Method for forming a cured film, and method for manufacturing a printed circuit board.

Abstract

The present invention provides a method for forming a cured film that has high resolution as a solder resist and maintains high adhesion to a metal surface even after high-temperature treatment. [Solution] A method for forming a cured film, comprising: a first step of forming a photosensitive resin layer made of a photosensitive resin composition on the surface of a substrate in which metal is exposed on at least a portion of the surface; and a third step of performing UV irradiation treatment on the photosensitive resin layer to cure the photosensitive resin layer and form a cured film, wherein in the first step, the photosensitive resin composition contains (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) an epoxy resin, and (D) an inorganic filler, and (C) the epoxy resin is a biphenyl skeleton A photosensitive resin composition is used, comprising an epoxy resin (C-1) having (C-1) and an epoxy resin (C-2) other than (C-1) that is solid or semi-solid at room temperature, wherein (D) the inorganic filler contains spherical silica (D-1) and barium sulfate (D-2), and the volume ratio of spherical silica (D-1) to barium sulfate (D-2) is 1:0.5 to 1:5. In the third step, UV irradiation treatment is performed in an environment where the temperature of the photosensitive resin layer on the substrate is 215°C or higher, and 1500 mJ / cm³ is applied. 2 The method for forming a cured film uses the above UV irradiation dose.

Description

[Technical Field]

[0001] The present invention relates to a method for forming a cured film and a method for manufacturing a printed circuit board. [Background technology]

[0002] Generally, in printed circuit boards used in electronic devices and the like, a solder resist layer is formed in the area of ​​the circuit board excluding the connection holes to prevent solder from adhering to unwanted parts of the printed circuit board during processes such as solder reflow when mounting electronic components onto the printed circuit board.

[0003] With the recent miniaturization and reduction of electronic devices, and the resulting increase in the precision and density of printed circuit boards, high resolution is required for the solder resist layer. Currently, the mainstream method for forming the solder resist layer is so-called photosolder resist, in which a photosensitive resin composition is applied to the substrate, dried, exposed to light, developed to form a pattern, and then the patterned resin is fully cured by heating or light irradiation. In addition, it has been proposed to form the solder resist layer using a photosensitive dry film without using the liquid photosensitive resin composition described above.

[0004] Incidentally, in the design of electrical and electronic components such as connectors and switches, as well as automotive parts, the use of composite materials of resin and metal components is progressing in order to achieve miniaturization and precision. Composite materials of resin and metal require high adhesion between the resin and metal to obtain waterproofing and sealing properties, but it is known that the adhesion between resin and metal decreases due to differences in their coefficients of linear expansion with temperature changes. Furthermore, in recent years, with the high temperatures during reflow processing of lead-free solder surface mounting in electrical and electronic component applications, if the heat resistance of the thermoplastic resin composition is insufficient, there has been a problem of reduced adhesion between the resin and metal due to warping and blistering of the resin. For this reason, in order to improve the adhesion between resin and metal, research is being conducted on thermoplastic resin compositions that have excellent adhesive strength between resin and metal and high metal adhesion even after high-temperature processing (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-227366 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, Patent Document 1 mentioned above is limited to thermoplastic resin compositions, and in the case of photosensitive resin compositions, high temperatures are reached during the reflow process of lead-free solder surface mounting, which reduces the adhesion between the resin and metal, causing peeling and making subsequent lamination impossible.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a method for forming a cured film that has high resolution as a solder resist and high adhesion to a metal surface even after high-temperature treatment, and a method for manufacturing a printed circuit board including the method for forming the cured film. [Means for solving the problem]

[0008] In response to the above problems, the inventors investigated and found that when curing a photosensitive resin layer obtained by coating and drying a photosensitive resin composition with UV irradiation, the UV irradiation dose of 1500 mJ / cm² is 2 We have found that the cured film formed as described above does not experience a decrease in adhesion between the resin and metal and does not peel off when subjected to high-temperature processing, such as during reflow soldering of lead-free solder surface mounts, thus not affecting subsequent lamination processes. The present invention is based on this finding.

[0009] In other words, the gist of this invention is as follows: [1] A first step of forming a photosensitive resin layer made of a photosensitive resin composition on a substrate in which metal is exposed on at least a portion of the surface, A method for forming a cured film, comprising a third step of performing UV irradiation treatment on the photosensitive resin layer to cure the photosensitive resin layer and form a cured film, In the first step, the photosensitive resin composition contains (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) an epoxy resin, and (D) an inorganic filler. The (C) epoxy resin contains an epoxy resin having a biphenyl skeleton (C-1) and an epoxy resin other than (C-1) that is solid or semi-solid at room temperature (C-2). The (D) inorganic filler contains spherical silica (D-1) and barium sulfate (D-2), Using a photosensitive resin composition in which the content ratio of the spherical silica (D-1) and the barium sulfate (D-2) is 1:0.5 to 1:5 by volume, In the third step, the UV irradiation treatment is performed in an environment where the temperature of the photosensitive resin layer on the substrate is 215°C or higher, and the UV irradiation treatment is performed at 1500 mJ / cm². 2 A method for forming a cured film using the above UV irradiation dose. [2] In the first step described above, A method for forming a cured film according to [1], comprising a dry film comprising a first film and a photosensitive resin layer on one side of the first film, wherein the photosensitive resin composition is applied and dried. [3] In the third step, the UV irradiation treatment is 2000 mJ / cm 2 A method for forming a cured film according to [1] or [2], using the above UV irradiation dose. [4] After the first step and before the third step, A method for forming a cured film according to any one of [1] to [3], comprising a second step of performing an exposure and development treatment on the photosensitive resin layer to form a pattern. [5] A method for manufacturing a printed circuit board comprising a substrate and a cured coating provided on at least a part of the surface of the substrate, A method for manufacturing a printed circuit board, comprising forming a cured film on at least a portion of the surface of the substrate by the cured film formation method described in any of [1] to [4]. [Effects of the Invention]

[0010] The method for forming a cured film of the present invention has resolution as a solder resist and can form a cured film having high adhesion to a metal surface even after high-temperature treatment. In addition, the method for manufacturing a printed wiring board of the present invention can obtain a printed wiring board provided with a cured film having resolution as a solder resist and high adhesion to a metal surface even after high-temperature treatment. [Brief Description of the Drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram for explaining an embodiment of the present invention. [Modes for Carrying Out the Invention]

[0012] In this specification, it is assumed that the numerical range represented by "~" includes the numerical values at both ends thereof.

[0013] [Definitions] Photosensitivity is the property of a substance to undergo a chemical change upon irradiation with light. In this specification, having photosensitivity means that the resin component contained in the photosensitive resin composition polymerizes and cures upon irradiation with light of a specific wavelength.

[0014] In this specification, being capable of pattern formation means that it is possible to transfer a pattern of a predetermined shape to a photosensitive resin layer made of a photosensitive resin composition by a photolithography process.

[0015] In this specification, being solid or semi-solid at room temperature means exhibiting solid or semi-solid at 15°C. The determination of solid or semi-solid can be carried out in accordance with the "Method for Confirming Liquid State" in Appendix 2 of the Ordinance on Tests and Properties of Dangerous Goods (Ordinance of the Ministry of Home Affairs No. 1 of 1989).

