) that has thermosetting properties. Thermosetting is defined as "the ability to change into a substantially infusible and insoluble product when cured by heating or other means such as radiation or a catalyst."

[0023] The above-described thermosetting properties may be exhibited by the reaction of reactive functional groups with each other when the thermosetting resin has reactive functional groups such as acidic groups, or may be exhibited by the reaction of reactive functional groups incorporated in each of the thermosetting resin and the curing agent (a-2) described below.

[0024] The resin (a-1) in the present disclosure includes acrylic resins, polyester resins, polyurethane resins, polyurethane-polyurea resins, polyamide resins, polyimide resins, polycarbonate resins, polyphenylene ether resins, styrene-based elastomers, fluororesins, and styrene maleic anhydride-based resins. These can be appropriately selected and used in combination. Among them, styrene-based elastomers, polyphenylene ether, polyimide, polyamide, and polyurethane are preferable from the viewpoints of high insulation properties derived from high hydrophobicity, dielectric properties, and high heat resistance derived from a low thermal decomposition point. Styrene-based elastomers, polyimide, polyamide, and polyurethane are more preferable. The above styrene-based elastomer refers to a block copolymer in which a portion composed of styrene and a portion composed of butadiene, isoprene, ethylene, etc. form a "block".

[0025] When the resin (a-1) in the present disclosure is a thermosetting resin, it preferably has reactive functional groups that can react with functional groups such as epoxy groups, maleimide, isocyanate groups, and carbodiimide groups and metal chelates possessed by the curing agent (a-2) described below. Examples of the reactive functional group include a carboxyl group, an acid anhydride group, a hydroxyl group (alcoholic hydroxyl group, phenolic hydroxyl group), an amino group, a cyanate group, an isocyano group, a cyanato group, an isocyanato group, an imidazole group, a pyrrole group, an acetal group, an acryloyl group, a methacryloyl group, a vinyl group, an aldehyde group, a hydrazide group, a hydrazone group, a phosphoric acid group, etc. It is preferably selected from the group consisting of a carboxyl group, an acid anhydride group, a hydroxyl group (alcoholic hydroxyl group, phenolic hydroxyl group), and an amino group, and may contain two or more types of reactive functional groups.

[0026] When the resin (a-1) has a carboxyl group, the acid value of the resin (a-1) is preferably 0.5 to 30 mg / KOH, more preferably 1 to 20 mg / KOH. By setting the acid value to 0.5 to 30 mg / KOH, the dielectric properties can be made good, and the thermal cycle resistance can be further improved.

[0027] [Thermoplastic resin] The thermoplastic resin is a resin having thermoplasticity among resins. Thermoplasticity is defined as "the ability to repeatedly soften by heating and harden by cooling through a temperature range peculiar to plastics, and to form the shape by flowing in the softened state and to repeatedly make the article state by molding, extrusion or molding".

[0028] [Curing agent (a-2)] The curing agent (a-2) in the present disclosure is a substance that promotes or regulates the curing reaction, and is defined as a substance having a molecular weight or weight average molecular weight (Mw) of less than 5,000. The curing reaction is defined as "polymerizing and / or crosslinking a prepolymer or polymerization composition by heating or other means such as radiation or a catalyst, and irreversibly increasing the elastic modulus". In the binder (A), from the viewpoint of forming polymerization and / or crosslinking by stimulation such as heat and expressing strong adhesiveness in the adhesive layer, the binder (A) of the present disclosure preferably contains a curing agent (a-2).

[0029] The above-mentioned curing reaction may be one in which the curing agents (a-2) react with each other, or may react with other components in the binder (A) such as the resin (a-1). When the resin (a-1) and the curing agent (a-2) undergo a curing reaction, from the viewpoint of efficiently carrying out the reaction, the resin (a-1) is preferably a thermosetting resin.

[0030] From the viewpoint that the curing reaction does not proceed during storage and occurs only during heating, as the combination of the thermosetting resin and the curing agent (a-2), it is preferable to select a combination that does not cause a crosslinking reaction at 50°C and promotes the curing reaction at 120°C to 200°C. Also, by appropriately combining two or more curing agents having different curing reaction start temperatures, the crosslink density of the adhesive layer in each temperature range may be controlled.

[0031] The curing agent (a-2) can be used without particular limitation as long as it can adjust the crosslink density of the adhesive layer to a suitable range. Among them, it is preferably at least one selected from the group consisting of epoxy compounds, maleimide compounds, isocyanate group-containing compounds, metal chelate compounds, and carbodiimide group-containing compounds.

[0032] <Epoxy group-containing compound> The epoxy group-containing compound may be any compound having an epoxy group in the molecule and is not particularly limited, but those having an average of 2 or more epoxy groups in one molecule can be preferably used. As the epoxy group-containing compound, for example, epoxy resins such as glycidyl ether type epoxy resins, glycidyl amine type epoxy resins, glycidyl ester type epoxy resins, or cyclic aliphatic (alicyclic) epoxy resins can be used.

[0033] Examples of glycidyl ether type epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AD type epoxy resin, cresol novolak type epoxy resin, phenol novolak type epoxy resin, α-naphthol novolak type epoxy resin, bisphenol A type novolak type epoxy resin, dicyclopentadiene type epoxy resin, tetrabromobisphenol A type epoxy resin, brominated phenol novolak type epoxy resin, tris(glycidyloxyphenyl)methane, or tetrakis(glycidyloxyphenyl)ethane, etc.

[0034] Examples of glycidyl amine type epoxy resins include tetraglycidyldiaminodiphenylmethane, triglycidyl para-aminophenol, triglycidyl meta-aminophenol, or tetraglycidyl metaxylylenediamine, etc.

[0035] Examples of glycidyl ester type epoxy resins include diglycidyl phthalate, diglycidyl hexahydrophthalate, or diglycidyl tetrahydrophthalate, etc.

[0036] Examples of alicyclic (cycloaliphatic) epoxy resins include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate, or bis(epoxycyclohexyl)adipate, etc.

[0037] As the epoxy group-containing compound, one of the above compounds can be used alone, or two or more of them can be used in combination. From the viewpoint of high adhesiveness, it is preferable to use bisphenol A type epoxy resin, cresol novolak type epoxy resin, phenol novolak type epoxy resin, tris(glycidyloxyphenyl)methane, tetrakis(glycidyloxyphenyl)ethane, or tetraglycidyl metaxylylenediamine as the epoxy group-containing compound, and those containing a trifunctional or higher epoxy group are more preferable from the viewpoint of heat resistance.

[0038] <Maleimide group-containing compound> As the maleimide group-containing compound, any compound having a maleimide group in the molecule may be used, and there is no particular limitation. However, those having an average of two or more maleimide groups in one molecule can be preferably used.

