JPH0770812B2 - Method of forming printed circuit board - Google Patents

Description

The present invention relates to a method for forming a printed circuit board, and more particularly to a method for easily and accurately forming a printed circuit on an insulating substrate by using a photo-curable cationic electrocoating material. is there.

Conventionally, to make a printed circuit board, a photosensitive resist film is generally laminated on a copper foil-clad laminate, and a photographic negative is overlaid to expose and develop a desired pattern. The printed circuit is formed on the insulating substrate by etching the foil and then removing the photosensitive film.

The thickness of the photosensitive film used in the above method is generally
Since it is thick at around 50 μm, the pattern of the circuit formed by exposure and development is not sharp, it is difficult to uniformly laminate the photosensitive film on the copper foil surface, and if dust etc. enter, it will be directly on the substrate It is easy to produce defective products because it cannot be laminated, defective products are likely to be laminated in the through holes, and even though the photosensitive film is expensive, it can be cut into various sizes and wasteful. It is a fact that there is a drawback, and the advent of means to replace the photosensitive film is desired.

The present inventors have completed the present invention as a result of intensive research to develop a method for forming a printed circuit board that eliminates these drawbacks.

That is, the present invention, when forming a printed circuit board, instead of using a photosensitive film, an amine value of 10 to 100, an unsaturated equivalent of 150 to 3,000 and a number average molecular weight of 300 or more, preferably 1,000 to 30,000 on a copper clad substrate. The cationic electrodeposition coating composition containing the developable photocurable cationic resin as a film-forming resin component has a film thickness of 3 to 50 µ, preferably 5 to 30 µ.
After coating in the range of, the photographic negative film or positive film is overlaid on this electrodeposition coating film to expose the desired pattern, the uncured electrodeposition coating film is removed by acid washing (development).
Then, the present invention relates to a method for forming a printed wiring board by etching the copper foil surface other than the pattern thereafter.

According to the present invention, there is no film loss, and since it is electrodeposition coating, it is possible to coat even the hole portion of the through hole, and since the coating material directly adheres to the copper surface, the defective rate is extremely low.

Hereinafter, the present invention will be described in detail.

The film-forming resin constituting the photocurable cationic electrodeposition coating composition used in the present invention is a resin having an amino group and an ethylenically unsaturated group such as an acryloyl group or a methacryloyl group in the resin skeleton. As the amino group, the primary and secondary amino groups are preferably tertiary amino groups because they easily cause an addition reaction with an ethylenically unsaturated group and have poor storage properties. Examples of the resin containing an ethylenically unsaturated group and an amino group include the following.

(1) A resin obtained by adding a primary or secondary amine to an epoxy compound, and then adding an ethylenically unsaturated group-containing isocyanate compound to the hydroxyl group; as the epoxy compound, a bisphenol A type epoxy resin or a bisphenol F type epoxy resin , Bisphenol S type epoxy resin, aliphatic epoxy resin, novolac type epoxy resin, styrene, methyl (meth) acrylate, vinyl monomer such as 2-hydroxyethyl (meth) acrylate and glycidyl group such as glycidyl (meth) acrylate A resin or the like obtained by copolymerizing an unsaturated monomer is used. As the amine, monoethylamine, monobutylamine, diethylamine, dibutylamine, monoethylmonoethanolamine, diethanolamine and the like are used.

Further, as the ethylenically unsaturated group-containing isocyanate compound, tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, 1,6-hexane diisocyanate and the like, one of the isocyanate groups of the diisocyanate compound 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate , 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and other compounds to which a hydroxy group-containing unsaturated monomer has been added, ethyl isocyanic acid methacrylate, and the like.

(2) A resin obtained by adding a compound containing an ethylenically unsaturated group and a carboxyl group to the epoxy group of a resin containing an epoxy group and a tertiary amino group; a resin containing an epoxy group and a tertiary amino group is It is obtained by reacting a part of the epoxy groups of the epoxy resin with a secondary amine. It is synthesized by adding a compound containing an unsaturated group such as (meth) acrylic acid and a carboxyl group to the remaining epoxy groups in this resin.