[0016] [Photosensitive Resin Composition] The method for forming a cured film according to this disclosure involves applying a photosensitive resin composition having the following composition. A photosensitive resin composition applicable to the method for forming a cured film according to the present disclosure contains (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) an epoxy resin, and (D) an inorganic filler. (C) The epoxy resin contains an epoxy resin having a biphenyl skeleton (C-1) and an epoxy resin other than (C-1) that is solid or semi-solid at room temperature (C-2). (D) The inorganic filler contains spherical silica (D-1) and barium sulfate (D-2). The ratio of spherical silica (D-1) to barium sulfate (D-2) by volume is 1:0.5 to 1:5. The following describes in detail each component of the photosensitive resin composition.

[0017] <(A) Carboxyl group-containing resin> (A) As the carboxyl group-containing resin, various conventionally known carboxyl group-containing resins having carboxyl groups in their molecules can be used. In particular, carboxyl group-containing photosensitive resins having ethylenically unsaturated double bonds in their molecules are preferred in terms of photocurability and developability. The ethylenically unsaturated double bonds are preferably derived from acrylic acid or methacrylic acid or derivatives thereof. When using only carboxyl group-containing resins that do not have ethylenically unsaturated double bonds, it is necessary to use a compound having multiple ethylenically unsaturated groups in its molecule, i.e., a photopolymerizable monomer, as described later, in combination to make the composition photocurable. Specific examples of carboxyl group-containing resins include the following compounds (which may be either oligomers or polymers):

[0018] (1) A carboxyl group-containing resin obtained by copolymerization of an unsaturated carboxylic acid such as (meth)acrylic acid with an unsaturated group-containing compound such as styrene, α-methylstyrene, lower alkyl (meth)acrylate, or isobutylene.

[0019] (2) A carboxyl group-containing urethane resin obtained by polyaddition reactions of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with carboxyl group-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

[0020] (3) A carboxyl group-containing photosensitive urethane resin obtained by polyaddition reactions of diisocyanate with (meth)acrylates or partially acid anhydride modified products thereof of difunctional epoxy resins such as bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bixylenol type epoxy resin, and biphenol type epoxy resin, carboxyl group-containing dialcohol compounds, and diol compounds.

[0021] (4) A carboxyl group-containing photosensitive urethane resin obtained by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as hydroxyalkyl (meth)acrylate, to the synthesis of the resin described in (2) or (3) above, and then terminally (meth)acrylicating it.

[0022] (5) A carboxyl group-containing photosensitive urethane resin obtained by adding a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule, such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate, to the synthesis of the resin of (2) or (3) above, and then (meth)acrylicating the terminal.

[0023] (6) A carboxyl group-containing photosensitive resin obtained by reacting a bifunctional or polyfunctional (solid) epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride to the hydroxyl groups present in the side chain.

[0024] (7) A carboxyl group-containing photosensitive resin obtained by reacting a polyfunctional epoxy resin, in which the hydroxyl groups of a bifunctional (solid) epoxy resin are further epoxidized with epichlorohydrin, with (meth)acrylic acid, and then adding a dibasic acid anhydride to the resulting hydroxyl groups.

[0025] (8) A carboxyl group-containing polyester resin obtained by reacting a bifunctional oxetane resin with dicarboxylic acids such as adipic acid, phthalic acid, and hexahydrophthalic acid, and then adding dibasic acid anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride to the resulting primary hydroxyl groups.

[0026] (9) A carboxyl group-containing resin obtained by reacting an epoxy compound having multiple epoxy groups in one molecule with a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule, such as p-hydroxyphenethyl alcohol, and an unsaturated group-containing monocarboxylic acid such as (meth)acrylic acid, and then reacting the alcoholic hydroxyl group of the resulting reaction product with a polybasic acid anhydride such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic acid.

[0027] (10) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0028] (11) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate, reacting the reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0029] (12) A carboxyl group-containing photosensitive resin obtained by adding a compound having one epoxy group and one or more (meth)acryloyl groups in one molecule to the resins of (1) to (11) above. In this specification, (meth)acrylate is a general term referring to acrylates, methacrylates, and mixtures thereof, and the same applies to other similar expressions.

[0030] The acid value of the carboxyl group-containing resin is preferably in the range of 30 to 150 mg KOH / g, and more preferably in the range of 50 to 120 mg KOH / g. An acid value of 30 mg KOH / g or higher of the carboxyl group-containing resin facilitates alkaline development, while an acid value of 150 mg KOH / g or lower is preferable because it provides sufficient resistance to the developer in the exposed area, allowing for reliable drawing of a normal resist pattern.

[0031] Furthermore, the weight-average molecular weight of the carboxyl group-containing resin varies depending on the resin skeleton, but is generally preferred to be in the range of 1,500 to 150,000, and more preferably in the range of 5,000 to 100,000. When the weight-average molecular weight is 1,500 or higher, the developability of the film in the exposed area is improved, and the resolution is excellent. On the other hand, when the weight-average molecular weight is 150,000 or lower, the solubility of the unexposed area is good, the resolution is excellent, and storage stability may also be improved. The weight-average molecular weight can be measured by gel permeation chromatography.

[0032] These carboxyl group-containing resins are not limited to those listed above and may be used individually or in mixtures of multiple types. In particular, carboxyl group-containing resins synthesized using phenol compounds such as the carboxyl group-containing resins (10) and (11) above as starting materials are preferable because they have excellent B-HAST resistance and PCT resistance.

[0033] <(B) Photopolymerization initiator> (B) The photopolymerization initiator is not particularly limited and any known one can be used. (B) The photopolymerization initiator may be used alone or in combination of two or more.

[0034] (B) Examples of photopolymerization initiators include, specifically, bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylphenylphosphine oxide. Bis-acylphosphine oxides such as tylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphine methyl ester, 2-methylbenzoyldiphenylphosphine oxide, and pivaloylphenylphosphine. Monoacylphosphine oxides such as isopropyl esters and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate, 1-hydroxycyclohexylphenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-hydro Hydroxyacetophenones such as xy-2-methyl-1-phenylpropan-1-one; benzoins such as benzoin, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether; benzoin alkyl ethers; benzophenones such as benzophenone, p-methylbenzophenone, Michlar's ketone, methylbenzophenone, 4,4'-dichlorobenzophenone, and 4,4'-bisdiethylaminobenzophenone;Acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-morpholinyl)phenyl]-1-bu Acetophenones such as tanone and N,N-dimethylaminoacetophenone; thioxanthones such as thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, and 2-amylanthraquinone Anthraquinones such as 2-aminoanthraquinone; ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzoic acid esters such as ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethyl benzoate, and p-dimethylbenzoate ethyl ester; 1,2-octanedione, 1-[4-(phenylthio)-,2-(O-benzoyloxime)], etanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetylo Examples include oxime esters such as xime; titanosenes such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl)titanium and bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium; phenyl disulfide 2-nitrofluorene, butyroin, anisoin ethyl ether, azobisisobutyronitrile, and tetramethylthiuram disulfide.