[0039] Specific examples of the maleimide group-containing compound in the present invention include o-phenylenebismaleimide, m-phenylenebismaleimide, p-phenylenebismaleimide, 4-methyl-1,3-phenylenebismaleimide, N,N'-(toluene-2,6-diyl)bismaleimide), 4,4'-diphenylmethanebismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethanebismaleimide, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(4-maleimidophenoxy)benzene, polyphenylmethane maleimide (CAS NO: 67784-74-1, reaction product of a polymer composed of formaldehyde and aniline and maleic anhydride), N,N'-ethylenebismaleimide, N,N'-trimethylenebismaleimide, N,N'-propylenebismaleimide, N,N'-tetramethylenebismaleimide, N,N'-pentamethylenebismaleimide, N,N'-(1,3-pentanediyl)bis(maleimide), N,N'-hexamethylenebismaleimide, N,N'-(1,7-heptanediyl)bismaleimide, N,N'-(1,8-octanediyl)bismaleimide, N,N'-(1,9-nonanediyl)bismaleimide, N,N'-(1,10-decanediyl)bismaleimide, N,N'-(1,11-undecanediyl)bismaleimide, N,N'-(1,12-dodecanediyl)bismaleimide, N,N'-[(1,4-phenylene)bismethylene]bismaleimide, N,N'-[(1,2-phenylene)bismethylene]bismaleimide, N,N'-[(1,3-phenylene)bismethylene]bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, N,N′-[(methylimino)bis(4,1-phenylene)]bismaleimide, N,N′-(2-hydroxypropane-1,3-diylbisiminobiscarbonylbisethylene)bismaleimide, N,N′-(dithiobisethylene)bismaleimide, N,N′-[hexamethylenebis(iminocarbonylmethylene)]bismaleimide, N,N′-carbonylbis(1,4-phenylene)bismaleimide, N,N′,N′′-Tris(ethylene)nitrilotris(maleimide), N,N’,N’’-Tris(4,1-phenylene)nitrilotris(maleimide), N,N′-p-Phenylenebis(oxy-p-phenylene)bismaleimide, N,N′-Methylenebis(oxy)bis(2-methyl-1,4-phenylene)bismaleimide, N,N’-Methylenebis(oxy-p-phenylene)bis(maleimide), N,N′-Dimethylsilylenebis[(4,1-phenylene)(1,3,4-oxadiazole-5,2-diyl)(4,1-phenylene)]bismaleimide, N,N’-[(1,3-phenylene)bisoxy-bis(3,1-phenylene)]bismaleimide, 1,1’-[3’-Oxospiro[9H-xanthene-9,1’(3’H)-isobenzofuran]-3,6-diyl]bis(1H-pyrrole-2,5-dione), N,N’-(3,3’-Dichlorobiphenyl-4,4’-diyl)bismaleimide, N,N’-(3,3’-Dimethylbiphenyl-4,4’-diyl)bismaleimide, N,N’-(3,3’-Dimethoxybiphenyl-4,4’-diyl)bismaleimide, N,N’-Methylenebis(2-ethyl-4,1-phenylene)bismaleimide, N,N’-Methylenebis(2,6-diethyl-4,1-phenylene)bismaleimide, N,N’-Methylenebis(2-bromo-6-ethyl-4,1-phenylene)bismaleimide, N,N’-Methylenebis(2-methyl-4,1-phenylene)bismaleimide, N,N’-Ethylenebis(oxyethylene)bismaleimide, N,N’-Sulfonylbis(4,1-phenylene)bis(oxy)bis(4,1-phenylene)bismaleimide, N,N’-Naphthalene-2,7-diylbis(oxy)bis(4,1-phenylene)bismaleimide, N,N’-p-Phenylenebis(oxy-p-phenylene)bismaleimide, N,N’-[(1,3-phenylene)bisoxy-bis(3,1-phenylene)]bismaleimide, N,N’-(3,6,9-Trioxaundecane-1,11-diyl)bismaleimide, N,N’-Isopropylidenebis[p-phenyleneoxycarbonyl(m-phenylene)]]bismaleimide, N,N'-[Isopropylidenebis[p-phenyleneoxycarbonyl(p-phenylene)]]bismaleimide, N,N'-[Isopropylidenebis[(2,6-dichlorobenzene-4,1-diyl)oxycarbonyl(p-phenylene)]]bismaleimide, N,N'-[(Phenylimino)bis(4,1-phenylene)]bismaleimide, N,N'-[Azobis(4,1-phenylene)]bismaleimide, N,N'-[1,3,4-Oxadiazole-2,5-diylbis(4,1-phenylene)]bismaleimide, 2,6-Bis[4-(maleimid-N-yl)phenoxy]benzonitrile, N,N'-[1,3,4-Oxadiazole-2,5-diylbis(3,1-phenylene)]bismaleimide, N,N'-[Bis[9-oxo-9H-9-phospha(V)-10-oxaphenanthren-9-yl]methylenebis(p-phenylene)]bismaleimide, N,N'-[Hexafluoroisopropylidenebis[p-phenyleneoxycarbonyl(m-phenylene)]]bismaleimide, N,N'-[Carbonylbis[(4,1-phenylene)thio(4,1-phenylene)]]bismaleimide, N,N'-Carbonylbis(p-phenyleneoxyp-phenylene)bismaleimide, N,N'-[5-tert-Butyl-1,3-phenylene bis[(1,3,4-oxadiazole-5,2-diyl)(4,1-phenylene)]]bismaleimide, N,N'-[Cyclohexylidenebis(4,1-phenylene)]bismaleimide, N,N'-[Methylenebis(oxy)bis(2-methyl-1,4-phenylene)]bismaleimide, N,N'-[5-[2-[5-(Dimethylamino)-1-naphthylsulfonylamino]ethylcarbamoyl]-1,3-phenylene]bismaleimide, N,N'-(Oxydibethylene)bismaleimide, N,N'-[Dithiobis(m-phenylene)]bismaleimide, N,N'-(3,6,9-Trioxaundecane-1,11-diyl)bismaleimide, N,Examples of polyfunctional maleimides include N'-(ethylenebis-p-phenylene)bismaleimide, BMI-689, BMI-1500, BMI-1700, BMI-3000, BMI-5000, BMI-9000 manufactured by Designer Molecules, ODA-BMI, BAF-BMI manufactured by JFE Chemical, and the like.

[0040] Examples also include polyfunctional maleimides obtained by reacting polyfunctional amines with maleic anhydride. Examples of polyfunctional amines include isophoronediamine, dicyclohexylmethane-4,4'-diamine, Jeffamine D-230, HK-511, D-400, XTJ-582, D-2000, XTJ-578, XTJ-509, XTJ-510, T-403, T-5000 having a terminal amino group-containing polypropylene glycol backbone manufactured by Huntsman Corporation, XTJ-500, XTJ-501, XTJ-502, XTJ-504, XTJ-511, XTJ-512, XTJ-590 having a terminal amino group-containing ethylene glycol backbone, and XTJ-542, XTJ-533, XTJ-536, XTJ-548, XTJ-559 having a terminal amino group-containing polytetramethylene glycol backbone.

