JPS60230135A - Photopolymerizable resin composition - Google Patents

Abstract

PURPOSE:To form the cross section of a plated circuit on a printed board into a rectangle and to obtain good electric characteristics by using benzylmethylketal as a photopolymn. initiator together with a specified binder resin and a bridging monomer. CONSTITUTION:A photopolymerizable resin compsn. comprises a binder resin made of a copolymer of methyl methacrylate, 1-4C alkyl acrylate, and a vinyl nomomer having carboxylic acid contains a monomer capable of cross-linking monomer having at least 2 ethylenically unsated. group and a polymn. initiator of a benzylmethylketal. A dry film resist is obtained by coating a support of polyester film or the like, with such a compsn. Such a resist is good in storage stability, operation efficiency, and step passage performance, and the section of the patterned resist can be formed into a rectangle and a superior pattern high in resolution can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a photopolymerizable resin composition used particularly for forming an alkali-developable dry film resist for printed wiring boards.

[Prior art]

FF used in dry film resists [as an intermediate initiator] is inexpensive, active against particles at a wavelength of 365 nm, has good heat resistance and storage stability (and does not produce corrosive or harmful compounds). Furthermore, performance is required such that it does not elute during the manufacturing process of printed circuit boards and cause harm to others.

Kut As a photopolymerization initiator that satisfies these properties.

Conventionally, Michler's ketone or 4,4'bisdiethylaminobenzophenone was used alone or a mixture of these and benzophenone, 2-ethylanthraquino/2-ethylanthraquino/.

2-tert, anthraquinones represented by butyl anthraquinone, 7 tons of 2,4 dimethylthioxa, 2,
Thioxa 7tons represented by 4di-isopropylthioxanthone/2-chlorothioxanthone are used.

Among these, Michler's Gato/Tobe/Dipheno/mixed systems are mainly used.

However, when a dry film resist is made using these photopolymerization initiators, exposed to light, developed, and buttered, it becomes a surface cross-linked type, and the cross-section of the resist pattern becomes an inverted trapezoid with the upper base longer than the lower base. Therefore, especially with the solder through-hole method that includes a plating process, When manufacturing a prime wiring board with a fine pattern 7 of n or less,
When electroplating is performed after patterning with a resist using the above photopolymerization initiator, the cross section of the plating pattern forming the two-circuit pattern 7 becomes a trapezoid with the upper base shorter than the lower base, and the electrical characteristics of the printed wiring board circuit are significantly deteriorated. There were 8 problems.

[Purpose of the invention]

In view of the above-mentioned prior art, an object of the present invention is to significantly improve the drowsiness characteristic of the printed wiring board circuit by making the cross section of the plated circuit board 7 of the printed wiring board rectangular.

[Structure of the invention] The original polymerizable resin crude product according to the present invention is as follows.

A binder resin comprising a copolymer of methyl methacrylate, an acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms, and a vinyl monomer containing a carboxylic acid group.

(Bl is a crosslinkable monomer having two ethylenically unsaturated groups in the molecule) and (C1 benzyl dimethyl ketal).

The binder resin constituting the composition of the present invention is as follows.

It consists of a copolymer obtained by polymerizing a monomer mixture consisting of methyl methacrylate, an acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms, and a carbo/acid group-containing vinyl monomer.

Examples of the acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms used to constitute the binder resin include methyl acrylate, ethyl acrylate, n-propyl acrylate, inglovir acrylate, and n-acrylate.
-Butyl.

acrylic acid sec, -butyl, acrylic acid tert,
-butyl etc. It is desirable to use one or more of these monomers in an amount of 2 to 70% by weight in the copolymer, and the content in the copolymer is 2i
I (If it is less than 8%, the dry film resist after exposure will be too hard and will easily cause resist peeling, and if it is less than 70%
Exceeding the weight will cause a cold flow phenomenon.

In addition, examples of carboxylic acid group-containing vinyl monomers used to form binder resins include acrylic acid, methacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconic acid, etc. It is preferable to use one or more of them so that the number of carbon atoms in the co-N combination ranges from 10 to 50. If a binder resin is used in an amount less than 10% by weight, development may not be possible or the development time may be too long (which may cause a decrease in resolution).

On the other hand, if a binder resin of 50% by weight or more is used, the development time becomes extremely short (and development control becomes difficult to obtain a high resolution pattern).

