JP2553048B2 - Method of forming resist film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a resist film on a printed wiring board where conductors are exposed in a printed wiring board manufacturing process.

[Conventional technology]

As a method of forming a resist film on a printed wiring board with exposed conductors, a method of printing a resist ink by a method such as screen printing and then curing it by heating or irradiating with ultraviolet rays is generally used.

However, in recent years, as the density of printed wiring boards has increased, photo-developing dry films and liquid resists have come to be used not only for forming conductor circuits of printed wiring boards but also for forming resist films. I came.

Usually, organic solvents such as trichloroethane and trichlene or inorganic alkalis such as caustic soda and sodium carbonate are often used as a developing method for photo-developing dry films and liquid resists. There are various problems such as pollution problems such as pollution, time and effort for solvent recovery, and soaring solvent cost. On the other hand, in the case of the latter alkali development, the resin used as a resist is generally required to contain a large amount of carboxyl groups from the viewpoint of development characteristics, but the presence of many carboxyl groups in the resist film is Deteriorates electrical insulation in a humid environment, and when using an inorganic alkali during development,
Since the carboxyl group on the surface of the exposed coating film after photocuring becomes an alkali salt such as sodium salt in alkali, it remains as a salt even after curing, which promotes hygroscopicity of the resist and causes a significant decrease in electrical insulation. Has become.

Therefore, currently, the solvent developing type, which does not deteriorate the characteristics of the resist, is predominant. However, the solvent-developing type has various other problems as described above, and this is the reason why the photo-developing type dry film and the liquid resist do not grow further in the market.

Furthermore, the improvement of the electrical insulation of fine lines is the most important issue along with the recent increase in the density of printed wiring boards.

[Means for solving problems]

The present inventors have studied various methods of applying a photo-developing resist on a printed wiring board with an exposed conductor and not using alkali development to significantly reduce the electrical insulation under high humidity. Has reached the present invention.

That is, according to the present invention, a photopolymerization initiator is mixed with (A) a carboxyl group-containing resin having an acid value of 30 to 500 (B) a polyvalent vinyl oligomer (C) a polyvalent epoxy compound on a printed wiring board with an exposed conductor. After forming a coating film of the composition consisting of the composition and irradiating it with ultraviolet light through a photomask of a desired plate, the unexposed portion is developed and removed with an aqueous solution of a tertiary amine or a tertiary alkanolamine, followed by heat treatment. The tertiary amine or the tertiary amine present on the exposed surface of the coating by
A method for forming a resist film, characterized in that a high-grade alkanolamine is removed by evaporation.

 Hereinafter, the present invention will be described in detail.

Examples of the carboxyl group-containing resin having an acid value of 30 to 500 used in the present invention include unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid or itaconic acid, maleic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and the like. Resins obtained by copolymerizing the monoesters and the like with a copolymerizable vinyl monomer are the most common, and suitable examples of the copolymerizable vinyl monomer include methyl methacrylate and ethyl methacrylate. , Butyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate,
Butyl acrylate, 2-ethylhexyl acrylate, styrene, α-methylstyrene, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2
-Hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, glycidyl methacrylate, glycidyl acrylate, t-butylaminoethyl methacrylate, t-butylaminoethyl acrylate, dimethylaminomethacrylate, dimethylaminoacrylate, acrylamide, methacrylamide, acrylonitrile, N-vinylpyrrolidone Etc.

The above-mentioned unsaturated carboxylic acid and these copolymerizable vinyl monomers are combined and polymerized in an appropriate ratio so as to have an acid value of 30 to 500, and (A) a resin containing a carboxyl group having an acid value of 30 to 500. Can be In addition, in the present invention, a polyester resin having an acid value of 30 to 500 obtained by combining a polyhydric alcohol and a polycarboxylic acid can also be used. When a resin having an acid value of less than 30 is used, it is unsuitable because the development becomes difficult in the alkali developing process, and when the acid value is more than 500, the electrical insulation of the formed resist film is poor and unsuitable. Yes, especially with an acid value of 30
It is preferably in the range of to 500.

Examples of the polyhydric vinyl oligomer (B) of the present invention include acrylic acid esters and methacrylic acid esters of polyhydric alcohols such as trimethylolpropane, trimethylolethane, trimethylolmethane, pentaerythritol, dipentaerythritol, and 1,3-butylene glycol. , 1,4-butylene glycol, 1,6-hexanediol, propylene glycol, tripropylene glycol, polypropylene glycol, ethylene glycol,
Preferred examples include polyethylene glycol, neopentyl glycol, dibromoneopentyl glycol, acrylic acid and methacrylic acid ester of tris (2-hydroxyethyl) isocyanuric acid. In addition, acrylic acid of alkylene oxide adduct of bisphenol A,
As the methacrylic acid ester, for example, 2,2bis (4-acryloxyethoxyphenyl) propane, 2,2bis (4-acryloxyproproxyphenyl) propane and the like can be used. Also, an adduct of a polyvalent epoxy compound and an unsaturated carboxylic acid such as acrylic acid or methacrylic acid can be used.

