JPH03235395A - Manufacture of copper through hole printed wiring board - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process of the little wiring board and to contrive to shorten the treating time for the wiring board by a method wherein an etching resist film made of a compound, such as 2-alkyl benzimidazole, is formed on the surface of the copper of a negative circuit pattern. CONSTITUTION:A negative resist film soluble in an alkaline and water-soluble liquid is formed by a printing method or a photograph method, then, is dipped in a solution, in which one or more kinds of a compound or compounds shown by Formula I and Formula II (In the formulas, R1 shows an alkyl group of 3 to 17 C, R2 to R4 show a lower alkyl group, (n) shows 0 to 2 and HA shows an organic or inorganic acid) is/are mixed, and an etching resist film consisting of a compound, such as 2-alkylbenzimidazole, 2-alkyl-alkylbenzimidazole, 2- phenylbenimidazole, 2-phenyl-alkylbenzimiazole or the like, is formed on the surface of copper. Subsequently, an obtained copper-clad laminated sheet is dried and after that, the sheet is brought into contact with an alkaline aqueous solution to remove the negative resist film and is treated with an alkaline etching liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) Conventional methods for manufacturing copper through-hole printed wiring boards have had many problems.

The present invention aims to provide a new manufacturing method that solves these problems.

Accordingly, the present invention provides the printed wiring board manufacturing industry with a method for manufacturing copper through-hole printed wiring boards in a short period of time, at low cost, and with high reliability.

(Prior Art) Methods for manufacturing copper through-hole printed wiring boards are broadly classified into hole drilling method, tenting method, and solder stripping method.

In the hole drilling method, a large number of holes are drilled at necessary locations in a double-sided steel clad laminate, and the board having the large number of holes is plated with chemical steel and then with electrical steel. After that, all the holes are filled with plugging ink to prevent the etching liquid from entering, and after protecting the copper plating inside the holes, the necessary circuits are formed as positive images on both sides of the board by printing or photography, and then etching is performed. By doing so, a copper through-hole wiring board is formed by removing the exposed copper, leaving the portion protected by the etching and plugging ink.

In the tenting method, after drilling, chemical steel plating and electrical steel plating are performed, a dry film is bonded together, a pattern image is exposed, and then etching is performed after development. The copper plating inside the hole is protected by a bonded dry film.

In the solder stripping method, the process up to electrical steel plating is as follows:
This is the same as the above two methods, but the difference is that the necessary circuits are formed by printing or photographing negative images.

This negative circuit is not an etching resist but a plating resist for the electrical solder plating to be performed later. Of course, this method does not require the use of filler ink. The necessary circuits are formed on the printed wiring board using negative images, and the areas other than the exposed copper are protected with a plating resist film. Next, electrical solder plating is performed on this exposed portion, and then the plating resist film is removed. A copper through-hole wiring board is then formed by removing the exposed copper, leaving the portions protected by solder.

(Problems to be Solved by the Invention) The above manufacturing method has drawbacks such as poor reliability of the etching resist film, easy production defects, low productivity, and high manufacturing cost.

In particular, recently there has been a demand to provide large quantities of products at low prices with short delivery times, making it difficult to meet these demands. Furthermore, the solder plating method has the disadvantage of causing pollution due to the hydrofluoric acid and lead used in the process, and requires a large amount of money to take measures to prevent pollution. In other words, it is a method for manufacturing copper through-hole wiring boards that has a reliability equivalent to or higher than that of the solder stripping method.The process is simple, requires only a short processing time, is inexpensive, and is also effective in preventing pollution and wastewater treatment. There has been a strong desire to develop a simple method.

(Means for Solving the Problems) As a means for solving the problems, the inventor searched for a substance that is cheaper, safer, and easier to remove than solder.

Of course, the material must be resistant to etching and protect the copper plated areas from the etching solution. In addition, since it is desired that the substance selectively form a film only on the steel surface, we focused on substances that react with steel, and as a result of intensive research, we finally found 2-alkylbenzimidazole, 2-alkylbenzimidazole,
It has been found that -alkyl-alkylbenzimidazole, 2-phenylbenzimidazole, and 2-phenylalkylbenzimidazole solve these problems all at once.