[0035] Among the above-mentioned photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, such as monoacylphosphine oxide-based and bisacylphosphine oxide-based photopolymerization initiators, are preferred because they possess photobleaching properties. Here, photobleaching, also known as photodecolorization or photodecolorization, is a reaction that occurs when a fluorescent substance in an excited state becomes chemically activated and unstable compared to its ground state. Specifically, when a compound acting as a photopolymerization initiator absorbs light in a specific wavelength range and generates radicals, the generation of radicals changes the structure of the compound, causing it to no longer absorb light in that wavelength range. As a result, it becomes easier for light in that wavelength range to pass through, making it easier for photocuring to occur to deeper layers. In particular, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (IRGACURE 819, manufactured by BASF Japan Ltd.), ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (IRGACURE TPO-L, manufactured by BASF Japan Ltd.) and the like can be suitably used.

[0036] Excluding oxime ester-based photopolymerization initiators, the amount of photopolymerization initiator blended is preferably 0.1 to 30 parts by mass, and more preferably 0.5 to 15 parts by mass, of (B) photopolymerization initiator per 100 parts by mass of (A) carboxyl group-containing resin, based on solid content. When the blending amount is 0.1 parts by mass or more, the photocurability of the photosensitive resin composition in this disclosure is good, the cured film (cured product) is less likely to peel off, and properties such as chemical resistance are also good. On the other hand, when the blending amount is 30 parts by mass or less, an outgassing reduction effect is obtained, and when the photosensitive resin composition in this disclosure is used as a solder resist, light absorption on the surface of the solder resist is good, and the deep curing performance is less likely to decrease.

[0037] Furthermore, the amount of oxime ester-based photopolymerization initiator blended is preferably 0.01 to 5 parts by mass of (B) photopolymerization initiator per 100 parts by mass of (A) carboxyl group-containing resin, and more preferably 0.5 to 3 parts by mass, based on solid content. When the blending amount is 0.01 parts by mass or more, the photocurability of the photosensitive resin composition in this disclosure is good, and properties such as heat resistance and chemical resistance are also good. On the other hand, when the blending amount is 5 parts by mass or less, when the photosensitive resin composition in this disclosure is used as a solder resist, light absorption on the surface of the solder resist is good, and the deep curing performance is less likely to decrease.

[0038] <(C) Epoxy resin> (C) The epoxy resin contains an epoxy resin having a biphenyl skeleton (C-1) and an epoxy resin other than (C-1) that is solid or semi-solid at room temperature (C-2). The epoxy resin having a biphenyl skeleton (C-1) and the epoxy resin other than the epoxy resin (C-1) that is solid or semi-solid at room temperature (C-2) have lower solubility in developer compared to liquid epoxy resins. In particular, the epoxy resin having a biphenyl skeleton (C-1) has high crystallinity and strong hydrophobicity, so by using it in combination with the epoxy resin that is solid or semi-solid at room temperature (C-2), when the photosensitive resin composition of this disclosure is used as a solder resist and a pattern is formed, the penetration of developer at the bottom of the opening can be reliably prevented. As a result, the occurrence of undercuts can be prevented and excellent resolution can be obtained. Furthermore, the cured film (cured product) obtained by the cured film formation method of this disclosure can be obtained to have excellent high temperature and high humidity resistance (PCT resistance) and excellent cold cycle resistance (TCT resistance).

[0039] As the epoxy resin (C-1) having a biphenyl skeleton, known and conventional polyfunctional epoxy resins having a biphenyl skeleton can be used. Examples include biphenyl skeleton-containing polyfunctional solid epoxy resins (NC-3000H, NC-3000, manufactured by Nippon Kayaku Co., Ltd.) and biphenyl-type epoxy resins (YX-4000, YL-6121HA, manufactured by Mitsubishi Chemical Corporation).

[0040] As for epoxy resins (C-2) that are solid or semi-solid at room temperature, other than those described in (C-1) above, known and commonly used epoxy resins can be used. Examples of epoxy resins that are solid at room temperature include bisphenol A type epoxy resin (JER1001, manufactured by Mitsubishi Chemical Corporation), bisphenol F type epoxy resin (JER4004P, manufactured by Mitsubishi Chemical Corporation), naphthalene type epoxy resin (HP-4700, manufactured by DIC Corporation), naphthalene skeleton-containing polyfunctional solid epoxy resin (NC-7000, manufactured by Nippon Kayaku Co., Ltd.), trisphenol epoxy resin (EPPN-502H, manufactured by Nippon Kayaku Co., Ltd.), dicyclopentadiene skeleton-containing polyfunctional solid epoxy resin (Epiclon HP-7200, manufactured by DIC Corporation), cresol novolac type epoxy resin (Epiclon N-690, manufactured by DIC Corporation), phenol novolac type epoxy resin (Epiclon N-770, manufactured by DIC Corporation), phosphorus-containing epoxy resin (TX0712, manufactured by Nippon Steel Chemical & Material Co., Ltd.), and tris(2,3-epoxypropyl) isocyanurate (TEPIC, manufactured by Nissan Chemical Corporation). Examples of epoxy resins that are semi-solid at room temperature include bisphenol A type epoxy resin (JER834, manufactured by Mitsubishi Chemical Corporation) and naphthalene type epoxy resin (HP-4032, manufactured by DIC Corporation).

[0041] In the photosensitive resin composition of this disclosure, the blending ratio of (C) epoxy resin is preferably such that the number of functional groups of the thermosetting component that react is 0.5 to 2.5 mol per 1 mol of carboxyl groups contained in (A) carboxyl group-containing resin, and more preferably 0.8 to 2.0 mol.

[0042] <(D) Inorganic filler> (D) The inorganic filler contains spherical silica (D-1) and barium sulfate (D-2). The volume ratio of spherical silica (D-1) to barium sulfate (D-2) is 1:0.5 to 1:5. The photosensitive resin composition in this disclosure contains spherical silica (D-1) and barium sulfate (D-2) in proportions within the above range. When used as a solder resist, it maintains the function of spherical silica in reducing the coefficient of thermal expansion (CTE), while the function of barium sulfate improves the deep curing properties of the coating film and suppresses undercutting. As a result, deterioration of developability due to undercutting can be effectively prevented, and consequently, the high temperature and high humidity resistance (PCT resistance) and thermal cycle resistance (TCT resistance) of the cured film (cured product) can be improved. The ratio of spherical silica (D-1) to barium sulfate (D-2) is preferably 1:1 to 1:4 by volume, and more preferably 1:1.5 to 1:3.5.

[0043] (D) The amount of inorganic filler added is preferably matched as closely as possible to the coefficient of linear thermal expansion of the substrate, such as a wiring board, on which a cured film is formed using the photosensitive resin composition. It is preferably 20% by mass or more, and more preferably 30% by mass or more, on a solid content basis, of the total amount of the photosensitive resin composition. (D) The total amount of inorganic filler, consisting of spherical silica (D-1) and barium sulfate (D-2), is 20% by mass or more on a solid content basis, of the total amount of the photosensitive resin composition. This lowers the coefficient of linear thermal expansion (CTE) of the photosensitive resin composition and improves TCT resistance.

[0044] (Spherical silica (D-1)) As for spherical silica (D-1), any spherical silica that can be used as a filler for electronic materials can be used, and one type may be used alone, or two or more types may be used in combination. Furthermore, the shape of the spherical silica does not have to be a perfect sphere, as long as it is spherical. Suitable spherical silica includes, for example, those with a sphericity of 0.8 or higher as measured as follows, but is not limited to this.