(3) After adding a primary amine to the monoepoxy compound and secondary amination, a diepoxy compound or a polyepoxy compound is added so that the equivalent number of the secondary amine and the epoxy group becomes 1: 2 or more, A resin in which the above-mentioned compound containing an ethylenically unsaturated group and a carboxyl group is added to the remaining epoxy group, or a resin in which the above-mentioned ethylenically unsaturated group-containing isocyanate compound is added to a hydroxyl group; as a monoepoxy compound, allyl glycidyl ether, Phenyl glycidyl ether, ethylene oxide, propylene oxide, butylene oxide, etc. are used. As the diepoxy compound or multi-epoxy compound, bisphenol type epoxy resin, aliphatic epoxy resin, novolac type epoxy resin or the like is used.

The photocurable cationic electrodeposition coating composition used in the present invention is water-soluble by neutralizing (0.1 to 1.0 equivalent) the cationic resin selected from the above (1) to (3) with an acid (for example, acetic acid, lactic acid, phosphoric acid, etc.). Of which the main component is a resin component that has been made water-dispersed or a water-insoluble photopolymerization initiator.

In order to further improve the fluidity of the water-soluble or water-dispersed resin component, a hydrophilic solvent (for example, isopropanol, n-butanol, t-butanol, methoxyethanol, ethoxyethanol, butoxyethanol, diethylene glycol, methyl ether, dioxane, tetrahydrofuran) is used. Etc.) can be added. The amount of the hydrophilic solvent used is preferably 300 parts by weight or less based on 100 parts by weight of the resin component.

Hydrophobic solvents (for example, petroleum-based solvents such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, 2-ethylhexyl alcohol) in order to increase the coating amount on the object to be coated. Alcohols, etc.) can also be added.
The amount of the hydrophobic solvent used is preferably 200 parts by weight or less based on 100 parts by weight of the resin component.

As the water-insoluble photopolymerization initiator, benzoin, benzoin methyl ether, benzoin ethyl ether, benzyl, diphenyl disulfide, tetramethyl thiuram monosulfide, eosin, thionine, diacetyl, Michler's ketone, anthraquinone, chloranthraquinone, methylanthraquinone, α-hydroxyisobutyl Phenone, p-isopropyl α-hydroxyisobutylphenone, α · α′-dichloro-4-phenoxyacetophenone, 1-hydroxy 1-cyclohexylacetophenone, 2.2-dimethoxy 2-phenylacetophenone, methylbenzoyl formate, 2-methyl-1. −
[4- (methylthio) phenyl] -2.morpholino-
Propene, thioxanthone, benzophenone, etc. can be applied, and the amount of these is preferably in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin component (solid content). However, if it exceeds 10 parts by weight, the mechanical strength of the cured film deteriorates. A water-soluble photopolymerization initiator is not preferable because it becomes difficult to electrodeposit in a state of being uniformly mixed with the photocurable resin. If necessary, dyes and pigments, fillers, additives and the like can be added.

The electrodeposition coating on the insulating substrate in the present invention is performed as follows. An electrodeposition coating bath containing a water-soluble or water-dispersed photocurable resin composition as a main component has a pH of 5 to 7 and a bath concentration of 3 to 25w.
t% preferably 5 to 20 wt%, bath temperature 15 to 40 ° C, suitably 2
Keep the temperature at 0-35 ℃ and then immerse the insulating substrate coated with copper foil as a cathode in the electrodeposition coating bath controlled in this way as a cathode.
It is performed by applying a current of 0V. In this case, it is appropriate that the energization time is 30 seconds to 5 minutes, and the film thickness obtained is a dry film thickness of 3 to 70 μm, preferably 5 to 50 μm.

After the electrodeposition coating, the object to be coated is lifted from the electrodeposition bath and washed with water, and then the water and solvent contained in the electrodeposition coating film are removed by air blow or hot air.

The feature of electrodeposition coating is that even if it has a complicated shape, a coating film can be applied uniformly, and a laminated circuit board usually has through holes. In order to protect the copper film in the through holes, especially by this electrodeposition coating, even coating is performed.

