JPH0122312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin composition for solder resist ink that is used for printed wiring circuit boards and has excellent heat resistance and electrical insulation properties. Solder resist ink is used to prevent solder from adhering to areas other than the intended areas when soldering components to a printed wiring circuit board, and to protect the circuits on the printed wiring circuit board.It has electrical insulation, heat resistance, This ink requires various properties such as adhesion, chemical resistance, and screen printability. Initially, melamine-based heat-curable solder resist inks were used, but later, epoxy-based heat-curable solder resist inks were developed that had excellent heat resistance, hardness, adhesion, and chemical resistance. It has become mainstream in printed wiring circuit boards for industrial equipment such as computers, where high reliability is important. On the other hand, since solder resist inks used for consumer printed wiring circuit boards require high workability and productivity, UV-curable solder resist inks made from acrylated epoxy resins and urethane resins are replaced by heat-curable epoxy-based solder resist inks. It has become the mainstream, replacing solder resist ink. However, as is well known, UV-curable solder resist is a system that hardens by causing a radical reaction when irradiated with UV rays, and the thicker the coating film, the poorer the internal curing properties, especially for printed wiring boards for industrial equipment. The thickness is 70μ with copper plating and solder plating.
It is thicker than m, and inevitably the solder resist coated on top of it is also partially thick.
A coating film thickness of 50 μm or more is obtained. Therefore, the curing reaction was not completely completed in areas that were not exposed to ultraviolet rays (lower edges of the circuit), and electrical insulation defects (including galvanic corrosion) were likely to occur. Therefore, in order to prevent these problems, it is necessary to create a coating film with a thickness of 20 μm or less by making the mesh of the screen finer and the thickness of the emulsion thinner. use was limited. By the way, with the recent miniaturization, higher functionality, resource saving, and lower cost of electronic equipment, there is a growing demand for improved precision in circuit pattern density for industrial printed circuit boards. The requirement has gone from 2 wires between the pins of a circuit to 3 to 5 wires between the pins. Current screen printing methods using epoxy-based or ultraviolet-curable solder resist inks have limited printing accuracy and poor dimensional accuracy due to screen elongation, and have not yielded satisfactory results. In addition, the UV-curable solder resist used in this screen printing method is made of 2-hydroxy ethyl acrylate, trimethylolmepropane triacrylate, etc.
Contains trifunctional monomers and various acrylate oligomers, etc., and these substances ooze out (migration) during screen printing, and when used on printed wiring boards with two or more pins,
This appeared as a serious defect such as non-soldering.
In order to prevent this, the coating thickness was reduced to improve resolution. However, in this case, the solder resist is not evenly coated between the circuits, resulting in a decrease in electrical insulation, and the solder resist's original function becomes ineffective. Recently, a photography method using dry film has been developed to improve resolution, but this method
Although it is possible to improve the resolution, the dry film does not penetrate between the circuits, causing blistering of the paint film.
It has problems such as poor adhesion. As a result of intensive research in view of the problems of the prior art as described above, the present inventors have developed a heat-resistant resin by combining a photopolymerizable vinyl ester resin and an epoxy vinyl ester resin that can be photopolymerized and heat-cured with amines. The present inventors have discovered that a solder resist ink with excellent properties, adhesiveness, chemical resistance, and electrical insulation properties can be obtained, leading to the completion of the present invention. Thus, according to the present invention, 10 to 40 of the vinyl ester resin (A-a) obtained by reacting 1 chemical equivalent of a phenol novolac type epoxy resin with 0.8 to 1.1 chemical equivalent of an unsaturated monobasic acid. Epoxy vinyl ester resin (A-b) obtained by reacting parts by weight and 1 chemical equivalent of cresol novolak type epoxy resin and 0.2 to 0.7 chemical equivalent of unsaturated monobasic acid
90 to 60 parts by weight of (A), organic solvent (B), photopolymerization initiator (C)
Furthermore, a resin composition for solder resist ink, which is composed of an amine curing agent (D) and has excellent heat resistance and high resolution, is provided. The phenol novolak type epoxy resin used in the present invention refers to a resin obtained by reacting a phenol novolak resin obtained from phenol and formaldehyde with epichlorohydrin or methylepichlorohydrin. The cresol novolak type epoxy resin refers to a resin obtained by reacting a cresol novolak resin obtained from cresol and formaldehyde with epichlorohydrin or methylepichlorohydrin. Typical unsaturated monobasic acids that react with each of the above resins include acrylic acid, methacrylic acid, crotonic acid, monomethyl maleate, monopropyl maleate, monobutyl maleate, sorbic acid, and mono(2- ethylhexyl) malate, etc. These unsaturated monobasic acids alone have 2
Of course, it can also be used in a mixture of more than one species. The vinyl ester resin used as component (A-a) in the present invention is prepared by esterifying the phenol novolac type epoxy resin and an unsaturated monobasic acid in the presence of an esterification catalyst, usually at 60 to 140°C, preferably at 80 to 80°C.
It is obtained by reacting at a temperature of 120°C.
The ratio of the phenol novolac type epoxy resin and the unsaturated monobasic acid in this case is 0.8 to 1.1 chemical equivalents of the unsaturated monobasic acid to 1 chemical equivalent of the phenol novolac type epoxy resin. Such vinyl ester resins preferably have unsaturated monobasic acids added to all of the epoxy groups. The above esterification catalysts include triethylamine, N,N-dimethylbenzylamine, N,N-
Known and commonly used catalysts such as tertiary amines such as dimethylaniline or diazabicyclooctane, or diethylamine hydrochloride, dimethyl acetate or dimethylamine nitrate can be used as is. Furthermore, when producing the vinyl ester resin, it is recommended to use a polymerization inhibitor for the purpose of preventing gelation and adjusting the storage stability or curability of the resulting resin. Typical polymerization inhibitors include hydroquinone, hydroquinones such as pt-butylcatechol or mono-t-butylhydroquinone; hydroquinone monomethyl ether or di-t-butylhydroquinone;
Examples include phenols such as p-cresol; quinones such as p-benzoquinone, naphthoquinone, or p-torquinone; and copper salts such as copper naphthenate. In addition, the epoxy vinyl ester resin used as the component (A-b) is synthesized from the cresol novolac type epoxy resin and the unsaturated monobasic acid in exactly the same manner as the vinyl ester resin that is the component (A-a). This can be obtained by however,
The ratio of cresol novolak type epoxy resin and unsaturated monobasic acid is 1 chemical equivalent of cresol novolak type epoxy resin and 0.2 to 0.2 to unsaturated monobasic acid.
It is 0.7 chemical equivalent. Such vinyl ester resin is preferably an epoxy vinyl ester resin containing a vinyl group and an epoxy group in one molecule obtained by adding an unsaturated monobasic acid to a part of the epoxy group of a cresol novolak type epoxy resin. . The vinyl ester resin thus obtained (A-
The resin composition (A) consisting of 10 to 40 parts by weight of a) and 90 to 60 parts by weight of the epoxy vinyl ester resin (A-b) is a stable resin when dissolved in a known and commonly used organic solvent (B). It is considered to be a solution. Representative organic solvents (B) include aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol and isopropyl alcohol; esters such as ethyl acetate and butyl acetate; 1,4-dioxane and tetrahydrofuran. ketones such as methyl ethyl ketone and methyl isobutyl ketone; glycol derivatives such as cellosolve and butyl cellosolve; alicyclic hydrocarbons such as cyclohexanone and cyclohexanol; and petroleum solvents such as petroleum ether and petroleum naphtha. These may be used alone or as a mixture of two or more.
Further, the concentration of these organic solvents is not particularly limited, but from the viewpoint of workability, it is preferably 10 to 40% by weight. Next, as the photopolymerization initiator (C), pt-butyltrichloroacetophenone, 2,2-diethoxyacetophenone, benzophenone, 4,4-
Bismethylaminobenzophenone, benzyl, benzoin, benzoin methyl ether, benzoin isobutyl ether, benzyl methyl ketal, methyl-o-benzoylbenzoate, α-
Examples include carbonyl compounds such as hydroxyisobutylphenone; sulfur compounds such as tetramethylthiuram monosulfide, thioxanthone, and 2-chlorothioxanthone; and azo compounds.