[0045] The sphericity of spherical silica is measured as follows: First, a photograph of the spherical silica is taken using a scanning electron microscope (SEM), and the area and perimeter of the particles observed in the photograph are used to determine the sphericity: (Sphericity) = {4π × (Area) ÷ (Perimeter)} 2 The calculation is performed using the formula shown in}. Specifically, the sphericity of spherical silica can be determined by using the average value of measurements taken for 100 particles using an image processing device.

[0046] The average particle size of the spherical silica is preferably 300 nm to 1000 nm, and more preferably 500 nm to 900 nm.

[0047] In this specification, the average particle diameter of spherical silica refers to the average particle diameter (D50) that includes not only the particle diameter of primary particles but also the particle diameter of secondary particles (aggregates), and is the D50 value measured by laser diffraction. An example of a laser diffraction measuring device is the Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd. The maximum particle diameter (D100) and particle diameter (D10) can also be measured similarly using the same device.

[0048] The method for producing spherical silica is not particularly limited, and methods known to those skilled in the art can be applied. For example, it can be produced by burning silicon powder using the VMC (Vaporized Metal Combustion) method. The VMC method involves forming a chemical flame with a burner in an oxygen-containing atmosphere, and adding a quantity of metal powder that constitutes part of the target oxide particles into this chemical flame in an amount that forms a dust cloud, causing deflagration to obtain oxide particles.

[0049] Examples of commercially available spherical silica include SO-C2, SO-E2, and SO-E3 from Admatex Co., Ltd., SFP-20M and SFP-30M from Denka Co., Ltd., Admanano and SO-E1 from Admatex Co., Ltd., UFP-30 from Denka Co., Ltd., the Seahostar series from Nippon Shokubai Co., Ltd., the Sciqas series from Sakai Chemical Industry Co., Ltd., and SG-SO100 from Kyoritsu Material Co., Ltd.

[0050] The spherical silica may be surface-treated to improve its dispersibility. The surface treatment method for the spherical silica is not particularly limited, and known and conventional methods can be used. As the surface treatment for the spherical silica, it is preferable to treat the surface of the spherical silica with a surface treatment agent having a curable reactive group, for example, a coupling agent having a curable reactive group as an organic group.

[0051] For surface treatment of spherical silica, coupling agents such as silane-based, titanate-based, aluminate-based, and zircoaluminate-based coupling agents can be used. Among these, silane-based coupling agents are preferred. Examples of silane-based coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, N-(2-aminomethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-anilinopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane. These silane-based coupling agents can be used alone or in combination. It is preferable that these silane-based coupling agents are pre-immobilized on the surface of spherical silica by adsorption or reaction. Here, the amount of coupling agent to be treated per 100 parts by mass of spherical silica is preferably 0.5 to 10 parts by mass. In this disclosure, reactive functional groups derived from coupling agents applied to spherical silica are not included in compounds having photocurable reactive groups or thermosetting functional groups.

[0052] Examples of photocurable reactive groups include ethylenically unsaturated groups such as vinyl groups, styryl groups, methacrylic groups, and acrylic groups. Among these, at least one of vinyl groups and (meth)acrylic groups is preferred.

[0053] Examples of thermosetting reactive groups include hydroxyl groups, carboxyl groups, isocyanate groups, amino groups, imino groups, epoxy groups, oxetanyl groups, mercapto groups, methoxymethyl groups, methoxyethyl groups, ethoxymethyl groups, ethoxyethyl groups, and oxazoline groups. Among these, at least one of amino groups and epoxy groups is preferred.

[0054] Furthermore, surface-treated spherical silica only needs to be included in the photosensitive resin composition in a surface-treated state. While it is also possible to separately blend untreated spherical silica and a surface treatment agent to surface-treat the spherical silica in the composition, it is preferable to blend pre-surface-treated spherical silica. By blending pre-surface-treated spherical silica, it is possible to suppress the reduction in crack resistance of the cured film (cured product) caused by residual surface treatment agent that was not consumed during the surface treatment, which may occur when the materials are blended separately. When pre-surface-treating spherical silica, it is preferable to blend a pre-dispersion in which spherical silica is pre-dispersed in a solvent or curable component. It is even more preferable to pre-disperse surface-treated spherical silica in a solvent and then blend this pre-dispersion into the composition, or to thoroughly surface-treat untreated spherical silica when pre-dispersing it in a solvent before blending this pre-dispersion into the composition.

[0055] Spherical silica (D-1) may be used in powder or solid form with other components such as (A) carboxyl group-containing resin, depending on the manner of use of the photosensitive resin composition in this disclosure, or it may be mixed with a solvent or dispersant to form a slurry and then blended with other components such as (A) carboxyl group-containing resin.

[0056] (Barium sulfate (D-2)) The barium(D-2) sulfate is not particularly limited, and any known type can be used. Furthermore, the barium(D-2) sulfate may be surface-treated by depositing at least one hydroxide or oxide of one or more metal elements selected from Al, Si, and Zr onto the barium sulfate. Examples of surface treatment agents for barium sulfate include hydrated silica, hydrated amorphous silicon dioxide, aluminum hydroxide, zirconium oxide, and organosilane compounds.

[0057] Examples of commercially available barium sulfate include, for example, precipitating barium sulfate #100, precipitating barium sulfate #300, precipitating barium sulfate SS-50, BARIACE B-30, BARIACE B-31, BARIACE B-32, BARIACE B-33, BARIACE B-34, BARIFINE BF-1, BARIFINE BF-10, BARIFINE BF-20, BARIFINE BF-40 from Sakai Chemical Industry Co., Ltd., and W-1, W-6, W-10, and C-300 from Takehara Chemical Industry Co., Ltd. One of these may be used alone as barium sulfate (D-2), or two or more may be used in combination.

[0058] The average particle size of barium sulfate is preferably 0.1 to 1 μm, and more preferably 0.1 to 0.5 μm.

[0059] The photosensitive resin composition in this disclosure may contain photopolymerizable monomers, thermosetting catalysts, colorants, organic solvents, and other optional components, within the range that achieves the effects of the present invention.

[0060] <Photopolymerizable monomers> The photosensitive resin composition in this disclosure may contain a photopolymerizable monomer. Photopolymerizable monomers are compounds having an ethylenically unsaturated double bond. Examples of such photopolymerizable monomers include alkyl(meth)acrylates such as 2-ethylhexyl(meth)acrylate and cyclohexyl(meth)acrylate; hydroxyalkyl(meth)acrylates such as 2-hydroxyethyl(meth)acrylate and 2-hydroxypropyl(meth)acrylate; mono- or di(meth)acrylates of alkylene oxide derivatives such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; hexanediol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, and dipentaerythritol Examples include polyhydric alcohols such as trishydroxyethyl isocyanurate or polyhydric (meth)acrylates derived from ethylene oxide or propylene oxide adducts thereof; (meth)acrylates derived from ethylene oxide or propylene oxide adducts of phenols such as phenoxyethyl (meth)acrylate and polyethoxydigestyl (meth)acrylate of bisphenol A; (meth)acrylates derived from glycidyl ethers such as glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; and melamine (meth)acrylate.