Further, in the anionic type, there is deposition of metal in the bath of the coated object in order to make the coated object an anode, or in the coating film, but in the case of the cationic type, there is no deposition of these metal copper ions and the substrate is also It is clean and has good bath stability.

Then, a photographic negative film or a positive film is superposed on the uncured photocurable electrodeposition coating film formed on the substrate, and exposed to light such as ultraviolet rays. The developing treatment is carried out by washing the uncured material of the coating film by spraying weak acid water on the unexposed area or immersing it in it. As the weakly acidic water, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, formic acid, ammonium sulfate water, ammonium chloride water or the like is usually used, and the weak acid water may be heated if necessary.

Ultraviolet rays are mainly used as the light rays used for the exposure, and examples of the apparatus for generating the ultraviolet rays include a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp and an arc lamp.

Then, the copper foil portion (non-circuit portion) exposed on the substrate by the developing treatment is removed by a usual etching treatment using a mixed solution of ammonium hydroxide and ammonium chloride or the like.

After that, the photo-cured coating film of the circuit pattern is also dissolved and removed by a solvent or a strong alkali to form a printed circuit on the substrate.

Hereinafter, the present invention will be described with reference to examples.

Synthesis Example 1 340 parts by weight of Epon 828 (Shell Chemical, epoxy resin), 210 parts by weight of diethanolamine, in a four-necked flask,
Add 733 parts by weight of methyl ethyl ketone and stir for 30
The mixture was kept at 2 ° C for 2 hours for tertiary amination. To another four-necked flask, 696 parts by weight of tolylene diisocyanate, 464 parts by weight of 2-hydroxyethyl acrylate and 1.0 part by weight of hydroquinone were added, and 1,160 parts by weight of an ethylenically unsaturated group-containing isocyanate obtained by reacting at 50 ° C. for 3 hours was added. The mixture was added to the above four flasks and reacted at 80 ° C. for 5 hours to obtain a photocurable cationic resin having an amine value of 66, an unsaturated equivalent of 428 and a number average molecular weight of 1,710.

Synthesis Example 2 617 parts by weight of n-butanol was placed in a four-necked flask 1
After heating to 10 ° C, 550 parts by weight of methyl methacrylate,
A mixed solution of 100 parts by weight of n-butyl acrylate, 350 parts by weight of glycidyl methacrylate, and 30 parts by weight of azobisisobutylnitrile is added dropwise over 3 hours. Then 110 ℃ 1
After being kept for a period of time, a mixed solution of 50 parts by weight of n-butanol and 5 parts by weight of valeronitrile was added dropwise over 1 hour and kept at 110 ° C. for 5 hours to obtain an acrylic resin having a number average molecular weight of about 10,000. 73 parts by weight of diethylamine was added to this acrylic resin solution and kept at 110 ° C. for 1 hour, then 108 parts by weight of acrylic acid and 0.6 part by weight of hydroquinone were added and further added.
By keeping at 110 ° C. for 4 hours, a photocurable cationic resin having an amine value of 47.5, an unsaturated equivalent of 807 and a number average molecular weight of about 12,000 was obtained.

Synthesis Example 3 Phenylglycidyl glycidyl ether 150 parts by weight, monobutylamine 73 parts by weight, methyl isobutyl ketone 282
After adding 2 parts by weight and keeping at 30 ℃ for 2 hours,
Epon 828357 parts by weight was added and the reaction was carried out at 50 ° C. for 2 hours. Add 79 parts by weight of acrylic acid and 0.6 parts by weight of hydroquinone, and add 110
After kept at 4 ° C for 4 hours, 580 parts by weight of the addition product of tolylene diisocyanate and 2-hydroxyethyl acrylate used in Synthesis Example 1 and 249 parts by weight of methyl isobutyl ketone were added and reacted at 90 ° C for 3 hours to give an amine value of 45, Unsaturated equivalent 413,
A photocurable cationic resin having a number average molecular weight of 1,240 was obtained.