[0041] <Compound containing isocyanate group> The isocyanate group-containing compound may be any compound having an isocyanate group in the molecule and is not particularly limited. Specific examples of the isocyanate group-containing compound having one isocyanate group in one molecule include n-butyl isocyanate, isopropyl isocyanate, phenyl isocyanate, benzyl isocyanate, (meth)acryloyloxyethyl isocyanate, 1,1-bis[(meth)acryloyloxymethyl]ethyl isocyanate, vinyl isocyanate, allyl isocyanate, (meth)acryloyl isocyanate, isopropenyl-α,α-dimethylbenzyl isocyanate, and the like. In addition, diisocyanate compounds such as 1,6 - diisocyanatohexane, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, xylylene diisocyanate, 2,4 - tolylene diisocyanate, toluene diisocyanate, 2,4 - tolylene diisocyanate, hexamethylene diisocyanate, 4 - methyl - m - phenylene diisocyanate, naphthylene diisocyanate, para - phenylene diisocyanate, tetramethylxylylene diisocyanate, cyclohexylmethane diisocyanate, hydrogenated xylylene diisocyanate, cyclohexyl diisocyanate, tolidine diisocyanate, 2,2,4 - trimethylhexamethylene diisocyanate, 2,4,4 - trimethylhexamethylene diisocyanate, m - tetramethylxylylene diisocyanate, P - tetramethylxylylene diisocyanate, dimer acid diisocyanate, etc., and compounds obtained by reacting equimolar amounts of hydroxyl - group, carboxyl - group, and amide - group - containing vinyl monomers can also be used as diisocyanate compounds.

[0042] Specific examples of the isocyanate - group - containing compounds having two isocyanate groups in one molecule include aromatic diisocyanates such as 1,3 - phenylene diisocyanate, 4,4'-diphenyldiisocyanate, 1,4 - phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4 - tolylene diisocyanate, 2,6 - tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6 - triisocyanatetoluene, 1,3,5 - triisocyanatobenzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4''-triphenylmethane triisocyanate, aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2 - propylene diisocyanate, 2,3 - butylene diisocyanate, 1,3 - butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4 - trimethylhexamethylene diisocyanate, etc. Aromatic aliphatic diisocyanates such as ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate [alias: isophorone diisocyanate], 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane and other alicyclic diisocyanates can be mentioned.

[0043] In addition, examples of the isocyanate group-containing compound having three isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates such as lysine triisocyanate, aromatic aliphatic polyisocyanates, alicyclic polyisocyanates, etc., and trimethylolpropane adducts of the diisocyanates described above, biuret bodies reacted with water, and trimers having an isocyanurate ring.

[0044] As the isocyanate group-containing compound, blocked isocyanate group-containing compounds in which the isocyanate groups in the various isocyanate group-containing compounds exemplified above are protected with ε-caprolactam, MEK oxime, etc. can also be used. Specifically, examples of the isocyanate group-containing compound include those in which the isocyanate group is blocked with ε-caprolactam, methyl ethyl ketone (hereinafter referred to as MEK) oxime, cyclohexanone oxime, pyrazole, phenol, and the like. In particular, a hexamethylene diisocyanate trimer having an isocyanurate ring and blocked with MEK oxime or pyrazole is very preferable when used in the present invention because it has excellent heat resistance. Further, from the viewpoint of heat resistance, it is preferable to have three or more functional isocyanate groups.

[0045] <Metal chelate compound> The metal chelate compound is an organometallic compound composed of a metal and an organic substance, and reacts with the reactive functional group of the binder resin (A) to form a crosslink. The type of the organometallic compound is not particularly limited, and examples thereof include organoaluminum compounds, organotitanium compounds, and organozirconium compounds. Further, the bond between the metal and the organic substance may be a metal-oxygen bond and is not limited to a metal-carbon bond. In addition, the bonding mode between the metal and the organic substance may be any of a chemical bond, a coordination bond, and an ionic bond. Further, from the viewpoint of heat resistance, it is preferable that the compound has three or more functional groups.

[0046] The organoaluminum compound is preferably an aluminum metal chelate compound. Examples of the aluminum metal chelate compound include ethyl acetoacetate aluminum diisopropylate, aluminum tris(ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum monoacetylacetonate bis(ethyl acetoacetate), aluminum tris(acetylacetate), aluminum monoacetylacetonate bis(ethyl acetoacetate), aluminum di-n-butoxide monomethyl acetoacetate, aluminum diisobutoxide monomethyl acetoacetate, aluminum di-sec-butoxide monomethyl acetoacetate, aluminum isopropylate, monosec-butoxyaluminum diisopropylate, aluminum-sec-butyrate, aluminum ethoxide, and the like.

[0047] The organic titanium compound is preferably a titanium metal chelate compound. Examples of the titanium metal chelate compound include titanium acetylacetonate, titanium tetraacetylacetonate, titanium ethyl acetoacetate, titanium octylene glycolate, titanium ethyl acetoacetate, titanium-1,3-propanedioxybis(ethyl acetoacetate), polytitanium acetylacetylacetonate, tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, darsally amyl titanate, tetra-tert-butyl titanate, tetrastearyl titanate, titanium isostearate, tri-n-butoxytitanium monostearate, di-i-propoxytitanium distearate, titanium stearate, di-i-propoxytitanium diisostearate, (2-n-butoxycarbonylbenzoyloxy)tributoxytitanium, and the like. The organic zirconium compound is preferably a zirconium metal chelate compound. Examples of the zirconium metal chelate compound include zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxyacetylacetonate bis(ethyl acetoacetate), zirconium dibutoxybis(ethyl acetoacetate), zirconium tetraacetylacetonate, normal propyl zirconate, normal butyl zirconate, zirconium stearate, zirconium octylate, and the like. Among these, the organic titanium compound and the organic zirconium compound are preferable from the viewpoint of thermosetting reactivity.

[0048] <Compound containing carbodiimide group> The carbodiimide group-containing compound is not particularly limited as long as it has a carbodiimide group in the molecule. Examples of the carbodiimide group-containing compound include Carbodilite V-01, V-03, V-05, V-07, V-09 (manufactured by Nisshinbo Chemical Inc.), cyclic carbodiimide (manufactured by Teijin Limited), and the like. From the viewpoint of heat resistance, those having an average of 3 or more carbodiimide groups in one molecule are preferable.

[0049] The curing agent (a-2) used in the present invention is preferably contained in a total amount of 1 to 30 parts by mass, more preferably 1 to 20 parts, and even more preferably 1 to 10 parts, based on 100 parts of the binder resin (A). By setting the addition amount of the curing agent (a-2) to 1 to 30 parts, the content of polar groups derived from the curing agent (a-2) contained in the adhesive resin sheet can be lowered, and the dielectric loss tangent can be lowered. Further, by controlling the addition amount of this curing agent (a-2), the Tg of the adhesive layer can be controlled within a preferable range, and both high flexibility and low dielectric loss tangent can be realized.

[0050] The functional group equivalent weight of the curing agent (a-2) component is preferably 50 to 1,000 g / eq, more preferably 50 to 500 g / eq, and even more preferably 50 to 300 g / eq. By being in this range, the crosslinking density becomes sufficient, a decrease in the storage modulus at high temperatures can be prevented, and side etching during laser processing can be suppressed. Also, by setting the functional group equivalent weight within the above range, the content of polar groups derived from the curing agent (a-2) contained in the adhesive resin sheet can be controlled, and the dielectric loss tangent can be lowered.