[0061] Photopolymerizable monomers can be used individually or in combination of two or more. The content of the photopolymerizable monomer is preferably 0.5 to 20 parts by mass per 100 parts by mass of (A) carboxyl group-containing resin, based on solid content. When the content is 0.5 parts by mass or more, the photocurability of the photosensitive resin composition is good, and pattern formation is easy during alkaline development after irradiation with active energy rays. On the other hand, when the content is 20 parts by mass or less, when the photosensitive resin composition is used as a solder resist, halation is less likely to occur and good resolution can be obtained.

[0062] <Thermosetting catalyst> The photosensitive resin composition in this disclosure may contain a thermosetting catalyst. Examples of thermosetting catalysts include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, and 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid dihydrazide and sebacate dihydrazide; and phosphorus compounds such as triphenylphosphine. Furthermore, S-triazine derivatives such as guanamine, acetoguanamine, benzoguanamine, melamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine isocyanuric acid adduct can also be used, and preferably these compounds that also function as adhesion imparters are used in combination with a thermosetting catalyst.

[0063] The thermosetting catalyst can be used alone or in combination of two or more types. The content of the thermosetting catalyst is preferably 0.5 to 20 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of (A) carboxyl group-containing resin, in terms of solid content. When the above content is 0.5 parts by mass or more, the heat resistance of the cured film (cured product) formed from the photosensitive resin composition is excellent. When the above content is 20 parts by mass or less, it leads to improved storage stability of the photosensitive resin composition.

[0064] <Coloring agent> The photosensitive resin composition in this disclosure may contain a colorant. As colorants, conventionally known colorants such as red, blue, green, yellow, white, and black can be used. Furthermore, the colorants may be pigments, dyes, or colorants.

[0065] Specifically, examples of colorants include those that have a Color Index (CI; issued by The Society of Dyers and Colourists) number.

[0066] Examples of red colorants include monoazo, dizazo, azolake, benzimidazolone, perylene, diketopyrrolopyrrole, condensed azo, anthraquinone, and quinacridone. Examples of blue colorants include phthalocyanine-based and anthraquinone-based compounds, and compounds classified as pigments can be used. In addition to these, metal-substituted or unsubstituted phthalocyanine compounds can also be used. Examples of green colorants include phthalocyanine-based, anthraquinone-based, and perylene-based compounds. In addition to these, metal-substituted or unsubstituted phthalocyanine compounds can also be used. Examples of yellow colorants include monoazo, disazo, condensed azo, benzimidazolone, isoindolinone, and anthraquinone. Examples of white coloring agents include rutile-type or anatase-type titanium dioxide. Examples of black colorants include carbon black, graphite, iron oxide, titanium black, anthraquinone, cobalt oxide, copper oxide, manganese, antimony oxide, nickel oxide, perylene, aniline, molybdenum sulfide, and bismuth sulfide. Other colorants, such as purple, orange, and brown, may be added to adjust the color tone.

[0067] From the viewpoint of improving the opacity of the cured film (cured product), the colorant content is preferably 0.18 to 0.50% by mass, and more preferably 0.20 to 0.40% by mass, based on solid content, per total amount of the photosensitive resin composition. When the colorant content is 0.18% by mass or more based on solid content, the cured film (cured product) formed from the photosensitive resin composition exhibits excellent circuit opacity, and when it is 0.50% by mass or less, the photosensitive resin composition exhibits superior resolution when used as a solder resist.

[0068] <Organic solvents> The photosensitive resin composition in this disclosure may contain an organic solvent for purposes such as preparing the composition or adjusting its viscosity when applying it to a substrate or film. The organic solvent is not particularly limited, and any known and commonly used organic solvent can be used. Examples of organic solvents include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, diethylene glycol monomethyl ether acetate, and tripropylene glycol monomethyl ether; esters such as ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons such as octane and decane; and petroleum-based solvents such as petroleum ether, petroleum naphtha, and solvent naphtha. Organic solvents can be used individually or in combination of two or more of these.

[0069] <Other optional ingredients> The photosensitive resin composition in this disclosure may further contain, as needed, components such as photoinitiators, cyanate compounds, elastomers, mercapto compounds, urethane catalysts, thixonating agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper damage inhibitors, antioxidants, rust inhibitors, thickeners such as fine silica, organic bentonite, and montmorillonite, defoamers and / or leveling agents such as silicone-based, fluorine-based, and polymer-based defoamers, silane coupling agents such as imidazole-based, thiazole-based, and triazole-based silane coupling agents, and phosphorus compounds such as phosphinates, phosphate ester derivatives, and phosphazene compounds. These components may include those known in the field of electronic materials.

[0070] The photosensitive resin composition in this disclosure may be used as a liquid resin composition or as a dry film. Furthermore, when used as a liquid resin composition, it may be a one-component composition or a two-component or more-component composition.

[0071] The photosensitive resin composition in this disclosure is useful for forming pattern layers as permanent coatings for printed circuit boards, such as solder resists, coverlays, and interlayer insulating layers, and is particularly useful for forming solder resists. Furthermore, since the photosensitive resin composition in this disclosure can form cured products with excellent film strength even when thin, it can be suitably used for forming pattern layers in printed circuit boards where thinness is required, such as semiconductor package substrates (printed circuit boards used in semiconductor packages). Moreover, the cured products obtained from the photosensitive resin composition in this disclosure have excellent resolution and thermal dimensional stability, making them suitably used for forming permanent coatings in semiconductor package substrates where fine pattern formation and high-density mounting are required.

[0072] [Dry film] The photosensitive resin composition in this disclosure can also be used in the form of a dry film comprising a first film (support (carrier) film) and a dried resin layer (photosensitive resin layer) made of the above photosensitive resin composition formed on the first film. In the present invention, the first film refers to a film that is at least adhered to the photosensitive resin layer when laminated onto a substrate such as a substrate by heating or the like so that the photosensitive resin layer side of the dry film is in contact with it. The first film may be peeled off from the photosensitive resin layer in a process after lamination. In particular, in the present invention, it is preferable to peel it off from the photosensitive resin layer in a process after exposure. When forming a dry film, the photosensitive resin composition in this disclosure is diluted with the above organic solvent to adjust to an appropriate viscosity, and applied to the first film to a uniform thickness using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, etc., and usually dried at a temperature of 50 to 130°C for 1 to 30 minutes to obtain a film. There are no particular restrictions on the coating film thickness, but generally, the film thickness after drying is appropriately selected within the range of 1 to 150 μm, preferably 10 to 60 μm.

[0073] As the first film, a plastic film is used, and it is preferable to use a plastic film such as a polyester film like polyethylene terephthalate (PET), a polyimide film, a polyamide-imide film, a polypropylene film, or a polystyrene film. There are no particular restrictions on the thickness of the first film, but it is generally appropriately selected within the range of 10 to 150 μm.

[0074] After forming a dry resin layer made of the photosensitive resin composition of this disclosure on the first film, it is preferable to further laminate a peelable second film (protective (cover) film) on the surface of the photosensitive resin layer for purposes such as preventing foreign matter from adhering to the surface of the photosensitive resin layer. The second film in this invention refers to a film that is peeled off from the photosensitive resin layer before lamination when integrally forming by lamination by heating or the like so that the photosensitive resin layer side of the dry film is in contact with a substrate such as a substrate. Examples of peelable second films include polyethylene film, polytetrafluoroethylene film, polypropylene film, surface-treated paper, etc., and it is sufficient that the adhesive force between the photosensitive resin layer and the second film is less than the adhesive force between the photosensitive resin layer and the first film when the second film is peeled off. The thickness of the second film is not particularly limited, but for example it can be 10 μm to 150 μm.