Example 1 After 1,000 parts by weight of the resin solution of Synthesis Example 1 was mixed with 35 parts by weight of α-hydroxyisobutylphenone, the mixture was neutralized with 24.7 parts by weight of acetic acid, and deionized water was added to the mixture to prepare a cationic type electrode having a solid content of 15% by weight. I got the paint. Using this electrodeposition coating bath, a copper clad laminate for printed wiring was used as a cathode, and a DC current of 120 V was applied for 3 minutes at a bath temperature of 30 ° C. for electrodeposition coating.

The coating film was washed with water and dried at 70 ° C. for 5 minutes to obtain a 20 μm-thick, non-sticky, smooth photosensitive film. Then, the negative film was brought into close contact with this coated plate by a vacuum device, and 150 mJ / cm ^{2 was} irradiated on each side by using a 3 KW ultra-high pressure mercury lamp. Next, the unexposed area is 3%
After washing with acetic acid solution, development, and washing with water, the copper foil is removed by etching with a mixed solution of ammonium hydroxide and ammonium chloride, and then the cured coating film on the exposed area is removed with a 7% caustic soda solution to form a sharp pattern. A printed circuit board was obtained. The copper surface of the obtained circuit had no elution of copper due to electrodeposition coating and had very good solderability.

Example 2 1,000 parts by weight of the resin solution of Synthesis Example 2 was added with 1-hydroxy 1-
After mixing 35 parts by weight of cyclohexylacetophenone,
It was neutralized with 18 parts by weight of acetic acid and deionized water was added to obtain a cationic electrodeposition coating composition having a solid content of 15% by weight.

A copper clad laminate with 1mm through holes is used as the cathode, and the bath temperature is 25 ° C.
Then, a direct current of 100 V was applied for 2 minutes to perform electrodeposition coating so that the film thickness was 15 μm. After draining and drying, a negative film is layered on the electrodeposition coating film and 100 mJ / cm on both sides with a high pressure mercury lamp.
It was exposed by irradiating light of ² . The inside of the through hole was also sufficiently electrodeposited and dried by irradiation with ultraviolet rays.

Next, the unexposed area was washed out with 3% acetic acid for development, washed with water, and the copper foil was removed by etching with ferric chloride. At this time, the copper film inside the through hole was not dissolved and the resist film was sufficiently formed on the electrodeposition coating film.

Then, the cured coating film was removed with trichloroethylene to obtain a printed circuit board having a sharp pattern.

Example 3 2-Methyl-1- was added to 1,000 parts by weight of the resin solution of Synthesis Example 3.
After mixing 35 parts by weight of [4- (methylthio) phenyl] -2.morpholinopropene, the mixture was neutralized with 17 parts by weight of acetic acid and deionized water was added to obtain a cationic electrodeposition coating composition with a solid content of 15% by weight. It was Using this electrodeposition coating bath, a copper clad laminate for printed wiring was used as a cathode, and a DC current was applied for 90 seconds at a bath temperature of 25 ° C. for 90 seconds for electrodeposition coating. The coating film was washed with water and dried to obtain a smooth photosensitive film having a film thickness of 30μ.

Then, a positive film is placed on this coating film by sticking it on top of each other, and 200 mJ / cm ^{2 on} both sides with a metal halide lamp.
Irradiate each. Then, it was washed out with 5% acetic acid and developed. This developing plate was dipped in a solder melt and solder was placed on the copper circuit. Thereafter, the cured film was peeled off with 5% caustic soda, and the exposed copper surface was etched with ferric chloride to obtain a printed wiring board.

Claims (1)

[Claims] 1. An amine substrate having an amino group and an ethylenically unsaturated group in the resin skeleton of an insulating substrate coated with copper foil having an amine value of 10 to 10
0, unsaturated equivalent 150-3,000 and number average molecular weight of 300 or more water-soluble or water-dispersible photo-curable cationic resin electrodeposition coating with a photo-curable cationic electrodeposition coating composition as a film-forming resin component, then, The photo-curable electrodeposition coating film formed on the substrate is subjected to exposure and development of a desired pattern through a negative film or a positive film, followed by etching treatment of copper foil other than the pattern. Method of forming a printed circuit board.