Photosensitive resin composition, solder resist ink, dry film and cured product

Abstract

The present invention relates to a photosensitive resin composition, a solder resist ink, a dry film and a cured product, the photosensitive resin composition contains an epoxy acrylic resin having a specific structure, and the epoxy acrylic resin having the specific structure is formed by adding an alpha, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, beta, and then adding dibasic acid anhydride to the beta-unsaturated monobasic acid a1 and the monobasic acid a2 with a specific structure. According to the invention, a certain proportion of monobasic acid a2 with a special structure is introduced into epoxy acrylate, so that the dispersibility of the photosensitive resin composition to pigments and fillers can be effectively improved; and the water absorption of the cured product is reduced, so that the lead-free tin spraying resistance and the wave soldering resistance are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit boards, and particularly to a photosensitive resin composition, a solder mask ink, a dry film and a cured product. Background Art

[0002] In the field of printed circuit board manufacturing, it is necessary to form a permanent solder mask layer on the circuit board. The solder mask layer has the following functions: during the use of the circuit board, it prevents oxidation and corrosion of the circuits and maintains insulation between the circuits. To meet the requirements of high precision, high density and environmental protection, photosensitive imaging solder resist that can be developed with a weakly alkaline aqueous solution has currently become the mainstream solder resist material for circuit boards.

[0003] For a circuit board with vias, in order to prevent solder from entering the vias or flux from diffusing through the vias to the back of the circuit board and contaminating the circuit board, resulting in defects, the industry often uses solder mask ink to fill the vias, which is completed together with the printing on the surface of the circuit board.

[0004] The prior art US Patent No. US5009982 discloses a photosensitive imaging solder resist composition with a photosensitive resin prepared by adding (meth)acrylic acid to o-cresol type epoxy resin and then adding a dibasic anhydride as the main resin, which has good photosensitivity, resolution and insulation. However, there are still the following deficiencies:

[0005] A. The ink prepared from the composition is prone to floating color, blooming or coarsening during storage, and the dispersion stability is insufficient;

[0006] B. When applied to the solder resist process for via filling, when the solder mask layer is cured and then placed in a normal environment for more than 8 hours, since the solder mask layer absorbs water in the environment, its heat resistance will decrease. At the same time, during the lead-free hot air leveling (referred to as lead-free solder spraying) or lead-free wave soldering process, especially the lead-free flux has stronger acidity than the leaded flux, and has a strong attack on the ester bond of the cured product at high temperature, resulting in the solder mask layer at the vias and on the fine lines being prone to blistering and peeling. The industry generally avoids this problem by reheating the circuit board, but this will additionally increase the operation process and energy consumption, resulting in additional cost increase.

[0007] C. For carrier circuit boards, it is required that the solder mask layer has good HAST (Highly Accelerated Stress Test - Temperature and Humidity) and PCT (Pressure Cooker Test) resistance, and the technology provided by the patent document US5009982 is also difficult to guarantee.

[0008] Patent document JP1997087346A discloses an energy ray-curable epoxy acrylate resin composition that can be used in photopolymerizable resins such as solder resists. It is obtained by reacting the hydroxyl groups of an epoxy acrylate resin, which is obtained by reacting an epoxy resin having two or more epoxy groups with an unsaturated monocarboxylic acid, with a polyanhydride, and mixing two or more epoxy acrylate resins having different acid values. The unsaturated monocarboxylic acids used include acrylic acid or methacrylic acid, their dimeric and trimeric acids, or 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. This energy ray-curable resin can be used in photopolymerizable resins such as solder resists and has advantages such as high sensitivity, excellent solvent drying stability, electrical properties, and plating resistance. However, the above-mentioned photosensitive resin composition still has problems of poor hygroscopicity and thus poor stability. That is, after the solder resist layer absorbs water in the environment, its heat resistance will decrease. At the same time, during the process of lead-free hot air leveling (referred to as lead-free solder spraying) or lead-free wave soldering, especially since lead-free soldering fluxes have stronger acidity than leaded soldering fluxes, they have a strong attack on the ester bonds of the cured product at high temperatures, resulting in easy blistering and peeling of the solder resist layer at through-holes and fine lines. Summary of the Invention

[0009] Based on this, it is necessary to provide a photosensitive resin composition, solder resist ink, dry film, and cured product that can improve the dispersibility of the photosensitive resin composition with respect to pigments and fillers, reduce the water absorption of the cured product, and improve the resistance to lead-free solder spraying and wave soldering.

[0010] In a first aspect, the present application provides a photosensitive resin composition, which is characterized in that it contains an epoxy acrylate resin with a specific structure. The epoxy acrylate resin with the specific structure is obtained by adding an α,β-unsaturated monocarboxylic acid a1 and a monocarboxylic acid a2 with a specific structure to an epoxy resin having two or more epoxy groups in one molecule, and then adding a dianhydride. Among them, the monocarboxylic acid a2 with the specific structure conforms to the following structural formula:

[0011]

[0012] Among them, R1 and R2 are hydrogen atoms or hydrocarbon chains having 2 to 15 carbon atoms, and R1 and R2 cannot be hydrogen atoms at the same time.

[0013] In one embodiment, in the structure of the monocarboxylic acid a2 with a specific structure, R1 and R2 are hydrogen atoms or hydrocarbon chains having 2 to 12 carbon atoms; preferably, R1 and R2 are hydrogen atoms or hydrocarbon chains having 2 to 10 carbon atoms. Preferably, the monocarboxylic acid a2 with a specific structure is at least one of 2-ethylhexanoic acid, neodecanoic acid, 2-phenylpropionic acid, 2-methylvaleric acid, and 2,2-dimethylvaleric acid.

[0014] In one embodiment, the α,β-unsaturated monocarboxylic acid a1 includes at least one of acrylic acid, (meth)acrylic acid, cinnamic acid, and crotonic acid. Preferably, at least one of methacrylic acid and acrylic acid is used. Preferably, the α,β-unsaturated monocarboxylic acid a1 is (meth)acrylic acid.

[0015] In one embodiment, the molar ratio of the sum of the α,β-unsaturated monocarboxylic acid a1 and the monocarboxylic acid a2 with a specific structure to the molar number of epoxy groups ranges from "0.95 - 1.1":1; preferably, the molar ratio of a1 to a2 ranges from 5:5 to 9.5:0.5, preferably, the molar ratio of a1 to a2 ranges from 6:4 - 9:1, and more preferably, the molar ratio of a1 to a2 ranges from 7:3 - 9:1.

[0016] In one embodiment, the dicarboxylic anhydride includes one or a combination of two or more of phthalic anhydride, maleic anhydride, methylmaleic anhydride, succinic anhydride, glutaric anhydride, nadic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride;

[0017] In one embodiment, the epoxy resin used for preparing the epoxy acrylate with a specific structure includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, phenoxy epoxy resin, phenolic epoxy resin, o-cresol novolac epoxy resin, biphenol novolac epoxy resin, cyclopentadiene novolac epoxy resin, and naphthol novolac epoxy resin. Preferably, o-cresol novolac epoxy resin is used.

