JPH0336422B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention particularly relates to a photopolymerizable resin composition used for forming an alkali-developable dry film resist for printed wiring boards. [Prior Art] A binder resin used in an alkaline-developable dry film resist must be soluble or swellable in a dilute alkaline aqueous solution and insoluble in water. As such a binder resin, a vinyl addition polymer containing a carboxylic acid group has conventionally been used. In particular, in commercially available alkali-developable resists, the content of carboxylic acid groups as copolymerized components is the minimum amount necessary to develop and resolve fine patterns, and furthermore, in addition to vinyl monomers containing carboxylic acid groups, the content of carboxylic acid groups is the minimum amount required to develop and resolve fine patterns. By selecting the copolymer components, the binder resin is designed to have low solubility in aqueous alkaline solutions. When such a resist is immersed in a stripping solution consisting of an alkaline aqueous solution alone in a stripping process after exposure, the cured resist swells and is stripped off while retaining the pattern form without forming into small pieces. For this reason, there were problems such as the peeled material getting wrapped around the conveyor roll in the peeling machine, and the cured resist sandwiched between the lower parts of the overhanging plating being difficult to peel off. Therefore, as a stripping solution, for example, a 5% aqueous sodium hydroxide solution to which an organic solvent such as butyl cellosolve is added is used to partially dissolve and strip the hardened resist. Use of such a peeling process increases the cost of chemicals, which is a cause of increased costs for manufacturing printed wiring boards. [Problems to be Solved by the Invention] The present invention overcomes the problems of the prior art as described above, and enables development using an alkaline aqueous solution alone.
Moreover, to provide a photopolymerizable resin composition capable of producing an all-alkaline dry film resist that causes fragmentation and peeling in which peeled pieces break into small pieces, similar to conventional solvent-developed resists, by using an alkaline aqueous solution alone during peeling. There is a particular thing. [Means for Solving the Problems] The photopolymerizable resin composition according to the present invention is (A) a copolymer of methyl methacrylate, methyl altalate, and methacrylic acid, and has 20 to 50 methacrylic acid units. Binder resin containing 5 to 60% by weight of methyl acrylate units (B), a crosslinkable monomer (C) having at least two ethylenically unsaturated groups in the molecule, a photopolymerization initiator, and (D ) 0.005 for the total amount of components (A), (B), and (C) above.
Consisting of ~1% by weight of 5-aminotetrazole. The binder resin constituting the composition of the present invention is a copolymer obtained by polymerizing a monomer mixture of methyl methacrylate, methyl acrylate, and acrylic acid. The content of methacrylic acid units in the copolymer is preferably 15 to 50% by weight, particularly 20 to 50% by weight. If a binder resin with a methacrylic acid unit content of less than 15% by weight is used, the cured resist will swell and peel off during peeling.
If it exceeds 50% by weight, the development time will be extremely short.
It becomes difficult to control development when obtaining a high-resolution pattern, and the water resistance of the cured portion also decreases. The content of methyl acrylate units in the copolymer is preferably 2 to 70% by weight, particularly 5 to 60% by weight. If the content of methyl acrylate monomer units is less than 2% by weight, the film becomes hard when it becomes an oxidized resist and is likely to peel off. Moreover, if it exceeds 70% by weight, the development time will be shortened, making it difficult to control the development when obtaining a high-resolution pattern. The weight average molecular weight of the binder resin used in the present invention is in the range of 40,000 to 300,000.
If the weight average molecular weight is less than 40,000, when it is wound into a roll as a dry film resist and stored, the resist composition oozes out from between the support films over time, which is called cold flow development, and the weight average molecular weight is less than 300,000. If it exceeds the range, unexposed areas will not be dissolved and development will not be possible, or development will take an extremely long time, resulting in a decrease in resolution and failure to cause crushing and peeling during peeling. Examples of the crosslinkable monomer having at least two ethylenically unsaturated groups in the molecule constituting the composition of the present invention include polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3 -Butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate In addition to polyester (meth)acrylates such as , pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate, epoxy(meth)acrylates, urethane(meth)acrylates, etc. may be mentioned. These may be used alone or in combination of two or more. The blending amount of the crosslinkable monomer is in the range of 10 to 150 parts by weight based on 100 parts by weight of the binder resin. If the amount is 150 parts by weight or more, the composition may not be applied uniformly, migration may occur in the resist layer after drying, or cold flow development may occur. On the other hand, if it is less than 10 parts by weight, the exposed areas of the resist will be rapidly dissolved in the developer, making development impossible. Examples of the photopolymerization initiator constituting the composition of the present invention include benzoin, benzoin alkyl ethers, benzophenone, Michler's ketone,
Examples include 4,4'-bis(diethylamino)benzophenone, acetophenones, benzyl ketals, anthraquinones, and thioxanthone. These may be used alone or in combination. The amount of photopolymerization initiator used is based on the crosslinkable monomer (B).
A range of 0.1 to 30% by weight is desirable. Furthermore, 5-aminotetrazole used in the present invention is an extremely effective component for improving the adhesion of photoresists to metal plates. The amount of this compound to be added to the composition cannot be absolutely determined depending on the composition components and composition ratio of the photoresist and the hardness of the photoresist after photocuring, but the amount to obtain an effective adhesion effect is determined by the binder. 0.005 to 1% by weight, preferably 0.025 to 0.5% by weight based on the total amount of resin (A), crosslinkable monomer (B) and photoinitiator (C)
