JPH0451592A - Manufacture of copper through-hole printed wiring board - Google Patents

Abstract

PURPOSE:To maintain high reliablity and to shorten the treatment time by a method wherein a required negative pattern is formed on the surface of a copper-clad laminated board, an etching resist film composed of a specific secondary alkylbenzimidazole compound is formed, this assembly is heated and dried, the negative pattern film is removed and the etching resist film is stripped. CONSTITUTION:A required negative pattern is formed on the surface of a copper-clad laminated board by using a resist which is soluble in an alkali aqueous solution; then, the copper-clad laminated board is brought into contact with an aqueous solution containing a salt of a secondary alkylbenzimidazole compound expressed by the general formula; an etching resist film composed of the secondary alkylbenzimidazole compound is formed on the copper surface of the copper-clad laminated board. Then, the copper-clad laminated board is heated and dried; the negative pattern film on the surface of the copper-clad laminated board is removed; after that, the board is brought into contact with an alkaline etchant; then, the etching resist film is stripped. Thereby, it is possible to manufacture a high-density copper through-hole printed wiring board.

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 with good reliability in a short period of time and at low cost. It is.

BACKGROUND OF THE INVENTION A method for manufacturing copper through-hole printed wiring boards that has been widely used in the past includes a method called a packing method. This method involves filling the through holes with filling ink to protect the holes, and then printing an etching resist.During the process, the solvent of the filling ink evaporates, causing the filling ink to shrink. There is a risk that the etching solution will enter the hole and dissolve the copper plating inside the through hole.
In addition, the thickness of the plugging ink tends to become thinner than the thickness of the substrate due to shrinkage, and the copper plating at the corners of the substrate and the holes tends to dissolve, causing a so-called edge breakage phenomenon, which provides a product with high reliability. I couldn't.

Additionally, the electrolytic solder plating method (solder through-hole 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. This method has drawbacks such as being time consuming and high in cost.

Japanese Patent Publications No. 50-27033 and No. 51-18896 disclose a method in which a solution containing an imidazole compound or its salt 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 on the copper surface and unnecessary body portions are removed by immersing it in an acidic etching solution. Because it is a basic 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.

Japanese Patent Publication No. 64-1954 describes a manufacturing method for copper through-hole printed wiring boards that solves these problems.
An aqueous solution containing a salt of an alkylimidazole compound is brought into contact with the surface of the copper-clad laminate on which a negative pattern has been formed to form an etching resist film made of the alkylimidazole compound on the copper surface of the copper-clad laminate, and then the copper-clad laminate is A method is disclosed in which the plate is heated and dried, the negative pattern is removed, and the plate is brought into contact with an alkaline etching solution.

However, when producing a copper through-hole printed wiring board with a high-density pattern of three or more bins by this method, the water repellency of the alkylimidazole compound film is not sufficient, so a chemical conversion coating of the alkylimidazole compound is used. When drying by heating after formation, water droplets tend to adhere to and remain on the copper surface on which the film is formed (for this reason, the chemical conversion film dissolves in the early stage of drying, resulting in thin areas of the etching resist film). , sometimes causing 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 after forming a film of an alkylimidazole compound on the copper surface, the DFR is likely to remain peeled off, and the peeling time is increased. It needed to be extended.

In the production of copper through-hole printed wiring boards with high-density patterns, chemical conversion coatings tend to remain peeled off in small-diameter holes such as through-holes for via holes with a diameter of 0.3 mm or less, resulting in longer peeling processing times and peeling. It was necessary to increase the temperature of the processing 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 Although it is possible to obtain a printed wiring board with low manufacturing cost and high reliability in the case of a pattern with a low or medium density, sufficient reliability cannot yet be obtained in the case of a pattern with a high density.

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

Means for Solving the Problems In view of the above circumstances, the inventors of the present invention have conducted intensive research and found that in order to manufacture a high-density copper through-hole printed wiring board, a resist that is soluble in an alkaline aqueous solution is used. to form a necessary negative pattern on the surface of the copper-clad laminate, and then bring the copper-clad laminate into contact with an aqueous solution containing a salt of a 2-position alkylbenzimidazole compound represented by the following general formula to form a copper-clad laminate. An etching resist film made of the 2-position alkylbenzimidazole compound is formed on the copper surface of the copper clad laminate, the copper clad laminate is heated and dried to remove the negative pattern film on the surface of the copper clad laminate, and then brought into contact with an alkaline etching solution. They have now found that the intended purpose can be achieved by subsequently peeling off the etching resist film, and have completed the present invention.