[0051] Further, from the viewpoint of enhancing heat resistance and improving cold heat cycle resistance, the curing agent (a-2) preferably has an aromatic structure in its structure.

[0052] The curing agent (a-2) can be used alone or in combination of two or more. It is preferable to use the curing agent (a-2) having a molecular weight or weight average molecular weight of 100 or more from the viewpoint of adjusting the storage modulus and glass transition temperature of the conductive composition.

[0053] It is preferable to blend 0.1 to 70 parts by mass, more preferably 10 to 20 parts by mass of the curing agent (a-2) with respect to 100 parts by mass of the resin (a-1). By setting the addition amount of the curing agent (a-2) to 0.1 part by mass or more, the density of the crosslinked structure of the cured layer can be optimized, the heat resistance can be enhanced, the resistance to thermal cycling can be improved, and the decrease in the elastic modulus of the adhesive layer at high temperatures can be suppressed. By setting the addition amount of the curing agent (a-2) to 70 parts by mass or less, it is possible to prevent the cured layer from becoming excessively hard, enhance the stress relaxation property at low temperatures, and improve the resistance to thermal cycling.

[0054] [Filler (B)] Next, the filler (B) used in the present invention will be described in detail. The adhesive layer of the present disclosure preferably contains the filler (B) in order to set the elastic modulus within a desired range.

[0055] The filler (B) is not particularly limited, and examples of its shape include spherical, powdery, fibrous, acicular, scaly, etc. Examples of the filler (B) include fluorine-based fillers such as polytetrafluoroethylene powder and its modified products, tetrafluoroethylene-perfluoroalkyl vinyl ether powder, tetrafluoroethylene-ethylene powder, tetrafluoroethylene-hexafluoropropylene powder, tetrafluoroethylene-vinylidene fluoride powder, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether powder, polychlorotrifluoroethylene powder, chlorotrifluoroethylene-ethylene powder, chlorotrifluoroethylene-vinylidene fluoride powder, polyvinylidene fluoride powder, polyvinyl fluoride powder, etc. In addition to polyethylene powder, polyacrylate ester powder, epoxy resin powder, polyamide powder, polyimide powder, polyurethane powder, liquid crystal polymer beads, polysiloxane powder, etc., polymer fillers such as core-shells with a multilayer structure using silicone, acrylic, styrene-butadiene rubber, butadiene rubber, etc.; (poly)phosphate-based compounds such as melamine phosphate, polymelamine phosphate, guanidine phosphate, polyguanidine phosphate, ammonium phosphate, polyammonium phosphate, amide ammonium phosphate, polyamide ammonium phosphate, carbamate phosphate, polycarbamate phosphate, etc., organic phosphate ester compounds, phosphazene compounds, phosphonic acid compounds, phosphinic acid aluminum compounds such as diethylphosphinic acid aluminum, methyl ethylphosphinic acid aluminum, diphenylphosphinic acid aluminum, ethyl butylphosphinic acid aluminum, methyl butylphosphinic acid aluminum, polyethylene phosphinic acid aluminum, etc., phosphorus-based fillers such as phosphine oxide compounds, phosphorane compounds, phosphoramide compounds, etc.; nitrogen-based fillers such as benzoguanamine, melamine, melam, melem, melon, melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole-based compounds, tetrazole compounds, diazo compounds, urea, etc.; Examples of inorganic fillers include silica, hollow silica, porous silica, mica, talc, kaolin, clay, hydrotalcite, wollastonite, zonnolite, silicon nitride, boron nitride, aluminum nitride, calcium hydrogen phosphate, calcium phosphate, glass flakes, hydrated glass, calcium titanate, sepiolite, magnesium sulfate, aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, calcium hydroxide, titanium oxide, tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide, antimony oxide, nickel oxide, zinc carbonate, magnesium carbonate, calcium carbonate, barium carbonate, zinc borate, aluminum borate, and the like.

[0056] From the viewpoint of reducing the coefficient of thermal expansion (CTE) of the adhesive layer, it is preferable to use fluorine-based fillers, boron nitride, liquid crystal polymers, silica, and phosphorus-based fillers, and more preferably fluorine-based fillers, boron nitride, phosphorus-based fillers, and silica. Since these fillers have a strong crystal structure, molecular vibration is small even in the high-frequency band, and the dielectric loss tangent is excellent. In the present disclosure, these fillers (B) can be used alone or in combination of two or more.

[0057] The content of the filler (B) in the adhesive resin sheet is preferably 3 to 50% by mass or less, more preferably 10 to 40% by mass, and particularly preferably 15 to 36% by mass with respect to the total mass of the adhesive layer. By containing 3% by mass or more of the filler, the elastic modulus of the adhesive layer can be moderately increased, and the occurrence of side etching during laser processing can be suppressed. Further, it has the effect of reducing the dielectric loss tangent. Also, by setting it to 50 parts by mass or less, the elastic modulus of the adhesive layer can be set within a suitable range, and the occurrence of cracks in the adhesive layer during drilling can be suppressed.

[0058] From the viewpoint of the dielectric loss tangent, the dielectric loss tangent of the filler (B) at 10 GHz is preferably 0.005 or less, more preferably 0.004 or less, and still more preferably 0.003 or less.

[0059] Average particle diameter D of filler (B) 50 is preferably 0.1 to 25 μm, more preferably 1 to 10 μm. The average particle diameter D of filler (B) 50 is 0.1 to 25 μm, and improvement in coatability can be expected

[0060] The method of adding filler (B) is not particularly limited, and any conventionally known method may be used. Specifically, methods include adding it to the polymerization reaction solution before or during the polymerization of resin (a-1), kneading filler (B) into binder (A) using a three-roll mill or the like, and preparing a dispersion containing filler (B) and mixing this into binder (A). In addition, a dispersant, thickener, etc. can also be used within a range that does not affect the physical properties of the adhesive layer in order to disperse filler (B) well and stabilize the dispersion state

[0061] [Other additives] In addition, to the adhesive resin sheet of the present invention, within a range that does not impair the object, further, as optional components, an energy ray absorber, dye, pigment, antioxidant, polymerization inhibitor, defoaming agent, leveling agent, ion scavenger, moisturizing agent, viscosity modifier, preservative, antibacterial agent, antistatic agent, antiblocking agent, infrared absorber, electromagnetic wave shielding agent, etc. can be added, and from the viewpoint of improving laser processability, it is preferable to blend an energy ray absorber such as a UV absorber

[0062] [Arithmetic mean roughness Sa] The arithmetic mean roughness Sa on the surface (B surface) of the adhesive layer of the present disclosure, which is opposite to the surface (A surface) where the release film is laminated, is defined in ISO 25178-2:2012, and is one of the parameters representing the three-dimensional surface property, and is a parameter obtained by expanding the arithmetic mean roughness (Ra) evaluated on a straight line to a surface. It represents the average of the absolute values of the height differences of each point with respect to the average surface of the surface

[0063] The arithmetic mean roughness Sa on the surface (B surface) of the adhesive layer of the present disclosure, which is opposite to the surface (A surface) where the release film is laminated, is preferably 0.05 to 2 μm. When the arithmetic mean roughness Sa of the B surface is 0.05 μm or more, the air bleeding property during lamination is improved, and padding can be suppressed. On the other hand, when Sa is 2 μm or less, the adhesion to the adherend during lamination can be enhanced, and the floating that causes padding can be suppressed. The arithmetic mean roughness Sa of the B surface is more preferably 0.15 to 1 μm, and even more preferably 0.3 to 0.5 μm.

