JPH02165603A - Varistor - Google Patents

Abstract

PURPOSE:To improve the surge strength of a varistor without enlarging a varistor substrate by a method wherein high resistance parts are formed in the electrode isolation parts of the varistor substrate. CONSTITUTION:Electrode isolation parts 7 having required widths W are formed between a first electrode film 5 on the edge part of the second main surface 2b of a varistor substrate 2 and a second electrode film 4 and between a second electrode film 6 on the edge part of the first main surface 2a of the varistor substrate 2 and a first electrode film 3. High resistance parts 8 are formed in both the electrode isolation parts 7 and 7 of the varistor substrate 2 so as to penetrate into the substrate 2 to the thickness direction. Therefore, even if both the electrode films facing each other with the electrode isolation part 7 between are made to come closer to each other, a current does not flow between the electrodes. With this constitution, effective electrode areas can be increased without enlarging the dimensions of the varistor substrate, so that the surge strength of the varistor can be improved while the small size is maintained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a chip-type varistor that functions as a voltage non-linear resistor, and in particular to a structure that can improve surge resistance without increasing the dimensions of the varistor substrate. Regarding.

[Conventional technology]

2. Description of the Related Art Conventionally, there has been a chip-type varistor shown in FIG. 3 as a resistor element whose resistance value changes non-linearly depending on an applied voltage. This varistor 10 has an upper surface 11a and a lower surface 11b of a rectangular varistor substrate 11 whose main component is zinc oxide.
respectively, the first electrode film 12. forming a second electrode film 13;
First electrode films connected to the first and second electrode films 12 and 13 are respectively connected to both side surfaces 11c and 11d of the varistor substrate 11.
゜A second external electrode film 14.15 is formed, and between the first external electrode film 14 and the second electrode film 13, and between the second external electrode film 15 and the first electrode film 12. It is configured by forming an electrode separation part 16 having a predetermined width W.

Here, the electrode films 1 facing each other with the electrode separation part 16 in between are
2.15 and 13.14 are too close to each other. During this time, current may leak and deteriorate the varistor characteristics. Therefore, the width W of the electrode separation section 16 has conventionally been set to be approximately 1.5 times the thickness H of the varistor substrate 11, thereby preventing current from flowing.

[Problem that the invention seeks to solve]

By the way, in order to increase the surge withstand capacity in the varistor IO, the first . This can be achieved by increasing the effective electrode length of the second electrode film 12, 13, and by extension the electrode area. However, in the conventional varistor 10 described above, the only way to increase the effective electrode length is to increase the size of the varistor substrate 11 (
However, there is a problem in that the varistor becomes larger accordingly.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a varistor that can improve surge resistance without increasing the size of the varistor substrate.

[Means for solving problems]

In the present invention, a first t electrode film and a second electrode film are formed on the first main surface and the second main surface of the varistor substrate, respectively, and the first and second electrode films are formed on the first side surface and the second side surface of the varistor substrate. the first . each connected to the membrane. forming a second external electrode film, and forming an electrode separation part of a predetermined width between the first external electrode film and the second electrode film and between the second external electrode film and the first electrode film; The varistor is characterized in that a high resistance portion is formed in the electrode separation portion of the varistor substrate.

Here, the above-mentioned high-resistance part is made by applying a paste of LlgCOs, which is one of the Li compounds, to the electrode separation part of a varistor substrate mainly composed of ZnO, for example, and baking the paste to transfer Li to the varistor substrate. This can be achieved by diffusing it into the substrate.

[Effect]

According to the varistor of the present invention, since the high resistance part is formed in the electrode separation part of the varistor substrate, even if the electrode films facing each other are brought close to each other with the electrode separation part in between, current will not flow between them. As a result, the area of the growth electrode can be increased without increasing the dimensions of the varistor substrate, and therefore the surge resistance can be improved while remaining small.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are diagrams for explaining a varistor according to an embodiment of the present invention.

In the figure, 1 is a chip type varistor of this embodiment,
A first electrode 1I13 is formed on the upper first main surface 2a of the varistor substrate 2, and a second electrode film 4 is formed on the lower second main surface 2b. Further, a first external electrode M5 is formed on the first side surface 2C of the varistor substrate 2,
One end surface of the first external electrode JI15 is connected to the first electrode film 3, and the other end surface extends to the edge of the second main surface 2b. Furthermore, a second side surface 2d opposite to the first side surface 2c
A second external electrode Ill6 is formed on the second external electrode Ill6, one end surface of the second external electrode II16 is connected to the second electric rod IllI4, and the other end surface extends to the edge of the first main surface 2a.