In the above-mentioned (B) polyvalent vinyl oligomer, only the exposed portion undergoes a curing reaction by irradiation with ultraviolet rays through a photomask, and the exposed portion becomes insoluble in a developing step described later,
This makes it possible to form a resist film corresponding to a desired plate.

The above-mentioned (C) polyhydric epoxy compound is an epoxy resin obtained by the reaction of polychlorophenol compounds such as bisphenol A, bisphenol F, novolac resin, cresol novolac resin and epichlorohydrin; phthalic anhydride, isophthalic acid, adipic acid and the like. Glycidyl ethers of polybasic alcohols such as glycidyl esters of dibasic acids, butanediol, tremethylolpropane, polypropylene glycol, and water-added bisphenol A;
Aniline, methylenedianiline, xylylenediamine,
Glycidyl-substituted products of amines such as diaminobenzophenone; so-called alicyclic epoxy compounds obtained by epoxidizing cycloolefins; triglycidyl isocyanurate and the like are used.

These (C) polyhydric epoxy compounds react with the carboxyl groups in the carboxyl group-containing resin of (A) in the heat treatment step after development, thereby significantly improving the electric insulation in a humid environment, It also improves the adhesion to the wiring conductor.

If necessary, vinyl-polymerizable monomers may be mixed with the above components (A), (B) and (C), but if these monomers evaporate in the coating step, they may be used. Since the properties of the resist film change depending on the conditions, it is desirable that the boiling point is at least 150 ° C or higher, preferably 200 ° C or higher. Excessive use of such a monomer increases the tackiness of the coating. However, since it becomes an obstacle to the work process, it is allowed to be used within the range where these obstacles do not occur.

The mixing ratios of (A), (B) and (C) described above are
The suitability value varies depending on the carboxyl group content of the resin of (A) and the epoxy group content of the polyvalent epoxy compound of (C), etc., but the carboxyl group content of all film forming components is 10 to 200 as an acid value. The ratio of carboxyl group to epoxy group is generally 1: 0.1 to 1:10, but most preferably 1: 0.2 to 1: 1.

Further, the weight ratio of the polyvalent vinyl oligomer (B) to all the film forming components is preferably 10 to 40% by weight.

A photopolymerization initiator is added to the above (A), (B) and (C) to make it possible to cure the UV-irradiated portion. Examples of such photopolymerization initiator include benzophenone, 4,4′-
Benzophenones such as bis- (dimethylamino) benzophenone and 4,4′-bis- (diethylamino); Benzoin alkyl ethers such as benzoin, benzoin butyl ether and benzoin isopropyl ether; 2,2-
Acetophenones such as diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone and 2,2-dichloro-4-phenoxyacetophenone; 2-hydroxy-2-methylpropiophenone, 4-isopropyl-2
-Hydroxy-2-methylpropiophenone and other propiophenones; 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-chloroanthraquinone and other anthraquinones; diethylthioxanthone, diisopropylthioxanthone, chlorthioxanthone and other thioxanthones; Other examples include benzyl, 1-hydroxycyclohexyl phenyl ketone, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propane and the like.

These photopolymerization initiators are used alone or as a mixture, and the amount used is such that the weight ratio in all the film-forming components is 0.1 to 2
It is 0% by weight, preferably 1 to 15% by weight.

The composition used in the present invention further has a function of dicyandiamide, which is a curing agent for an epoxy compound, dibasic acid hydrazide, imidazole in combination, leveling property, defoaming, adhesion improvement, and thixotropy imparting property. Known aids, colorants, fillers and the like may be blended and used, and each of these components is usually dissolved or dispersed in an organic solvent and applied on a printed wiring board with an exposed conductor, and the solvent is added. Evaporation removes to form a film.

In the present invention, next, the printed wiring board on which the coating film is formed is irradiated with ultraviolet rays through a photomask having a desired plate. This photomask may be brought into close contact with the coating or may be exposed to ultraviolet rays as parallel rays at a certain distance from the coating.

In the UV-exposed area, radical species are generated by the decomposition of the photopolymerization initiator, and the polymerization reaction of the polyvalent vinyl oligomer (B) and a vinyl-polymerizable monomer that may be used in combination occurs.