[0075] In addition, in this disclosure, a photosensitive resin layer may be formed by applying and drying the photosensitive resin composition in this disclosure onto the second film, and the first film may be laminated on its surface. That is, in this disclosure, when manufacturing a dry film, either the first film or the second film may be used as the film on which the photosensitive resin composition in this disclosure is applied.

[0076] [How to form a cured film] The method for forming a cured film according to the present disclosure comprises a first step of forming a photosensitive resin layer made of a photosensitive resin composition on at least a portion of the surface of a substrate on which metal is exposed on at least a portion of the surface, The method includes a third step of irradiating a photosensitive resin layer with UV light to cure the photosensitive resin layer and form a cured film. Furthermore, the method for forming a cured film according to this disclosure may include a second step between the first step and the second step, in which a photosensitive resin layer is exposed and developed to form a pattern.

[0077] <1st process> In the first step, a photosensitive resin layer made of a photosensitive resin composition is formed on at least a portion of the surface of the substrate.

[0078] The substrate is not particularly limited as long as at least a portion of its surface is exposed to metal. Examples of substrates include printed circuit boards with circuits pre-formed with copper, flexible printed circuit boards, as well as copper-clad laminates for high-frequency circuits made of materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / nonwoven epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluororesin / polyethylene / polyphenylene ether, polyphenylene oxide / cyanate, etc., including copper-clad laminates of all grades (FR-4, etc.), metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, wafers, etc., with at least a portion of the surface exposed to metal.

[0079] A method for forming a photosensitive resin layer is to apply a liquid resin composition, adjusted to a viscosity suitable for the application method using the above-mentioned photosensitive resin composition and the above-mentioned organic solvent, to the surface of a substrate using methods such as dip coating, flow coating, roll coating, bar coating, screen printing, or curtain coating, and then volatilize and dry (pre-dry) the organic solvent contained in the resin composition at a temperature of, for example, 60 to 100°C. Methods for volatilization and drying include using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, etc. (a method in which hot air in the dryer is brought into countercurrent contact with a heat source equipped with a steam-heated air heating method, and a method in which hot air is blown onto the support from a nozzle). This forms a tack-free photosensitive resin layer on the substrate.

[0080] Furthermore, when using a dry film instead of a liquid resin composition, the photosensitive resin layer is bonded to the surface of the substrate using a laminator or the like so that the photosensitive resin layer is in contact with the substrate, thereby forming a photosensitive resin layer on the surface of the substrate.

[0081] The dry film is preferably laminated onto the substrate under pressure and heat using a vacuum laminator or the like. By using such a vacuum laminator, even if the circuit-formed substrate has irregularities on its surface, the dry film adheres closely to the circuit board, preventing the inclusion of air bubbles and improving the ability to fill in depressions on the substrate surface. The pressure is preferably around 0.1 to 2.0 MPa, and the heating is preferably around 40 to 120°C.

[0082] <Second process> In the second step, the photosensitive resin layer is exposed and developed to form a pattern. Specifically, a photomask with a predetermined pattern is prepared, and the photosensitive resin layer is exposed by selectively irradiating it with active energy rays through the photomask. The unexposed areas are then developed with a dilute alkaline aqueous solution (for example, a 0.3-3% by mass sodium carbonate aqueous solution) to form the pattern of the cured product. In the case of a dry film, after exposure, the first film is peeled off the dry film and developed to form a patterned cured product on the substrate. However, if the properties are not impaired, the first film may be peeled off the dry film before exposure, and the exposed photosensitive resin layer may be exposed and developed.

[0083] Exposure machines used for active energy ray irradiation include devices equipped with high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, mercury short-arc lamps, etc., that irradiate ultraviolet light in the range of 350 to 450 nm. Alternatively, a direct imaging device (for example, a laser direct imaging device that directly draws images with a laser using CAD data from a computer) may be used as the exposure machine. The lamp light source or laser light source of the direct imaging device is one whose maximum wavelength is in the range of 350 to 450 nm. The exposure amount for image formation (pattern formation) varies depending on the thickness of the photosensitive resin layer, etc., but is generally 10 to 1000 mJ / cm². 2 It can be within the range of 20 to 800 mJ / cm², preferably 20 to 800 mJ / cm². 2 It can be within the range of

[0084] As a development method after exposure, dipping method, shower method, spray method, brush method, etc. can be mentioned. Further, as the developer, an alkaline aqueous solution such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amines, etc. can be used.

[0085] <Third Step> In the third step, UV irradiation treatment is performed on the cured product having a pattern formed in the second step to further cure the cured product and form a cured film. For the UV irradiation treatment, the above-mentioned exposure machine can be used. Further, the UV irradiation amount (exposure amount) of the UV irradiation treatment is 1500 mJ / cm 2 or more, and preferably 2000 mJ / cm 2 or more. Thereby, for example, even after a high-temperature treatment such as 215°C or more and 1500 mJ / cm 2 or more, a cured film having high adhesion to the metal surface can be formed.

[0086] The UV irradiation treatment is performed in an environment where the temperature of the photosensitive resin layer on the substrate is 215°C or more. The temperature of the photosensitive resin layer on the substrate is preferably 230°C or more, and more preferably 250°C or more. According to the method for forming a cured film of the present disclosure, by performing heat curing simultaneously with the UV irradiation treatment, a cured film having stronger coating film strength can be obtained.

[0087] The method for forming a cured film of the present disclosure may include only the first step and the third step without including the above-mentioned second step. That is, in the above-mentioned second step, it is not for the purpose of forming a cured film by performing exposure and development treatment on the photosensitive resin layer to form a pattern (for example, solder resist application), but without including the second step, it is cured without forming a pattern in the photosensitive resin composition to form a cured film, and it may be applied to, for example, a mold application (sealing application).

[0088] [Cured Film] The cured film (cured product) in this disclosure is obtained by curing a photosensitive resin layer obtained by applying and drying the photosensitive resin composition in this disclosure, or a photosensitive resin layer of a dry film, in the method for forming a cured film in this disclosure, and has high adhesion to metal surfaces. Furthermore, the photosensitive resin composition and dry film in this disclosure have excellent resolution and thermal dimensional stability.

[0089] [Printed wiring board] The printed circuit board in this disclosure has a cured coating (cured product) obtained by the cured coating formation method of this disclosure on at least a portion of the surface of the substrate.

[0090] [Manufacturing method for printed circuit boards] The present disclosure is a method for manufacturing a printed circuit board comprising a substrate and a cured coating provided on at least a portion of the surface of the substrate, wherein the cured coating is formed by the method for forming a cured coating according to the present disclosure.

[0091] After forming a cured film on the substrate as described above, components such as electronic elements are mounted on the substrate by solder reflow. Solder reflow can be carried out by conventionally known methods. Solder reflow is generally performed under processing conditions such as 245-260°C for 5-10 seconds.

[0092] According to the method for manufacturing printed circuit boards of this disclosure, even when high temperatures are reached during the reflow process of lead-free solder surface mounting, the adhesion of the cured film to the metal surface does not decrease, and peeling does not occur, so subsequent lamination processes and other steps can be carried out without problems. [Examples]

[0093] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following, "parts" and "%" all refer to mass unless otherwise specified.