[0064] [Method for Controlling Arithmetic Mean Roughness Sa] As a method for controlling the arithmetic mean roughness Sa of the B surface of the present disclosure, a conventionally known method for adjusting the surface shape of an object can be applied, different methods can be applied respectively, or a common method can be applied. Specifically, methods such as polishing the surface using abrasive paper, shot blasting method of spraying abrasive on the surface of the adhesive layer with compressed air, forming an adhesive layer on a film having a predetermined arithmetic mean roughness Sa, laminating a protective sheet, and then removing the film to transfer the unevenness of the film surface, a method of pressing a film having a predetermined arithmetic mean roughness Sa and an adhesive layer to transfer the unevenness of the film surface, and a method of controlling the surface unevenness by containing particulate matter in the adhesive layer can be mentioned.

[0065] [Cured Layer] The adhesive layer of the present disclosure is preferably cured by heating or stimulation such as active energy rays such as ultraviolet rays. The cured adhesive layer is referred to as a cured layer. As a method for curing the adhesive layer, a conventionally known method can be applied and can be appropriately selected according to the type of curing agent used. When the adhesive layer is thermosetting, it is preferable because strong interlayer adhesion can be achieved by bringing adherends into contact with both sides of the adhesive layer and performing a heat press.

[0066] The heating temperature is preferably 150 to 200 °C, and more preferably 160 to 180 °C. Also, the heating time is preferably 10 to 120 minutes, and preferably 30 to 60 minutes.

[0067] When curing the adhesive layer using a hot press, the pressing pressure is preferably 1 to 5 MPa, more preferably 2 to 3 MPa. The temperature and time are the same as above.

[0068] [|Er 25 -Er 250 |] In the cured layer obtained by heating the adhesive layer of the present disclosure at 180 °C for 60 minutes, the difference |Er 25 | between the storage modulus (Er 250 ) at 25 °C and the storage modulus (Er 25 -Er 250 ) at 250 °C is preferably 0.1 to 100,000 MPa. When |Er 25 -Er 250 | is 0.1 MPa or more, crack generation can be suppressed by stress relaxation during temperature rise from low temperature, and the resistance to thermal cycling can be improved. On the other hand, when |Er 25 -Er 250 | is 100,000 MPa or less, moisture in the air is incorporated during temperature drop, and appearance defects (foaming) due to moisture evaporation during subsequent temperature rise can be suppressed, improving the resistance to thermal cycling. |Er 25 -Er 250 | is more preferably 1 to 10,000 MPa, and even more preferably 10 to 1,000 MPa.

[0069] The storage modulus of the cured layer can be adjusted to a desired value, for example, by adjusting the molecular weight of the resin in the adhesive layer, adjusting the amount of the curing agent contained in the adhesive layer, or further changing the skeleton of the resin in the adhesive layer.

[0070] [Elongation at break] The elongation at break of the cured layer obtained by heating the adhesive layer of the present disclosure at 180 °C for 60 minutes is preferably 50 to 1,000%. When the elongation at break is 50% or more, when the printed wiring board is drilled, the cured layer can moderately relieve stress and suppress crack generation. On the other hand, when it is 1,000% or less, the generation of burrs (curl of the cured layer) during drilling can be suppressed. The breaking elongation is more preferably 80 to 500%, and even more preferably 100 to 300%.

[0071] The breaking elongation of the cured layer can be adjusted to a desired value, for example, by adjusting the amount of the filler contained in the adhesive layer or by using a resin with lower elasticity.

[0072] [Release Film] The release film serves as a support for the adhesive layer in the adhesive sheet for printed wiring boards and has a function of protecting the adhesive layer from being damaged or contaminated.

[0073] Examples of the release film include plastic sheets such as polyethylene terephthalate, polyethylene naphthalate, polyvinyl fluoride, polyvinylidene fluoride, rigid polyvinyl chloride, polyvinylidene chloride, nylon, polyimide, polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polycarbonate, polyacrylonitrile, polybutene, soft polyvinyl chloride, polyvinylidene fluoride, polyethylene, polypropylene, polyurethane, ethylene-vinyl acetate copolymer, polyvinyl acetate, etc., glassine paper, fine paper, kraft paper, coated paper, etc., various non-woven fabrics, synthetic paper, metal foil, and composite films combining these. Among these, from the viewpoint of easy adjustment of the storage elastic modulus by blending of material components, plastic sheets are preferred, and among them, polyethylene terephthalate and polyethylene naphthalate having both rigidity and flexibility are more preferred.

[0074] The surface of the release film may be subjected to a mat treatment as necessary. Examples of the mat treatment method include sand mat, etching mat, coating mat, chemical mat, and kneaded mat.

[0075] The release film may be coated with a release agent in order to improve the peelability from the adhesive layer. As the release agent, hydrocarbon resins such as polyethylene and polypropylene, higher fatty acids and their metal salts, higher fatty acid soaps, waxes, animal and vegetable oils and fats, mica, talc, silicone-based surfactants, silicone oil, silicone resin, fluorine-based surfactants, fluorine resin, fluorine-containing silicone resin, melamine resin, acrylic resin, etc. are used. As the coating method of the release agent, a conventionally known method, for example, a gravure coating method, a kiss coating method, a die coating method, a lip coating method, a comma coating method, a blade coating method, a roll coating method, a knife coating method, a spray coating method, a bar coating method, a spin coating method, a dip coating method, etc. can be used.

[0076] The thickness of the release film is not particularly limited, but from the viewpoint of giving the release film appropriate rigidity (stiffness) and suppressing the breakage of the release film during peeling, it is preferably 10 μm or more, and preferably 100 μm or less from the viewpoint of thinning the film. [Method for manufacturing an adhesive resin sheet for printed wiring board] The method for manufacturing an adhesive resin sheet for a printed wiring board is, for example, after applying a coating solution containing a resin (a-1), a curing agent (a-2), a filler (B) and other optional components and a solvent to one side of a release film, removing and drying the liquid medium such as the organic solvent contained therein by heating exposure at usually 40 to 150 ° C for 30 seconds to 10 minutes, and laminating another release film on the surface of the formed adhesive resin sheet, an adhesive resin sheet with release films on both sides can be obtained. By laminating release films on both sides, surface contamination of the adhesive resin sheet can be prevented. By peeling off the release film, the adhesive resin sheet can be isolated. Either the same type or different types of the two release films can be used. By using release films with different peelabilities, the peel force can be made stronger or weaker, so that it becomes easier to peel off in order.