is within the range of If it's too much, the sensitivity will decrease, and if it's too little, plating will likely occur during solder plating. The compositions of the invention can also be used in the absence of a diluting solvent, but solvents which dissolve the binder resin and whose boiling point is not very high, such as methyl ethyl ketone, methylene chloride, methylene chloride/methyl alcohol mixtures, isopropyl alcohol or isopropyl It is desirable to use a mixture with other solvents containing alcohol as the main component. The amount of the solvent used is 200% by weight or less, preferably 100 to 200% by weight, based on the composition. When the composition of the present invention is used in the presence of a solvent, the solvent is added to the composition, or the binder resin is produced by solution polymerization using the above-mentioned solvent, or the solvent is further added to the composition. A method of additional addition can be adopted. When using a solution-polymerized binder resin, the solvent is preferably isopropyl alcohol or a mixed solvent of 80% by weight or more of isopropyl alcohol and 20% by weight or less of methylene chloride, methyl ethyl ketone, or the like. The composition of the present invention may also contain components such as thermal polymerization inhibitors, dyes, plasticizers, and fillers, if necessary. To form a dry film resist using the composition of the present invention, the composition is applied onto a support and, if a solvent is used, the solvent is spattered off. To apply the composition to the support, a blade coater, rod coater, knife coater, roll doctor coater, comma coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, curtain coater, etc. can be used. These selections are determined by coating weight, coating liquid viscosity, coating speed, etc. As the support, a plastic film such as polyester is mainly used. When using a flammable solvent, use a dryer equipped with an air-heating heat source using steam for safety reasons, and use a method that brings the hot air inside the dryer into countercurrent contact and blows it onto the support from a nozzle. method etc. are used. The shape of the dryer can be selected depending on the purpose, such as an arch type or a flat type. If necessary, the dry film after drying may be laminated with a protective film such as polyethylene or polypropylene. The dry film resist produced as described above can be used as an etching resist or a plating resist, and has excellent storage stability, workability, and process passability, and can provide a high-resolution pattern. [Example] The present invention will be specifically described below with reference to Examples. Examples 1 to 8, Comparative Examples 1 to 4 Into a 1000 ml four-neck flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, 200 g of isopropyl alcohol and a monomer of the composition shown in Table 1 were added under a nitrogen atmosphere. Add 200g of the liquid and raise the temperature of the water bath to 80℃ while stirring. Next, 1.0 g of azobisisobutyronitrile dissolved in 10 g of isopropyl alcohol was added and polymerized for 4 hours. Next, 1.0 g of azobisisobutyronitrile was added to 10
Dissolve in 30 g of isopropyl alcohol and add 30
After adding the mixture in 5 portions at intervals, the internal temperature of the flask was raised to the boiling point of isopropyl alcohol, and polymerization was carried out at that temperature for 2 hours. After the polymerization was completed, 100 g of isopropyl alcohol was added and the polymerization reaction product was taken out from the flask to prepare a binder resin solution. The polymerization rate of the monomer mixture in each composition was 99.5% or more. Next, a photopolymerizable resin composition having the following composition was prepared using these binder resin solutions. Binder resin solution 228 parts by weight Trimethylolpropane triacrylate
50 〃 Tetraethylene glycol diacrylate
20 〃 Benzophenone 1.0 〃 Michler's ketone 0.2 〃 5-aminotetrazole 0.4 〃 Methylene blue 0.75 〃 The prepared composition was stirred with a propeller type mixer and coated with a blade coater to a thickness of 25 μm and a width of 360 μm.
It was applied to a coating width of 340 mm on a 340 mm polyester film. Next, hot air was sent in a countercurrent flow through a Kratz-type dryer with a width of 400 mm, a height of 100 mm, and a length of 8 m to give a dry coating thickness of 50 μm. The coating speed at this time was 5 m/min, the air speed in the dryer was 3 m/min, and the hot air temperature was 90°C. Next, a polyethylene protective film having a thickness of 35 μm was laminated onto the dried coating film, and the film was then wound onto a roll. The obtained dry film resist was heat laminated with the coated film surface on a copper clad laminate while peeling off the protective film.
After the temperature of the copper-clad laminate returned to room temperature, a photo tool was brought into close contact with the surface of the polyester film, and the film was exposed to light using an ultra-high pressure mercury lamp. Photo tools are 50μm, 60μm,
Line and space patterns with widths of 80 μm and 100 μm were used. In addition, ultra-high pressure mercury lamps are manufactured by Ushio Inc.
Irradiation was performed at 100 mJ/cm ² using USH-102D. The exposure intensity at this time was determined by the Ushio Inc. ultraviolet intensity meter UIT.
Attach the UVD-365P receiver to the -100 and measure.
It was set to 5mw/ ^cm2 . After exposure, the support film was left for 20 minutes and developed with a 1% aqueous sodium carbonate solution. Developing temperature: 30℃, spray pressure: 1.4Kg/cm ²
The distance between the spray and the substrate was 10 cm. 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 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 for 1 minute. Then, it was placed in a copper sulfate plating tank and plated at 2.3 A/dm ² for 75 minutes. The temperature at this time was 22°C. Immediately after plating, rinse with water, immerse in 15% borofluoric acid aqueous solution, and then soak for 18 minutes.
High-slow solder plating was performed at 1.8 A/dm ² and 22°C. The composition of the solder polishing liquid is as follows. Tin 15 g / Lead 10 g / Free borofluoric acid 400 g / Free boric acid 21.6 g / Peptone 5.2 g / After plating, it was washed with water and then dried. Table 1 shows the developability and plating resistance of dry film.
It was shown to. Using the sample after solder plating, the resist was removed with a 5% aqueous sodium hydroxide solution. Peeling is 55
The stripping solution was adjusted to a temperature of .degree. C., the spray pressure was 1.0 Kg/ ^cm.sup.2, and the distance between the spray and the substrate was 10 cm. The state of peeling at this time was visually observed. The results are also shown in Table 1.

