JPH01272187A - Manufacture of electric circuit board - Google Patents

Abstract

PURPOSE:To prevent deterioration of a photoresist mask by forming a coat film of a metal or a metal compound on a precious metal foil for producing an electronic circuit pattern before etching the same. CONSTITUTION:The surface of a substrate is coated with a photoresist mask 3, which is then exposed and developed to form openings 4 in the photoresist mask. The openings 4 are then covered with a metal or a metal compound. The substrate is dipped in an organic solvent at 60 deg.C for one hour so that the photoresist mask 3 is removed together with the titanium nitride thin film 5 located on the photoresist mask and openings 6 are formed to expose a precious metal foil 2. The parts of the precious metal foil 2 exposed in the openings 6 are etched off with an etching solution of aqua regia type having an increased concentration of hydrochloric acid. As a result, an electronic circuit 12 is left unetched under the titanium nitride thin film 5. The titanium nitride thin film 5 is removed with an etching solution principally composed of ammonium hydrogen fluoride. The electronic circuit is obtained in this manner.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the manufacture of electric circuit boards, and more particularly to a method of manufacturing an electric circuit board in which an electric circuit is formed on a base material.

(Prior art and its problems) With the recent development of the electrical and electronic industries, electrical circuit boards are processed into various shapes and used in parts and products. Under these circumstances, electrical circuit boards with electrical circuits formed on a base material are being manufactured by taking advantage of the electrical properties of precious metals.

There are two ways to form an electric circuit: one is to print paste or noble metal ink on a base material and then perform a baking process to form an electric circuit directly, and the other is to cover the noble metal foil formed on the base material with a photoresist mask and then expose and develop it. There is a method of etching away the precious metal foil through processing to form an electric circuit.

The former method is advantageous in terms of fine patterning, but since the electrical circuit is formed by sintering the precious metal, the precious metals in the electrical circuit do not fit together well, and the tensile strength and hardness are lower than that of homogeneous materials. When used as an electric circuit, it is difficult to maintain a constant composition, so it is unsuitable for electric circuit boards that require wear resistance and electrical properties when in contact, and those where the electric circuit board or current collector rotates at high speed. There are problems that are even more obvious.

Further, an electric circuit board requires a certain electric circuit thickness in the sliding portion, and in order to increase the thickness, it is necessary to perform printing and firing processes multiple times.

The latter method is suitable for the above-mentioned method of forming an electric circuit on an electric circuit board, since a strong electric circuit with a stable composition is previously formed on the base material.

However, since oxidizing liquids such as aqua regia and nitric acid are used to etch precious metal foils, the longer etching time causes deterioration of the photoresist masking material, which tends to disrupt electrical circuit patterns and makes it difficult to create fine patterns. There are some problems.

(Objective of the Invention) The present invention was made to solve the drawbacks of the conventional method of manufacturing electric circuit boards, and by improving the masking method, it is possible to improve The purpose of the present invention is to provide a method for manufacturing a circuit board.

(Means for Solving the Problems) The present invention is a method for manufacturing an electric circuit board, in which a noble metal foil formed on a base material is covered with a photoresist mask, and an opening is formed in the photoresist mask by exposure and development processing. a first step, and a second step of coating at least the opening with a metal or metal compound, and then removing the photoresist mask to expose the noble metal foil under the photoresist mask, and the noble metal foil in the exposed area. This method of manufacturing an electric circuit board includes a third step of removing the metal or metal compound by etching and forming an electric circuit under the coating with the metal or metal compound.

(Function) Electrical circuit boards include slip rings, encoders, and the like, and are made by forming circuit patterns of noble metal foil as electrical sliding parts on base materials such as glass epoxy, ceramic, and Bakelite.

Precious metal foils include single precious metals such as gold, silver, platinum, and palladium, as well as noble metal alloys such as gold-silver alloys, gold-platinum alloys, silver-palladium alloys, platinum-palladium alloys, gold-silver-palladium alloys, all-platinum palladium alloys, and copper. Some are made of noble metal-based alloys with base metals such as nickel, zinc, etc.