[0018] In one embodiment, the amount of the epoxy acrylate resin with a specific structure is 10% - 60% by weight of the photosensitive resin composition, preferably 30% - 50%.

[0019] In one embodiment, the photosensitive resin composition further includes an epoxy resin containing two or more epoxy groups in one molecule as a thermosetting component;

[0020] In one embodiment, the photosensitive resin composition further includes one or more polyacrylate monomers;

[0021] In one embodiment, the photosensitive resin composition further includes one or more photoinitiators.

[0022] In one embodiment, the photosensitive resin composition is used for via filling of a circuit board or solder mask of a circuit board.

[0023] In one embodiment, the photosensitive resin composition comprises the following components: an epoxy acrylate resin having a specific structure, an epoxy resin, an acrylate monomer, a photoinitiator, dicyandiamide, a filler, phthalocyanine green, a solvent, and an additive, wherein the additive comprises a leveling agent, fumed silica, and an antifoaming agent;

[0024] Preferably, the photosensitive resin composition comprises the following components: an epoxy acrylate resin having a specific structure, an o-cresol novolac epoxy resin, micronized melamine triglycidyl ether, dipentaerythritol hexaacrylate, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propane, 2-isopropyl-thioxanthone, dicyandiamide, fine barium sulfate, micronized talc powder, a DBE solvent, SOLVESSO 150, a leveling agent BYK-354, fumed silica R-972, and an antifoaming agent;

[0025] Preferably, the photosensitive resin composition comprises the following components in parts by mass: 42 parts of an epoxy acrylate resin having a specific structure, 5 parts of an o-cresol novolac epoxy resin, 4 parts of micronized melamine triglycidyl ether, 5 parts of dipentaerythritol hexaacrylate, 3.5 parts of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propane, 0.8 part of 2-isopropyl-thioxanthone, 0.3 part of dicyandiamide, 28 parts of fine barium sulfate, 4 parts of micronized talc powder, 4 parts of a DBE solvent, 1 part of SOLVESSO 150, 0.2 part of a leveling agent BYK-354, 0.9 part of fumed silica R-972, and 0.8 part of an antifoaming agent KS-66.

[0026] In a second aspect, the present application provides a solder resist ink comprising the photosensitive resin composition described in any one of the above embodiments.

[0027] In a third aspect, the present application further provides a solder resist dry film having a resin layer formed from the photosensitive resin composition described in any one of the above embodiments.

[0028] In a fourth aspect, the present application further provides a solder resist cured product, which is obtained by curing the photosensitive resin composition described in any one of the above embodiments, or the solder resist cured product is obtained by curing the solder resist ink described in any one of the above embodiments.

[0029] The above photosensitive resin composition. Compared with the prior art, in the present invention, a certain proportion of monobasic acid a2 with a special structure is introduced into the epoxy acrylate, which can effectively improve the dispersibility of the photosensitive resin composition to the pigment and filler; reduce the water absorption of the cured product, thereby improving the resistance to lead-free spray tin and wave soldering. Theoretical speculation believes that: the monobasic acid with a special structure has a longer carbon chain and a larger molecular weight, which increases the hydroxyl equivalent of the cured product of the photosensitive resin composition after curing, and can reduce the content of polar groups hydroxyl in the cured product. Therefore, the water absorption of the cured product can be reduced; there is one or two hydrocarbon groups on the α-carbon of the carboxyl group, which has a steric effect on the ester group, can further reduce the water absorption, and can also reduce the aggressiveness of the flux to the ester bond at high temperature in the lead-free spray tin and wave soldering processes, so that the solder mask at the via hole and on the fine circuit is not easy to bubble and peel. At the same time, due to the better coating effect of the longer carbon chain on the pigment and filler, there is a better barrier effect, and the pigment and filler are not easy to precipitate and agglomerate after dispersion, improving the stability of the photosensitive resin composition during storage, and not easy to appear floating color or coarsening phenomenon. Detailed Embodiments

[0030] To facilitate the understanding of the present invention, in order to make the above objects, features and advantages of the present invention more obvious and understandable, the detailed embodiments of the present invention will be described below. Many specific details are set forth in the following description to fully understand the present invention, and the preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] In a first aspect, the present application provides a photosensitive resin composition, characterized in that it contains an epoxy acrylate resin with a specific structure, and the epoxy acrylate resin with a specific structure is obtained by adding an α,β-unsaturated monobasic acid a1 and a monobasic acid a2 with a specific structure to an epoxy resin containing two or more epoxy groups in one molecule, and then adding a dibasic anhydride. Among them, the monobasic acid a2 with a specific structure conforms to the following structural formula:

[0032]

[0033] Among them, R1 and R2 are hydrogen atoms or hydrocarbon chains with 2 to 15 carbon atoms, and R1 and R2 cannot be hydrogen atoms at the same time. For example, in the structure of a monobasic acid a2 with a specific structure, R1 and R2 are hydrogen atoms or hydrocarbon chains with 2 to 12 carbon atoms; preferably, R1 and R2 are hydrogen atoms or hydrocarbon chains with 2 to 10 carbon atoms. Preferably, the monobasic acid a2 with a specific structure is at least one of 2-ethylhexanoic acid, neodecanoic acid, 2-phenylpropionic acid, 2-methylvaleric acid, 2,2-dimethylvaleric acid, and is not limited thereto.

[0034] Regarding the above photosensitive resin composition, compared with the prior art, in the present invention, introducing a certain proportion of monobasic acid a2 with a special structure into epoxy acrylate can effectively improve the dispersibility of the photosensitive resin composition to pigments and fillers; reduce the water absorption of the cured product, thereby improving the resistance to lead-free solder spraying and wave soldering. Theoretical speculation believes that: the monobasic acid with a special structure has a longer carbon chain and a larger molecular weight, which increases the hydroxyl equivalent of the cured product of the photosensitive resin composition after curing, can reduce the content of polar groups hydroxyl in the cured product, so it can reduce the water absorption of the cured product; there is one or two hydrocarbon groups on the α-carbon of the carboxyl group, which has a steric effect on the ester group, can further reduce the water absorption, and can also reduce the aggressiveness of the flux to the ester bond at high temperature in the lead-free solder spraying and wave soldering processes, making the solder mask at through holes and fine lines not prone to blistering and peeling. At the same time, due to the better coating property of the longer carbon chain to pigments and fillers and the better barrier effect, the pigments and fillers are not prone to precipitation and agglomeration after dispersion, improving the stability of the photosensitive resin composition during storage and not prone to floating color or coarsening.