The method of the present invention involves chemical steel plating, electrical steel plating, followed by resist ink soluble in alkaline aqueous solution, alkaline phenomenon type liquid resist, or alkaline phenomenon type photosensitive film to form a negative circuit on a steel clad laminate. Then, as an active ingredient, a compound general formula represented by the following general formulas (I) and (n) (wherein R1 is an alkyl group having 3 to 17 carbon atoms, R2
is a lower alkyl group, n is 0 to 2 HA is an organic or inorganic acid).

(However, in the formula, R3 and R4 are lower alkyl groups, and n is 0 to 2
, HA indicates an organic or inorganic acid).

Compounds such as 2-alkylbenzimidazole, 2-alkyl-alkylbenzimidazole, 2-phenylbenzimidazole, 2-phenyl-alkylbenzimidazole, etc. are applied to the copper surface by immersing it in a solution of one type or a mixture of two or more types. After drying the steel clad laminate thus obtained, the photosensitive film or resist film is removed by contacting it with an alkaline aqueous solution and then treated with an alkaline etching solution to achieve the above purpose. We have found that this can be achieved satisfactorily and have completed the present invention.

Compounds suitable for the practice of the invention are 2-n-propyl-benzimidazole, 2-n-propyl-methylbenzimidazole, 2-n-propyl-dimethylbenzimidazole, 2-n-butyl-benzimidazole, 2-n-
-butyl-methylbenzimidazole, 2-n-butyl-dimethylbenzimidazole, 2-n-pentyl-benzimidazole, 2-n-pentyl-methylbenzimidazole, 2-n-pentyl-dimethylbenzimidazole, 2-n- xyl-benzimidazole, 2-n
-hexyl-methylbenzimidazole, 2-n-hexyl-dimethylbenzimidazole, 2-n-hebutyl-benzimidazole, 2-n-hebutyl-methylbenzimidazole, 2-n-heptyl-dimethylbenzimidazole, 2 -n-octyl-benzimidazole,
2-n-ogutyl-methylbenzimidazole, 2-n
-Octyl-dimethylbenzimidazole, 2-n-
Nonyl-benzimidazole, 2-n-nonyl-methylbenzimidazole, 2-n-nonyl-dimethylbenzimidazole, 2-n-decyl-benzimidazole,
2-n-decyl-methylbenzimidazole, 2-n-
Decyl-dimethylbenzimidazole, 2-n-undecyl-benzimidazole, 2-n-undecyl-methylbenzimidazole, 2-n-undecyl-dimethylbenzimidazole, 2-n-dodecyl-benzimidazole, 2-n-dodecyl- Methylbenzimidazole, 2-n-dodecyl-dimethylbenzimidazole, 2-n-tridecyl-benzimidazole, 2-n
-tridecyl-methylbenzimidazole, 2-n-tridecyl-dimethylbenzimidazole, 2-n-tetradecyl-benzimidazole, 2-n-tetradecyl-methylbenzimidazole, 2-n-tetradecyl-dimethylbenzimidazole, 2-n- Pentadecyl-benzimidazole, 2-n-pentadecyl-methylbenzimidazole, 2-n-pentadecyl-dimethylbenzimidazole, 2-n-hexadecyl-benzimidazole, 2-n-hexadecyl-methylbenzimidazole, 2-n-hexadecyl- Dimethylbenzimidazole, 2-n-heptadecyl-benzimidazole, 2-n-heptadecyl-methylbenzimidazole,
2-n-heptadecyl-dimethylbenzimidazole,
2-isopropyl-benzimidazole, 2-isopropyl-methylbenzimidazole, 2-isopropyl-
Methylbenzimidazole 2-isobutyl-benzimidazole, 2-isobutyl-methylbenzimidazole, 2-isobutyl-dimethylbenzimidazole, 2-
isopentyl-benzimidazole 2-isopentyl-
Methylbenzimidazole, 2-isopentyl-dimethylbenzimidazole, 2-isohexyl-henreimidazole, 2-isohexyl-methylbenzimidazole, 2-isohexyl-dimethylbenzimidazole,
2-neopentyl-benzimidazole, 2-neopentyl-methylbenzimidazole, 2-neopentyl-
Dimethylbenzimidazole, 2-sec-butyl-benzimidazole, 2-sec-butyl-methylbenzimidazole, 2-8ec-butyl-dimethylbenzimidazole 2-tert-butyl-benzimidazole, '2-tert-butyl-methylbenz Imidazole, 2-tert-butyl-dimethylbenzimidazole, 2-phenyl-benzimidazole, 2-phenyl-
Methylbenzimidazole, 2-phenyl-dimethylbenzimidazole, 2-tosyl-benzimidazole,
2-tosyl-methylbenzimidazole, 2-tosyl-
Dimethylbenzimidazole, 2-xylyl-benzimidazole 2-xylyl-methylbenzimidazole 2
-xylyl-dimethylbenzimidazole, 2-mesityl-benzimidazole, 2-mesityl-methylbenzimidazole, 2-mesityl-dimethylbenzimidazole, 2-tert-phenyl-benzimidazole 2-tert-phenyl-methyl It is formed from benzimidazole, 2-tert-phenyl-dimethylbenzimidazole, and organic or inorganic acids. Typical examples of these acids are acetic acid, formic acid, capric acid, glycolic acid, varanitrobenzoic acid, These include paratoluenesulfonic acid, picric acid, oxalic acid, succinic acid, phosphorous acid, maleic acid, acrylic acid, fumaric acid, tartaric acid, adipic acid, hydrochloric acid, sulfuric acid, phosphoric acid, lactic acid, and oleic acid. Also, metal compounds such as acetic acid steel, sulfuric acid steel, cuprous chloride, chlorinated steel, hydroxide steel, oxidized steel, cuprous oxide, cupric oxide, phosphate steel, carbonated steel, or methanol, ethanol. It is also possible to use a mixture of water-soluble solvents such as , isopropyl alcohol butanol, and acetone in any proportion.