In the present invention, the development is carried out with an aqueous solution of a tertiary amine or a tertiary alkanolamine. Examples of the tertiary amine or tertiary alkanolamine include trimethylamine, triethylamine, trebutylamine, dimethylbenzylamine, triethanolamine,
Triisopropanolamine, dimethylethanolamine,
Diethyl ethanolamine or the like is used. These are usually used as an aqueous solution of 0.1 to 10% by weight.

By contacting with the aqueous solution of the above-mentioned tertiary amine or tertiary alkanolamine, the unexposed areas of the ultraviolet light are eluted, and only the exposed areas remain as a film on the printed wiring board to complete the development.

In the present invention, after the development as described above, it is usually 10
Heat treatment is performed at a temperature of about 0 ° C. to 200 ° C. to evaporate and remove the remaining tertiary amine or tertiary alkanolamine. The heating temperature and time are not particularly limited, but it is usually preferably 10 minutes or longer at 100 ° C., 3 minutes or longer at 150 ° C., and 20 seconds or longer at 200 ° C.
Of course, the upper limit temperature and time are allowed within the range where thermal deterioration or deformation of the printed wiring board does not occur. In this heating step, the tertiary amine or tertiary alkanolamine present by forming a salt on the surface of the coating film is dissociated during development,
This accelerates the crosslinking reaction between the carboxyl group and the epoxy group in the coating film, and at the same time forms a resist film which is evaporated and removed and hardened.

The resist film formed as described above exhibits excellent electrical insulation even in a humid environment, and enables production of an excellent reliability high-density printed wiring board.

 Hereinafter, the present invention will be described more specifically with reference to Examples.

〔Example〕

Example 1 (a) Copolymer consisting of 50% methyl methacrylate 20% butyl acrylate 10% ethyl acrylate 20% methacrylic acid (acid value 130) (Viscosity measurement with 50% methyl ethyl ketone solution 6500 cps 25
45 ° C.) (b) Epicoat 828 (Shell) 30 (c) Trimethylolpropane triacrylate 10
(D) Aronix M-315 (manufactured by Toagosei Kagaku) 5
(E) Benzophenone 4 (f) 4,4-bis- (dimethylamino) benzophenone
2 (g) Kamaya-PM-2 (manufactured by Nippon Kayaku Co., Ltd.) 3 (h) Phthalocyanine Green 3 (i) Methylethylketone 100 A photosensitive solution was prepared by the above composition, and a doctor blade was placed on a printed wiring board with an exposed conductor. After applying uniformly using the above, it is dried at 70 ° C for 10 minutes. The film thickness of the dried coating film was 21μ on the copper circuit.

Next, through a desired photomask, it was exposed for 90 seconds with a 5 KW ultra-high pressure mercury lamp (distance 50 cm) (Oak Seisakusho).
The integrated light quantity was 400 mJ / cm ² .

Development was carried out by immersing the exposed coating film in a 2% by weight aqueous triethanolamine solution (30 ° C.) for 2 minutes. The unexposed area was easily developed to obtain the desired image. Further, heat treatment was performed at 150 ° C. for 30 minutes. The pencil hardness (JIS D-0202) of this coating film was 5H, and the adhesion (JIS D-0202) after cross-cut was 100/100. Also, this coating is acetone, methyl ethyl ketone, trichlene,
No abnormality was observed even after soaking for 12 hours in the organic solvent of trichloroethane. 10% hydrochloric acid, 10% sulfuric acid, 10%
There was no defect in the coating film even after being immersed in the aqueous sodium hydroxide solution for 12 hours. Adhesion after cross cutting (JIS D
-0202) were all 100/100.

On the other hand, it was found that even if this coating film was dipped in a solder bath at 270 ° C. for 30 seconds, the coating film had no blistering or peeling and that it could withstand normal soldering and solder air leveler.

The insulation resistance value (JIS-Z-3197 comb type electrode) was measured and found to be 8.3 × 10 ¹² Ω after an initial value of 5.2 × 10 ¹³ Ω at 60 ° C. and 95% humidity for 10,000 hours.

It was found that the protective film obtained from these things has sufficient properties as a solder resist for printed wiring boards.

Examples 2 to 5 The following photosensitive compositions were produced.