[0035] For example, the preparation process of the epoxy acrylate resin with a specific structure is as follows: Epoxy resin is added to a solvent, and after dissolution, α,β-unsaturated monobasic acid a1 and monobasic acid a2 with a specific structure are added and reacted, and then a dibasic anhydride is added for reaction to obtain. For example, the solvent is at least one of solvents of types such as esters, ketones, ether esters, and aromatics. For example, the solvent is preferably diethylene glycol monomethyl ether acetate. For example, the preparation process of the epoxy acrylate resin with a specific structure is as follows: Diethylene glycol monomethyl ether acetate is introduced with air, heated to 90 °C, o-cresol novolac epoxy resin is added, and after complete dissolution, α,β-unsaturated monobasic acid a1, monobasic acid a2, monomethyl hydroquinone, and triphenylphosphine are added, then the temperature is raised to 100 °C and reacted for 20 hours until the acid value drops below 3 mg / g, the temperature is lowered to 90 °C, and a dibasic anhydride is added and reacted for 10 hours to obtain the epoxy acrylate resin with the specific structure.

[0036] The above photosensitive resin and its composition provided by the present application have excellent dispersion stability to pigments and fillers; the cured product obtained subsequently has excellent moisture resistance, good resistance to lead-free solder spraying and wave soldering, and the solder mask at through holes and fine lines is not prone to problems such as blistering and peeling.

[0037] In order to solve the problems in the background art of the present invention, the applicant has conducted in-depth research on the photosensitive resin composition, and as a result, it has been found that introducing a certain proportion of monobasic acid a2 with a special structure into the epoxy acrylate can effectively improve the dispersibility of the photosensitive resin composition to pigments and fillers; reduce the water absorption of the cured product, thereby improving the resistance to lead-free spray soldering and wave soldering.

[0038] The epoxy acrylate in the present invention is obtained by adding an α,β-unsaturated monobasic acid a1 and a monobasic acid a2 with a specific structure to an epoxy resin having two or more epoxy groups in one molecule and then adding a dibasic anhydride. There is no particular limitation on the epoxy resin of the present application, as long as it contains two or more epoxy groups in one molecule, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenoxy type epoxy resin, phenolic type epoxy resin, o-cresol type phenolic epoxy resin, biphenol type phenolic epoxy resin, cyclopentadiene type phenolic epoxy resin, naphthol type phenolic epoxy resin, etc. can be cited. One epoxy resin can be used, or two or more epoxy resins can be used. Considering the sensitivity, dryness after pre-baking, and heat resistance, o-cresol type phenolic epoxy resin is preferably used.

[0039] In one of the embodiments, the α,β-unsaturated monobasic acid a1 includes at least one of acrylic acid, (meth)acrylic acid, cinnamic acid, and crotonic acid. Preferably, at least one of methacrylic acid and acrylic acid is used. Preferably, the α,β-unsaturated monobasic acid a1 is (meth)acrylic acid. It should be noted that there is no special limitation on the α,β-unsaturated monobasic acid a1, as long as it is an α,β-unsaturated monobasic acid, such as (meth)acrylic acid, cinnamic acid, crotonic acid, etc. Preferably, methacrylic acid and acrylic acid are used, and more preferably, acrylic acid is used.

[0040] In one embodiment, the molar ratio of the sum of the α,β-unsaturated monocarboxylic acid a1 and the monocarboxylic acid a2 with a specific structure to the molar number of epoxy groups ranges from "0.95 - 1.1":1; preferably, the molar ratio of a1 to a2 ranges from 5:5 to 9.5:0.5, preferably, the molar ratio of a1 to a2 ranges from 6:4 - 9:1, more preferably, the molar ratio of a1 to a2 ranges from 7:3 - 9:1. It should be noted that the molar ratio of the sum of the molar numbers of the α,β-unsaturated monocarboxylic acid a1 and the monocarboxylic acid a2 with a specific structure to the molar number of epoxy groups in the epoxy resin ranges from "0.9 - 1.1":1, preferably "0.95 - 1.05":1. If the ratio is too small, gelation or poor developability is likely to occur during the reaction; if the ratio is too large, the acid reaction is incomplete and not preferred. The ratio range of a1 to a2 is the molar ratio range of a1 to a2 from 5:5 - 9.5:0.5, preferably 6:4 - 9:1, more preferably 7:3 - 9:1. If the ratio is too low, it is not preferred because the acryloyl group content in the photosensitive resin is too low, resulting in a decrease in photocuring sensitivity and poor developability; if the ratio is too high, the effect of the present invention cannot be achieved due to the too low ratio of the monocarboxylic acid a2 with a specific structure.

[0041] In one embodiment, the dicarboxylic anhydride includes one or a combination of two or more of phthalic anhydride, maleic anhydride, methylmaleic anhydride, succinic anhydride, glutaric anhydride, nadic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride; the dicarboxylic anhydride imparts a certain acid value to the photosensitive resin, making the photosensitive resin weakly base-developable. Examples include phthalic anhydride, maleic anhydride, methylmaleic anhydride, succinic anhydride, glutaric anhydride, nadic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, etc. One or a combination of two or more of the above anhydrides can be used. The acid value range of the photosensitive resin is 30 - 150 mg / g KOH, preferably 60 - 120 mg / g KOH, more preferably 70 - 100 mg / g KOH. If the acid value is lower than 30 mg / g KOH, the developability is insufficient and not preferred; if the acid value exceeds 150 mg / g KOH, it is not preferred because the developer is likely to erode the exposed part of the solder mask and cause excessive side etching of the solder dam during development.

[0042] In this application, when the epoxy resin reacts with α,β-unsaturated monocarboxylic acid a1 and monocarboxylic acid a2 with a specific structure, a well-known method can be used. For example, considering the convenience of operation, an inert solvent with a boiling point range of 90-250°C is used. The reaction usually requires heating, and a heat inhibitor and a reaction catalyst are further added as needed. The reaction temperature is 60-150°C, preferably 70-140°C, and more preferably 70-120°C. The reaction time is 4-32 hours, preferably 8-24 hours. As the catalyst, amine substances such as N,N-dimethylbenzylamine, triethylamine, DMP-30, imidazoles, quaternary ammonium salts such as triphenylphosphine, triphenylantimony, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, quaternary phosphonium salts such as tetraphenylphosphonium bromide, benzyltriphenylphosphonium bromide, and organic metal salts such as chromium octoate and zinc octoate can be cited. As the inhibitor, phenolic inhibitors such as p-methoxyphenol, hydroquinone, and p-tert-butylphenol can be used.

[0043] For example, the photosensitive resin composition further includes an epoxy resin containing two or more epoxy groups in one molecule as a thermosetting component. Examples include bisphenol A epoxy resin, bisphenol F epoxy resin, phenoxy epoxy resin, phenolic epoxy resin, o-cresol novolac epoxy resin, biphenol novolac epoxy resin, cyclopentadiene novolac epoxy resin, naphthol novolac epoxy resin, etc. Tris(2,3-epoxypropyl) isocyanurate, a copolymer type epoxy group-containing acrylic resin with (meth)acrylate and glycidyl methacrylate as monomers, etc. One or more of these resins can be used as the epoxy resin. For example, the epoxy acrylate includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, phenoxy epoxy resin, phenolic epoxy resin, o-cresol novolac epoxy resin, biphenol novolac epoxy resin, cyclopentadiene novolac epoxy resin, naphthol novolac epoxy resin. Preferably, o-cresol novolac epoxy resin is used.

