JPH04159794A - Manufacture of copper through hole printed wiring board - Google Patents

Abstract

PURPOSE:To inexpensively manufacture a highly reliable copper-through hole printed wiring board in a short processing time by bringing a copper-coated laminated plate into contact with an alkaline etching liquid after the laminated plate is dried by heating and a negative pattern film is removed from the surface of the laminated plate, and then, removing an etching resist film. CONSTITUTION:After a required negative pattern is formed on the surface of a copper-coated laminated plate by using a resist soluble in an alkaline aqueous solution, an etching resist film composed of a 2-(alkyl thio) bezimidazole compound is formed on the copper surface of the laminated plate by bringing the laminated plate into contact with an aqueous solution containing the compound. Then, after the laminated body is dried by heating and the negative pattern film is removed from the surface of the laminated plate, the etching resist film is removed by bringing the laminated plate into contact with an alkaline etching liquid. Therefore, an inexpensive copper-through hole printed wiring board which is extremely low in fraction defective and high in reliability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for manufacturing copper through-hole printed wiring boards, particularly for manufacturing high-density printed wiring boards in a short period of time, at low cost, and with good reliability. be.

BACKGROUND OF THE INVENTION The most widely used method for manufacturing copper through-hole printed wiring boards in the past is the filling method. In this method, the through ball is filled with packing ink to protect the holes, and then an etching resist is printed.During the process, the solvent of the filling ink evaporates, causing the filling ink to shrink. Therefore, there is a risk that the etching liquid may enter the hole and damage the copper plating inside the through ball.Also, due to shrinkage, the thickness of the filling ink tends to become thinner than the thickness of the board, which may cause the contact between the board and the hole. Since the copper plating on the corners easily melts and causes a so-called edge breakage phenomenon, it has not been possible to provide a highly reliable product.

Furthermore, the electrolytic solder plating method (solder through ball method) is known as a method for obtaining highly reliable products, but while this method can provide more reliable products than the plugging method, it is difficult to manufacture. There were disadvantages such as it took a lot of time and cost 1 was high.

Japanese Patent Publication No. 50 27033 and 51-18896 discloses that a solution containing an imidazole compound or a salt thereof having a long-chain alkyl group at the 2-position is directly printed on the surface of a copper-clad laminate by silk screen printing, and then air-dried. A method for manufacturing a printed wiring board is disclosed in which a positive etching resist film is formed and unnecessary copper parts are removed by immersing it in an acidic etching solution. Because it is a sexual substance,
When it comes into contact with an acidic etching solution, a part of it is eluted, etching parts that should be protected as circuits, resulting in many defective products.When manufacturing copper through-hole printed wiring boards, a separate process is required. This method requires the troublesome work of coating the surface of a small copper-plated through hole with a solution containing an imidazole compound or its salt, which is difficult to implement industrially.

As a manufacturing method for copper through-hole printed wiring boards that solves these problems, Japanese Patent Publication No. Sho 64'-1954 discloses that an aqueous solution containing a salt of an alkylimidazole compound is applied to the surface of a copper-clad laminate on which a negative pattern has been formed. An etching resist I/film made of an alkyl-6-imidazole compound is formed on the copper surface of the copper-clad laminate by contacting it, and then the copper-clad laminate is heated and dried, the negative pattern is removed, and alkaline etching is performed. A method of contacting a liquid is disclosed.

However, when manufacturing copper through-hole prints 1 to wiring boards with a high-density pattern of three or more pins by this method, the alkylimidazole compound film does not have sufficient brine properties. When drying by heating after forming a chemical conversion film, water droplets tend to adhere to and remain on the copper surface on which the film has been formed, and as a result, the chemical conversion film dissolves in the early stage of drying, resulting in thinner etching resist films in some areas. This sometimes causes wire breaks or dents in the circuit.

In addition, when a negative pattern is formed using a dry film (hereinafter referred to as DFR), when removing the negative pattern, which has a film of an alkylimidazole compound formed on the copper surface, it is likely that the DFR will remain peeled off. It was necessary to extend the peeling time.

In the temporary production of copper through-hole printed wiring in high-density patterns, it is easy for chemical conversion coatings to remain peeled off in small diameter holes such as through balls for hire holes with a diameter of 0.3 mm or less, resulting in an extension of the peeling time and a problem with the peeling process. It was necessary to increase the temperature of the solution and increase the concentration of the stripping solution.