Aspects of processing in the present invention will be described. The surface of the copper is polished, degreased, pickled, and washed with water, followed by 2
- 0.01 to 40% of alkylbenzimidazole, 2-alkyl-alkylbenzimidazole, 2-phenylbenzimidazole, 2-phenyl-alkylbenzimidazole or a derivative thereof, preferably 0.1
Immerse in a solution containing ~5% of the above acids necessary to dissolve these derivatives. The temperature range for immersion is 0 to 100"C, but preferably 30 to 50"C.The immersion time can range from several seconds to several tens of minutes, and 40 to 50"C.
At a temperature of 50°C, 1 to 3 minutes is appropriate. 2-alkylbenzimidazole, 2-alkyl-alkylbenzimidazole, 2-phenylbenzimidazole, 2-
Suitable P of phenyl-alkylbenzimidazole solution
H is possible as long as it is acidic, but preferably 5.0 or less. The amount of adhesion increases as the processing temperature increases and the processing time increases. Such 2-alkylbenzimidazole, 2-alkyl-alkylbenzimidazole, 2-phenylbenzimidazole, 2-phenyl-
The present invention is characterized in that it focuses on the fact that the high film-forming ability of alkylbenzimidazole can be fully utilized industrially as a chemically stable etching-resistant resist film.

Note that the method of the present invention can be carried out on both rigid printed wiring boards and flexible printed wiring boards.

The present invention will be specifically explained below with reference to Examples.

Example 1 Holes were drilled in a FR-4 double-sided steel clad laminate with a thickness of 1 and 6 m/m, and steel plating with a thickness of 25 to 30 μm was formed inside the hole and on both sides by chemical steel plating and then electroplating. I let it happen. Next, a resist ink containing acrylic acid and styrene copolymer as main components (trade name: rKM-10J, manufactured by Taiyo Ink Manufacturing Co., Ltd.) was screen printed to form a negative resist film with a thickness of about 20μ, and heated at a temperature of 80°C. It was dried for 10 minutes. In addition, a photosensitive film (product name: rA-225J manufactured by Fuji Hunt Co., Ltd.) was laminated, exposed, and developed to a film of 25 μm.
A negative resist film was formed. A steel clad laminate on which a negative circuit has been formed using the above printing method or photographic method is immersed in a 20% sodium persulfate aqueous solution for 30 seconds to soft etch the copper surface, and then 2-alkylbenzimidazole or 2-alkyl- The copper clad laminate was immersed in a 1% solution of alkylbenzimidazole and treated at a temperature of 50° C. for 3 minutes with slow movements. After that, the copper clad laminate was washed with water for 140 minutes.
An etching resist film was formed by drying at °C for 10 minutes. Next, the negative resist film was removed with a 3% aqueous sodium hydroxide solution to expose the copper in areas that did not need to be left as a circuit, and then an alkaline etching agent (trade name "A Process" manufactured by Melchilag Co., Ltd.) was used. So, liquid temperature 5
Etching was carried out by passing the steel clad laminate for 120 seconds during spraying at 0°C. After that, 5% steel clad laminate
The etching resist film was dissolved and removed by immersion in a hydrochloric acid aqueous solution to produce a copper through-hole printed wiring board.

The test results are shown in Table 1.

Example 2 A hole was drilled in a FR-4 double-sided steel clad laminate with a thickness of 1 or 6 m/m, and then chemical steel plating was applied, followed by electrical steel plating, thereby forming a 25-30μ thick copper plating inside the hole and on both sides. was formed.

Next, a resist ink containing acrylic acid and styrene copolymer as main components (trade name: rKM-10, manufactured by Taiyo Ink Manufacturing Co., Ltd.) was screen printed to form a negative resist film with a thickness of about 20 μm. Dry at temperature for 10 minutes. In addition, a photosensitive film (trade name "A-225" manufactured by Fuji Hunt Co., Ltd.) was laminated, exposed, and developed to a 25μ film.
A negative resist film was formed. Furthermore, the copper-clad laminate on which a negative circuit was formed using the above printing method was immersed in a 20% sodium persulfate aqueous solution for 30 seconds to soft-etch the steel surface, and then 2-phenylbenzimitazole or A steel clad laminate was immersed in a 1% solution of 2-phenyl-alkylbenzimidazole and rotated slowly at 50°.
It was treated for 3 minutes at a temperature of C. Thereafter, the steel clad laminate was washed with water and dried at 140°C for 10 minutes to form an etching resist film. Then, with 3% sodium hydroxide aqueous solution,
The negative resist film was removed to expose copper in areas that did not need to remain as a circuit. Next, using an alkaline etching agent (trade name "A Process" manufactured by Melchilag Co., Ltd.), the steel clad laminate was etched at a temperature of 50"C while spraying.
Etching was performed by passing the film for a second. Thereafter, the steel clad laminate was immersed in a 5% aqueous hydrochloric acid solution to dissolve and remove the etching resist film to produce a steel through-hole wiring board.

The test results are shown in Table 2.

(Effects of the Invention) The manufacturing method of the present invention improves productivity, reduces productivity costs, reduces harmful substances in wastewater, and is particularly effective in manufacturing copper through-hole printed wiring boards with high reliability. It is effective and vines.

Claims (1)

[Claims] A negative resist film soluble in an alkaline aqueous liquid is formed by a printing method or a photographic method, and then a general compound represented by the following general formulas (I) and (II) is used as an active ingredient. Formula▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (However, in the formula, R_1 is an alkyl group having 3 to 17 carbon atoms, R
_2 is a lower alkyl group, n is 0 to 2, and HA is an organic or inorganic acid). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (However, in the formula, R_3 and R_4 are lower alkyl groups, and n is 0.
~2, HA represents an organic or inorganic acid). Compounds such as 2-alkylbenzimidazole, 2-alkyl-alkylbenzimidazole, 2-phenylbenzimidazole, 2-phenyl-alkylbenzimidazole, etc. are applied to the copper surface by immersing it in a solution of one type or a mixture of two or more types. Copper through-hole wiring characterized in that an etching resist film is formed, the copper-clad laminate thus obtained is dried, and then brought into contact with an alkaline aqueous solution to remove the negative resist film and treated with an alkaline etching solution. Method of manufacturing the board.