[0077] [Metal-clad laminate] The metal-clad laminate is formed by laminating a metal foil and an insulating film via a cured layer which is a cured product of an adhesive layer. Such a metal-clad laminate can be obtained, for example, by stacking a metal foil and an insulating film on each side of the adhesive layer of an adhesive sheet for printed wiring boards (this process is sometimes referred to as temporary bonding), and then subjecting it to a heating or hot pressing process to thermally cure the adhesive layer between the metal foil and the insulating film. For the metal-clad laminate, both outermost layers on both sides may be metal foils, such as metal foil / cured layer / insulating film / cured layer / metal foil, and an inner layer of metal foil can also be provided. When laminating metal foils and insulating films using multiple adhesive layers, after going through temporary bonding multiple times, the heat curing of the multiple adhesive layers can be performed all at once.

[0078] [Printed Wiring Board] By processing the metal foil in the metal-clad laminate through etching or the like to form a signal circuit and a ground circuit, a printed wiring board can be obtained. By bonding the adhesive layer of the adhesive sheet for printed wiring boards to the circuit surface and heat curing it, the signal circuit can be protected or it can be used as a substrate for further multi-layerization. As a method for providing a signal circuit and a ground circuit, for example, a photosensitive etching resist layer is formed on the metal foil in the metal-clad laminate, exposed through a mask film having a circuit pattern, only the exposed portion is cured, and then the metal foil in the unexposed portion is removed by etching, and then the remaining resist layer is peeled off, etc., to form a conductive circuit from the metal foil.

[0079] [Electronic Device] Using the printed wiring board of the present invention, various electronic devices such as smartphones, tablet terminals, personal computers, televisions, and cameras can be manufactured.

Example

[0080] Hereinafter, the present disclosure will be described more specifically with reference to Examples and Comparative Examples, but the present disclosure is not limited only to the following Examples. In the following, "parts" and "%" are values based on "parts by mass" and "wt%", respectively. Further, the acid value and weight average molecular weight (Mw) of the resin (a-1), and D 50 The measurement of the average particle diameter was performed by the following method.

[0081] [Acid value of resin (a-1)] Based on the neutralization titration method of JIS K 0070, the measured acid value (mgKOH / g) was determined by converting it to a solid content basis. Approximately 1 g of the sample was precisely weighed into a conical flask with a stopper, and 100 mL of a mixed solution of tetrahydrofuran / ethanol (volume ratio: tetrahydrofuran / ethanol = 2 / 1) was added and dissolved. To this, a phenolphthalein test solution was added as an indicator, and titrated with a 0.1N alcoholic potassium hydroxide solution. The end point was determined when the indicator maintained a light red color for 30 seconds. The acid value was determined by the following formula (unit: mgKOH / g). Acid value (mgKOH / g) = (5.611 × a × F) / S However, S: Sampling amount of the sample (g) a: Consumption amount of 0.1N alcoholic potassium hydroxide solution (mL) F: Titer of 0.1N alcoholic potassium hydroxide solution

[0082] [Weight average molecular weight (Mw) of resin (a-1)] The measurement of Mw was performed by GPC (gel permeation chromatography) "HPC-8020" (manufactured by Tosoh Corporation). GPC is a liquid chromatograph that separates and quantifies substances dissolved in a solvent (THF; tetrahydrofuran) based on the difference in their molecular sizes. In this measurement, two columns of "LF-604" (manufactured by Showa Denko KK: GPC column for rapid analysis: 6 mm ID × 150 mm size) were connected in series and used, and the measurement was performed under the conditions of a flow rate of 0.6 mL / min and a column temperature of 40°C. The determination of Mw was performed in terms of polystyrene conversion.

[0083] [D of filler (B)] 50 Average particle diameter D50 The average particle diameter was measured using a laser diffraction / scattering particle size distribution analyzer LS13320 (manufactured by Beckman Coulter). The value was obtained by measuring the conductive filler with a Turbula dry powder sample module, and it is the particle diameter at which the cumulative value in the particle size cumulative distribution is 50%. The refractive index was set to 1.6.

[0084] <Raw material> [Binder (A)] 《Resin (a-1)》 (a-1)-1: Polyamide resin, acid value 10 mg KOH / g, weight average molecular weight 21,000, Tg 55 °C (manufactured by Toyochem Co., Ltd.) (a-1)-2: Styrene-based elastomer, FG1901GT (maleic acid-modified styrene-based elastomer), acid value 10 mg KOH / g, weight average molecular weight 95,000, Tg 80 °C (manufactured by Kraton Corporation) (a-1)-3: Polyurethane resin, acid value 10 mg KOH / g, weight average molecular weight 12,0 000, Tg 25 °C (manufactured by Toyochem Co., Ltd.) (a-1)-4: Polyester resin, Vylon 637, acid value 5 mg KOH / g, weight average molecular weight 30,000, Tg 21 °C polyester resin (manufactured by Toyobo Co., Ltd.) (a-1)-5: YuMex 1001 (maleic acid-modified polypropylene), acid value 26 mg KOH / g (manufactured by Sanyo Chemical Industries, Ltd.) (a-1)-6: Polyimide resin, acid value 9 mg KOH / g, weight average molecular weight 45,000, Tg 50 °C (manufactured by Toyochem Co., Ltd.) [Curing agent (a-2)] (a-2)-1: Epoxy group-containing compound, Denacol EX-614B (manufactured by Nagase ChemteX Corporation, sorbitol polyglycidyl ether, tetrafunctional, functional group equivalent 173 g / eq.) [Filler (B)] B-1: UF-310 (manufactured by Tokuyama Corporation, silica, average particle diameter D 50 ; 3.5 μm) [UV absorber (C)] C-1: Tinuvin 326 (manufactured by BASF Japan, benzotriazole-containing compound)

[0085] 〈Manufacture of Adhesive Sheet for Printed Wiring Board〉 100 parts of binder resin (a-1)-1, 20 parts of curing agent (a-2)-1, 15 parts of filler B-1 and UV absorber C-1 were charged into a container in terms of solid content, and a mixed solvent (toluene:MEK = 9:1 (weight ratio)) was added so that the non-volatile content concentration became 30%, and the mixture was stirred with a disper for 10 minutes to obtain a resin composition (coating solution). The obtained coating solution was applied onto a release film with a thickness of 50 μm (a polyethylene terephthalate (PET) film coated with a release agent) using a doctor blade so that the thickness after drying was 25 μm, and dried at 100°C for 2 minutes, and then an adhesive sheet for printed wiring board of Example 1 was obtained. 〈Examples 2 to 46, Comparative Examples 1 to 2〉 As shown in Tables 1 to 6, adhesive sheets for printed wiring boards of Examples 2 to 46 and Comparative Examples 1 to 2 were obtained in the same manner as in Example 1 except that the amounts of the binder resin, curing agent, and filler were changed. The arithmetic mean roughness Sa of the surface (B surface) of the adhesive layer on the side opposite to the surface (A surface) on which the release film was laminated was adjusted by polishing the surface using abrasive paper.

