JPH047500B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photopolymerizable resin composition that has improved adhesion to metal surfaces and is used particularly for forming photoresists for printed wiring boards. The production of printed wiring boards using photoresists generally consists of the following steps. (1) Layer photoresist on a substrate such as a glass/epoxy copper-clad laminate. (2) Actinic rays are irradiated through the patterned mask film so that an image can be formed. (3) Selectively dissolve and remove the uncured portions of the photoresist using a suitable developer to expose the copper surface and form a resist pattern. (4) After electrolytic copper plating is applied to the exposed copper surface, electrolytic solder plating is performed. (5) Peel off the cured resist with an appropriate solvent to expose the copper surface. (6) Using the solder plating layer as a resist, the exposed copper surface is etched with an appropriate solvent to obtain a printed wiring board in which the solder coated portion becomes the wiring section. In these manufacturing processes, a particularly important performance requirement for the photoresist is that the photoresist is not attacked by a liquid such as a plating solution, and that the substrate coated with the photoresist can be sufficiently protected.
In particular, peeling of the hardened resist that occurs during high-slow solder plating causes the plating liquid to seep between the hardened resist and the copper surface, causing solder to be plated in areas other than the circuit area, causing short circuits between conductors, and expansion of the conductor width. , problems such as irregularities in the shape of the peripheral portion of the conductor occurred. These problems are due to the lack of adhesion between the cured resist and the copper surface. Therefore, research and development of adhesion promoters has been conducted, such as benzotriazole and benzimidazole as described in U.S. Pat. No. 3,622,334. It has been proposed to add a complex nitrogen-containing compound to a photopolymerizable resin composition. However, in order to manufacture printed wiring boards using wiring with narrow line widths due to recent advances in high density and high precision, it is necessary to increase the amount of the heterocyclic nitrogen-containing compound added in order to obtain a high precision pattern. This is causing new problems. That is, an increase in the amount of benzotriazole or benzimidazole has conventionally caused discoloration of dyes essential for confirming the pattern shape of photoresists and decreased the sensitivity of photoresists. On the other hand, if the amount of photopolymerization initiator added is increased to improve sensitivity, the cross section of the resolved pattern becomes an inverted trapezoid, resulting in a decrease in resolution. In addition, increasing the amount of additives with low molecular weights is undesirable because it promotes dissolution of the cured resist layer in many steps, resulting in a decrease in the resistance of the resist film. As a result of intensive studies to overcome the conventional problems described above, the inventors of the present invention have found that by adding an extremely small amount of a specific compound to a photopolymerizable resin composition, the adhesion to metal surfaces can be improved. They found that it could be improved and completed the present invention. That is, the gist of the present invention is as follows: (a) a thermoplastic polymer for a binder, (b) a crosslinkable monomer having at least one ethylenically unsaturated group in the molecule, (c) a photopolymerization initiator, and (d) A photopolymerizable resin composition comprising lofin. The photopolymerizable resin composition of the present invention is characterized by containing lofin, so it has excellent adhesion between the photoresist and the copper plate, and prints fine patterns without causing any phenomena such as resist peeling or plating. It is suitable for manufacturing wiring boards. As the thermoplastic polymer for the binder constituting the composition of the present invention, various polymers can be used as long as they are soluble or swellable in the developer used. As a specific example, in the case of a photoresist using 1,1,1 trichloroethane as a developer, polymethyl methacrylate or a copolymer containing methyl methacrylate as a main component is used. Specific examples of monomers used for copolymerization with methyl methacrylate include methyl acrylate, ethyl (meth)acrylate (meaning ethyl acrylate or ethyl methacrylate, hereinafter the same), (meth)acrylic acid n
