JPS60202902A - Ceramic varistor - 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 the Invention The present invention relates to a ceramic varistor, and more particularly to a small leadless surge voltage absorbing element that can be directly mounted on a printed wiring board.

Conventional configurations and their problems In response to the trend toward smaller, lighter, and thinner electronic devices, component parts have been mounted at high density.In order to facilitate high-density mounting, various parts have been made into chips. Progress is being made. Chip elements without lead terminals are also desired for surge voltage absorbing elements.

FIG. 1(-) is a plan view of a conventional ceramic varistor, and FIG. 1(b) is a front sectional view thereof. The ceramic varistor shown in the figure is a square plate-shaped voltage nonlinear resistance element 1 whose main component is zinc oxide or the like, and an electrode 2 that is connected to a part of the opposite side through the end face. be.

In this case, it is necessary to establish the relationship il>tl in FIG. Tsumashi, if this relationship is reversed, the ballista characteristics will be I! , the result is that it only functions for one period, resulting in a low surge absorption capacity.

Incidentally, ceramic varistors, which are sintered bodies containing zinc oxide as a main component, are widely used as surge voltage absorbing elements because of their excellent nonlinearity and surge absorption performance, but the sintered bodies are brittle and When used as a chip component, it is necessary to ensure a thickness suitable for practical use. However, the first
The relationship C in the figure >tl, that is, the distance between electrodes facing each other on the same plane needs to be larger than the thickness of the element, and as a result, the effective area where the sintered body functions as a varistor decreases. This cannot be said to have fully fulfilled its purpose, as the chip elements of this type of dress are small and intended for high-density mounting.Recently, as shown in Figure 2, the area of the element has been utilized more effectively. Then, electrodes are arranged on opposing surfaces of a square plate-shaped ceramic varistor element, grooves are formed between the electrodes facing each other on the same surface, and the distance between the electrodes on the same surface is made smaller than the thickness of the ceramic varistor element. There is something smaller.

Figure 2 (body 2) is a plan view of the ceramic varistor, and Figure 2 (b) is a front sectional view thereof, where the same parts as in Figure 1 are given the same numbers. This ceramic varistor is made by adding small amounts of oxides such as bismuth, cobalt, manganese, and antimony to zinc oxide, mixing them, and hydraulically forming them at 1100 to 14 o
Sintered at 0°C and cut into a rectangular plate-like element 1 with a predetermined thickness.
get. As shown in FIG. 2, grooves 3 are provided on the front and back surfaces of this element 1 at positions where the front and back sides are symmetrical, leaving a small portion at one end. The groove 3 was cut by rotating a diamond blade at high speed. Silver paste was printed in a predetermined pattern on the front and back surfaces of the element 1 thus obtained, and the silver paste was applied to the other end face by a transfer method to obtain an electrode 2. This is heat treated at 700-900'C to produce a chip-shaped ceramic sonic varistor as shown in FIG. The ceramic varistor made in this way is sufficient in terms of miniaturization, but considering the price, it requires processes such as cutting the sintered body and grooving with a diamond blade, so mass production is not satisfactory. I can't say that.

Purpose of the Invention In view of the problems of the conventional example, the present invention provides a small, high-performance chip-shaped surge ceramic varistor at a low cost, which makes more effective use of the area of the element and secures the same performance in a smaller size. The purpose is to

Structure of the Invention In order to achieve the above object, the present invention includes a ceramic varistor element in the form of a rectangular plate obtained by stacking sheets and cutting them, and a first ceramic varistor element formed on the opposing surface of the ceramic varistor element. The first electrode has a second electrode and faces the first electrode on the same surface of the ceramic varistor element. A groove is provided at the interval between the second electrodes by cutting the sheet, and the groove is made smaller than the thickness of the varistor element.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 3(a) and (
This will be explained with reference to FIGS. 4(a) and 4(b).

FIG. 3(-) is a plan view of a ceramic varistor laminated with sheets, and FIG. 3(b) is a front sectional view thereof. Third
The figure shows the top and bottom parts of a sheet in which trace amounts of oxides such as zinc oxide VC, bismuth, cobalt, manganese, and antimony are added, mixed, dissolved in a solvent, wet-formed into a sheet, and cut to a size of 3 °C. The grooves are arranged at intervals of ℃2 in the lower part. After lamination, it is cut at locations A and B and C with the same dimensions as dimension 13, and fired at 1100° C. to 1400° C. to obtain a square plate-shaped element 4. Silver paste is printed in a predetermined pattern on the front and back surfaces of this element 40 as shown in FIG. 4, and the electrode 2 is obtained by applying silver paste to the end surface by a transfer method. This is heat-treated at 700 to 900°C to obtain a chip-shaped ceramic varistor as shown in FIG. At this time, the thickness tl of the element 4 is 1.5 mm, and the thickness tl of the groove 3 is 1.0 mm.

The depth of the groove 3 is 0.5 mm. The leakage current when a predetermined voltage was applied to this element 4 corresponded to the characteristics of the element thickness tl. Further, even when an impulse was applied, there was no discharge in the groove 3 (between opposing electrodes), but when the load was increased, the element was destroyed. This proves that the varistor is functioning between the opposing electrodes 2 on the front and back surfaces.

Effects of the Invention As detailed above, according to the present invention, the area of the rectangular plate-like element can be effectively utilized, and a smaller glue-dressed varistor (surge absorption element) can be provided at a lower cost.

[Brief explanation of the drawing]

Fig. 1(a) is a plan view of a conventional ceramic varistor, Fig. 1(a) is a front sectional view thereof, Fig. 2(a) is a plan view of another conventional ceramic varistor, and Fig. 2(b) is a plan view of a conventional ceramic varistor. 30 is a plan view of a multilayer varistor element according to an embodiment of the present invention, FIG. 3(b) is a front view thereof, and FIG. 4(-)
is a plan view of ceramics (risk) of one embodiment of the present invention;
FIG. 4(b) is a front sectional view thereof. 1... Ceramic varistor element, 2... Electrode, 3... Groove, 4... Laminated ceramics (risk element. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st)
figure

Claims (1)

[Claims] A square plate-shaped ceramic varistor element obtained by laminating and cutting the sheets, and a first ceramic varistor element formed on the opposing surface of the ceramic varistor element. The first electrode has a second electrode and faces the first electrode on the same surface of the ceramic varistor element. A ceramic varistor, in which a groove is provided at the interval between the second electrodes by a cut in the sheet, and the groove is smaller than the thickness of the varistor element.