JPH04307902A - Variable resistor - Google Patents

Abstract

PURPOSE:To provide a variable resistor where the stripe plating of a terminal is dispensed with and the electric connection between the resistor and the terminal is stable. CONSTITUTION:In a terminal 2 where the plating film 13 of tin or tin alloy is applied, through a nickel or copper plating film 12, all over the surface, the electrode 2a is exposed at the surface of a resin board 1. A humidity- resistant conductive resin film 6a is provided at this electrode 2a and its periphery. Furthermore, a resistor 5 is provided at the surface of the resin board 1, and one end of the resistor 5 is arranged on the surface of the humidity- resistant conductive resin film 6a. Hereby, the external humidity tending to penetrate into the resistor 5 is intercepted by the humidity-resistant conductive resin film 6a.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-fixed variable resistor that includes a substrate having a resistor on its surface and on which a slider can slide.

0002

[Prior Art and Problems] In this type of variable resistor, the electrode portion of the terminal is exposed on the surface of a substrate on which the terminal is integrally molded, and a resistor is provided to cover this electrode portion. The resistor is electrically connected. By the way, in a variable resistor with this structure, if the electrode part of the terminal is made of a metal that has good solderability and is inexpensive, such as tin or a tin alloy (for example, solder), moisture that has entered the resistor will leak into the electrode part. There was a risk that the oxidation film would reach the resistor and form an oxide film at the interface with the resistor, making the electrical connection between the resistor and the terminal unstable. This phenomenon is particularly noticeable when the resistor contains a phenolic resin binder. For this reason, relatively corrosion-resistant nickel or the like is used as the terminal material, and the portion to be soldered to the printed wiring board, that is, the terminal portion, is plated with stripes of tin, tin alloy, or the like. Alternatively, the entire terminal was first plated with nickel, and then stripe plating of tin or tin alloy was applied, leaving only the electrode portion.

However, this stripe plating requires complicated masking work, which is one of the obstacles to reducing manufacturing costs. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a variable resistor that does not require stripe plating of terminals and has a stable electrical connection between the resistor and the terminals.

0004

[Means and effects for solving the problems] In order to solve the above problems, a variable resistor according to the present invention has a pair of terminals each having a tin film or a tin alloy film on the surface thereof, each exposed on the surface of a substrate. It has an electrode portion, the electrode portion is covered with a moisture-resistant conductive resin film, and an end portion of a resistor provided on the surface of the substrate is disposed on the surface of the moisture-resistant conductive resin film. It is characterized by

In the above structure, since the electrode portion of the terminal is covered with the moisture-resistant conductive resin film, external moisture that has entered the resistor is blocked by the moisture-resistant conductive resin film and does not reach the electrode portion. Therefore, even if a tin film or a tin alloy film is provided over the entire surface of the terminal, no oxide film is formed at the interface between the electrode portion of the terminal and the resistor. Here, as a material for the moisture-resistant conductive resin film, for example, an epoxy resin containing Ag powder is used.

[0006] Furthermore, if a tin or tin alloy film is provided on the surface of a terminal with a nickel film or copper film interposed therebetween, the excellent adhesion of the nickel film or copper film to other metal materials makes it possible to bond the terminal to the surface of the terminal. The electrical connection reliability of the resistor is further improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a variable resistor according to the present invention will be described below with reference to the accompanying drawings, along with a method of manufacturing the same. First, a frame 10 in which a large number of terminals 2, 3, and 4 are connected is fabricated by punching or drawing a long iron plate, brass plate, or the like, as shown in FIG. One ends of the terminals 2 and 3 are bent at two places to form electrode parts 2a and 3a. One end of the terminal 4 is an annular collector electrode portion 4a. Further, a stopper portion 4c is provided on the strip-shaped portion that is in contact with the collector electrode portion 4a. A nickel or copper plating film 12 is applied to the entire surface of this terminal frame 10.
After forming, a plating film 13 of tin or a tin alloy (for example, solder, etc.) is formed (see FIG. 4). Therefore, it is no longer necessary to carry out stripe plating, which was conventionally necessary. The nickel or copper plating film 12 has excellent adhesion to other metal materials, and the tin or tin alloy plating film 13 is firmly attached to the terminal frame 10 through the nickel or copper plating film 12. In close contact.

Next, as shown in FIG. 2, a frame 10 is insert-molded from a heat-resistant resin such as polyphenylene sulfide to produce a frame 11 of the resin substrate 1. In the terminals 2 and 3, electrode portions 2a and 3a are exposed on the upper surface of the resin substrate 1, and the other ends are led out from the front end surface of the resin substrate 1. In the terminal 4, the outer peripheral portion of the collector electrode portion 4a is embedded in the inner peripheral portion of the hole 1a of the resin substrate 1, and the other end is led out from the inner end surface of the resin substrate 1.

Next, as shown in FIGS. 3 and 4, the electrode portions 2a and 3 of the terminals 2 and 3 exposed on the surface of the resin substrate 1 are
Moisture-resistant conductive resin films 6a and 6b are provided on a and its surrounding area by a method such as screen printing or transfer. For the moisture-resistant conductive resin films 6a and 6b, an epoxy conductive resin containing Ag powder, which has excellent heat resistance, or the like is used. Furthermore, a resistor 5 is provided in a substantially arc shape on the surface of the resin substrate 1 by a method such as screen printing or transfer. Both ends of the resistor 5 completely cover the moisture-resistant conductive resin films 6a and 6b. In this case, both ends of the resistor 5 do not necessarily need to completely cover the resin films 6a, 6b, but may cover part of the resin films 6a, 6b. Both ends of the resistor 5 are electrically connected to the electrode portions 2a, 3a of the terminals 2, 3 via resin films 6a, 6b, respectively. For this resistor 5, a carbon-based resistance material is used, for example.

Next, as shown in FIG. 5, a slider 7 is attached to the upper surface of the resin substrate 1. The approximately disk-shaped slider 7 has two approximately arc-shaped slits 8 on its outer circumference, and the portion where the slits 8 are provided is curved to form a protrusion 8a. A recess 7a is provided in the center of the slider 7, and a square hole 9 is formed in the recess 7a. This square hole 9 is provided with four tongue pieces 9a, 9b, 9c, and 9d (9d is not shown) each having one side. A pair of locking portions 7b and 7c that lock onto a stopper 4c provided on the terminal 4 are formed on the opposite side of the slider 7 from the protrusion 8a. The slider 7 is placed on the resin substrate 1 so that the protrusion 8a is in contact with the surface of the resistor 5, and the four tongue pieces 9a, 9b, 9c, 9d are inserted into the hole 1a of the substrate 1.
The surface of the resistor 5 is attached to the substrate 1 in a state in which the protrusion 8a is slidable by caulking the collector portion 4a of the terminal 4 protruding from the terminal 4. At this time, as shown in FIG. 6, the recess 7a of the slider 7 may be placed directly on the upper surface of the collector portion 4a of the terminal 4, or the recess 7a may be placed directly on the resin substrate 1 or on the substrate 1.
It may be placed so as to straddle the collector portion 4a.

Next, the frame 11 is cut away at predetermined locations to form individual variable resistors. Disconnected terminals 2, 3,
4 is bent to form an insert terminal. Also,
The stopper portion 4c is cut up and placed on the edge of the resin substrate 1. The variable resistor with the above configuration has terminals 2, 3, and 4.
Since there is no need to perform stripe plating when plating, the plating process can be simplified. In addition, since the moisture-resistant conductive resin films 6a and 6b can block external moisture that has entered the resistor 5, even if the entire surface of the terminals 2 and 3 is plated with tin or tin alloy,
There is no need to worry about the formation of oxide films on the surfaces of the electrode parts 2a and 3a, and a variable resistor with highly reliable electrical connection between the resistor and the terminals can be obtained.

It should be noted that the variable resistor according to the present invention is not limited to the above-mentioned embodiments, but can be modified in various ways within the scope of the gist thereof. Although the above embodiment has a structure in which the terminal 4 is embedded in the resin substrate 1, the terminal 4 may be made independent and attached to the substrate by caulking with a fastener or the like. The slider may likewise have any shape. Further, the method for forming a film of tin alloy or the like on the terminal is not necessarily limited to the plating method, and may be formed by, for example, a dipping method. Further, in the above embodiment, the nickel film or tin film was formed after punching a long iron plate, etc., but it is also possible to form the nickel film or tin film on the iron plate, etc. and then perform punching, etc. good.

[0013]

As is clear from the above description, according to the present invention, since the electrode portion of the terminal is covered with a moisture-resistant conductive resin film, the moisture from the outside that has entered the resistor is absorbed by the moisture-resistant conductive resin film. This prevents an oxide film from forming on the surface of the electrode portion of the terminal. Therefore, a variable resistor with highly reliable electrical connection between the resistor and the terminal can be obtained.

Furthermore, since there is no need to perform stripe plating that involves complicated masking work on the terminals, manufacturing costs can be reduced. Furthermore, it is possible to easily plate terminals with complex shapes.

[Brief explanation of drawings]

1 to 6 show an embodiment of a variable resistor according to the present invention.

FIG. 1 is a perspective view for explaining a manufacturing method.

FIG. 2 is a perspective view for explaining the manufacturing method.

FIG. 3 is a perspective view for explaining the manufacturing method.

FIG. 4 is a vertical sectional view taken along line X-X' in FIG. 3;

FIG. 5 is a perspective view showing the appearance of a variable resistor.

FIG. 6 is a vertical sectional view taken along the Y-Y' line in FIG. 5;

[Explanation of symbols]

1...Resin substrate 2, 3...terminal 2a, 3a...electrode part 5...Resistor 6a, 6b...Moisture-resistant conductive resin film 7...Slider 12...Nickel or copper plating film 13... Tin or tin alloy plating film

Claims (2)

[Claims] 1. A variable resistor in which a slider is rotatably provided on a substrate provided with a resistor on the surface, and the slider can slide on the resistor, the surface of which is provided with a tin film or a tin alloy. A pair of terminals provided with a film each have an electrode portion exposed on the surface of the substrate, the electrode portion is covered with a moisture-resistant conductive resin film, and the resistor is provided on the surface of the moisture-resistant conductive resin film. A variable resistor characterized in that an end portion of the variable resistor is arranged. 2. The variable resistor according to claim 1, wherein the pair of terminals have a tin film or a tin alloy film provided on the surface with a nickel film or a copper film interposed therebetween.