JPS5824923B2 - Manufacturing method of variable resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a variable resistor constituted by a circuit board having a resistance circuit on a support.

As a resistor circuit board, a conductor and a terminal electrode that are separated from each other are formed on a support plate (hereinafter referred to as a conductor circuit board), and a resistor is printed between the conductor and the electrode of this conductor circuit board. It has been known.

The above-mentioned circuit board for conductors can be made by laminating copper foil on an insulator support plate such as an epoxy-glass laminate or a paper-phenol laminate, and then covering the copper foil with a photoresist in a conductor circuit pattern. However, it is known that the copper foil portion not covered with photoresist is etched with a chemical etching solution, and then the photoresist film is removed.

However, in the above conductor circuit board, the conductor circuit is provided with several electrodes selected by a brush, the resistor to be selected is interposed in the conductor circuit, and the circuit resistance is determined by selecting the electrodes by the brush. When manufacturing a variable resistor with a configuration that changes the value, the electrodes are made of thick copper foil, which creates a step around the electrode that makes it difficult for the brush to slide, requiring a large amount of torque to move the brush. , problems such as noticeable wear of brushes and electrodes are unavoidable.

As described above, the conductor circuit board described above is not only unsuitable for use in variable resistors, but also has the following general drawbacks.

In other words, since the support is an insulator with poor heat dissipation,
The thick copper foil must be etched with a chemical etching solution, which is unsuitable for high-power applications, and this etching takes a considerable amount of time, resulting in poor manufacturing efficiency.

The method of manufacturing a variable resistor according to the present invention is a method that can solve the above-mentioned difficulties, in which a conductor circuit with a resistor interposed is provided on a support, and several electrode parts of the conductor circuit are When manufacturing a resistor whose circuit resistance value is changed by selection with a brush, a metal body is used as the above-mentioned support, and the electrode and Isomorphic.

A depression of the same size is formed, an insulating layer is coated on the entire surface of the support with a uniform thickness, a metal film is deposited on the entire surface of the insulating layer by electroless plating, and then a metal film containing the above-mentioned electrode is formed. Cover the part that has a negative image relationship with the conductor circuit with a resist film, and apply the conductor metal to the exposed metal film part that is not covered with the resist film in a thickness equal to y to the depth of the recess described above. Electrolytic plating is performed, and the plated conductor is coated with a resist metal for the conductor.Then, the resist film is removed, and the metal film exposed by this removal is coated with the resist metal. This method is characterized in that it is removed with a non-corrosive corrosive liquid, and a resistor is printed between the resistors in the conductor circuit thus formed.

In the present invention, a depression having the same shape and size as the electrode is formed in the part of the metal support where the electrode is to be disposed, and an insulating coating and an electroless plating layer are provided on the depression to increase the depth of the depression. An electrode is formed by plating a conductive metal with a thickness equal to y.

The base surface of the support is as high as the thickness of the insulating coating, and the flushness of the electrode with respect to this base surface is determined by the depth of the depression A, the thickness of the electroless plating layer B, and the plating thickness of the conductor metal. Let C be ``A-(B+C)''.

Therefore, since C and B in A are 1/10 of A and C,
The top surface of the electrode is substantially coincident with the veil surface of the insulating layer.

Therefore, the brush slides smoothly against the electrode without strain.

Further, according to the present invention, since a variable resistor having a metal body as a support can be obtained, it is possible to provide a variable resistor that has excellent heat dissipation properties and is suitable for high power.

Furthermore, the conductor circuit is formed by plating the conductor metal, and unlike the conventional example, there is no need for etching of the copper foil, which takes a long time, so that manufacturing time can be shortened.

Metal supports used in the present invention include aluminum, iron, copper, nickel, brass, stainless steel, and steel.

Cutting, electrical discharge machining, press working, etc. are used to form the depressions in these metal supports.

For the insulating coating material, paints and adhesives such as epoxy, polyurethane, polyester, acrylic, and alkyd resins are used.

These may contain catalysts and activators for electroless plating applied after insulation coating.

A normal chemical copper plating bath or nickel plating bath can be used for electroless plating.

To form the resist film, a method is used in which the resist film is coated with a liquid or film-like photoresist material, and then exposed to light through a negative image and developed, or by screen printing of a liquid resist material.

Examples of the present invention will be described below.

Example: On an aluminum plate with a thickness of 1.5 mm, depressions (of the same shape and size as the electrodes) were formed at positions corresponding to the electrodes of the variable resistor to be manufactured.
A depth of about 40μ) is created by press working.

This aluminum plate was degreased with trichlorethylene, washed with 10% hydrochloric acid water, and after drying, an epoxy resin of the following composition was applied to the entire surface of the support plate by dipping,
This coating layer was heated to 120°C for 1 hour and then (110°C,
It was cured under heating conditions for 6 hours to form an insulating coating.

Epoxy resin composition Epicote 828 (bisphenol type epoxy resin manufactured by Shell Chemical Co., Ltd.) 100 parts by volume Hexahydrophthalic anhydride 75 Dimethylbenzylamine
17 Next, using a commercially available electroless copper plating bath composition, electroless copper was deposited on the above insulating coating by a conventional method to form a metal film.

A dry photopolymer film (manufactured by DuPont, trade name Liston 16S) is laminated on this metal film,
Exposure and development were carried out in a conventional manner to expose the metal film in the pattern of a conductor circuit including electrodes.

A conductor is formed on this exposed metal film by electrolytic plating of copper to a thickness g equal to the depth of the recess described above, that is, approximately 40μ, and a thick layer of gold is deposited on the conductor as a cyst-forming metal. Electrolytic plating was carried out at a thickness of 1 μm.

After this electrolytic plating, the remaining photoresist is peeled off and removed by a conventional method, and then immersed in a 40°C etching solution with the following composition for 1 minute to remove the metal film (electroless copper plating film) on the surface from which the photoresist has been removed. Corroded and removed.

Etching bath formulation ammonium persulfate 200g water
11 After etching is completed, thoroughly rinse with water, dry, and apply printed resistor paste to the area where the resistor of the conductor circuit is to be inserted using a 200-mesh screen.

After this printing, the resistance paste was cured and stabilized by heating at 270° C. for 20 minutes to obtain a variable resistor.

Claims (1)

[Claims] 1. A conductor circuit in which a resistor is interposed is provided on a support, and several electrode portions of the conductor circuit are selected with a brush to change the circuit resistance value. When manufacturing,
A metal body is used as the support, and a depression having the same shape and size as the electrode is formed on the surface of the metal support in the area where the electrode is to be placed, and a depression is formed uniformly over the entire surface of the support. Cover the insulating layer with a thickness, apply a metal film to the entire surface of the insulating layer by electroless plating, and then cover the part that has a negative image relationship with the conductor circuit including the electrodes with a resist film. Then, conductor metal is electrolytically plated on the exposed metal film portion that is not covered with the resist film to a thickness y equal to the depth of the recess described above, and the resist metal for the conductor is plated on the plated conductor. After that, the resist film is removed, and the metal film exposed by this removal is removed with a corrosive solution that does not corrode the resist metal. A method for manufacturing a variable resistor, characterized in that a resistor is printed between the resistors in the circuit. 2. The method for manufacturing a variable resistor according to claim 1, wherein the insulating layer is formed of an insulating material containing a catalyst for electroless plating. 3. The method for manufacturing a variable resistor according to claim 1, wherein the insulating layer is formed of an insulating material containing an activator. 4. The method for manufacturing a variable resistor according to claim 1, wherein the insulating layer is formed of an insulating material containing a catalyst and an activator for electroless plating.