[0094] <Synthesis of carboxyl group-containing photosensitive resin varnish A> In an autoclave equipped with a thermometer, a nitrogen introduction device / alkylene oxide introduction device, and a stirring device, 119.4 parts by mass of novolac-type cresol resin (product name "Shonol CRG951", manufactured by Aica Kogyo Co., Ltd., OH equivalent: 119.4), 1.19 parts by mass of potassium hydroxide, and 119.4 parts by mass of toluene were introduced. The system was then heated and the temperature increased while stirring and nitrogen was purged into the system. Next, 63.8 parts by mass of propylene oxide were gradually added dropwise to 125-132°C and 0-4.8 kg / cm³. 2 The reaction was carried out for 16 hours. After cooling to room temperature, 1.56 parts by mass of 89% phosphoric acid was added to the reaction solution and mixed to neutralize the potassium hydroxide, yielding a propylene oxide reaction solution of novolac-type cresol resin with a solid content of 62.1% and a hydroxyl value of 182.2 mg KOH / g (307.9 g / eq.). This solution contained an average of 1.08 moles of alkylene oxide added per equivalent of phenolic hydroxyl groups. 293.0 parts by mass of the alkylene oxide reaction solution of the obtained novolac-type cresol resin, 43.2 parts by mass of acrylic acid, 11.53 parts by mass of methanesulfonic acid, 0.18 parts by mass of methylhydroquinone, and 252.9 parts by mass of toluene were introduced into a reactor equipped with a stirrer, thermometer, and air blowing tube. Air was blown in at a rate of 10 ml / min, and the mixture was reacted at 110°C for 12 hours while stirring. Of the water produced by the reaction, 12.6 parts by mass of water was distilled off as an azeotropic mixture with toluene. The mixture was then cooled to room temperature, and the resulting reaction solution was neutralized with 35.35 parts by mass of 15% aqueous sodium hydroxide solution, followed by washing with water. Subsequently, toluene was removed by distillation in an evaporator while substituting with 118.1 parts by mass of diethylene glycol monoethyl ether acetate to obtain a novolac-type acrylate resin solution. Next, 332.5 parts by mass of the obtained novolac-type acrylate resin solution and 1.22 parts by mass of triphenylphosphine were charged into a reactor equipped with a stirrer, thermometer, and air blowing tube. Air was blown in at a rate of 10 ml / min, and while stirring, 60.8 parts by mass of tetrahydrophthalic anhydride were gradually added. The mixture was reacted at 95-101°C for 6 hours, and after cooling, it was removed. In this way, a solution of a photosensitive carboxyl group-containing resin with a solid content of 70% by mass and an acid value of 87.7 mgKOH / g of the solids was obtained.

[0095] <Preparation of photosensitive resin composition> Each component was blended according to the formulations shown in Table 1 below, pre-mixed in a stirrer, dispersed in a three-roll mill, and kneaded to prepare the respective photosensitive resin compositions. The amounts in the table are in parts by mass. The obtained photosensitive resin compositions of the examples and comparative examples were evaluated as follows.

[0096] <Preparation of dry film> Each photosensitive resin composition of the examples and comparative examples was appropriately diluted with methyl ethyl ketone, and then applied to a PET film (Toray Industries, FB-50, 16 μm thick) using an applicator so that the thickness of the photosensitive resin layer after drying would be 15 μm. The film was then dried at 80°C for 30 minutes to obtain a dry film.

[0097] <Fabrication of evaluation substrates for resolution> The dry film prepared by the above method was heat-laminated onto a printed circuit board with chemically polished (MEC Corporation CZ-8101) copper circuits using a vacuum laminator (Nikko Materials Co., Ltd. CVP-300) under the conditions of pressure: 0.4 MPa, 80°C, 1 minute, and vacuum: 3 hPa. The board was then flat-pressed at 70°C and 0.5 MPa to obtain a printed circuit board with an unexposed photosensitive resin layer (dry film). This board was exposed to a standard exposure dose using a φ80 μm photomask and an exposure apparatus equipped with a high-pressure mercury lamp (short arc lamp), and the PET film was peeled off. Subsequently, a 1% by mass Na2CO3 aqueous solution at 30°C was sprayed at a pressure of 2 kg / cm². 2 Developing was performed for 60, 90, and 120 seconds under the specified conditions to obtain a substrate with a patterned cured material. This substrate was then subjected to an integrated exposure of 1000 mJ / cm² in a UV conveyor oven (QRM-2082-E-02: manufactured by Oak Manufacturing Co., Ltd.). 2 , 1500 mJ / cm 2 , 2000 mJ / cm 2 After irradiating each sample with ultraviolet light under the specified conditions, the cured material was heated at 160°C for 60 minutes to fully cure it.

[0098] <Preparation of a cured coating> The surface of an ultra-thin copper foil (35 μm) with a carrier is chemically polished, and a photosensitive resin layer of dry film is bonded to the polished side. Subsequently, it is laminated using a vacuum laminator (CVP-300: manufactured by Nikko Materials Co., Ltd.) in the first chamber at 80°C under the conditions of a vacuum pressure of 4.0 hPa, a vacuum time of 30 seconds, a press pressure of 0.4 MPa, and a press time of 30 seconds, and then in the second chamber at 80°C under a press pressure of 8 kgf / cm². 2 The copper foil and the photosensitive resin layer were pressed together under conditions of a 60-second press time.

[0099] Next, using a DI exposure machine (Mms60, manufactured by Okou Seisakusho Co., Ltd.), after exposure from the dry film, the PET film was peeled off from the dry film to expose the photosensitive resin layer. Then, development was carried out for 60 seconds at 30 °C and a spray pressure of 0.2 MPa using a 1 mass% Na2CO3 aqueous solution to form a cured product. Subsequently, in a UV conveyor furnace equipped with a high-pressure mercury lamp, irradiation was performed on the cured product at exposure amounts of 1000 mJ / cm 2 , 1500 mJ / cm 2 , 2000 mJ / cm 2 respectively, and then heating was carried out at 160 °C for 60 minutes to completely cure the cured product to form each cured film.

[0100] <Fabrication of Evaluation Substrate for Peel Test> The cured films obtained as described above were each passed through a reflow furnace (NJ08M-82, manufactured by EIGHTECH TECTRON) 15 times under the conditions of 175 to 260 °C. After that, the copper foil side of the obtained cured film was attached to a T-11 UV substrate (dimensions: 150 mm x 95 mm, plate thickness: 1.6 mm) with a room temperature curing two-component epoxy resin adhesive (manufactured by Three Bond) of epoxy and amine, and then using a vacuum laminator (CVP-300, manufactured by Nichco Materials Co., Ltd.), lamination was carried out in the first chamber at 60 °C under the conditions of a vacuum pressure of 4.0 hPa, a vacuum time of 30 seconds, a press pressure of 0.4 MPa, and a press time of 30 seconds to make the copper foil and the substrate adhere closely.

[0101] <Fabrication of Evaluation Substrate for DMA Measurement> The cured films obtained as described above were peeled off only the cured film from the copper foil. For the samples to be measured after reflow, the cured films obtained as described above were each passed through a reflow furnace (NJ08M-82, manufactured by EIGHTECH TECTRON) 15 times under the conditions of 175 to 260 °C. And only the cured film was peeled off from the copper foil.