Problems to be Solved by the Invention Recently, as the density of printed wiring boards has progressed, conventional filling methods and solder plating methods have problems in terms of reliability and cost, and the method using the above-mentioned alkylimidazole compound The method has a low manufacturing cost and can provide a highly reliable printed wiring board in the case of a pattern of low or medium density, but it is not yet possible to obtain sufficient reliability in the case of a pattern of high density.

In order to manufacture such high-density printed wiring boards,
It is desired to develop a method that can maintain high reliability equivalent to or better than the currently used methods such as filling method, solder paste method, etc., has a short processing time, and has a low manufacturing cost. .

Means to Solve the Problem The inventors of the present invention have conducted intensive research in view of the above circumstances, and have found that in order to manufacture high-density copper through-hole print I/wiring boards, a resist soluble in an alkaline aqueous solution is required. is used to form a necessary negative pattern on the surface of the copper-clad laminate, and then the copper-clad laminate is brought into contact with an aqueous solution containing a 2-alkylthio)benzimidazole compound to form the necessary negative pattern on the copper surface of the copper-clad laminate. - forming an etching resist I film made of an alkylthio)benzimidazole compound, heating and drying the copper clad laminate to remove the negative pattern film on the surface of the copper clad laminate, and then contacting it with an alkaline etching solution;
It was discovered that the intended purpose could be achieved by peeling off the etching resist film, and the present invention was completed.

Typical 2-(
As the alkylthio)-, nizimidazole compounds, 2-(propylthio)benzimidazole represented by
2-(Butylthio)benzimidazole, 2-(pentylthio)benzimidazole, 2-(hexylthio)benzimidazole, 2-(heptylthio)benzimidazole, 2-(octylthio)benzimidazole, 2
- (nonylthio)benzimidazole, 2-(undecylthio)benzimidazole and 2-(hepcudecyldio)benzimidazole, 2-(propylthio)-5-methylbe represented by the general formula = 10
- zuimidazole, 2-(propylthio)-4,5-dimethylbenzimidazole, 2-(butylthio)-5-
Chlorobenzimidazole, 2-(butylthio)-5
-Nitrobenzimidazole, 2-(pentylthio)-
4-methylbenzimidazole, 2-(pentylthio)
-5-methylbenzimidazole, 2-(pentylthio) -5,6-cyclopenzimidazole, 2-(
hexylthio)-5,6-dimethylbenzimidazole, 2-(hexylthio)-5-diI-lovenzimidazole, 2-(heptylthio)-4-methylbenzimidazole, 2-(heptylthio)-5-methylbenzimidazole, 2-(heptylthio)-5-chlorobenzimidazole, 2-(octylthio)-5,6-cyclopenzimidazole, 2-(octylthio)-5
-chlorobenzimidazole, 2 (nonylthio) 4
-Methylbenzimidazole, 2-(nonylthio)-5
-Methylbenzimidazole, 2-(nonylthio)-4
, 5-dimethylbenzimidazole, 2-(nonylthio)-5-nitrohenzimidazole, l-(undecylthio)-4-methylbenzimidazole and 2-(heptadecylthio)-5-methylbenzimidazole and general formula (r) and General formula (II) [However, in the formula, R8 is the same as above. 2-(propylthio)-4-, which is a mixture of compounds represented by
Methylbenzimidazole and 2-(propylthio)-5
- a mixture of methylbenzimidazole, a mixture of 2-(butylthio)-4-methylbenzimidazole and 2-(butylthio)-5-methylbenzimidazole, 2-
(pentylthio)-4-methylbenzimidazole and 2
- a mixture of (pentylthio)-5-methylbenzimidazole, a mixture of 2-(h;
Methylbenzimidazole and 2-(heptylthio)-5
- a mixture of methylbenzimidazole, 2-(octylthio)-4-methyl-, a mixture of nizimidazole and 2-(octylthio)-5-methylbenzimidazole,
A mixture of 2-(nonylthio)-4-methylbenzimidazole and 2-(nonylthio)-5-methylbenzimidazole, a mixture of 2-(undecylthio)-4-methylbenzimidazole and 2-(undecylthio)-5-methylbenzimidazole and a mixture of 2(heptadecylthio)-4-methylbenzimidazole and 2-(heptadecylthio)-5-notylbenzimidazole.

