JPS61231702A - Manufacture of circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to the manufacture of circuit boards for mounting various electronic components used in various electronic devices, and contact circuit boards for various electronic components such as switches and encoders. It is about law.

(Structure of a conventional example and its problems) A conventional method for manufacturing a circuit board will be explained with reference to FIG. Phenol laminate plate 1 serving as a substrate shown in FIG. 1(a)
After forming a photosensitive resin layer 3 as shown in FIG. 1(b) on the copper 1'i2 attached to the surface, a selective light-shielding plate 4 having a predetermined pattern is covered and light 5 is irradiated. . When this is subjected to a development process, a part of the copper foil 2 is selectively exposed in a predetermined pattern as shown in FIG. 1(c). This is chemically etched to remove the exposed copper M2 as shown in FIG. 1(d), and then the remaining photosensitive resin layer 3 is peeled off to form a predetermined area as shown in FIG. 1(e). A circuit board with a pattern is obtained.

However, during etching, the side surfaces of the copper foil on which the wiring circuit is formed are corroded, resulting in lines that are thinner than the designed line width, and in the case of fine designed line widths, disconnections occur, making it difficult to form high-density wiring circuit boards. 6 In addition, the effective usage rate of copper M2 used for circuit wiring is generally low at 5% to 30%, and it is difficult to further plate the wiring with precious metals such as gold. When doing so, there is a problem in that a lead wire is required for electrical continuity, which increases the number of unnecessary wiring parts in the final product, which also causes an increase in manufacturing costs.

In addition, in the case of a circuit board used as a sliding contact where a brush made of metal or the like slides on the wiring circuit, there is a step at the boundary between the phenol laminate that is the base and the wiring circuit, so the sliding contact There was also the problem that the lifespan was short and that when the brush slid, it got caught on the above-mentioned steps, causing malfunction.

As a countermeasure for this, the thickness of copper i1 is increased from 6 μm to 13 μm.
Methods have been adopted to make the copper foil as thin as possible, but there are manufacturing limits to how thin copper foil can be, so this has not been a fundamental solution.

In addition, in order to eliminate the above-mentioned level difference, a wiring circuit is formed on a phenol laminate or an epoxy laminate by the above-mentioned etching method, and then the surface is heated and pressurized with a hard mirror plate to form a bond between the wiring circuit and the substrate surface. There is also a known method of making the same plane, but it is difficult to completely eliminate the level difference, and not only does it not solve the difficulty of high-density wiring, but the process of heating and pressurizing a hard mirror plate makes it difficult to define the circuit. There is a problem that the product may shift from its position, and furthermore, the heating and pressurizing process requires a long time, resulting in an expensive product.

(Objective of the Invention) The present invention solves all of the above-mentioned problems, and it is easy to form a high-density wiring circuit board, has a high material yield, and is highly suitable for mass production, so it can be manufactured at an extremely low cost. and,
The present invention aims to provide a method of manufacturing a circuit board that dramatically improves the sliding life when used as a sliding contact circuit board since a smooth surface with no steps can be obtained.

(Structure of the Invention) The present invention involves exposing a photosensitive resin layer formed on a conductive temporary substrate to light with an arbitrary pattern, developing the pattern to selectively expose the temporary substrate, and furthermore, exposing the exposed portion of the temporary substrate. This is a circuit board manufacturing method in which a circuit board is obtained by applying plating to a desired thickness, then bonding it to the main base using an adhesive, and then removing the temporary base. The circuit board has no step difference at the boundary between the wiring circuit and the surface of the substrate, and is formed smoothly.

(Description of Embodiments) An embodiment of the present invention will be described with reference to FIG. Figure 2(a)
to h) are cross-sectional views showing step by step the method for manufacturing a circuit board according to the present invention.

As shown in FIGS. 2(a) and 2(b), the surface of a stainless steel plate 6 with a thickness of 0.1 mm and a surface roughness of 0.05 μm, which will serve as a temporary substrate, is exposed to light to a film thickness of approximately 1 μm. Resin (
0FPR-2' (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is uniformly applied using a spinner and then dried to form a photosensitive resin layer 3.

As shown in FIGS. 2(c) and (d), it is a selective light shielding plate with a line width of 1 μm to 100 μm and a length of 10 mm.
After the positive film 4 was brought into close contact with the above photosensitive resin layer 3 and exposed for 10 seconds using Canon PLA-300F, it was developed using a developer (manufactured by Tokyo Ohka Kogyo Co., Ltd., special developer) and washed with water. After that, it was dried at a temperature of 150° C. for 10 minutes to obtain an exposed pattern of stainless steel that matched the pattern of the positive film 4.

Next, as shown in FIG. 2(e), the above stainless steel exposed pattern was coated with full plating (trade name: AUROBOND TN, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) with a thickness of 0.5 μm, and then Nickel plating was applied to a thickness of 1.5 μm to form a plating layer 7.

Next, remover liquid (manufactured by Tokyo Ohka Kogyo Co., Ltd., special remover liquid)
When the photosensitive resin layer 3 is peeled off using a method, the state shown in FIG. 2(f) is obtained. Furthermore, as shown in FIG. 2(g), an epoxy resin 8 (
Manufactured by Amicon Far East, product number 927-10
E) is applied over the entire surface to a thickness of 1.5 to become the main base.
After adhering to the μm epoxy glass laminate 9, the temperature was 90°C.
The epoxy resin 8 is cured by heating at 0° C. for 20 minutes.

After curing the epoxy resin 8, when the stainless steel plate 6 of the temporary base is peeled off, a mirror-like surface is created by transferring the plating layer 7 of the temporary base to the epoxy glass laminate 9 of the main base, as shown in FIG. 2(h). A circuit board is obtained.

For comparison with the circuit board according to the invention described above, a circuit board with the same circuit pattern was made using a conventional etching method. In other words, a 1.0 mm thick copper foil with a thickness of 6 μm is pasted.
Etched a 5mm epoxy laminate and further added a 1μ thick layer.
A circuit board was obtained by applying full plating to a thickness of 0.5 μm on the base plating of 0.5 μm.

The table below shows the results of measuring the line widths of the circuit patterns for the above examples and comparative examples and comparing them with design values.

Unit μm Comparison of line width of circuit patterns As you can see from the table, with the conventional etching method.

In general, the designed line width is thin, so if the line width is 5 μm, disconnection will occur, and if the line width is 1 μm, no circuit pattern will be formed.However, in the embodiment according to the present invention, any line width can be faithfully reproduced. There is.

In addition, a nickel silver brush with a contact radius of 1.4+ml was slid in the width direction of the circuit pattern on each side at a contact pressure of Log, and the electrical ON-OFF state was analyzed using a spectrum analyzer. , In the comparative example circuit pattern,
While chattering occurred as expected in the experiment both during ON→OFF and OFF→ON, in the circuit pattern of the example, no chattering occurred even after repeated sliding 200,000 times.

The conductive temporary substrate in the present invention is preferably a metal foil such as stainless steel foil, titanium foil, or aluminum foil with a surface roughness of 5 μm or less, or a composite foil in which these metal foils are laminated and integrated with a synthetic resin film. Alternatively, a conductive synthetic resin film can be selected and used. Furthermore, it goes without saying that for the final substrate, not only a phenol laminate or an epoxy laminate, but also a ceramic substrate, a metal plate, a synthetic resin molded product, etc. can be arbitrarily selected.

(Effects of the Invention) According to the method for forming a circuit board according to the present invention, since a circuit pattern is formed by plating on the exposed portion of a temporary conductive substrate, a copper foil on which a circuit pattern is formed as in the conventional etching method is used. There is no phenomenon of corrosion on the side surfaces of the etching process, and therefore, the wiring line width of the circuit does not become thinner than the design value, and high-density wiring circuit boards with a line width of about 1 μm to 5 μm can be easily manufactured, and it can be easily manufactured using conventional etching methods. A highly reliable, high-quality circuit board can be obtained without fear of disconnection. Further, for plating, it is only necessary to use the plating material for only the circuit parts necessary for the 11 products, and the thickness of the plating layer can be freely selected, so there is no wastage of materials, and the product can be manufactured at an extremely low cost.

Furthermore, in the case of products such as various switches and encoders that use the circuit surface as a sliding contact, both the plating layer of the wiring circuit and the surface of the base are formed on the same smooth plane.
The sliding life is approximately 100 times longer than that of conventional contact boards.
It shows an incredible elongation of 1,000 times, and the sliding feel is smooth without any feeling of catching like conventional products, and there are no malfunctions due to catching.

As explained above, not only can all of the conventional defects in quality, design, and performance be eliminated, but also it is excellent in mass production, which has a significant effect on reducing manufacturing costs.

[Brief explanation of drawings]

Figures 1 (a) to e) are cross-sectional views depicting the conventional circuit board manufacturing method in the order of steps, and Figures 2 (a) to h) depicting the circuit board manufacturing method according to the present invention in the order of the steps. FIG. 1.9...Substrate, 2...Copper foil, 3...Photosensitive resin layer, 4...Selective light shielding plate, 5...Light, 6...Temporary base, 7... Plating layer, 8...
Epoxy resin. Patent applicant: Matsushita Electric Industrial Co., Ltd. Figure 1: Elm

Claims (5)

[Claims] (1) After forming a photosensitive resin layer on a temporary conductive substrate, covering this with a selective light-shielding plate, and irradiating light from above to expose at least a part of the photosensitive resin layer, A development process is performed, and the portions where the photosensitive resin layer is removed and the temporary substrate is exposed are plated to selectively form a plating layer, and then a plating layer is formed on the photosensitive resin layer and the plating layer, or on the main substrate. A method for manufacturing a circuit board, which comprises applying an adhesive to the substrate and fixing it to the main substrate, and then removing the temporary substrate by a physical or chemical method. (2) After plating, the photosensitive resin layer is peeled off, and an adhesive is applied on the temporary substrate and the plating layer or on the main substrate to fix it to the main substrate. A method for manufacturing a circuit board according to scope item (1). (3) The method for manufacturing a circuit board according to claim (1), wherein the plating layer is a plurality of metal layers. (4) Among multiple plating layers, the first plating layer is gold, platinum,
The method for manufacturing a circuit board according to claim 3, wherein the metal is selected from silver, rhodium, and palladium. (5) After forming the plating layer or peeling off the photosensitive resin layer, a single or multiple electrical resistance layer is formed on the circuit surface formed by plating. A method for manufacturing a circuit board according to any one of items 1) to (4).