[0044] In one embodiment, the photosensitive resin composition further includes one or more polyacrylate monomers; the photosensitivity of the composition can be improved by using polyacrylate monomers in the photosensitive resin composition. Examples include di(meth)acrylates of dihydric alcohols such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate; (meth)acrylates of trihydric alcohols such as glycerol tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated / propoxylated trimethylolpropane tri(meth)acrylate, and ethoxylated / propoxylated tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate; (meth)acrylates of tetrahydric alcohols such as pentaerythritol tetra(meth)acrylate, bis(trimethylolpropane) tetra(meth)acrylate, and ethoxylated / propoxylated pentaerythritol tetra(meth)acrylate; dipentaerythritol penta(meth)acrylate; and dipentaerythritol hexa(meth)acrylate. One or more than two polyacrylate monomers can be used.

[0045] In one embodiment, the photosensitive resin composition further comprises one or more photoinitiators. Photoinitiators used in the photosensitive resin composition include benzoin and its alkyl ethers, acetophenones such as acetophenone, benzil dimethyl ketal; anthraquinones such as methyl anthraquinone and ethyl anthraquinone; thioxanthones such as 2,4 - diethyl thioxanthone and 2 - isopropyl thioxanthone; benzophenones such as tetramethyl benzophenone, tetraethyl benzophenone, 4 - benzoyl - 4'- methyl diphenyl sulfide; α - amino ketones such as 2 - methyl - 1 - [4 - (methylthio)phenyl] - 2 - morpholino - 1 - propane, 2 - (4 - methylbenzyl) - 2 - (dimethylamino) - 1 - (4 - morpholinophenyl) - 1 - butanone, 2 - benzyl - 2 - dimethylamino - 1 - (4 - morpholinophenyl) butanone; acylphosphine oxides such as 2,4,6 - trimethylbenzoyl - diphenyl - phosphine oxide, bis(2,4,6 - trimethylbenzoyl) - benzylphosphine oxide, 2,4,6 - trimethylbenzoyl - ethyl - phenyl - phosphinate (TPO - L); α - hydroxy ketones such as 1 - hydroxy - cyclohexyl - phenyl ketone, 2 - hydroxy - 2 - methyl - 1 - phenyl - 1 - propanone; benzoyl formate esters such as benzoyl formate, bis(ethylene glycol) benzoyl formate; oxime ester compounds such as 1 - [4 - (phenylthio)phenyl] - 1,2 - octanedione 2 - (O - benzoyl oxime) (OXE - 01), 1 - [9 - ethyl - 6 - (2 - methylbenzoyl) - 9H - carbazol - 3 - yl] ethanone 1 - (O - acetyl oxime) (OXE - 02); and hexaarylbiimidazoles such as bis(2 - chlorophenyl) - tetraphenylbiimidazole (BCIM). Tertiary amines such as N,N - dimethyl - ethyl p - benzoate, N,N - diethyl - ethyl p - benzoate, and triethylamine; and synergists or sensitizers such as coumarins can also be used together with the photoinitiator. These photoinitiators can be used alone or in combination of multiple kinds. The proportion of these photoinitiators is 0.01 - 10% of the total weight of the photosensitive resin composition, preferably 0.1 - 3%.

[0046] To reduce the shrinkage rate during curing and improve the hardness and electrical insulation of the cured product, known inorganic fillers can be added to the photosensitive resin composition of the present invention, including calcium carbonate, crystalline silica, fused silica, silicon carbide, alumina, titanium dioxide, zirconia, talc, titanium dioxide, barium sulfate and other inorganic fillers. The proportion is 0 - 60% of the total weight of the photosensitive resin composition, preferably 10 - 45%.

[0047] To improve the adhesion of the cured product to the copper surface of the circuit board, for example, the photosensitive resin composition further comprises an adhesion additive, and the adhesion additive includes at least one of dicyandiamide, melamine, and imidazole compounds. Dicyandiamide, melamine, and imidazole compounds can be added to the photosensitive resin composition of the present invention. These compounds can not only improve the adhesion to the copper surface but also assist the curing agent to promote the curing of the thermosetting component epoxy resin.

[0048] To adapt to screen printing or other coating operation methods, the photosensitive resin composition of the present invention can be diluted to a suitable working viscosity using one or a combination of two or more solvents such as esters, ketones, ether esters, and aromatic hydrocarbons.

[0049] The photosensitive resin composition of the present invention can also use known additives as needed, such as inorganic or organic pigments like phthalocyanine blue, phthalocyanine green, bisazo yellow, carbon black, titanium white, crystal violet, DPP red, pigment violet, etc.; polysiloxane, polyacrylate type defoamers; polysiloxane, polyacrylate type leveling agents; rheology aids such as fumed silica, organically modified bentonite; p-methoxyphenol, 2,6-di-tert-butylphenol, hydroquinone, phenothiazine, sulfur ether type heat stabilizers.

[0050] The photosensitive resin composition of the present invention can be manufactured by mixing each component using known mixing methods such as a three-roll mill, sand mill, ball mill, etc. For easy storage, the photosensitive resin can be mixed with a photoinitiator, additives, and some fillers as a first premix; the epoxy resin, acrylate monomer, and some fillers can be mixed as a second premix. When in use, the first and second premixes are temporarily mixed.

[0051] The photosensitive resin composition of the present invention can be coated on a substrate in a required thickness by known methods such as screen printing, roll coating, electrostatic spraying, and air spraying, and then pre-baked at a temperature of 50 - 90°C for 30 - 90 minutes to volatilize the solvent and form a dry coating. A partially transparent negative film is placed in contact with the coating, and selectively exposed with ultraviolet light to form a latent image. Developed with a 0.6 - 1.5% aqueous solution of sodium carbonate (potassium) (of course, other alkaline solutions can also be used) to obtain the required pattern. Finally, the developed coating is cured at a temperature of 120 - 160°C for 40 - 90 minutes for secondary curing to obtain a final cured product. The photosensitive resin composition of the present invention is coated on a support, dried to form a dry coating film, and then a protective film is covered on the dry coating film. A solder mask dry film composed of a support, a dry coating film, and a protective film is provided. The thickness of the dry coating film is 10 - 100 μm. As the support, for example, a polyethylene terephthalate film with a thickness of 10 - 50 μm can be used; as the protective film, for example, polyethylene or polypropylene films with a thickness of 10 - 50 μm can be used.

[0052] In one embodiment, the amount of the epoxy resin with a specific structure is 10% - 60% by weight of the photosensitive resin composition, preferably 30% - 50%. In this way, the dispersibility of the photosensitive resin composition to pigments and fillers can be further improved, the water absorption of the cured product can be reduced, and the resistance to lead-free spray tin and wave soldering can be enhanced.

[0053] In one embodiment, the photosensitive resin composition is used for via filling of a circuit board or solder mask of a circuit board. That is, the use in via filling of a circuit board or solder mask of a circuit board. Of course, in addition to the uses of the photosensitive resin composition of the present application, it should be understood that the uses of the photosensitive resin composition are not limited thereto.

[0054] For the above photosensitive resin composition, compared with the prior art, introducing a certain proportion of monobasic acid a2 with a special structure into the epoxy acrylate in the present invention can effectively improve the dispersibility of the photosensitive resin composition to the pigment and filler; reduce the water absorption of the cured product, thereby improving the resistance to lead-free spray tin and wave soldering. Theoretical speculation believes that: the monobasic acid with a special structure has a longer carbon chain and a larger molecular weight, which increases the hydroxyl equivalent of the cured product of the photosensitive resin composition after curing, and can reduce the content of polar groups hydroxyl in the cured product, so the water absorption of the cured product can be reduced; there is one or two hydrocarbon groups on the α-carbon of the carboxyl group, which has a steric effect on the ester group, can further reduce the water absorption, and can also reduce the aggressiveness of the soldering flux to the ester bond at high temperature during the lead-free spray tin and wave soldering processes, so that the solder mask at the via and on the fine circuit is not prone to blistering and peeling. At the same time, due to the better coating property of the longer carbon chain to the pigment and filler, there is a better barrier effect, and the pigment and filler are not prone to precipitation and agglomeration after dispersion, which improves the stability of the photosensitive resin composition during storage and is not prone to floating color or coarsening.

[0055] In a second aspect, the present application provides a solder mask ink, including the photosensitive resin composition described in any of the above embodiments. For example, the solder mask ink is obtained by dispersing and preparing the photosensitive resin composition described in any of the above embodiments. For example, to adapt to screen printing or other coating operation methods, the photosensitive resin composition of the present invention can be diluted to a suitable working viscosity using one or a combination of two or more of solvents such as esters, ketones, ether esters, and aromatic hydrocarbons.

[0056] In a third aspect, the present application further provides a solder mask dry film, which has a resin layer, and the resin layer is formed from the photosensitive resin composition described in any of the above embodiments. For example, the resin layer is prepared by coating the photosensitive resin composition described in any of the above embodiments on a film and drying.

[0057] In a fourth aspect, the present application further provides a solder mask cured product, which is obtained by curing the photosensitive resin composition described in any of the above embodiments, or the solder mask cured product is obtained by curing the solder mask ink described in any of the above embodiments.

[0058] The photosensitive resin composition of the present invention can be coated on a substrate in a required thickness by known methods such as screen printing, roll coating, electrostatic spraying, and air spraying. Then, it is pre-baked at a temperature of 50 - 90 °C for 30 - 90 minutes to volatilize the solvent and form a dry coating. A partially transparent negative film is placed in contact with the coating, and selectively exposed with ultraviolet light to form a latent image. It is developed with a 0.6 - 1.5% aqueous solution of sodium carbonate (potassium) (of course, other alkaline solutions can also be used) to obtain the required pattern. Finally, the developed coating is cured at a temperature of 120 - 160 °C for 40 - 90 minutes for secondary curing to obtain a final cured product. The photosensitive resin composition of the present invention is coated on a support and dried to form a dry coating film, and then a protective film is covered on the dry coating film. A solder mask dry film composed of a support, a dry coating film, and a protective film is provided. The thickness of the dry coating film is 10 - 100 μm. As the support, for example, a polyethylene terephthalate film with a thickness of 10 - 50 μm can be used; as the protective film, for example, a polyethylene or polypropylene film with a thickness of 10 - 50 μm can be used.

[0059] The present invention will be specifically described below through preparation examples, examples, and comparative examples, but the present invention is not limited to the embodiments of the present invention. Unless otherwise specified, the "parts" or "%" described below are all by weight.

[0060] Preparation Example 1

[0061] 162 grams of the solvent diethylene glycol monomethyl ether acetate (DCAC) was added to a 1000 ml four-necked flask, air was introduced, and it was heated to 90 °C. 215 grams (1 mol of epoxy groups) of cresol novolac epoxy resin NPCN-704 (epoxy equivalent 215, softening point 90 °C) from Nan Ya Plastics was added. After complete dissolution, 57.6 grams (0.8 mol) of acrylic acid, 34.5 grams (0.2 mol) of neodecanoic acid, 0.45 grams of MEHQ (monomethyl ether of hydroquinone), and 2.1 grams of triphenylphosphine were added. The temperature was raised to 100 °C and reacted for 20 hours until the acid value dropped below 3 mg / g. Then, the temperature was lowered to 90 °C, 54 grams of pseudocumene and 92.8 grams of tetrahydrophthalic anhydride were added, and reacted for 10 hours to obtain a resin with a solid content of 65% (i.e., an epoxy acrylate resin containing a specific structure), with a solid content acid value of 85 mg / g KOH, denoted as A1.

[0062] Preparation Example 2

[0063] Add 159 g of the solvent diethylene glycol monomethyl ether acetate (DCAC) to a 1000 ml four-necked flask, introduce air, heat to 90 °C, add 215 g of cresol novolac epoxy resin Nan Ya Plastics NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy groups), after complete dissolution, add 57.6 g of acrylic acid (0.8 mol), 28.9 g of 2-ethylhexanoic acid (0.2 mol), 0.45 g of MEHQ, and 2.1 g of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 53 g of durene and 91.3 g of tetrahydrophthalic anhydride, and react for 10 hours to obtain a resin with a solid content of 65%, a solid acid value of 85 mg / g KOH, denoted as A2.

[0064] Preparation Example 3

[0065] Add 165 g of the solvent diethylene glycol monomethyl ether acetate (DCAC) to a 1000 ml four-necked flask, introduce air, heat to 90 °C, add 215 g of cresol novolac epoxy resin Nan Ya Plastics NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy groups), after complete dissolution, add 50.4 g of acrylic acid (0.7 mol), 51.7 g of neodecanoic acid (0.3 mol), 0.45 g of MEHQ, and 2.1 g of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 55 g of durene and 95.9 g of tetrahydrophthalic anhydride, and react for 10 hours to obtain a resin with a solid content of 65%, a solid acid value of 85 mg / g KOH, denoted as A3.

[0066] Preparation Example 4

[0067] Add 162 g of the solvent diethylene glycol monomethyl ether acetate (DCAC) to a 1000 ml four-necked flask, introduce air, heat to 90 °C, add 215 g of cresol novolac epoxy resin Nan Ya Plastics NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy groups), after complete dissolution, add 50.4 g of acrylic acid (0.7 mol), 43.3 g of 2-ethylhexanoic acid (0.3 mol), 0.45 g of MEHQ, and 2.1 g of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 54 g of durene and 93.5 g of tetrahydrophthalic anhydride, and react for 10 hours to obtain a resin with a solid content of 65%, a solid acid value of 85 mg / g KOH, denoted as A4.

[0068] Preparation Example 5

[0069] Add 180 g of the solvent diethylene glycol monomethyl ether acetate (DCAC) to a 1000 ml four-necked flask, introduce air, heat to 90 °C, add 215 g of cresol novolac epoxy resin South Asia Plastics NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy group moles), after complete dissolution, add 28.8 g of acrylic acid (0.4 mol), 103.4 g of neodecanoic acid (0.6 mol), 0.45 g of MEHQ, and 2.1 g of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 60 g of durene and 103.5 g of tetrahydrophthalic anhydride, and react for 10 hours to obtain a resin with a solid content of 65%, a solid content acid value of 84 mg / g, denoted as B1.

[0070] Preparation Example 6

[0071] Add 165 g of the solvent diethylene glycol monomethyl ether acetate (DCAC) to a 1000 ml four-necked flask, introduce air, heat to 90 °C, add 215 g of cresol novolac epoxy resin South Asia Plastics NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy group moles), after complete dissolution, add 28.8 g of acrylic acid (0.4 mol), 86.5 g of 2-ethylhexanoic acid (0.6 mol), 0.45 g of MEHQ, and 2.1 g of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 55 g of durene and 100 g of tetrahydrophthalic anhydride, and react for 10 hours to obtain a resin with a solid content of 65%, a solid content acid value of 85 mg / g KOH, denoted as B2.

[0072] Preparation Example 7

[0073] Add 165 g of the solvent diethylene glycol monomethyl ether acetate (DCAC) to a 1000 ml four-necked flask, introduce air, heat to 90 °C, add 215 g of cresol novolac epoxy resin South Asia Plastics NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy group moles), after complete dissolution, add 50.4 g of acrylic acid (0.7 mol), 51.7 g of decanoic acid (0.3 mol), 0.45 g of MEHQ, and 2.1 g of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 55 g of durene and 95.9 g of tetrahydrophthalic anhydride, and react for 10 hours to obtain a resin with a solid content of 65%, a solid content acid value of 85 mg / g KOH, denoted as B3.

[0074] Preparation Example 8

[0075] In a 1000 ml four-necked flask, add 162 grams of the solvent diethylene glycol monomethyl ether acetate (DCAC), introduce air, heat to 90 °C, add 215 grams of o-cresol novolac epoxy resin South Asia Plastic NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy groups), after complete dissolution, add 50.4 grams of acrylic acid (0.7 mol), 43.3 grams of octanoic acid (0.3 mol), 0.45 grams of MEHQ, and 2.1 grams of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 54 grams of durene and 93.5 grams of tetrahydrophthalic anhydride, react for 10 hours to obtain a resin with a solid content of 65%, a solid content acid value of 85 mg / g KOH, denoted as B4.

[0076] Preparation Example 9

[0077] In a 1000 ml four-necked flask, add 152 grams of the solvent diethylene glycol monomethyl ether acetate (DCAC), introduce air, heat to 90 °C, add 215 grams of o-cresol novolac epoxy resin South Asia Plastic NPCN-704 (epoxy equivalent 215, softening point 90 °C) (1 mol of epoxy groups), after complete dissolution, add 72 grams of acrylic acid (1 mol), 0.45 grams of MEHQ, and 2.1 grams of triphenylphosphine. Raise the temperature to 100 °C and react for 20 hours until the acid value drops below 3 mg / g. Then cool to 90 °C, add 51 grams of durene and 87.5 grams of tetrahydrophthalic anhydride, react for 10 hours to obtain a resin with a solid content of 65%, a solid content acid value of 85 mg / g KOH, denoted as B5.

[0078] Preparation of the photosensitive resin composition: In each of the examples and comparative examples, the respective materials were mixed according to the formulation in Table 1 and kneaded with a three-roll mill to obtain the photosensitive resin composition.

[0079] Table 1 Composition ratios of the photosensitive resin compositions of each example and comparative example

[0080]

[0081]

[0082] Among them, the components in Table 1 are as follows:

[0083] Epoxy resin 1: o-cresol novolac epoxy resin NPCN-704, South Asia Plastic;

[0084] Epoxy resin 2: micronized TGIC, Huangshan Huahui; that is, micronized melamine triglycidyl ester;

[0085] Acrylate monomer: dipentaerythritol hexaacrylate;

[0086] Photoinitiator 1: 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propane, Tianjin Yingli;

[0087] Photoinitiator 2: 2-isopropyl-thioxanthone, Tianjin Yingli;

[0088] Filler 1: Fine barium sulfate;

[0089] Filler 2: Microfine talc powder;

[0090] Solvent 1: DBE, Dow Chemical; It should be noted that the DBE solvent, also known as dibasic acid ester, dimethyl dibasic acid ester, polyol dibasic ester or methyl ester of nylon acid (NME), is an environmentally friendly high-boiling solvent. The DBE solvent is mainly composed of dimethyl succinate, dimethyl glutarate, dimethyl adipate and their mixtures in different proportions.

[0091] Solvent 2: SOLVESSO 150, ExxonMobil; SOLVESSO 150 is an aromatic solvent oil, specifically belonging to high-boiling aromatic solvents and paint solvent oils.

[0092] Additive 1: Leveling agent BYK-354;

[0093] Additive 2: Fumed silica R-972, Evonik Chemicals;

[0094] Additive 3: Defoaming agent KS-66, Shin-Etsu Chemical.

[0095] Performance evaluation test:

[0096] The photosensitive resin compositions prepared in each example and comparative example were subjected to a performance evaluation test. Specimens were prepared and the performance evaluation test was carried out according to the following method, and the evaluation results were recorded in Table 2.

[0097] Evaluation of pigment and filler dispersion: Take 300 grams of the prepared photosensitive resin composition, seal it in a PP material tank, add 5% of the DBE solvent, and observe whether there is any floating color phenomenon on the surface after 30 days.

[0098] ◎: The surface color is uniform and there is no floating color phenomenon;

[0099] ○: A small amount of dot-like color aggregation;

[0100] X: Obvious large amount of color aggregation.

[0101] Production of samples for shadow property and sensitivity evaluation: The photosensitive resin composition was coated on a polished copper plate substrate by 100-mesh screen printing, and the wet film thickness was controlled to be 30 - 34 μm. It was baked in an oven with circulating air at 75 °C for 30 minutes, 40 minutes, 50 minutes, 60 minutes, and 70 minutes respectively to volatilize the solvent. The samples for sensitivity evaluation were baked under the conditions of 75 °C and 40 minutes.