[0086] <Measurement of Toluene Content in Adhesive Layer> The obtained adhesive resin sheet was cut into pieces with a width of 1 cm and a length of 5 cm and put into a vial as a test piece, and then the toluene content in the adhesive layer was measured by headspace chromatography (HS-GC) using a GC system (Nexis GC-2030, manufactured by Shimadzu Corporation). The toluene content was obtained by measuring the peak area attributed to toluene in the chart obtained when the vial was heated at 200°C for 30 minutes.

[0087] <Measurement of Arithmetic Mean Roughness Sa of B Surface> The arithmetic mean roughness Sa of the B side was obtained by observing the surface of the adhesive layer on the side opposite to the surface (A side) where the release film was laminated of the obtained adhesive sheet for printed wiring boards using a confocal microscope (OPTELICS HYBRID+ manufactured by Lasertec, objective lens magnification 20×), measuring five arbitrary locations in accordance with ISO25178, and then analyzing and calculating using data analysis software (LMeye8).

[0088] <Measurement of Storage Elastic Modulus of Cured Layer> The storage elastic modulus of the cured layer was measured by the DMA method. A cured layer obtained by peeling the release film after heating the obtained adhesive sheet for printed wiring boards at 180°C for 60 minutes was cut into test pieces with a width of 5 mm and a length of 30 mm. Using a dynamic viscoelasticity measuring device "DVA200" (manufactured by IT Measurement and Control Co., Ltd.), after cooling to 0°C, the temperature was raised to 300°C at a heating rate of 10°C / min, and the storage elastic modulus was determined from the viscoelasticity curve obtained when measuring the viscoelasticity at a vibration frequency of 10 Hz.

[0089] <Evaluation> The obtained adhesive sheet for printed wiring boards was evaluated for impedance matching, padding, thermal cycle resistance, and processability according to the following methods. The evaluation results are shown in Tables 1 to 6.

[0090] [Impedance Matching] Impedance matching was evaluated using a printed wiring board 100 having a coplanar circuit with an electromagnetic wave shield in which electromagnetic wave shield sheets were laminated on both sides shown in Fig. 1.

[0091] Fig. 1 shows a schematic plan view of the front main surface of a flexible printed wiring board 90 having a coplanar circuit (hereinafter also referred to as a wiring board having a coplanar circuit), and Fig. 2 shows a schematic plan view of the back surface side. First, a double-sided CCL "R-F775" (manufactured by Panasonic Corporation) in which rolled copper foils with a thickness of 12 μm were laminated on both sides of a polyimide film 50 with a thickness of 50 μm was prepared. Then, six through-holes 2 (diameter 0.1 mm) were provided in the vicinity of each of the four rectangular corner portions. In the figure, for the sake of illustration, only two through-holes 2 are shown at each corner portion. Next, after performing electroless plating, electrolytic plating was performed to form a copper plating film 3 with a thickness of 10 μm, and electrical continuity between the front main surface and the back surface was ensured through the copper plating film formed in the through-holes 2. Thereafter, as shown in Fig. 1, two signal wirings 4 with a length of 10 cm were formed on the main surface of the polyimide film 1, a ground wiring 5 parallel to the signal wiring 4 was provided outside thereof, and a ground pattern 6 was formed in a region including the through-holes 2 in the short side direction of the polyimide film 1 extending from the ground wiring 5.

[0092] Thereafter, the copper foil formed on the back surface of the polyimide film 1 was etched to obtain a back surface side ground pattern 7 as shown in Fig. 2 at a position corresponding to the ground pattern 6. The inspection specifications for the appearance and tolerances of the circuit were set to the JPCA standard (JPCA-DG02).

[0093] Next, a polyimide film (thickness 12.5 μm) was bonded to the surface where the adhesive layer of the adhesive sheet for the printed wiring board of Example 1 was exposed, and vacuum lamination was performed. After the obtained laminate was attached to the front main surface side of the polyimide film 1, it was heated and pressed at 180 °C and 2 MPa for 60 minutes to obtain a wiring board having a coplanar circuit provided with a cover coat layer 10. Thereafter, nickel plating (not shown) was performed on the copper foil pattern exposed from the cover coat layer 10, and then gold plating (not shown) treatment was performed.

[0094] Next, as shown in Fig. 1, an electromagnetic shielding sheet (LIOELM TSS210 manufactured by Toyochem Co., Ltd.) 20 composed of a laminate of a conductive layer / insulating layer was prepared, and a release treatment sheet (not shown) provided on the conductive adhesive layer 1 of the electromagnetic shielding sheet 20 was peeled off. Then, with the conductive adhesive layer 1 of the electromagnetic shielding sheet 20 on the inner side, the signal wiring on the main surface side of the wiring board 90 having a coplanar circuit was covered with a cover coat layer, and the electromagnetic shielding sheet was bonded to the wiring board 20 such that the cover coat layer was absent and the electromagnetic shielding sheet was in contact with the ground wiring X. By bonding to this location, the electromagnetic shielding sheet and the ground wiring 5 were electrically connected. Furthermore, as shown in Fig. 3, an electromagnetic shielding sheet (LIOELM TSS210 manufactured by Toyochem Co., Ltd.) 20 composed of a laminate of a conductive layer / insulating layer was prepared, and a release treatment sheet (not shown) provided on the conductive adhesive layer 1 of the electromagnetic shielding sheet 20 was peeled off. Then, with the conductive adhesive layer 1 of the electromagnetic shielding sheet 20 on the inner side, it was pressure-bonded to the entire back side of the wiring board 90 having a coplanar circuit under the conditions of 170 °C, 2.0 MPa, and 30 minutes to obtain a wiring board 100 having a coplanar circuit with an electromagnetic shielding layer. In Fig. 3, the back side ground pattern 7 is shown in a perspective view.

[0095] In addition, the width of the ground wiring 5 was 100 μm, and the distance between the ground wiring 5 and the signal wiring 4 was 1 mm.

[0096] A network analyzer E5071C (manufactured by Agilent Japan) was connected to the exposed signal wiring 4 of the wiring board 100 having a coplanar circuit with an electromagnetic shielding sheet, a 15 GHz sine wave was input, and impedance matching was evaluated by measuring the maximum width at which the difference from the reference impedance was the largest. The reference impedance was defined as 100 Ω when not connected to the signal wiring. ◎: The maximum width of the characteristic impedance difference is less than 40 Ω. Extremely good. ○: The maximum width of the characteristic impedance difference is 40 Ω or more and less than 50 Ω. Good. △: The maximum width of the characteristic impedance difference is 50 Ω or more and less than 60 Ω. Usable. ×: The maximum width of the characteristic impedance difference is 60 Ω or more. Not usable.

[0097] [Padding] The uneven surface of the above sample was temporarily adhered to the copper foil on one side of a double-sided copper-clad laminate (manufactured by DuPont, TAS124500) with 12-μm copper foil laminated on both sides of a polyimide film using a vacuum laminator (small-sized pressure-type vacuum laminator V-130 manufactured by Nichco Materials Co., Ltd.). Then, the following was used as the criterion to evaluate that there were no appearance defects such as floating or foaming at the adhesive layer / copper foil interface visually. Thirty evaluation samples were prepared. ◎: The number of samples with appearance defects is less than 3. It is an extremely good result. ○: The number of samples with appearance defects is 3 to less than 6. It is a good result. △: The number of samples with appearance defects is 6 to less than 9. It is within the practical range. ×: The number of samples with appearance defects is 9 or more. Not practical.