These can be used alone or as a mixture of two or more, and the amount used is vinyl ester resin (A-
The amount is preferably 0.5 to 10 parts by weight based on the total of 100 parts by weight of a) and the epoxy vinyl ester resin (A-b). Further, as the amine curing agent, ethylenediamine, diethylenetriamine, triethylenetriamine, diethylaminopropylamine,
Aliphatic polyamines such as xylylene diamine; aromatic polyamines such as metaphenylene diamine, diaminodiphenylmethane, and diaminodiphenylsulfone; fats such as menthanediamine, isophorone diamine, and bis(4-amino-3-methylcyclohexyl)methane. Cyclic polyamine; dicyandiamide; 2-methylimidazole, 2-ethyl-
Imidazole compounds such as 4-methylimidazole and 1-benzyl-2-methylimidazole; tertiary amines such as benzyldimethylamine, tridimethylaminomethylphenol, and dimethylaminomethylphenol; and amine complex compounds such as BF ₃ and monoethylamine. Can be mentioned. Furthermore, the resin composition of the present invention may contain various additives, such as fillers such as silica, talc, and clay; thixotropic agents such as Aerosil; silicone and fluorine-based leveling agents and antifoaming agents; and colorants. can be added for the purpose of improving various performances of the solder resist ink. Next, the present invention will be specifically explained using reference examples and examples. Hereinafter, all parts and percentages are based on weight unless otherwise specified. Reference Example 1 Into a three-neck flask equipped with a thermometer, stirrer, and condenser, 1800 parts of phenol novolac type epoxy resin "Epicron N-740" (epoxy resin manufactured by Dainippon Ink and Chemicals Co., Ltd.) with an epoxy equivalent of 180 was added. (equivalent to 10 epoxy groups), 720 parts of acrylic acid (equivalent to 10 carboxyl groups), and hydroquinone.
Add 1.26 parts and 10.1 parts of triethylamine;
By raising the temperature to 110°C and continuing the reaction for 6 hours, a vinyl ester resin (A-a-1) having an acid value of 3 and an epoxy equivalent of 20,000 or more was obtained. Reference Example 2 In the same reaction apparatus as Reference Example 1, an epoxy equivalent
1850 parts (equivalent to 10 epoxy groups) of bisphenol A type epoxy resin "Epicron 850" (epoxy resin manufactured by the same company), 720 parts of acrylic acid (equivalent to 10 carboxyl groups), 1.29 parts of hydroquinone.
and 10.3 parts of triethylamine to 110 parts
By raising the temperature to ℃ and continuing the reaction for 7 hours, a vinyl ester resin (A'-a-1) having an acid value of 2 and an epoxy equivalent of 20,000 or more was obtained. Reference Example 3 Similarly to Reference Example 1, a cresol novolak type epoxy resin with an epoxy equivalent of 220 “Epiclon N-
Add 2200 parts (equivalent to 10 epoxy groups) of ``660'' (epoxy resin manufactured by the same company), 360 parts of acrylic acid (equivalent to 5 carboxyl groups), 1.28 parts of hydroquinone, and 10.2 parts of triethylamine, and heat to 110°C. By raising the temperature and continuing the reaction for 4 hours, the acid value
0.5, an epoxy vinyl ester resin (A-b-1) having an epoxy equivalent of 620 was obtained. Reference Example 4 Similarly to Reference Example 1, a cresol novolak type epoxy resin “Epiclon N-
Add 2,300 parts (equivalent to 10 epoxy groups) of ``680'' (epoxy resin manufactured by the same company), 216 parts of acrylic acid (equivalent to 3 carboxyl groups), 1.26 parts of hydroquinone, and 10.1 parts of triethylamine, and heat to 120°C. By raising the temperature and continuing the reaction at that temperature for 3 hours, an epoxy vinyl ester resin (A-b-2) having an acid value of 0.6 and an epoxy equivalent of 410 was obtained. Reference Example 5 Similar to Reference Example 1, bisphenol A type epoxy resin “Epicron 1050” with an epoxy equivalent of 470 was used.