[0102] Production of samples for hygroscopicity evaluation: The photosensitive resin composition was coated on a PET film using a wire bar coater, and the wet film thickness was controlled to be 30 - 34 μm. It was baked in an oven with circulating air at 75 °C for 40 minutes. It was exposed using a 7KW exposure machine without placing a film at an energy of 300 mj / cm 2 and then baked at 150 °C for 60 minutes. Finally, the PET film was peeled off to obtain a free cured film as the sample for hygroscopicity evaluation.

[0103] Production of samples for solder resistance: The photosensitive resin composition was coated on a circuit board with copper traces and 0.4 - 0.5 mm vias by 100-mesh screen printing, and the wet film thickness was controlled to be 30 - 34 μm. It was baked in an oven with circulating air at 75 °C for 40 minutes. It was exposed using a 7KW exposure machine without placing a film at an energy of 300 mj / cm 2 and developed in a 1.0% sodium carbonate aqueous solution for 60 seconds. Finally, it was baked at 150 °C for 60 minutes. Samples for solder resistance evaluation were obtained.

[0104] Production of samples for volume resistance measurement: The photosensitive resin composition was coated on a 20 cm × 20 cm single-sided polished copper plate substrate by 100-mesh screen printing, and the wet film thickness was controlled to be 30 - 34 μm, with 2 cm left blank around. It was baked in an oven with circulating air at 75 °C for 40 minutes. It was exposed using a 7KW exposure machine without placing a film at an energy of 300 mj / cm 2 and then baked at 150 °C for 60 minutes. Samples for volume resistance measurement were obtained.

[0105] Development property evaluation: The samples for development property evaluation were developed using a developing machine. The developer concentration was 1.0% sodium carbonate, the temperature was 30 °C, the pressure was 2.0 kgf / cm 2 , the time was 60 seconds, and it was rinsed with city water for 60 seconds. The copper surface of the substrate was visually observed under white light to check for residues.

[0106] ◎: Completely clean, no residue at all;

[0107] ○: Slightly foggy residue, acceptable;

[0108] X: Obviously foggy, unacceptable.

[0109] Sensitivity evaluation: Place a 21-step exposure ruler on the sensitivity evaluation sample piece and expose it with a 7KW exposure machine at energies of 200 mj / cm 2 , 300 mj / cm 2 , 400 mj / cm 2 respectively. Develop it with a developing machine. The concentration of the developing solution is 1.0% sodium carbonate, the temperature is 30°C, the pressure is 2.0 kgf / cm 2 , and the time is 60 seconds. Wash it with city water for 60 seconds. Visually observe the number of coated grids remaining on the substrate.

[0110] Hygroscopicity evaluation: Weigh the hygroscopicity sample piece with a balance with a minimum reading of 0.1 mg and record it as m1; immerse the weighed sample piece in deionized water, take it out after standing at room temperature for 24 hours, dry it at room temperature and then weigh it again, record it as m2, and calculate the weight gain rate according to the formula (m2 - m1) / m1.

[0111] Solder resistance evaluation: Divide the solder resistance sample piece into two parts. One part is tested immediately after post-curing; the other part of the sample piece is placed in a constant temperature and humidity chamber at 30°C and 80% RH for 8 hours and then evaluated. Evaluation method ①: Apply rosin-based flux on the sample piece, immerse it in molten tin at 260°C, take it out after 10 seconds, naturally cool it to room temperature, wipe off the flux, and repeat twice. Finally, wash the sample piece with water and dry it. Evaluation method ②: The steps are the same as evaluation method ①, except that the rosin-based flux is changed to lead-free solder spray flux and the temperature of the molten tin is changed to 288°C. Visually observe whether there are bubbles or coating peeling on the solder mask of the vias and circuits; if there are no bubbles and coating peeling, then stick 3M tape on the sample piece and pull it up at a 90° angle, and visually observe whether there is coating peeling.

[0112] ◎: There are no bubbles and coating peeling before and after the tape test;

[0113] ○: There are no bubbles and coating peeling before the tape test, but there are bubbles or coating peeling during the tape test;

[0114] X: There are bubbles or coating peeling before the tape test.

[0115] Volume resistivity test:

[0116] Volume resistance test before humidification: Before the test, heat the volume resistance sample piece in an oven at 150°C for 30 minutes, and test the volume resistivity according to the method of IPC-TM-640 2.5.17E; Volume resistance test after humidification: Place the sample piece that has completed the volume resistance test before humidification in a constant temperature and humidity chamber at 60°C and 85% for 24 hours, take it out and place it in a drying oven to cool to room temperature and then test the volume resistivity.

[0117] Table 2 Performance test results of each example and each comparative example

[0118]

[0119] The unit of volume resistivity in the table is: Ω.mm; 5E11 means 5×10 11 .

[0120] From the test results of Table 1 and Table 2, it can be seen that the embodiments 1, 2, 3, and 4 have excellent balanced performance in terms of properties such as pigment and filler dispersibility, developability, sensitivity, hygroscopicity, solder resistance, and volume resistivity; in Comparative Examples 1 and 2, the ratio of the α,β-unsaturated monobasic acid a1 to the monobasic acid a2 with a specific structure in the photosensitive resin exceeds the scope of the present invention, resulting in insufficient developability and low sensitivity; in Comparative Examples 3 and 4, the specific structure monobasic acid a2 of the present invention is not used in the photosensitive resin, and good effects cannot be obtained; furthermore, from Embodiments 1 and 3, it can be known that better effects will be obtained when both R1 and R2 in the specific structure monobasic acid a2 are hydrocarbon chains.

[0121] The photosensitive resin composition provided by the present application has the possibility of industrial utilization. As described above, the photosensitive resin and its composition of the present invention can be used as a solder resist material for circuit boards, and have good performance in terms of developability, sensitivity, hygroscopicity, solder resistance, and volume resistivity. Especially in terms of hygroscopicity, solder resistance, and volume resistivity, the reliability of the solder resist coating on the circuit board is significantly improved, and it can be used for carrier board circuit boards with high requirements for electrical reliability. In addition, by using the photosensitive resin and its composition of the present invention, a dry solder resist coating film can be formed by coating on a support film, providing a solder resist dry film composed of a support film, a dry solder resist coating film, and a protective film.

[0122] Regarding the above photosensitive resin composition, compared with the prior art, introducing a certain proportion of the monobasic acid a2 with a special structure into the epoxy acrylate in the present invention can effectively improve the dispersibility of the photosensitive resin composition to pigments and fillers; reduce the water absorption of the cured product, thereby improving the resistance to lead-free spray soldering and wave soldering. Theoretical speculation believes that: the special structure monobasic acid has a longer carbon chain and a larger molecular weight, which increases the hydroxyl equivalent of the cured product of the photosensitive resin composition after curing, can reduce the content of polar group hydroxyls in the cured product, and thus can reduce the water absorption of the cured product; there is one or two hydrocarbon groups on the α-carbon of the carboxyl group, which has a steric hindrance effect on the ester group, can further reduce the water absorption, and can also reduce the aggressiveness of the flux to the ester bond at high temperature during the lead-free spray soldering and wave soldering processes, making it difficult for the solder resist layer at the via holes and fine lines to appear blistering and peeling. At the same time, due to the better coating effect of the longer carbon chain on the pigments and fillers and the better barrier effect, the pigments and fillers are not easily precipitated and agglomerated after dispersion, improving the stability of the photosensitive resin composition during storage and not easily showing floating color or coarsening.