Representative examples of the 2-position alkylbenzimidazole compounds used in carrying out the method of the present invention include 2-propylbenzimidazole, 2-butylbenzimidazole, 2-pentylbenzimidazole, 2-hexylbenzimidazole, and 2-hebutylbenzimidazole. There are benzimidazole, 2-octylbenzimidazole, 2-nonylbenzimidazole, 2-decylbenzimidazole, 2-undecylbenzimidazole and their salts, and when benzimidazole having an alkyl group with a small number of carbon atoms is used, copper Part of the chemical conversion film formed on the surface of the metal tends to be eluted by washing with water, and when benzimidazole having an alkyl group with a large number of carbon atoms is used,
Since a large amount of organic or inorganic acid is required to dissolve benzimidazole and produce a treatment solution, 2-pentylbenzimidazole, 2-hexylbenzimidazole, 2-hebutylbenzimidazole, 2-octylbenzimidazole, 2 -nonylbenzimidazole and their salts are particularly preferred.

In carrying out the method of the present invention, the alkylbenzimidazole 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, the alkylbenzimidazole compound is poorly soluble in water, so the alkylbenzimidazole 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, para-nitrobenzoic acid, para-toluenesulfonic acid, picric acid, salicylic acid, oxalic acid,
Succinic acid, maleic acid, fumaric acid, tartaric acid, adipic acid, hydrochloric acid, sulfuric acid, phosphoric acid, lactic acid, oleic acid, phthalic acid, etc., in the range of 0.01 to 15%, preferably 0.2 to 15%, based on water. It may be added at a rate of 5%.

Furthermore, in carrying out the method of the present invention, by adding copper ions to the 2-position alkylbenzimidazole compound, it is possible to promote the formation of a chemical conversion film on the copper surface. Examples include copper powder, cuprous chloride, cupric chloride, copper hydroxide, phosphorus, copper acetate, copper sulfate, copper nitrate, copper bromide, and the like.

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 an alkylbenzimidazole compound on the copper surface of a copper-clad laminate in the method of the present invention will be described.

The copper surface is finished by polishing, degreasing, acid washing, etc., and then 0.01 of a salt of an alkylbenzimidazole compound is applied.
It is immersed in an aqueous solution containing ~5%, preferably 0.1-2%, for several seconds to several minutes. The temperature of the processing liquid at this time is 0 to 10
0°C, preferably 30 to 50°C.

The amount of the alkylbenzimidazole 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 present invention, a method of immersing a copper-clad laminate in an aqueous solution containing a salt of an alkylbenzimidazole compound is usually adopted, but the method is not particularly limited to this, and any contact method can be used, such as A method such as allowing the treatment liquid to flow down along the copper-clad laminate is 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. Applying vibration to the treatment solution is also effective in preventing air bubbles from adhering to the copper surface.

In carrying out the method of the present invention, a copper-clad laminate is brought into contact with an aqueous solution containing a salt of an alkylbenzimidazole compound to form a chemical conversion film on the copper surface, and after being washed with water and taken out, the colorless and transparent chemical conversion film is removed. It should be forcibly dried by heating until it turns brown, and the heating conditions in this case are usually 80℃.
It is desirable to heat for a few minutes to several tens of minutes in the temperature range of ~150°C. If the temperature is below 80°C, it will take a long time to heat, and if it exceeds 150°C, it will be heated uniformly in a short time. Requires equipment to do this.

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 sodium hydroxide or potassium hydroxide, or use an alkaline etching solution. Ammonium double salts are common, and ammonia-ammonium chloride-copper salts are particularly preferred. Furthermore, since the alkylbenzimidazole chemical conversion film on the copper surface is not soluble in an alkaline aqueous solution, unnecessary portions of the copper can be easily etched by using an alkaline etching solution.

When copper is brought into contact with an aqueous solution containing a salt of an alkylbenzimidazole compound, a film grows due to the complex formation reaction between the alkylbenzimidazole compound and copper and the effects of hydrogen bonding between the alkylbenzimidazoles and van der Waals forces. Eventually, a stable chemical conversion film containing a benzene ring conjugated with an alkylbenzimidazole-copper complex is formed on the copper surface.

Therefore, when a copper-clad laminate is immersed in an aqueous solution containing a salt of an alkylbenzimidazole compound, a chemical conversion film of alkylbenzimidazole can be easily formed on the copper surface in the through-hole and the circuit portion where the negative pattern is not formed. can.

