JPS60165010A - Circuit board for slide contact - 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] (Field of Application of the Invention) The present invention is applicable to potentiometers, switches, etc. (prior art and problems thereof) Generally, in potentiometers, etc., a resistor paste is printed and fired on a ceramic substrate. A resistor is formed. Figure 1 shows the surface roughness of this conventional circuit board for potentiometers.As is clear from the figure, the board surface has roughness of around 2 to 3 μm to begin with, but a resistor with a thickness of 10-odd μm is used. When the resistor surface is formed, the resistor surface has a 7~'i3p in comparison between the maximum peak and the highest peak.
In addition to a difference of approximately 3 m, irregularities of approximately 3 to 4 μm are continuously formed. Therefore, the sliding contacts (multi-contact pieces, etc.) that slide on the resistor are likely to wear out during high-speed, long-term use, and the contact pressure also tends to vary, making them unreliable. For example, after 2.5 million cycles ( (One cycle means that the sliding contact moves back and forth over the resistor once.) It was not possible to pass the life test on the bottom side.

(Objective of the Invention) The present invention has been made in view of the above points, and its object is to improve the lifespan by providing a circuit board having a circuit pattern for sliding contacts with a smooth surface. The aim is to improve contact reliability.

(Summary of the Invention) In order to achieve this object, the present invention is characterized in that a glass layer with a mirror surface is formed on a substrate, and a circuit pattern on which a sliding contact slides is formed on the glass layer. shall be.

Embodiment of the Invention FIG. 2 shows a schematic cross-sectional view of a circuit board for a potentiometer according to an embodiment of the invention.

In the same figure, 1 is a plate thickness 1 made of alumina ceramic.
．． The substrate has a roughness of about 0.000, and its surface has a surface roughness equivalent to that of the conventional structure described above. 2 is 1 formed on substrate 1
A glass layer of 0-20 μm thick, in this example about 1
The thickness is set to 5pffl.

The glass layer 2 is formed by applying a glass paste containing 5iQ2, PbO, and B2O3 to a predetermined thickness by screen printing, and then firing it to remove the solvent, and has a mirror surface. The degree of mirror polishing of the glass layer 2 depends on its firing temperature and components (depending on the firing temperature, and after various studies, the inventor found that when using glass paste with the above components and under certain firing conditions, the sliding contact circuit It has been found that the mirror surface is suitable for use as a board.

That is, the softening temperature of the glass layer 2 is about 750°C,
The firing temperature is 750°C, 790°C, 830°C, 850°C,
As is clear from Figure 3, which shows the evaluation of appearance and practicality at 870°C, the firing temperature was 850°C, 870°C.
℃, the surface is mirror-like and suitable for practical use. (here,
In Figure 3, the evaluation indicated by ○ indicates that the practicality is satisfied in the sense of completely clearing the above-mentioned 2.5 million cycle life, △ indicates that it is inferior to ○, and × indicates that there is no practicality. . ) Therefore, it is necessary to fire the glass layer 2 at a firing temperature that is about 100°C or more higher than the softening temperature, and when this condition is added to 44, the surface of the glass layer 2 will be completely smooth as shown in Figure 4. Become.

Reference numeral 3 denotes a resistor 1 formed on the glass layer 2, in which RuO2-based resistor paste is applied by screen printing and fired at about 850'C.

The film thickness of this resistor 3 is set to about 10 to 30 μm,
In this example, this is about 15 μm. Reference numeral 4 denotes a conductor (current collector) similarly formed on the glass layer 2. In this example, an Ag-Pd based conductive paste was applied by screen printing and baked at about 850°C. The thickness of the conductor 4 is set to about 10 to 30 pm, and in this embodiment, it is about 15 μm. 5 is
This is a multi-brush type sliding contact piece that slides on the resistor 3 and conductor 4.

In the circuit board having the above configuration, when the surface roughness of the resistor 3 is measured, it is found that l p+? It was found that the surface of the resistor 3 was extremely smooth, with irregularities of approximately 1.0 m in diameter being approximately evenly distributed, and irregularities of approximately 2 .mu.m being present in rare cases. In addition, in a durability test using this circuit board,
It was confirmed that there were no problems with practical performance even after long-term use of 2.5 million cycles.

In the above embodiment, materials fired at a relatively high temperature were used for the resistor 3 and the conductor 4, and a circuit board for a potentiometer was shown that can be used even in an environment of about 150°C. The film thickness of the circuit pattern is also arbitrary.

(Effects of the Invention) As described above, according to the present invention, since the circuit pattern for the sliding contact is formed on the mirror-surfaced glass layer, the surface of the circuit pattern becomes smooth, resulting in long life and high contact reliability. can be guaranteed. Further, even when the circuit pattern is formed by thick film printing technology, the surface roughness is good and the productivity is high.

[Brief explanation of drawings]

Fig. 1 is a graph showing the surface roughness of a conventional circuit board, Fig. 2 is a schematic sectional view of a circuit board according to an embodiment of the present invention, and Fig. 3 is a graph showing the relationship between the firing temperature of the glass layer and the surface roughness. A table showing the relationship, FIG. 4, is a graph showing the surface roughness in the configuration of FIG. 2. 1...Substrate 2...Crow layer 3...Resistor 4...Conductor 5...Sliding contact piece Patent applicant Konokuru Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] K) A sliding device characterized in that a glass layer with a mirror surface is formed on a substrate, and a circuit pattern on which sliding contacts slide is formed on the glass layer by thick film printing. Circuit board for contacts. (2) The circuit board for sliding contacts according to claim (1), wherein the circuit pattern has a surface roughness of 2μ7n or less. (3) The glass layer is made of a material containing 5IO2, PbO, and B2O3 and has a softening point of around 750°C, and is fired at a temperature about 100°C or more higher than the softening point to give a mirror surface. A circuit board for sliding contacts according to claim (2).