[0123] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. It should be noted that phrases such as "in one embodiment of the present application", "for example", "again, for example", etc. are intended to illustrate the present application rather than limit the present application. The above-described embodiments only express several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A photosensitive resin composition, characterized in that, Epoxy acrylate resin with a specific structure, the epoxy acrylate resin with the specific structure is obtained by adding α,β-unsaturated monocarboxylic acid a1 and monocarboxylic acid a2 with a specific structure to an epoxy resin containing two or more epoxy groups in one molecule, and then adding a dibasic anhydride. Among them, the monocarboxylic acid a2 with a specific structure conforms to the following structural formula: In the formula, R1 and R2 are hydrogen atoms or hydrocarbon chains with 2-15 carbon atoms, and R1 and R2 cannot be hydrogen atoms at the same time.

2. The photosensitive resin composition according to claim 1, wherein In the structure of the monocarboxylic acid a2 with a specific structure, R1 and R2 are hydrogen atoms or hydrocarbon chains with 2-12 carbon atoms; preferably, R1 and R2 are hydrogen atoms or hydrocarbon chains with 2-10 carbon atoms. Preferably, the monocarboxylic acid a2 with a specific structure is at least one of 2-ethylhexanoic acid, neodecanoic acid, 2-phenylpropionic acid, 2-methylvaleric acid, 2,2-dimethylvaleric acid.

3. The photosensitive resin composition according to claim 1 or 2, characterized in that, The α,β-unsaturated monocarboxylic acid a1 includes at least one of acrylic acid, (meth)acrylic acid, cinnamic acid, crotonic acid. Preferably, at least one of methacrylic acid and acrylic acid is used. Preferably, the α,β-unsaturated monocarboxylic acid a1 is (meth)acrylic acid.

4. The photosensitive resin composition according to claim 3, characterized in that, The molar ratio range of the sum of the molar amounts of the α,β-unsaturated monocarboxylic acid a1 and the monocarboxylic acid a2 with a specific structure to the molar amount of the epoxy group is "0.95-1.1":1, preferably "0.95-1.05":1; preferably, the molar ratio range of a1 to a2 is 5:5 to 9.5:0.

5. Preferably, the molar ratio range of a1 to a2 is 6:4-9:

1. More preferably, the molar ratio range of a1 to a2 is 7:3-9:1; And / or, the dibasic anhydride includes one or a combination of two or more of phthalic anhydride, maleic anhydride, methylmaleic anhydride, succinic anhydride, glutaric anhydride, nadic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride; And / or, the epoxy resin used to prepare the epoxy acrylate with a specific structure includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, phenoxy epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, biphenol phenolic epoxy resin, cyclopentadiene epoxy resin, naphthol epoxy resin. Preferably, the epoxy acrylate is o-cresol epoxy resin; and / or, the preparation process of the epoxy acrylate resin with a specific structure is as follows: add the epoxy acrylate resin with a specific structure to a solvent, after dissolution, add α,β-unsaturated monocarboxylic acid a1 and monocarboxylic acid a2 with a specific structure to react, and then add a dibasic anhydride to react to obtain. Preferably, the solvent is at least one of solvents such as esters, ketones, ether esters, aromatic hydrocarbons, etc.; preferably, the solvent is preferably diethylene glycol methyl ether acetate.

5. The photosensitive resin composition according to claim 1, wherein The amount of the epoxy acrylate resin with a specific structure is 10%-60% of the weight of the photosensitive resin composition, preferably 30%-50%.

6. The photosensitive resin composition according to claim 1, wherein, The photosensitive resin composition further includes an epoxy resin containing two or more epoxy groups in one molecule; And / or, the photosensitive resin composition further includes one or more polyacrylate monomers; And / or, the photosensitive resin composition further comprises one or more photoinitiators; And / or, the photosensitive resin composition further comprises inorganic fillers, and the inorganic fillers include at least one of calcium carbonate, crystalline silica, fused silica, silicon carbide, alumina, titanium dioxide, zirconia, talc powder, titanium dioxide, barium sulfate; And / or, the photosensitive resin composition further comprises adhesion additives, and the adhesion additives include at least one of dicyandiamide, melamine, imidazole compounds; And / or, the photosensitive resin composition further comprises a solvent. Preferably, the solvent is at least one of ester solvents, ketone solvents, ether ester solvents, aromatic solvents, etc.; preferably, the solvent is preferably diethylene glycol monomethyl ether acetate.

7. The photosensitive resin composition according to claim 6, wherein The photosensitive resin composition comprises the following components: an epoxy acrylate resin with a specific structure, an epoxy resin, an acrylate monomer, a photoinitiator, dicyandiamide, a filler, phthalocyanine green, a solvent and additives, and the additives include a leveling agent, fumed silica and an antifoaming agent; Preferably, the photosensitive resin composition comprises the following components: an epoxy acrylate resin with a specific structure, o-cresol novolac epoxy resin, micronized melamine, dipentaerythritol hexaacrylate, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propane, 2-isopropyl-thioxanthone, dicyandiamide, fine barium sulfate, micronized talc powder, DBE solvent, SOLVESSO 150, leveling agent BYK-354, fumed silica R-972 and antifoaming agent; Preferably, the photosensitive resin composition comprises the following components in parts by mass: 42 parts of an epoxy acrylate resin with a specific structure, 5 parts of o-cresol novolac epoxy resin, 4 parts of micronized melamine, 5 parts of dipentaerythritol hexaacrylate, 3.5 parts of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propane, 0.8 part of 2-isopropyl-thioxanthone, 0.3 part of dicyandiamide, 28 parts of fine barium sulfate, 4 parts of micronized talc powder, 4 parts of DBE solvent, 1 part of SOLVESSO 150, 0.2 part of leveling agent BYK-354, 0.9 part of fumed silica R-972 and 0.8 part of antifoaming agent KS-66.

8. A solder mask ink, characterized in that Comprising the photosensitive resin composition according to any one of claims 1 to 7.

9. A solder mask dry film, characterized in that, It has a resin layer, and the resin layer is formed from the photosensitive resin composition according to any one of claims 1 to 7.

10. A solder mask cured product, characterized in that, The solder resist cured product is obtained by curing the photosensitive resin composition according to any one of claims 1 to 7, or the solder resist cured product is obtained by curing the solder resist ink according to claim 8.

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