-propyl, isopropyl (meth)acrylate,
(meth)acrylate n-butyl, (meth)acrylate isobutyl, (meth)acrylate t-butyl,
(meth)acrylic acid 2-ethylhexyl, (meth)
(meth)acrylic acid esters such as lauryl acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate;
Examples include styrene. On the other hand, in the case of a photoresist that uses a dilute alkaline solution such as sodium carbonate as a developer, the above-mentioned (meth)acrylic acid ester or styrene and a carboxylic acid such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, etc. Examples include copolymers with Although the molecular weight and composition of the copolymer of the thermoplastic resin for the binder of the present invention cannot be determined unconditionally depending on the purpose of use, the molecular weight range is preferably 20,000 to 200,000 from the viewpoint of development or film properties. Examples of the crosslinkable monomer having at least one ethylenically unsaturated group in the molecule constituting the composition of the present invention include polyethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, Examples include polyester acrylates such as trimethylolpropane triacrylate, epoxy acrylates, and urethane acrylates, and these are used alone or in combination in an amount of 25 to 50% by weight in the composition. If the amount of crosslinkable monomer used is less than 25% by weight, the strength of the cured film will not be sufficient, and if it exceeds 50% by weight, the photoresist will become too soft and cold flow will easily occur. The photopolymerization initiator constituting the composition of the present invention is known, for example, benzophenone, Michler's ketone,
Examples include 4,4'-bis(diethylamino)benzophenone, t-butylanthraquinone, 2-ethylanthraquinone, thioxanthones, benzoin alkyl ethers, and benzyl ketals, and these may be used alone or in combination of two or more.
The amount of photopolymerization initiator used in the composition is 0.5 from the viewpoint of cost, pattern finish, resolution, etc.
~5% by weight. Furthermore, the lofin used in the present invention is an extremely effective component for improving the adhesion of photoresist to metal plates. The amount of this compound to be added to the composition cannot be determined unconditionally depending on the composition and composition ratio of the photoresist, and the hardness of the photoresist after photocuring, but the amount to obtain an effective adhesion effect is 0.001-1 in the composition
% by weight, preferably in the range 0.01-0.5% by weight. If it's too much, the sensitivity will decrease, and if it's too little, plating will likely occur during solder plating. The composition of the present invention can be used as is, but it is better to use a solvent that dissolves the base resin and whose boiling point is not too high, such as methyl ethyl ketone, methylene chloride, a mixture of methylene chloride/methyl alcohol, or isopropyl alcohol. A favorable result can be obtained. The amount of solvent used is 200% by weight or less, preferably 100% by weight based on the composition.
~200% by weight. A plasticizer, a thermal polymerization inhibitor, a filler, etc. may be added to the composition of the present invention, if necessary. The photopolymerizable resin composition of the present invention having the above-described component composition is used by being laminated onto a metal surface, such as copper, nickel, or chromium, preferably copper. It is used either by applying it as a liquid resist to a metal surface and, after drying, covering it with a protective film, or by laminating it onto a metal surface as a dry film photoresist. The thickness of the photoresist layer varies depending on the application, but the thickness after drying is about 5 to 100 μmm. As a protective film when used as a liquid resist, an inert polyolefin film such as polyethylene or polypropylene is preferably used.
Dry film photoresist is made by applying a photopolymerizable resin composition onto a polyester support film.