The thickness of the noble metal foil is preferably in the range of 10 to 1100 Al, which is 100 or more in the third step, which will be described later.
This is because a phenomenon such as side etching of the electric circuit occurs and the electric circuit pattern becomes easily disordered, but this does not mean that the present invention cannot be applied.

In addition, in items 10 and below, it is difficult to obtain flatness when crimping the precious metal foil onto the base material, so it is difficult to make the thickness of the electrical circuit constant when it is made into a product, which affects the electrical characteristics of the electrical circuit board. This is because it gives

In the first step, a noble metal foil formed on a base material is covered with a photoresist mask, and an opening is formed in the photoresist mask by exposure and development.

In this step, the noble metal foil portion is covered with a photoresist mask, and, contrary to the conventional method, an exposure and development process is performed to open the portion that will become the electric circuit pattern.

As photoresist masks for making electric circuits, there are cinnamic acid resists that have good adhesion to precious metals and are resistant to oxidizing etching solutions. Any suitable photoresist mask may be used.

Precious metal foil has poor adhesion to photoresist when used for boat fishing, so it is particularly advisable to select a noble metal foil with good adhesion.

In the examples described below, a dry film called Riston (trade name) is used as a photoresist mask, but it is easier to handle than conventional cinnamic acid resists and can form higher-density electrical circuit patterns. . Furthermore, this resist could not be used to manufacture electrical circuit boards using conventional processes.

In a second step, the opening is coated with a metal or metal compound, and then the photoresist mask is removed to expose the noble metal foil underneath the photoresist mask.

This process involves coating the openings of the parts that will become the electric circuit pattern obtained in the previous process with a metal or metal compound, and then removing the parts where the precious metal foil is covered with a photoresist mask. is inverted, and the portion that will become the electric circuit pattern is covered with metal or a metal compound, and the portion of the noble metal foil other than the electric circuit pattern is exposed.

Methods for covering the openings include a first method in which only the openings are covered by wet electrolytic plating, and a second method in which the entire surface is covered by wet electroless plating or dry plating.

When coating with the first method, organic solvents, brushing,
Photoresist masks can be easily removed using a combination of chemical and mechanical methods, such as applying and peeling tape.

When coating with the second method, the photoresist mask is also covered with a thin film of metal or metal compound, so
Adding operations such as heating to the above method makes it easier to remove the photoresist mask.

The thickness of the metal or metal compound coating is 0.01-5.
Approximately 0.0 tEn is suitable, wet plating is slightly thicker at 0.1 to 3.0 tEn, and dry plating is 0.02 to 1.0 tEn.
It is preferable to make the coating thinner, and when coating by the second method, the thinner the coating is, the better.

The metal or metal compound coating material is selected depending on the etching solution for the noble metal foil and will be described later.

In the third step, the exposed areas of the noble metal foil are etched away and an electrical circuit is formed under the coating with the metal or metal compound.

This process involves etching the precious metal foil portion exposed in the previous process to leave the electrical circuit underneath the electrical circuit pattern coated with the metal or metal compound obtained in the previous process, thereby forming an electrical circuit. Ru.

The etching solution should preferably be one that can etch the precious metal foil without damaging the metal or metal compound coating, and should be selected taking into account the type of metal or metal compound coating, the type and thickness of the precious metal foil, the density of the circuit, etc. do.

As a specific combination, aqua regia, iodine etching liquid,
When using oxidizing acids such as a mixed acid of hydrochloric acid and nitric acid with a high concentration of hydrochloric acid, nitric acid, sulfuric acid, nitric acid, sodium chloride-sulfuric acid-nitric acid, etc. Coating with aqua regia metal or aqua regia resistant compound is preferable.

When electrolytic etching is performed using an oxidizing neutral or alkaline etching solution such as an iodine etching solution, a mixed solution of sodium cyanide and hydrogen peroxide, or an alkali cyanide solution, the above-mentioned aqua regia-resistant metals may be used. Alternatively, in addition to coating with an aqua regia-resistant compound, a coating with an alkali-resistant metal such as nickel or chromium can be applied.