[0102] <Measurement of Substrate Temperature in UV Conveyor Furnace> As shown in Figure 1, thermocouples were attached to a substrate (core: 0.1 mm, conductor thickness: 35 / 35 μm, SR thickness: 20 / 18 μm, total: 0.208 mm), and the temperature changes inside a UV conveyor furnace were tracked, and the peak temperature was measured.

[0103] <Evaluation of adhesion after reflow (peel test)> The sample prepared using the method described above was cut to a width of 21 mm (short side) and a length of 95 mm (long side). Then, one end of the short side was peeled off from the hardened film and copper foil, and the peeled area was clamped with a gripper. Using an Autograph (AG-X: Shimadzu Corporation), the copper plating layer was peeled off over a length of 35 mm at a 90-degree angle at a speed of 50 mm / min, and the peel strength (N / cm) was measured and evaluated according to the following criteria. The results are shown in Table 1. ◎: Peel strength after reflow: 8 N / cm or higher ○: Peel strength after reflow: 2N / cm or more and less than 8N / cm ×: Peel strength after reflow less than 2 N / cm

[0104] <Evaluation of the change in Tg before and after reflow (DMA measurement)> Tg was measured using DMA (RSA-G2: TA Instruments) and evaluated according to the following criteria. The results are shown in Table 1. ◎: Change in Tg before and after reflow below 26℃ ○: Change in Tg before and after reflow (26°C to less than 35°C) ×: Change in Tg before and after reflow above 35℃

[0105] <Resolution Evaluation> The size of the developer undercut at the bottom of the φ80 μm aperture pattern of the evaluation substrate obtained by the above method was evaluated by cross-sectional observation. The results are shown in Table 1. ◎: No undercuts are visible. ○: Undercut less than 5 μm. ×: Undercut of 5-10 μm, or residue present at the opening.

[0106] The components *1 to *13 in Table 1 below are as follows: *1: The above-mentioned synthetic varnish A (70% solids content) *2: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide *3: jER834 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin (semi-solid at room temperature, epoxy equivalent: 250), (C-1) *4: NC-3000H (manufactured by Nippon Kayaku Co., Ltd., biphenyl-phenol type epoxy resin (solid at room temperature, epoxy equivalent: 290), (C-2) *5: jER828 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin (liquid at room temperature, epoxy equivalent: 190)) *6: SFP-30M (manufactured by Denka Co., Ltd., spherical silica, average particle size: 0.8 μm, specific gravity: 4.4 g / cm³) 3 ), (D-1) *7: BRIACE B-31 (manufactured by Sakai Chemical Industry Co., Ltd., barium sulfate, amorphous, average particle size: 0.3 μm, specific gravity: 2.2 g / cm³) 3 ), (D-2) *8: DPHA (manufactured by Nippon Kayaku Co., Ltd., dipentaerythritol pentaacrylate) *9: Melamine (manufactured by Nissan Chemical Corporation) *10: DICY (manufactured by Mitsubishi Chemical Corporation, dicyandiamide)

[0107] [Table 1]

[0108] As is clear from Table 1, Examples 1 to 4 use a photosensitive resin composition containing (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) an epoxy resin, and (D) an inorganic filler, wherein (C) the epoxy resin contains an epoxy resin having a biphenyl skeleton (C-1) and an epoxy resin other than (C-1) that is solid or semi-solid at room temperature (C-2), and (D) the inorganic filler contains spherical silica (D-1) and barium sulfate (D-2), with the volume ratio of spherical silica (D-1) to barium sulfate (D-2) being 1:0.5 to 1:5, and the curing treatment by UV irradiation (UV irradiation treatment) is 1500 mJ / cm². 2 Using the above UV irradiation dose, and with heat curing, the peak temperature of the substrate in the UV conveyor furnace was 215°C or higher. As a result, it was confirmed that a cured film with excellent resolution as a solder resist and adhesion (peel strength) after reflow was obtained, and that it had high adhesion to the metal surface even after high-temperature treatment.

[0109] Comparative Example 1 showed no undercuts and excellent solder resist resolution, but the UV curing treatment (UV irradiation treatment) was 1000 mJ / cm². 2 (1500 mJ / cm 2 Using a UV irradiation dose of less than 100°C, the peak temperature of the substrate in the UV conveyor furnace during heat curing after UV irradiation (UV irradiation treatment) was 170°C (less than 215°C), resulting in a change in Tg of 35°C or more before and after reflow. As a result, the stress on the solder resist increased, leading to insufficient adhesion (peel strength) after reflow. Comparative Example 2 used a photosensitive resin composition that contained only spherical silica (D-1) and no barium sulfate (D-2) as the (D) inorganic filler. As a result, undercuts of less than 5 μm were observed in the resolution of the solder resist. Furthermore, the curing treatment by UV irradiation was 2000 mJ / cm². 2Using the specified UV irradiation dose, during heat curing after UV irradiation (UV curing treatment), the peak temperature of the substrate in the UV conveyor furnace was 260°C, yet the change in Tg before and after reflow was 35°C or more. As a result, the stress on the solder resist increased, leading to insufficient adhesion (peel strength) after reflow. Comparative Example 3 used a photosensitive resin composition that did not contain an epoxy resin (C-1) having a biphenyl skeleton as the (C) epoxy resin, resulting in insufficient resolution as a solder resist.

Claims

1. A first step of forming a photosensitive resin layer made of a photosensitive resin composition on a substrate in which metal is exposed on at least a portion of the surface, A method for forming a cured film, comprising a third step of performing UV irradiation treatment on the photosensitive resin layer to cure the photosensitive resin layer and form a cured film, In the first step, the photosensitive resin composition contains (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) an epoxy resin, and (D) an inorganic filler. The (C) epoxy resin contains an epoxy resin having a biphenyl skeleton (C-1) and an epoxy resin other than (C-1) that is solid or semi-solid at room temperature (C-2). The (D) inorganic filler contains spherical silica (D-1) and barium sulfate (D-2), A photosensitive resin composition is used in which the content ratio of the spherical silica (D-1) and the barium sulfate (D-2) is 1:0.5 to 1:5 by volume. In the third step, the UV irradiation treatment is performed in an environment in which the temperature of the photosensitive resin layer on the substrate is 215°C or higher, and the UV irradiation treatment is performed at 1500 mJ / cm². ２ A method for forming a cured film using the above UV irradiation dose.

2. In the first step described above, A method for forming a cured film according to claim 1, comprising a dry film comprising a first film and a photosensitive resin layer on one side of the first film, wherein the photosensitive resin composition is applied and dried.

3. In the third step, the UV irradiation treatment is 2000 mJ / cm². ２ A method for forming a cured film according to claim 1, using the above UV irradiation dose.

4. After the first step, and before the third step, A method for forming a cured film according to claim 1, comprising a second step of performing an exposure and development treatment on the photosensitive resin layer to form a pattern.

5. A method for manufacturing a printed wiring board comprising a base material and a cured coating provided on at least a portion of the surface of the base material, A method for manufacturing a printed circuit board, comprising forming a cured film on at least a portion of the surface of the substrate by the method for forming a cured film according to any one of claims 1 to 4.

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