JPH0124883Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a ceramic varistor, and particularly to a small leadless surge voltage absorbing element that can be directly attached to 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 in 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.

Figure 1a is a perspective view of a conventional varistor, Figure 1b
is a sectional view thereof. The varistor shown in the figure is a rectangular plate-shaped voltage nonlinear resistance element 1 whose main component is zinc oxide or the like, and an electrode 2 formed thereon so as to be connected to a part of the opposite side through the end face. .
In this case, the relationship ₁ > t ₁ in FIG. 1 must be established. In other words, if this relationship were reversed, the varistor characteristics would function only between ₁ and the surge absorption capacity would decrease.

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 using chip parts, it is necessary to ensure a thickness suitable for practical use. However, in Fig. 1b
₁ > t ₁ , that is, the distance between opposing electrodes on the same plane needs to be larger than the thickness of the element, and as a result, the effective area of the sintered body to function as a varistor decreases. Since leadless chip elements are small and intended for high-density packaging, it cannot be said that the purpose is fully achieved.

Purpose of the invention In view of the problems of the prior art, the present invention is to obtain a small, high-performance chip-shaped ceramic varistor that more effectively utilizes the area of the element and secures the same performance in a smaller size.

Structure of the invention In the present invention, electrodes are disposed 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 spacing between the electrodes on the same surface is adjusted using the ceramic varistor element. It is made smaller than the thickness of the varistor element.

DESCRIPTION OF THE EMBODIMENT The following is an example of the present invention as shown in Figures 2a and b.
Explain with reference to. FIG. 2a is a perspective view of the varistor according to the present invention, and FIG. 2b is a sectional view thereof.
Parts that are the same as those in the figures are given the same numbers. First, in this invention, small amounts of oxides such as bismuth, cobalt, manganese, and antimony are added to zinc oxide, mixed, hydraulically formed, fired at 1,100 to 1,400℃, and cut into square plates of a predetermined thickness. Element 1 is obtained. As shown in FIG. 2, grooves 3 were provided on the front and back surfaces of this element 1 at positions where the front and back sides were 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 end surfaces by a transfer method to obtain electrodes 2. This was heat-treated at 700-900°C to obtain a chip-shaped ceramic varistor as shown in FIG. At this time, the thickness _t1 of the element 1 was 1.0 mm, the width of the groove 3 was 0.5 mm, and the depth of the groove 3 was 0.5 mm. This element 1
The leakage current when a specified voltage is applied to the element thickness
The characteristics corresponded to those of _t1 . 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.

Furthermore, in view of practical performance, the flexural strength and weather resistance of the element were improved by filling the grooves 3 with epoxy resin.

Effects of the Invention As detailed above, according to the present invention, the square plate-like element area can be effectively utilized and a smaller leadless chip varistor (surge absorption element) can be put to practical use.

[Brief explanation of the drawing]

FIG. 1a is a perspective view of a conventional example, FIG. 1b is a sectional view thereof, FIG. 2a is a perspective view of an embodiment of the present invention, and FIG. 2b is a sectional view thereof. 1... Ceramic varistor element, 2... Electrode,
3...Groove.

Claims (1)

[Claims for Utility Model Registration] (1) A square plate-shaped ceramic varistor element having grooves at positions where the front and back sides are symmetrical with one end left slightly on the front and back sides and the end faces connected thereto. A ceramic varistor, wherein electrodes are formed except for the groove portion, and the width of the groove formed on the front and back surfaces is smaller than the thickness of the ceramic varistor element. (2) The ceramic varistor according to claim 1, wherein the grooves provided on the front and back surfaces of the ceramic varistor element are filled with an insulating material.