A second external electrode lfI located between the first external electrode film 5 and the second electrode film 4 located at the edge of the second main surface 2b of the varistor substrate 2, and a second external electrode film 4 located at the edge of the first main surface 2a. An electrode separation part 7 having a predetermined width W is formed between the film 6 and the first electrode film 3.

Then, the picture electrode separation section 7 of the varistor substrate 2. A high resistance portion 8 is formed in the film so as to penetrate in the thickness direction. This high resistance portion 8 is formed by diffusing Ll into the varistor substrate 2 to form an insulating portion, and has a surface resistivity of 100 MΩ or more. As a result, the width W of the electrode separation section 7 is approximately 1/4 of the thickness H of the varistor substrate 2.

Next, the effects of this embodiment will be explained.

According to the chip type varistor l of this embodiment, the high resistance part 8 made by diffusing Li is formed in the picture electrode separation part 7 of the varistor substrate 2, so that the first external electrode film 5 and the second electrode film 4 and between the second external electrode film 6 and the first electrode film 3, the width W between the second external electrode film 6 and the first electrode film 3 can be narrowed. Second electrode film 3
．． The effective length Ll of the poles 1i facing 4, that is, the electrode area can be increased, and as a result, the surge resistance can be improved without increasing the dimensions of the varistor substrate. That is, when the external dimensions of the varistor substrate 2 of this embodiment are made the same as the conventional external dimensions L' (see Fig. 3), the effective electrode length Li is set to be thicker than the conventional length ( Furthermore, if the surge resistance is kept the same, the external dimensions can be made smaller than in the past, and miniaturization can be achieved.

For example, in a conventional varistor (see Figure 3), the external dimension L of the varistor substrate is 20mm, the thickness H is 2fi, and the width W' of the electrode separation part is 3mm (thickness H x 1.5 times). , the length l of each external electrode film from the edge of the varistor substrate to the electrode separation part
If ' is one crane, the effective electrode length of the first and second electrode films is L-20-(3+1)X2-12.

On the other hand, in this embodiment, the radiation W of the electrode separation section 7 is set to 0.
．． Since it can be shortened to 5 M (1/4 of the thickness of the varistor substrate), if the external dimension Ll + thickness H1 of the varistor substrate 2 and the length l of the external electrode film are kept the same as before, the effective electrode length L+ -20 (0,5+1)X2 =17
The effective electrode length can be increased by 5 mm (approximately 40%). Furthermore, if the growth length is set to 12 cranes, which is the same as before, the external dimension L8 can be reduced to 15 m without lowering the surge resistance.

Further, the high resistance portion 8 is formed by applying electrode paste to the varistor substrate 2 to form each electrode film.
Since it can be formed by applying a COx paste and baking it together, the manufacturing cost does not increase.

〔Effect of the invention〕

As described above, according to the varistor according to the present invention, since the high resistance portion is formed in the electrode separation portion of the varistor substrate, the first varistor can be removed without increasing the dimensions of the varistor substrate. This has the effect of increasing the effective electrode area of the second electrode film and improving surge resistance accordingly.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining a chip type varistor according to an embodiment of the present invention, in which FIG. 1 is a perspective view thereof, FIG. 2 is a side view thereof, and FIG. 3 is a conventional chip varistor. FIG. 3 is a side view showing a mold varistor. In the figure, 1 is a chip type varistor, 2 is a varistor substrate, 2a is a first main surface, 2b is a second main surface, 2C is a first side surface,
2d is the second side surface, 3 is the first electrode film, 4 is the second electrode film, 5
is the first external electrode film, 6 is the second external electrode film, 7 is the electrode separation part, 8 is the high resistance part, and W is the width of the electrode separation part. Figure 1

Claims (1)

[Claims] (1) A first electrode film and a second electrode film are formed on the first main surface and the second main surface of the varistor substrate, respectively, and the first and second electrode films are formed on the first side surface and the second side surface of the varistor substrate. forming first and second external electrode films connected to each other, and between the first external electrode film and the second electrode film, and between the second external electrode film and the first electrode film. A varistor comprising an electrode separation part of a predetermined width, characterized in that a high resistance part is formed in the electrode separation part of the varistor substrate.