(Example 2) (a) Copolymer consisting of 45% styrene 45% methyl methacrylate 10% methacrylic acid (acid value 65) (Viscosity measurement with 50% methyl ethyl ketone solution 4500 cps25
℃) 40 (parts by weight) Epicoat 100 / (manufactured by Shell Co.) 20 (c) Trimethylolpropane triacrylate 15
(D) Pentaerythritol triacrylate 15
(E) Benzophenone 5 (f) 4,4-bis- (dimethylamino) benzophenone
2 (g) Kamaya-PM-2 (manufactured by Nippon Kayaku Co., Ltd.) 2 (h) Phthalocyanine green 2.5 (i) Butyl cellosolve acetate 100 (Example 3) (a) Monobutyl ester of 1: 1 styrene-maleic acid copolymer Compound (acid value 204) (Viscosity measurement with 50% methyl ethyl ketone solution 9500cps25
℃) 75 (parts by weight) (b) Triglycidyl isocyanurate 20 (c) Dipentaerythritol hexaacrylate 15
(D) 2-hydroxyethyl methacrylate 5
(E) Benzophenone 4 (f) 4,4-bis- (dimethylamino) benzophenone
2 (g) 1-hydroxycyclohexyl phenyl ketone 2
(H) Benzotriazole 1.5 (i) Phthalocyanine Green 3 (j) Cellosolve Acetate 150 (Example 4) To 100 parts by weight of the photosensitive composition of Example 3, 30 parts by weight of talc and 2 parts by weight of Aerosil were added to prepare a three-roll roll or the like. A viscous liquid capable of being screen-printed was manufactured by uniformly dispersing it using a kneader.

Example 5 (a) Polyester resin consisting of 48% phthalic anhydride 45% hydrogenated bisphenol A 7% trimethylolpropane (acid value 67) (50% methyl ethyl ketone solution 12800 cps 25 ° C.) 55 (parts by weight) (b) Cresol novolac Type epoxy resin 15
(Nippon Kayaku Co., Ltd. EOCN-103) (c) Aronix M-325 (Toa Gosei Chemical Co., Ltd.) 20
(D) trimethylolpropane triacrylate 10
(E) 2-hydroxyethyl acrylate 5
(F) 2-Methyl- [4- (methylthio) phenyl]-
2-morpholino-1-propane 3 (g) t-butyl anthraquinone 3 (h) p-dimethylaminobenzoic acid etimester 2
(I) Benzotriazole 1.5 (j) Phthalocyanine tree 3 (k) 1/1 mixed solvent of butyl cellosolve / toluene 85
Each of the above-mentioned photosensitive liquids was adjusted and applied uniformly on a printed wiring board having an exposed conductor in the same manner as in Example 1 using a doctor blade. However, Example 4 was applied by screen printing using a 150 mesh polyester monofilament screen. After coating, the solvent was removed by evaporation by drying at 80 ° C for 15 minutes to form a tack-free film. Next, it was exposed through a desired photomask for 2 minutes using a 5 KW ultra-high pressure mercury lamp (same as in Example 1). After exposure, 2% by weight triethanolamine or 1.5% by weight
Development was carried out by immersing the above in an aqueous solution of triethylamine (30 ° C.) for 2 minutes each. The unexposed area was dissolved to obtain the desired image. Furthermore, heat treatment was performed at 140 ° C. for 40 minutes to completely cure the coating.

The characteristics of the resist film obtained below were evaluated according to Example 1, and the results are shown in Table 1.

(Comparative Examples 1 to 5) A resist film was formed according to the working process of Example 1 using the photosensitive liquids of Examples 1 to 5, but only in the developing process, 2% by weight was used instead of triethanolamine or triethylamine.
Using an aqueous solution of sodium carbonate Was developed and the characteristics of the resist film were evaluated according to Example 1. The results are shown in Table 2.

From the above results, it can be seen that unless an amine-based aqueous solution is used as a developing solution, the resist film properties, in particular, solvent resistance, acid / alkali resistance, and insulation resistance under high temperature and high humidity are significantly reduced.

 ─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-58-169143 (JP, A) JP-A-57-114141 (JP, A) JP-A-56-8145 (JP, A) JP-A 61- 175636 (JP, A)

Claims (1)

(57) [Claims] 1. A photopolymerization initiator is added to (A) a carboxyl group-containing resin having an acid value of 30 to 500, (B) a polyvalent vinyl oligomer (C) and a polyvalent epoxy compound on a printed wiring board having an exposed conductor. After forming a coating film of the composition consisting of the composition and irradiating it with ultraviolet light through a photomask of a desired plate, the unexposed portion is developed and removed with an aqueous solution of a tertiary amine or a tertiary alkanolamine, followed by heat treatment. The tertiary amine or the tertiary amine present on the exposed surface of the coating by
A method for forming a resist film, which comprises dissociating a high-grade alkanolamine to promote a crosslinking reaction between a carboxyl group and an epoxy group in the coating film, and at the same time, removing by evaporation to form a hardened resist film.