The water resistance of the hardened portion also decreases.

The weight average molecular weight of the binder resin used in the present invention is in the range of 40,000 to 200,000.

When the weight average molecular weight is less than 40,000, the resist composition oozes out through the support film over time when the dry film resist is wound and stored on tosite roll. A so-called cold flow phenomenon occurs, and if the weight average molecular weight exceeds 200,000, unexposed areas will not dissolve and development will not be possible or development will take an extremely long time, resulting in a decrease in resolution.

In the molecules constituting the composition of the present invention, there is a small amount (both the two ethylenically unsaturated phase monomers are 2, for example, polyethylene glycol di(meth)acrylate, probilene/glycol di(meth)acrylate), 1. 3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)
Acrylate, l,6-hexanethiol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate,
In addition to polyester (meth)acrylates such as pentaerythritol tetra(meth)acrylate, epoxy (meth)acrylates, urethane (meth)acrylates, and the like can be mentioned. These may be used alone or in combination of two or more.

The blending ratio of binder resin/crosslinkable monomer (1 total) is 273
It can be in the range of ~9. If the blending ratio is less than 273, the composition may not be applied uniformly, or migration may occur in the resist layer after drying, or a cold flow phenomenon may occur. - If it exceeds 9,000,000, the original part of the resist will be rapidly dissolved by the developer, making development impossible.

The be/zyl dimenal ketal constituting the composition of the present invention is used as a 9-component polymerization initiator, and is generally 0.2 to 2 degrees Celsius by weight, preferably 0.2 degrees Celsius, relative to the resist solid content in the two compositions.
It is best to use it in a range of 5 to 165% by weight, and the amount used is more than 2% by weight.

This not only promotes the dark reaction of the resist and shortens the life of the resist, but also makes it difficult to select the exposure intensity and exposure time to obtain an appropriate exposure amount.

On the other hand, since there is a limit to the light intensity of commercially available ultra-high pressure mercury lamps at less than 0.2 gb, it is necessary to take a longer exposure time of 9 hours. This causes a decrease in resolution.

Although the composition of the present invention can be used in the absence of a diluting solvent, it can dissolve the binder resin and have a boiling point too high (
No solvents 9 e.g. methyl ethyl ketone, methylene chloride/,
It is preferred to use methylene chloride/methyl alcohol mixtures, mixtures containing isopropyl alcohol or inpropyl alcohol as a main component with other solvents, and the like.

The amount of the solvent used is 200% by weight or less, preferably 100 to 200% by weight, based on one composition.

When the composition of the present invention is used in the presence of a solvent, the solvent may be added to and mixed with the two compositions, or the above-mentioned solvent may be used for solution polymerization when producing the binder resin, or the solvent may be further added thereto. A method of adding additionally, etc. can be adopted. When using a solution-polymerized binder resin, a mixed solvent of 80% by weight or more of isopropyl alcohol or inpropyl alcohol and 20% by weight or less of methylene chloride, methyl ethyl keto 7, etc. is preferable.

The composition of the present invention may optionally contain an adhesion promoter.

Ingredients such as thermal polymerization inhibitors, dyes, plasticizers and fillers may also be added. To form a dry film resist using the composition of the present invention, one composition is coated on a support, If a solvent is used, scatter the solvent. To apply the composition to the support, a grate coater, a rod coater, a knife coater, a roll doctor coater, a comma coater, a reverse roll coater, a transfer roll coater, a gravure coater, a kiss roll coater, a curtain coater, etc. can be used. These selections are determined by the coating weight, viscosity of the coating solution, coating speed, etc. (Plastic films such as polyester are mainly used as the support. As for the dryer, when using flammable solvents, For safety reasons, use a heat source that uses steam to simulate air heating.
A method in which the hot air in the dryer is brought into countercurrent contact, a method in which the hot air is blown onto the support from a nozzle, etc. are used. The shape of the dryer is an arch type.

The flat type is selected and used depending on the purpose.

If necessary, the dry film after drying may be laminated with a protective film such as polyethylene or polypropylene.

The dry film resist produced by VC as described above has excellent storage stability and workability as an etch/g resist or a brating resist.

High-resolution butter with excellent process passing performance can be obtained.

〔Effect of the invention〕

The noteworthy points of the photopolymerizable composition of the present invention are as follows.