(Epoxy resin made by the same company) 4700 parts (Epoxy group
By adding 288 parts of acrylic acid (equivalent to 4 carboxyl groups), 2.49 parts of hydroquinone and 20.0 parts of triethylamine, raising the temperature to 116°C and continuing the reaction at that temperature for 4 hours, An epoxy vinyl ester resin (A'-b-1) having an acid value of 0.7 and an epoxy equivalent of 920 was obtained. Examples 1 to 3 and Comparative Examples 1 to 3 Vinyl ester resins and epoxy vinyl ester resins and epoxy resins obtained in Reference Examples 1 to 5,
A solder resist ink is mixed with an organic solvent, an acrylic monomer, a photopolymerization initiator, and an amine curing agent according to the compounding ratios shown in Table 1, and the paste is printed onto a copper through-hole printed wiring board with a thickness of 30 to 40 μm by screen printing. It was applied to a film thickness of . First, the paint film
After drying at 130℃ for 5 minutes, apply negative film.
A 5KW ultra-high pressure mercury lamp was used to irradiate ultraviolet light with a wavelength of around 350 nm and an intensity of 20 mw/cm ² for 60 seconds, and then the unirradiated parts of the coating film were removed using an organic solvent such as trichlorethylene. After that, heat it in a hot air dryer at 130℃.
Heat curing was performed for 30 minutes, and various performance tests were conducted on each of the obtained specimens. The results are shown in Table 1. The various performance tests shown in the table were conducted according to the following test methods. [Drying properties of coating film] Solder resist ink was applied to a copper through-hole printed wiring board, and after drying at 130°C for 5 minutes, the drying properties of the coating film were evaluated by a method according to JIS K-5400. The judgment criteria are as follows. 〇...Without tack ×...With tack [Solvent resistance] Using a 5KW ultra-high pressure mercury lamp, the wavelength
The film was irradiated with ultraviolet light around 350 nm with an illuminance of 20 mw/cm ² for 60 seconds, and then the unirradiated areas were removed with Triclean, and the condition of the coating film in the irradiated areas was evaluated. The judgment criteria are as follows. 〇……No abnormality ×……Dissolved or swelled [Solder resistance] 2 to 60% tin molten solder at 260℃
The condition of the coating film after being immersed for minutes was evaluated.
The judgment criteria are as follows. 〇... No abnormality in the appearance of the paint film ×... Blistering, melting, peeling [Goban adhesion] Adhesion after cutting 100 goblets of 1 x 1 mm in size on the paint film of the specimen and peeling off with cellophane tape (according to JIS D-0202). [Surface insulation resistance] A specimen coated on a Mil standard IPC-840B-25 test pattern board at 80℃, 95%
It was left in an RH atmosphere for 240 hours, and the surface insulation resistance of the coating film was measured according to JIS-Z-3197. From the results shown in Table 1, it can be clearly seen that the coating film obtained using the composition of the present invention is excellent in heat resistance, adhesion, solvent resistance, and electrical insulation. 【table】

Claims (1)

[Claims] 1 A (a) 1 chemical equivalent of a phenol novolac type epoxy resin and 0.8 to 1.1 of an unsaturated monobasic acid.
10 to 40 parts by weight of a vinyl ester resin obtained by reacting with a chemical equivalent of (b) 1 part of a cresol novolak type epoxy resin
Consisting of 90 to 60 parts by weight of an epoxy vinyl ester resin obtained by reacting a chemical equivalent with 0.2 to 0.7 chemical equivalent of an unsaturated monobasic acid, B an organic solvent, C a photopolymerization initiator, and D an amine curing agent. A resin composition for solder resist ink, characterized by: