JPH1041111A - Resistance element for variable resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent migration of silver from occurring, with low cost, without deteriorating other characteristics in a resistance element for a variable resistor which is used for various electronic device. SOLUTION: The peripheries of a current collector layer 4, lead-out electrode components 3A, 3B and 5 which are silver pattern parts, printed/formed with silver paste, out of a resistor layer 2, the current collector layer 4 and the lead-out electrodes 3A, 3B and 5 of both the layers of a resistance element for a variable resistor, are covered with covering parts 6A and 6B of narrow width using carbon paint of the same material as the resistor layer 2. Thereby silver migration is easily prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable resistor for use in variable resistors used in various electronic devices, which prevents silver migration from occurring.

[0002]

2. Description of the Related Art In recent years, as variable resistors used in various electronic devices have been reduced in size and improved in performance, those used in high humidity have been increasing. When a DC voltage is applied in such a case, a failure may occur due to migration of silver, such as a short circuit or poor insulation between silver patterns.

[0003] As a method of preventing silver migration of a resistance element for a variable resistor, as disclosed in JP-B-46-2876 and JP-A-50-22137, a carbon pattern wider than a silver pattern is used. Coating methods are known.

As disclosed in Japanese Patent Application Laid-Open No. 58-74002, a polyimide resin, an aromatic amine-based curing agent or an acid anhydride-based curing agent is used as an undercoat of a silver pattern on an insulating substrate. A method of providing a migration barrier layer using an epoxy resin or the like is also known.

[0005]

However, in the resistance element for a variable resistor according to the above-mentioned conventional migration preventing method, the former is covered with the carbon pattern up to the point where the silver pattern and the terminal are electrically connected, and compared with silver. Therefore, carbon has a problem that the specific resistance is considerably high and the contact resistance at the connection with the terminal is high, which leads to an increase in the circuit resistance of the variable resistor. Was added to the cost.

In the latter case, since a migration barrier layer, which is relatively more expensive than carbon paint, is formed by printing on the front surface of the silver pattern, there is a problem that the material cost and the number of printing steps are increased, and the cost is increased. Was.

SUMMARY OF THE INVENTION The present invention is to solve such a conventional problem and, when used by applying a DC voltage in high humidity, prevents the occurrence of silver migration, and prevents terminals from being printed. It is an object of the present invention to provide an inexpensive resistance element for a variable resistor that can suppress an increase in contact resistance of a contact portion with a pattern and that is inexpensive.

[0008]

According to the present invention, there is provided a resistor element for a variable resistor, wherein a resistor layer, a current collector layer, and a lead electrode portion of both are formed by printing with a silver paste. The periphery of the silver pattern portion is covered with carbon paint of the same material as the resistor layer.

According to the present invention, the occurrence of silver migration can be prevented at low cost without deteriorating other characteristics.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a resistor layer to which a sliding contact is slid on an insulating substrate is formed by printing with carbon paint, and a current collector layer is formed by printing with silver paint. Both lead-out electrode portions are formed by printing with silver paint in parallel with the ends of the insulating substrate, and the periphery of the silver pattern portion formed by printing with silver paint is formed as a resistance element for a variable resistor in which the periphery of the silver pattern portion is coated with carbon paint. In addition, there is an effect that generation of migration can be prevented even when the device is used by applying a DC voltage in high humidity.

According to a second aspect of the present invention, in the first aspect of the present invention, the periphery of the silver pattern portion is printed and coated with carbon paint of the same material as the resistor layer at the same time when the resistor layer is printed. In addition, there is an effect that the occurrence of silver migration of the resistance element for a variable resistor can be prevented inexpensively without increasing the number of printing steps.

According to a third aspect of the present invention, in the first or the second aspect of the present invention, the connecting portion between the lead-out electrode portion of the resistor layer and the current collector layer is connected to a terminal connected to the lead-out electrode portion. Is prevented from being coated with carbon paint, and has the effect that the occurrence of silver migration of the variable resistor element can be prevented without increasing the contact resistance with the terminal.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a portion of the silver pattern portion where the sliding contact is slid is not covered with carbon paint. This has the effect of preventing the occurrence of silver migration in the variable resistor resistor element without increasing the contact resistance of the sliding contact.

According to a fifth aspect of the present invention, in the first aspect of the present invention, only the portion of the silver pattern portion facing the other conductive printing portion is coated with carbon paint. It is possible to most effectively prevent the occurrence of silver migration in the resistance element for a variable resistor only in a necessary portion, and has an effect that it is advantageous for miniaturization of a product.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a rotary variable resistor according to an embodiment of the present invention.
1, reference numeral 1 denotes an insulating substrate made of a phenolic resin laminate or the like, 2 denotes a horseshoe-shaped resistor layer formed by printing carbon paint thereon, and 3A and 3B denote silver paint on both ends of the resistor layer 2. The current collector layer 4 is formed by printing silver paint in the center of the inside of the resistor layer 2, and the lead electrode section 5 integrally formed with the current collector layer 4 The lead-out electrodes 3A and 3B of the body layer 2 are arranged at a predetermined interval at an end of the insulating substrate 1.

The opposite edges of the three lead-out electrode portions 3A, 3B and 5 and the edge of the current collector layer 4 are covered with narrow covering portions 6A and 6A by printing carbon paint, respectively.
B.

Reference numerals 7A, 7B and 7C denote terminals made of a metal material. As shown in FIGS. 1 and 2, the lead-out electrode portions 3A, 3B and 5 of the resistor layer 2 and the current collector layer 4 are caulked. It is connected.

The respective lead-out electrode portions 3A, 3B and 5
The part for caulking the terminals 7A, 7B and 7C of
The coating portion 6A made of carbon paint is set so as not to be covered, and the outer ends of the lead-out electrode portions 3A and 3B are not provided with the coating portion 6A made of carbon paint because there is no conductive portion facing them.

Reference numeral 8 denotes a sliding contact made of an elastic metal, as shown in FIGS. 1 and 3, the elastic contacts 8A and 8A.
B is in elastic contact with the resistor layer 2 and the current collector layer 4 on the insulating substrate 1, and the resistor layer 2
And the collector layer 4 is slidably contacted.

The portion of the current collector layer 4 where the elastic contact 8B slides is set so as not to be covered with the coating 6B made of carbon paint.

The coating portions 6A and 6B are formed by printing carbon paint which covers the periphery of the lead electrode portions 3A, 3B and 5 and the current collector layer 4. First, the lead electrode portions 3A, 3B and 5 are formed by silver paint. In addition, by forming the current collector layer 4 by printing and then printing it simultaneously with the resistor layer 2 using carbon paint of the same material as the resistor layer 2, the number of printing steps can be increased most easily. It can be formed without.

The variable resistor according to the present invention is constructed as described above. A rotary variable resistor using the variable resistor according to the present invention can be used in general without taking measures against silver migration. In addition to the variable resistor of the above, and a variable resistor that has been subjected to a silver migration prevention method according to the prior art, a comparative test was conducted by applying a DC voltage in high humidity. Although silver migration was observed in several tens of hours, silver was not observed in the variable resistor using the silver migration preventing method according to the related art and the rotary variable resistor using the variable resistor according to the present invention. No migration was observed.

In the rotary variable resistor using the variable resistor according to the present invention, the contact resistance of the contact portion between the resistor, the terminal and the sliding contact is low.
The maximum attenuation of the variable resistor was exactly the same as that of the variable resistor without silver migration prevention measures.

The resistance element for a variable resistor according to the present invention can be applied not only to a rotary variable resistor but also to a slide variable resistor. It is needless to say that the substrate is not limited to a plate, and various insulating substrates such as glass epoxy resin, polyester, polyethylene naphthalate, and polyphenylene sulfide may be used.

[0025]

As described above, according to the present invention, the periphery of the lead-out electrode portion and the current collector layer formed by printing with silver paint of the resistance element for the variable resistor is made of carbon paint of the same material as the resistor layer. By performing print coating simultaneously with the formation of the resistor layer, silver migration can be generated without substantially increasing the cost compared to a general variable resistor resistor element and without deteriorating characteristics such as an increase in contact resistance value. An advantageous effect is obtained that a resistance element for a variable resistor that can be prevented can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view of a resistance element for a variable resistor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line DD of FIG.

FIG. 3 is a partial cross-sectional view taken along line EE of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Resistor layer 3A, 3B, 5 Lead-out electrode part 4 Current collector layer 6A, 6B Cover part 7A, 7B, 7C Terminal 8 Sliding contact 8A, 8B Elastic contact

Claims (5)

[Claims] 1. A resistor layer on which a sliding contact is slid on an insulating substrate is formed by printing with carbon paint, and a current collector layer is formed by printing with silver paint, and both lead-out electrodes are arranged in parallel with the end of the insulating substrate. A resistive element for a variable resistor, formed by printing with silver paint and coating the periphery of a silver pattern portion printed with silver paint with carbon paint. 2. The variable resistor according to claim 1, wherein the periphery of the silver pattern portion is printed and coated with carbon paint of the same material as the resistor layer at the same time when the resistor layer is formed by printing. 3. The connecting portion between a resistor layer and a lead electrode portion of a current collector layer which is connected to a terminal connected to the lead electrode portion is not covered with carbon paint.
The resistance element for a variable resistor according to any one of the preceding claims. 4. The variable resistor according to claim 1, wherein a portion of the silver pattern portion where the sliding contact slides is not covered with carbon paint. 5. The variable resistor according to claim 1, wherein only a portion of the silver pattern portion facing the other conductive printed portion is covered with carbon paint.