Furthermore, when the alkylbenzimidazole chemical conversion film on the copper surface is heated and dried, a certain polymerization reaction occurs in the alkylbenzimidazole/copper complex, producing a hard chemical conversion film with excellent resisting properties during etching. The defective rate is significantly reduced.

The chemical conversion film of alkylbenzimidazole on the copper surface forms a dense and uniform film, so it has good water repellency. After the coating is obtained and etched, the copper circuit is less likely to be dented or disconnected.

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

Since alkylbenzimidazole has low basicity, it is difficult to adsorb to DFR used to form a negative pattern (it is thought that the releasability of DFR does not deteriorate).

Examples 1 to 9 1.6 mm thick glass epoxy double-sided copper clad laminate [FR-
4. A small hole was made in the product name: R-1705 (Made by Matsushita Electric Works ■), and electroless copper plating was then applied to electrolytic copper plating to form a 20-30 μm copper plating inside the hole and on both sides. .

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 .degree.

Furthermore, the substrate was immersed in a 5% hydrochloric acid aqueous solution and washed with water to clean the copper surface. After that, the copper clad laminate was treated with a treatment solution having the composition shown in Table 1 under the treatment conditions shown in the table. The thickness of the alkylbenzimidazole chemical conversion coating deposited on the 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 sodium hydroxide solution, and the resulting board was dried by heating at a temperature of 120'C for 10 minutes. Next, using an alkaline etching agent [ammonia-ammonium chloride-copper L, specific gravity 1.1-1.2, trade name: A-Process (manufactured by Meltex]], the substrate on which the chemical conversion film was formed was etched at a temperature of 50°C. Each was sprayed for etching, and then immersed in a 3.5% aqueous hydrochloric acid solution to dissolve and remove the etching resist film on the circuit, producing a copper through-hole printed wiring board.

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

The thickness of the alkylbenzimidazole chemical conversion coating is determined by immersing a test piece of a predetermined size in a 0.5% hydrochloric acid aqueous solution and measuring the concentration of dissolved imidazoles using an ultraviolet spectrophotometer. This is converted into thickness.

Examples 10 to 14 and Comparative Examples Water-soluble DFR (trade name: 5ES-105,
(manufactured by Mitsubishi Rayon ■)] 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), imidazole adsorption carbon on DFR (D when the amount of imidazole on the copper surface is taken as 100)
amount of imidazole on FR), peeling time of DFR (120
``After heating and drying at a temperature of 120°C for 10 minutes, spray a 3% NaOH aqueous solution at a liquid temperature of 50°C.The time required to completely peel off the chemical conversion film. After that, add a 3.5% HCI aqueous solution to a liquid temperature of 50°C.
The results are shown in Table 2 (the time required for the chemical conversion coating in the small diameter hole of 0.3 amφ to be completely peeled off by spraying at 0.3° C.).

Copper-clad laminates obtained by the same treatment as the 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 etching resist film on the circuit was dissolved and removed by immersion in a 3.5% aqueous hydrochloric acid solution to produce a high-density copper through-hole printed wiring board.

None of the substrates using alkylbenzimidazole had wire breakage or dents in the copper circuits, but the substrates using alkylimidazole in the comparative example had some dents in the copper circuits.

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

Procedural amendment July 19, 1990 1990 Patent Application No. 162433 2, Name of invention Method for manufacturing copper through-hole printed wiring board 3, Person making the amendment Relationship to the case: Patent applicant 4, Reasons for refusal Date of notification Issue 5, Detailed explanation of the invention column 6 of the specification to be amended, Contents of the amendment (1) ``r Naoh'' in line 8 from the bottom of page 17 of the specification.

Claims (1)

[Claims] (1) A necessary negative pattern is formed on the surface of the copper-clad laminate using a resist soluble in an alkaline aqueous solution, and then the copper-clad laminate is coated with a salt of a 2-position alkylbenzimidazole compound represented by the following general formula. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, in the formula, R represents an alkyl group with 3 or more carbon atoms, and HA represents an organic or inorganic acid.) An etching resist film made of the 2-position alkylbenzimidazole compound is formed on the copper surface of the copper clad laminate, the copper clad laminate is heated and dried to remove the negative pattern film on the surface of the copper clad laminate, and then brought into contact with an alkaline etching solution. 1. A method for manufacturing a copper through-hole printed wiring board, the method comprising: then peeling off an etching resist film.