In addition, when the noble metal foil is silver and palladium, noble metal coatings such as gold, platinum, and rhodium may be used, so there are various combinations.

After the third step, the electric circuit board undergoes a finishing process to become a product, but the thin film of metal or metal compound remaining on the electric circuit pattern is removed by peeling, polishing, or treatment with a separate etching solution. An electric circuit board as an electric contact is obtained through processes such as , external processing, etc.

Further, when a noble metal is used in the thin film of metal or metal compound, it is not necessary to remove it.

The electrical circuit part is used as a sliding part, but the strength and characteristics of the precious metal foil remain unchanged, and it can be used in the same way as conventional ones. can get.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Example 1) FIGS. 1 to 5 schematically represent a method of forming an electric circuit on an electric circuit board according to the present invention.

Figure 1 shows a glass epoxy base material (thickness 1.6 mm) 1 on which a platinum-gold-silver alloy foil (thickness 35 JJn) 2 is pasted, which is then covered with a photoresist mask and opened in the photoresist mask by exposure and development. The process of making the section is shown. First, the surface of the substrate is covered with a photoresist mask (Liston) 3, and then exposed and developed to form an opening 4 in the photoresist mask.

Next, as shown in FIG. 2, the opening 4 is coated with a metal or a metal compound. In this example, the entire surface was coated with a thin film (0, ha) of titanium nitride 5 by OoC and magnetron sputtering.

Furthermore, the organic solvent (1,1,1-)lychloroethane)6
The photoresist mask 3 and the thin film of titanium nitride 5 on the photoresist mask were removed by immersion at 0°C for 1 hour.
As shown in FIG. 3, an opening 6 is provided to expose the noble metal N2.

The exposed part of the precious metal foil 2 where the opening 6 was formed was removed by etching with an aqua regia-based etching solution with a high concentration of hydrochloric acid (hydrochloric acid: nitric acid: water = 6:1:3), as shown in Fig. 4. An electrical circuit 12 remains unetched under the titanium nitride thin film 5.

The thin film of titanium nitride 5 was removed using an etching solution containing ammonium hydrogen fluoride as a main component to obtain an electric circuit board having a cross section as shown in FIG.

After external processing and polishing, this was made into a disc-shaped slip ring having a plurality of arcuate electric circuits around the center.

(Example 2) FIGS. 6 to 10 also schematically represent a method of forming an electric circuit on an electric circuit board according to the present invention.

Figure 6 shows a glass epoxy base material (thickness 1.6 mm) 7 on which a gold-silver alloy foil (thickness 20mm) 8 is pasted, which is then covered with a photoresist mask and exposed and developed to open an opening in the photoresist mask. The process of making the section is shown. First, the surface of the substrate is covered with a photoresist mask (Riston) 9, and then exposed and developed to form an opening 10 in the photoresist mask.

Next, as shown in FIG. 7, the opening 10 is coated with a metal or a metal compound.
was coated with a thin film of nickel 11 (1.5 mm) by wet nickel plating.

Furthermore, the photoresist mask 9 is removed by immersion in an organic solvent (1,1,1-)lychloroethane), and an opening is formed to expose the noble metal foil 8 as shown in FIG.

As shown in Fig. 9, the opening where the precious metal foil 8 is exposed is made of 10% potassium cyanide and 3% hydrogen peroxide solution.
The electrical circuit 13 remains unetched under the nickel thin film 11.

The thin film of nickel 11 was removed using an etching solution containing ferric nitrate as a main component to obtain an electric circuit board having a cross section as shown in FIG.

After external processing and polishing, this was made into a disc-shaped slip ring having a plurality of arcuate electric circuits around the center.

(Conventional Example) FIGS. 11 and 12 schematically show a conventional method of forming an electric circuit on an electric circuit board.

Figure 11 shows glass epoxy base material (thickness 1.6 mm) 1
A substrate on which a platinum-gold-silver alloy foil (thickness: 35 Jln) 2 is filled is covered with a photoresist mask (cinnamic acid resist) 3, and exposed and developed to form an opening 14 in the photoresist mask 3.