The cross-sectional shape of a patterned resist can be resolved into a rectangle. As a result, the cross section of the plating pattern on the printed wiring board also becomes rectangular, and the conductive area can be sufficiently widened for the determined line width.
Conventionally, this occurs when the cross section of the resist pattern becomes an inverted trapezoid when manufacturing a printed wiring board having a fine pattern.

It is possible to eliminate deterioration in electrical properties due to trapezoidalization and reduction of the cross section of the plating pattern.

〔Example〕

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

Examples 1-5. Comparative examples 1 to 5 A photopolymerizable resin composition having the following composition was prepared.

(1) Binder resin, resin 286 m parts (2) Trimethylolpropane triacrylate 50'N parts (3)
Tetraethylene glycol diacrylate 20 parts by weight (4) Be/citriazole 0.4 parts by weight (5)
Methylene blue 0.75i parts (6) Photopolymerization initiator The composition shown in Table 1 of Table 1 was stirred with a propeller type mixer.

The coating was applied to a coating width of 340 m on a polyester film having a thickness of 25 μm and a width of 360 m using a blade coater.

Next, hot air was fed through a flat type dryer having a width of 4001 nL, a height of 100 m, and a length of 8 rn in a countercurrent manner so that the dry coating thickness was 50 μm.

The coating speed at this time was 5 ml/min, and the wind speed in the dryer was 3
ff for 17 minutes, and the hot air temperature was set to 90°C.

A 25 μm thick polyethylene protective film was then laminated onto the dried coating and then wound onto a roll. The obtained dry film resist is thermally laminated to a copper clad laminate (copper clad laminate) while removing the protective film.
After the temperature of the @stretched laminate returned to room temperature, a photo tool was placed in close contact with the polyester film surface and exposed to an ultra-high pressure mercury lamp. Photo tools are 50μm and 60μm.

A lie/and space pattern with widths of 80 μm and 100 μm was used. In addition, the ultra-high pressure mercury lamp is Ushio Inc. U8H-
102D was used for irradiation.

The exposure intensity at this time is Ushio Inc.'s ultraviolet intensity meter UIT-1.
Attach a photodetector UVD-365P to the 00 and measure.
5 my/cR". N light diameter was allowed to stand for 20 minutes, the support film was peeled off, and the film was developed with a 1% IJum aqueous solution. Development was carried out at a solution temperature of 30°C and a spray pressure of 1.4 kg.
/cIIL” and the distance between the spray and the substrate is 10cII.
I did it as L. Next, it was immersed in a neutral detergent aqueous solution at room temperature for about 1 minute, and after degreasing, it was spray washed with water in an overflow tank for about 1 minute, and then immersed in an about 20% ammonium persulfate aqueous solution for 1 minute. After spray washing with water was performed again for about 1 minute, it was immersed in an approximately 15% sulfuric acid aqueous solution for 1 minute, and spray washing was performed again with water for 1 minute. Then, it was placed in a sulfuric acid steel plating bath for 75 minutes*2.3 A/
Plating was performed using DM.

The temperature at this time was 22°C. Immediately after plating, it was washed with water and immersed in a 15% borofluoric acid aqueous solution.

Then, high-slow solder plating was performed for 18 minutes at 1.8 A/dm'' and 22°C.

The composition of the solder plating solution is as follows.

Tin 151/11 Lead 10P/Il Free borofluoric acid 4001/1 Free boric acid 21.61/lj Peptone 5.2P/11 After plating, it was washed with water and then dried.

Table 21C shows the exposure time and resolution, the cross-sectional shape of the resist pattern after development, and the cross-sectional shape of the plating pattern after plating when each dry film resist was used for optimal exposure. The resist cross section and the cross section of the printed wiring board after plating were obtained by cutting out the printed wiring board after resist patterning and plating, encapsulating it in epoxy resin, polishing the cross section together with the resin, and observing it under a °C microscope.

Table 2

Claims (1)

[Scope of Claims] t (A) A Pi/Da resin comprising a copolymer of methyl methacrylate, an acrylic acid alkyl ester having an alkyl group having carbons a1 to 4, and a vinyl monomer containing a carboxylic acid group. (Bl is a photopolymerizable resin composition containing a crosslinkable monomer having two ethylenically unsaturated groups in the molecule and (C1 be/zyl dimethyl ketal)