【table】

[Table] Examples 9 to 15, Comparative Examples 5 and 6 Using the system of Example 3, the amount of 5-aminotetrazole added was varied as shown in Table 2, and the state of the resist after plating was evaluated.

[Table] Comparative Examples 7, 8 Using the system of Example 3, using 1-phenyltetrazole (Comparative Example 7) or 5-phenyltetrazole (Comparative Example 8) instead of 5-aminotetrazole,
The state of the resist after plating was evaluated. The results obtained are shown in Table 3.

〔Effect of the invention〕

The dry film resist made from the photopolymerizable composition of the present invention can be peeled off using an alkaline aqueous solution alone.For this reason, conventionally, a solvent such as butyl cellosolve is added to an alkaline aqueous solution to partially dissolve the peeled pieces. It is possible to eliminate the increase in printed circuit board production costs that would otherwise be caused by adding additives.

Claims (1)

[Scope of Claims] 1 (A) A copolymer of methyl methacrylate, methyl acrylate and methacrylic acid, containing 20 to 50% by weight of methacrylic acid units and 5 to 60% by weight of methyl acrylate units. Binder resin (B) Crosslinkable monomer having at least two ethylenically unsaturated groups in the molecule (C) Photopolymerization initiator and (D) The above components (A), (B), and (C) 0.005 for total amount
A photopolymerizable resin composition comprising ~1% by weight of 5-aminotetrazole.