As shown in Fig. 12, the exposed part of the precious metal foil 2 is filled with an aqua regia-based etching solution with a high concentration of hydrochloric acid (
Etch and remove with hydrochloric acid: nitric acid: water = 6:1:3) to form an electric circuit. As shown in FIG. 12, the photoresist mask 3 was damaged and peeled off due to oxidation of the aqua regia etching solution, and the damaged and peeled portions were etched away.

Next, the photoresist mask 3 is coated with an organic solvent (1,1,
1-) After removing the ring by dissolving it with dichloroethane), and further processing and polishing, it was made into a disk-shaped slip ring with multiple arcuate electrical circuits around the center, but the electrical circuit pattern was disordered compared to the previous example. It became an electrical circuit board.

(Effects of the Invention) The present invention provides a method for manufacturing an electric circuit board in which a first step is to cover a noble metal foil formed on a base material with a photoresist mask and to form an opening in the photoresist mask through exposure and development treatment. a second step of coating the opening with a metal or a metal compound, then removing the photoresist mask to expose the noble metal foil under the photoresist mask, etching away the noble metal foil in the exposed area, The method for manufacturing an electric circuit board includes a third step of forming an electric circuit under the coating with the metal or metal compound.

During etching, an electrical circuit pattern is formed by coating metal or metal compound on the precious metal foil, and then etching is performed, which solves the problems associated with the deterioration of conventional photoresist masks, and makes the electrical circuit pattern less likely to be disturbed. There are advantages.

In addition to being able to obtain electrical circuit boards with finer patterns than conventional methods, this method also has other effects such as being applicable to applications other than sliding electrical circuit boards, making it revolutionary compared to conventional methods of manufacturing electrical circuit boards. , it can be said that the effect of the invention is great.

(Embodiments) The present invention has the features described in the claims, and examples of embodiments thereof are as follows.

(2) The method according to claim 1, wherein the metal or metal compound coating consists of a thin film of an aqua regia-resistant metal or an aqua regia-resistant compound.

(3) The method according to claim 1, wherein the metal or metal compound coating consists of a thin film of an alkali-resistant metal or alkali-resistant compound.

(4) The method according to claim 1, wherein the metal or metal compound coating consists of a thin film of noble metal.

(5) The thin film of an aqua regia-resistant metal or an aqua regia-resistant compound is selected from titanium, niobium, tantalum, titanium nitride, and an aqua regia-resistant metal oxide, and the etching of the precious metal foil is performed using an oxidizing acid. The method according to claim 1 and embodiment (2).

(6) The thin film of alkali-resistant metal or alkali-resistant compound is titanium, niobium, tantalum, nickel, chromium,
A single substance or alloy selected from the group consisting of nickel alloys, chromium alloys, titanium nitride, or aqua regia-resistant metal oxides, and etching of the precious metal foil is performed using an etching solution containing alkali cyanide or alkali iodide. The method according to claim 1 and embodiment (3), characterized in:

(7) The method according to claim 1 and embodiment (4), wherein the noble metal thin film is made of a single substance or an alloy selected from the group consisting of gold, platinum, and rhodium.

(8) The metal or metal compound coating has a thickness of 0.01mm to 5mm. (The method according to claim 1 and embodiments (2) to (7), characterized in that the film thickness is lcin.

[Brief explanation of the drawing]

1 to 10 schematically show an example of the implementation of the present invention. FIG. 11 and FIG. 12 schematically show a conventional example. Applicant Tanaka Kikinzoku Kogyo Co., Ltd. Calculation 7 diagram Calculation 10 diagram

Claims (1)

[Claims] 1. In a method for manufacturing an electric circuit board, a first step of covering a noble metal foil formed on a base material with a photoresist mask and forming an opening in the photoresist mask by exposure and development treatment; a second step of coating with a metal compound and then removing the photoresist mask to expose the noble metal foil under the photoresist mask; etching away the noble metal foil in the exposed area and removing the metal or metal compound under the coating; A method for manufacturing an electric circuit board, comprising a third step of forming a precious metal circuit.