[0098] [Thermal cycle resistance] (Sample preparation) An adhesive layer of an adhesive sheet for printed wiring boards was bonded to the copper foil on one side of a double-sided copper-clad laminate with 12-μm copper foil laminated on both sides of a 50-μm polyimide film, and temporarily adhered using a vacuum laminator. Next, the release film was peeled off, and the polyimide film side of a single-sided copper-clad laminate with a 50-μm polyimide film and a 12-μm copper foil laminated thereon was similarly temporarily adhered to the exposed adhesive layer using a vacuum laminator, and then thermally cured at 180 °C for 1 hour under 2 MPa by hot pressing to obtain an evaluation sample having a laminated structure of copper foil / polyimide film / copper foil / hardened layer / polyimide film / copper foil. (Evaluation) The thermal cycle characteristics of the above sample were evaluated. The processing conditions were 15 minutes at -30 °C and 15 minutes at 150 °C as one cycle. After 2000 cycles, the cross-section was observed with a laser microscope (VK-X100 manufactured by Keyence Corporation) at a magnification of about 20 to 500 times. Thirty evaluation samples were prepared. ◎: The number of samples with peeling is less than 3. It is an extremely good result. ○: The number of samples with peeling is 3 to 6%. It is a less than good result. △: The number of samples with peeling is 6 to less than 9. It is within the practical range. ×: The number of samples with peeling is 9 or more. It is not practical.

[0099] [Workability] The workability was tested separately for laser workability and drill workability, and a comprehensive workability evaluation was performed based on the test results.

[0100] [Laser Workability] For the evaluation sample with a laminated structure of copper foil 31 / polyimide film 30 / hardened layer 32 of the adhesive layer / copper foil 31 / polyimide film 30 / copper foil 31 shown in Fig. 4, a UV-YAG laser (Model 5335, manufactured by ESI) was used to irradiate the laser from the upper surface of Fig. 4, and blind via processing with a diameter of 100 μm was performed up to the boundary between the cured product of the adhesive layer and the double-sided copper-clad laminate. Next, the cross-section of the blind via portion 34 was observed with a laser microscope (VK-X100, manufactured by Keyence) at a magnification of about 20 to 500 times, and the maximum length of the side etching (the horizontal direction is etched beyond the designed opening diameter) occurring in the cured product of the adhesive layer was measured, and the evaluation was performed according to the following criteria. A: 5 μm or less B: Larger than 5 μm and 7 μm or less C: Larger than 7 μm and 10 μm or less D: Larger than 10 μm

[0101] [Drill Workability] For the evaluation sample with a laminated structure of copper foil 31 / polyimide film 30 / hardened layer 32 of the adhesive layer / copper foil 31 / polyimide film 30 / copper foil 31 shown in Fig. 5, a printed circuit board drill hole opener NB-1S212 (manufactured by Via Mechanics) was used to perform through-hole processing with a diameter of 100 μm from the upper surface of Fig. 5 up to the boundary between the cured product of the adhesive layer and the double-sided copper-clad laminate. Next, when observing the cross-section of the through-hole portion 35 with a laser microscope (VK-X100 manufactured by Keyence Corporation) at a magnification of about 20 to 500 times, the number of samples in which cracks occurred in the cured product of the adhesive layer was measured, and evaluation was performed according to the following criteria. In addition, the total number of samples used for evaluation was 30. A: The number of samples with cracks is less than 10%. B: The number of samples with cracks is 10% to less than 20%. C: The number of samples with cracks is 20% to less than 30%. D: The number of samples with cracks is 30% or more.

[0102] Based on the above results of laser processability and drill processability, the processability of each example and comparative example was evaluated according to the following criteria. ◎: Both laser processability and drill processability are evaluated as A. Extremely good. ○: Either laser processability or drill processability is evaluated as A, and either is evaluated as B or C. Good result. △: Both laser processability and drill processability are evaluated as B or C. Within the practical range. ×: Either laser processability or drill processability is evaluated as D. Not practical.

[0103] [Temporary adhesiveness] The adhesive layer of the printed wiring board adhesive sheet was bonded to the copper foil on one side of a double-sided copper-clad laminate in which 12-μm copper foil was laminated on both sides of a 50-μm polyimide film, and temporarily adhered with a vacuum laminator. Next, when peeling off the release film, it was visually observed whether the adhesive layer could be transferred without floating or peeling off from the copper foil, and evaluation was performed according to the following criteria. The number of evaluation samples was 30. ◎: The number of samples with transfer defects is less than 3. Extremely good result. ○: The number of samples with transfer defects is 3 to less than 6. Good result. △: The number of samples with transfer defects is 6 to less than 9. Within the practical range. ×: The number of samples with poor transcription is 9 or more. Not practical.

[0104]

Table 1

[0105]

Table 2

[0106]

Table 3

[0107]

Table 4

[0108]

Table 5

[0109]

Table 6

Explanation of Symbols

[0110] 1 Polyimide film 2 Through hole 3 Copper plating film 4 Signal wiring 5 Ground wiring 6 Ground pattern 7 Backside ground pattern 10 Cover coat layer 20 Electromagnetic shielding sheet 30 Polyimide film 31 Copper foil 32 Cured product of adhesive layer (cured layer) 33 Side etching 34 Blind via part 35 Through-hole part 90 Printed wiring board having a coplanar circuit 100 Printed wiring board having a coplanar circuit with electromagnetic shielding

Claims

1. An adhesive sheet having a release film laminated on at least one surface (surface A) of an adhesive layer, wherein the adhesive layer contains 5 to 15,000 ppm of toluene, and the adhesive layer is used as a member for interlayer adhesion of a printed wiring board. An adhesive sheet for a printed wiring board, characterized in that.

2. The surface (surface B) of the adhesive layer on the side opposite to the surface (surface A) of the adhesive layer on which the release film is laminated, The adhesive sheet for a printed wiring board according to claim 1, wherein the arithmetic mean roughness Sa determined in accordance with ISO 25178-2:2012 is 0.05 to 2 μm.

3. The storage modulus (Er ２５ ) and the storage modulus at 250°C (Er ２５０ ) difference |Er ２５ -Er ２５０ 2. The adhesive sheet for printed wiring boards according to claim 1, wherein | is 0.1 to 100,000 MPa.

4. The adhesive sheet for a printed wiring board according to claim 1, wherein the elongation at break of the cured layer obtained by heating the adhesive layer at 180° C. for 60 minutes is 50 to 1,000%.

5. A metal-clad laminate having a cured layer of the adhesive layer according to claims 1 to 4.

6. A printed wiring board having the metal-clad laminate according to claim 5.

7. An electronic device having the printed wiring board according to claim 6.

Images