The 2-alkylthio)benzimidazole compound used in the method of the present invention can be synthesized by a known method. That is, a benzimidazole compound and an alkyl halide are added to 2-mercap 1 in an organic solvent such as alcohol or N,N-dimethylformamide in the presence of a dehydrohalogenating agent such as potassium hydroxide or calcium hydroxide. It can be obtained by reacting, and the reaction formula is as follows.

(In the formula, X represents a halogen atom) The 2-mercap I benzimidazole compound, which is a raw material for the 2-alkylthio)benzimidazole compound, can be produced by several methods.

For example, it can be obtained by reacting 0-phenylene diamines and carbon disulfide in the presence of alkali hydroxide, and the reaction formula is as follows.

I At this time, for the purpose of synthesizing a 2-mercaptohenzimidazole compound, 2,3-diaminotoluene and 3,4
-If we use 'II metal ring of diaminotoluene, 4
A mixture of a methyl-2-mercabutohenzimidazole compound and a 5-methyl-2-merkabutobenzimidazole compound is obtained, and this mixture is alkylated without being separated to form 4-medyyl-2-alkylthio. ) Benzimidazole compound and 5-methyl-2-
Mixtures of alkylthio)benzimidazole compounds can be obtained.

When a 2-alkylthio)penzimidazole having an alkyl group with a small number of carbon atoms is used in the practice of the present invention, a part of the chemical conversion film formed on the surface of the copper metal tends to be eluted by washing with water after forming the film. In addition, if a 2-alkylthio)henzimidazole having an alkyl group with a large number of carbon atoms is used, a large amount of organic acid is required to form a treatment solution. are particularly suitable.

In carrying out the method of the present invention, the 2-alkylthio)benzimidazole compound may be added in a proportion of 0.01 to 5%, preferably 0.1 to 2%, based on water.

In carrying out the method of the present invention, since the 2-alkylthio)benzimidazole compound is poorly soluble in water,
A 2-alkylthio)benzimidazole compound may be reacted with an organic or inorganic acid to form a water-soluble salt.

Organic or inorganic acids used in carrying out the method of the invention include formic acid, acetic acid, capric acid, propionic acid,
Glycolic acid, acrylic acid, paranitrobenzoic acid, rose 1 to luene sulfonic acid, picric acid, silicylic acid, oxalic acid, succinic acid, -7leic acid, fumaric acid, tartaric acid, adipic acid, hydrochloric acid, phosphoric acid, lactic acid, oleic acid, phthalic acid It is an acid, etc., and may be added in a range of 0.01 to 40%, preferably 0.2 to 20%, based on water.

Furthermore, in carrying out the method of the present invention, by adding copper ions to the 2-alkylthio)benzimidazole compound, it is possible to promote the formation of a chemical conversion film on the copper surface,
Typical substances that generate copper ions used in this case include copper powder, cuprous chloride, cupric chloride, copper hydroxide,
These include copper phosphorus, copper acetate, copper sulfate, copper nitrate, and copper bromide.

In this case, it is desirable to stabilize the pH of the solution by adding a buffering substance such as ammonia or amines, and the amines used in this case include methylamine, dimethylamine, ethylamine, monoethanolamine , jetanolamine, triethanolamine, etc.

An aspect of the treatment for forming a chemical conversion film of a 2=(alkylthio)benzimidazole compound on the copper surface of a copper-clad laminate in the method of the present invention will be described.

The surface of the copper is finished by polishing, degreasing, acid washing, etc., and then immersed in an aqueous solution containing 0.1 to 5%, preferably 0.1 to 2%, of a 2-alkylthio)henzimidazole compound for several seconds to several minutes. . At this time, the temperature of the processing liquid is 0.
-100°C, preferably 30-50°C.

The amount of the 2-alkylthio)benzimidazole compound attached to the copper surface increases as the liquid temperature increases or as the treatment time increases.

In carrying out the method of the invention, usually 2-alkylthio)
A method is adopted in which the copper-clad laminate is immersed in an aqueous solution containing a benzimidazole compound, but the method is not particularly limited to this, and any contact method may be used, such as flowing a treatment liquid along the copper-clad laminate. Other methods are also possible.

In addition, in order to bring the copper surface of the copper clad laminate into sufficient contact with the treatment solution, it is preferable to vibrate the copper clad laminate in the treatment solution or to stir the treatment solution, and also to apply ultrasonic waves. It is also effective to apply vibrations to the treatment solution by causing the copper surface to be exposed to air bubbles.

In carrying out the method of the present invention, a copper-clad laminate is brought into contact with an aqueous solution containing a 2-alkylthio)benzimidazole compound to form a chemical conversion film on the copper surface, which is washed with water and taken out. The coating should be forcibly dried by heating until it turns brown. In this case, the heating conditions are usually 80 to 150°C, preferably several minutes to several tens of minutes, and 80°C or lower. It takes a long time to heat the material, and if the temperature exceeds 150.degree. C., a device that heats the material uniformly in a short period of time is required.

In carrying out the method of the present invention, in order to remove the negative pattern on the surface of a copper-clad laminate, it is convenient to contact it with an aqueous solution containing a strong basic substance such as thorium hydroxide or potassium hydroxide, or alkaline etching. As the liquid, ammonium double salts are generally used, and ammonia-ammonium chloride-copper salts are particularly suitable. Also, 2-
The conversion coating of (alkylthio)henzimidazole is
A-19= Since it is not soluble in an aqueous alkali solution, unnecessary parts of the copper can be easily etched by using an alkaline endender solution.

Effect When copper is brought into contact with an aqueous solution containing a 2-(alkylthio)benzimidazole compound, a complex formation reaction between the 2-(alkylthio)benzimidazole compound and copper, hydrogen bonding between the 2-alkylthio)benzimidazole, and van der Waals forces occur. Both actions result in film growth and ultimately a stable conversion film containing a Hensen ring conjugated to a 2-alkylthio)benzimidazole-copper complex is formed on the copper surface.

Therefore, when a copper-clad laminate is immersed in an aqueous solution containing a 2-alkylthio)benzimidazole compound, a chemical conversion coating of 2-alkylthio)benzimidazole can be easily formed on the copper surface of the through-pole and the circuit portion where the negative pattern is not formed. can be formed.

Furthermore, when the chemical conversion coating of 2-alkylthio)benzimidazole on the copper surface is heated and dried, the 2-alkylthio)-
A certain polymerization reaction occurs in the nizimidazole/copper complex, resulting in a hard chemical conversion film with excellent resisting properties during etching, and the defective rate of the etching agent is significantly reduced.

The chemical conversion film of 2-(alkylthio)benzimidazole on the copper surface forms a dense and uniform film, so it has good water repellency, and after film formation, partial elution is unlikely to occur, resulting in a uniform film. A thick chemical conversion coating is obtained,
Copper circuits are less likely to be dented or disconnected after etching.

In addition, the chemical conversion coating is resistant to deterioration due to heat drying, so
The chemical conversion film after etching can also be easily peeled off using an acidic aqueous solution.

Since 2-(alkylthio)benzimidazole has low basicity, it is difficult to adsorb to DFR used to form a negative pattern, and it is considered that the releasability of DFR does not deteriorate.

Examples 1 to 11 1, 6 mm thick glass epoxy double-sided copper clad laminate [F
R-4, product name: R4705 (manufactured by Matsushita Electric Works)], a small hole is drilled, electroless copper plating is applied, and then electrolytic copper plating is applied 7 times to coat the inside of the hole and both sides with a 20-30μ copper plating. was formed.

Next, alkali-soluble resist ink [product name 2KM-1]
0 (manufactured by Taiyo Ink Manufacturing Co., Ltd.)] by screen printing to form a negative pattern coating film with a thickness of about 20 μm.
It was dried for 10 minutes at a temperature of 'C.

Further, the substrate was immersed in a 5% hydrochloric acid aqueous solution and washed with water to clean the copper surface, and then treated with a treatment solution having the composition shown in Table 1 under the treatment conditions shown in the table. The thickness of the 2-alkylthio)benzimidazole chemical conversion coating deposited on the same surface was as shown in Table 1.

The resist ink on the copper-clad laminate obtained by performing the same treatment as the substrate was removed using a 3% aqueous solution of 1-lium hydroxide, and the resulting board was dried by heating at a temperature of 120° C. for 10 minutes.

Next, an alkaline etching agent [ammonia-ammonium chloride-copper system, specific gravity 1.1-1.2, trade name 2A Gushi! The etching process was carried out by spraying the chemical conversion film on the substrate at a temperature of 50°C using a 3.5% aqueous solution of hydrochloric acid to remove the etching resist film on the circuit. By dissolving and removing it, a copper through-pole wiring board was manufactured.

None of the substrates had any disconnections or dents in the copper circuits.

The thickness of the chemical conversion coating of 2-(argylthio)--nzimidazole can be determined by immersing a test piece of a specified size in a 0.5% aqueous hydrochloric acid solution and measuring the concentration of the dissolved imidazoles using an ultraviolet spectrophotometer. It is measured and converted into the thickness of the chemical conversion film.

-24 - Examples 12 to 17 and Comparative Examples A copper-clad laminate plated with electrolytic copper similar to that used in Example 1 was coated with water-soluble DFR [trade name: Sε5405, (
(manufactured by Mitsubishi Raycon Aji)] to form a high-density negative pattern.

Further, the substrate was immersed in a 5% hydrochloric acid aqueous solution and washed with water to clean the copper surface. After the copper surface was treated with a treatment solution having the composition shown in Table 2 under the treatment conditions shown in the same table, the results were as follows: Water repellency (visual observation), adsorption degree of imidazoles in DFR- (the amount of imidazole on DFR when the amount of imidazole on the copper surface is taken as 100), peeling time of DFR (12
After heating and drying at a temperature of 0°C for 10 minutes, spray a 3% NaOH aqueous solution at a temperature of 50°C to determine the time required to completely remove the coating and the peeling time of the chemical conversion film (10 minutes at a temperature of 120°C). After heating and drying, a 3.5% 11C1 aqueous solution was sprayed at a liquid temperature of 50'C, and the time required for the chemical conversion coating in the small diameter hole of 0.3 mrrlφ to be completely peeled off) is shown in Table 2.
The results were as shown in .

Copper-clad laminates obtained by the same treatment as the above substrate were each heated and dried at a temperature of 120°C for about 10 minutes, and then etched using the same alkaline etching agent as used in Example 1. Thereafter, the substrate was immersed in a 3.5% aqueous hydrochloric acid solution to dissolve and remove the Entin Breath 1 film on the circuit, producing a high-density copper through-pole printed wiring board.

2- None of the boards using (argylthio)benzimidazole caused any disconnections or depressions in the copper circuit, but the board using alkyl imidazole in the comparative example
A dent occurred in some of the copper circuits.

Effects of the Invention According to the method of the present invention, it is possible to manufacture high-density copper through-ball printed wiring boards that are inexpensive, have an extremely low defective rate, and are highly compatible with multiple applications. The effect is remarkable.

Claims (4)

[Claims] (1) A necessary negative pattern is formed on the surface of a copper-clad laminate using a resist soluble in an alkaline aqueous solution, and then the copper-clad laminate is coated with a 2-( The above 2-(
After forming an etching resist film made of an alkylthio)benzimidazole compound, heating and drying the copper-clad laminate, and removing the negative pattern film on the surface of the copper-clad laminate,
A method for manufacturing a copper through-hole printed wiring board, which comprises contacting with an alkaline etching solution and then peeling off an etching resist film. (2) The method according to claim (1), wherein a 2-(alkylthio)benzimidazole compound represented by the following general formula is used. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, in the formula, R_1 represents an alkyl group with 3 or more carbon atoms. (3) The method according to claim (1), which uses a 2-(alkylthio)benzimidazole compound represented by the following general formula. General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, in the formula, R_1 is the same as above, R_2, R_
3 and R_4 represent a lower alkyl group, a halogen atom, a nitro group, or a hydrogen atom, and at least one of them is a lower alkyl group, a halogen atom, or a nitro group. (4) The method according to claim (1) using a mixture of 2-alkylthio)benzimidazole compounds represented by the following general formulas (I) and (II) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [However, R_1 in the formula is the same as above. ] General formula (I
I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [However, R_1 in the formula is the same as above. ]