After drying, a polyolefin protective film is laminated. Next, actinic light is irradiated through a negative or positive mask pattern film called artwork. As the active light, a carbon arc lamp, an ultra-high-pressure mercury lamp, a high-pressure mercury lamp, a xenon lamp, etc., which effectively emit ultraviolet rays, are used. Although the exposure amount cannot be determined unconditionally, it should be 300 mj/cm ² or less, preferably
It is 50 to 200 mj/ ^cm2 . After exposure to actinic light, the unexposed portions are washed and removed using a suitable developer to obtain a resist pattern of the cured portions. Developer solutions need to be safe and stable. However, the most important point is the operability of development, that is, the difference in dissolution rate between the cured and uncured areas of the photoresist is extremely large, and it is important to select a solvent as the developer that allows the dissolution rate of the uncured areas to be appropriately fast. be. Generally, in solvent-developed photoresists, 1, 1,
1. For trichloroethane and alkaline development type photoresists, dilute solutions of sodium carbonate and the like are preferably used. There are various developing methods such as a dip method, a paddle method, and a spray method, but the high-pressure spray method is most suitable for improving resolution. Copper sulfate plating and copper pyrophosphate plating are used for electrolytic copper plating performed after development, and high-slow solder plating is often used for solder plating. The photopolymerizable resin composition of the present invention has extremely excellent resist performance for wiring processing of metal laminates, particularly for wiring processing of copper-clad laminates used in printed wiring boards. It is suitable for wiring processing that requires high density. Hereinafter, the present invention will be explained in more detail with reference to Examples, in which parts represent parts by weight. Examples 1 to 6, Comparative Example 1 A photosensitive resin composition having the following composition was applied on a glass/epoxy copper-clad laminate: 100 parts of polymethyl methacrylate (molecular weight (M _N )=60000) 50 parts of pentaerythritol triacrylate Benzophenone 1〃 Michler's Ketone 0.2〃 Hydroquinone 0.05〃 Malachite Green 0.1〃 Methyl Ethyl Ketone 150〃 Lofin Apply the changing amount with a doctor knife, dry it and diffuse the methyl ethyl ketone to increase the thickness of the photoresist.
It was set to 50 μm. A 25 μm thick polyethylene film was laminated on top of this as a protective film, and the artwork was then placed in close contact with the film and exposed to light using an ultra-high pressure mercury lamp. Artwork is 50μm, 60μm, 80μm,
A 100 μm line and space pattern was used. The ultra-high pressure mercury lamp used for exposure was manufactured by Ushio Inc.
The exposure intensity at this ^time was measured using an ultraviolet intensity meter UIT manufactured by Ushio Inc.
Attach the UVD-365P receiver to the -100 and measure.
2mw/ ^cm2 constant. After exposure, the protective film was left for 20 minutes and developed in a DuPont "C" processor containing 1,1,1-trichloroethane. The temperature is kept at 18-20℃, and the passing speed is 200cm/
minutes, and the spray pressure was adjusted to 1.4 Kg/cm ² . The developed product was then immersed in a neutral detergent aqueous solution at room temperature for about 1 minute, degreased, sprayed with water in an overflow tank for about 1 minute, and then washed with water in an overflow tank for about 1 minute.
1 in an aqueous solution of ammonium persulfate at a concentration of 20% by weight.
Soaked for minutes. Subsequently, spray washing was performed again for about 1 minute, followed by immersion in an approximately 15% sulfuric acid aqueous solution for 1 minute, and spray washing was performed again for 1 minute. Next, copper pyrophosphate plating tank (PH=8.2~8.4,
Plating was carried out at 2.7 A/dm ² for 45 minutes at a temperature of 50±2° C.). After plating, immediately wash with water, immerse in 15% boric acid aqueous solution, and then use the following composition: Tin 15g (per solder plating solution) Lead 10g ( ) Free boric acid 400g ( ) Free boric acid 21.6g ( ) ) Solder plating was carried out in a high-slow solder plating bath with 5.2 g peptone ( ) at 1.5 A/dm ² at room temperature. After finishing plating, it was washed with water and dried. In order to observe the development of the plating product, a sample was cut out and the cross section of the resist was observed using an optical microscope. The results are shown in Table 1. Examples 2 to 8 Changing the additive lofin to benzotriazole,
Plating was performed in the same manner as in Example 1, except that the amount used and the exposure amount were as shown in Table 1, and the performance was evaluated. The results obtained are shown in Table 1. 【table】

Claims (1)

[Scope of Claims] 1 (a) Thermoplastic polymer for binder (b) Crosslinkable monomer having at least one ethylenically unsaturated group in the molecule (c) Photopolymerization initiator and (d) Lofin A photopolymerizable resin composition consisting of: