JPS5861601A - Voltage nonlinear resistor - 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 The present invention relates to a voltage nonlinear resistor using strontium titanate semiconductor ceramic.

BACKGROUND ART Voltage nonlinear resistors (hereinafter referred to as varistors) have nonlinear voltage-current characteristics, and are used for purposes such as stabilizing voltages in various devices and suppressing abnormal voltages by utilizing these characteristics.

In general, the voltage-current characteristics of a varistor are expressed by the following formula, where ■
is the current flowing through the varistor, ■ is the voltage across the varistor, C
is a constant. Further, α is a nonlinear coefficient, and the larger α is, the better the nonlinearity is.

In order to express the rising voltage, a constant current of 1 mA is passed through the varistor, and the voltage appearing across the varistor at this time is measured, and this is defined as the varistor voltage.

Typical types of varistors include silicon h-bite varistors, silicon varistors, and zener diodes. Among these, silicon diodes and zener diodes are commonly connected in series for those with a varistor voltage of 10 V or less. Moreover, since the energy withstand capacity is small, the rupture phenomenon of the element is observed when an overcurrent flows.In order to make the voltage-current characteristics roughly symmetrical, it is necessary to connect the elements in parallel and in opposite directions. It was necessary to take measures.

In addition, there are varistors for low voltages below IOV in which silver electrodes are formed on the surface of barium titanate-based semiconductor ceramics, but they have large variations in varistor voltage and nonlinear coefficient, making them unsuitable for practical use. there were.

Therefore, an object of the present invention is to provide a varistor suitable for use with low electric juice.

Another object of the present invention is to provide a varistor with a large nonlinear coefficient and small variations in characteristics.

That is, the gist of the present invention is characterized in that an electrode mainly composed of copper is formed on the surface of strontium titanate-based semiconductor ceramic.

The present invention will be explained in detail below according to examples.

Strontium titanate-based semiconductor porcelain with a composition of 5
The raw materials were mixed to obtain a product consisting of 999.6 mol% of rTi0 and 0.4 mol% of Y203, and the mixed raw material was calcined in air at 1100°C, and then the calcined product was crushed, and then a binder was added and the particles were sized. , and further the size is 8IllISφ
, and was molded into a disk with a thickness of 0.35 m5+. Thereafter, the molded body was fired at a temperature of 1350° C. in a nitrogen atmosphere to obtain a semiconductor ceramic plate.

A copper paste containing non-reducible glass frit was applied to both sides of the obtained semiconductor ceramic plate, and baked at a temperature of 600° C. for 30 minutes in a nitrogen atmosphere to produce a varistor. In addition, the non-reducible glass frit used had the following composition, and the glass frit ratio to copper powder was 4.5 (copper powder):
95.5 (glass frit).

Non-reducible galanucrite: Zn040 heavy alcohol%, 8203
27% by weight, SiO28% by weight, Na2O3% by weight, C
aO or de heavy stitching%, CdO6% by weight, 3nQ26% by weight.

When the voltage across the 10 varistors obtained in this example was measured when the current flowing through the varistors was 1 mA, a mean value of 1.5 V was obtained, and a nonlinear coefficient (
When α) was measured, it showed a value of α=8. Further, the variation in each characteristic was also small.

In addition to the above-mentioned examples, the varistor voltage and non-linear coefficient were measured with different amounts of copper paste applied. showed that.

Further, in the above-described embodiments, the copper electrodes were formed by processing copper paste, but the same effect can be obtained by forming them by sputtering, vapor deposition, non-electrolytic plating, etc.

As described above, the varistor according to the present invention exhibits voltage nonlinearity based on the barrier layer formed at the contact surface between the strontium titanate-based semiconductor ceramic and the electrode mainly composed of copper, and exhibits voltage nonlinearity in the low voltage region. can be used. Moreover, a large nonlinear coefficient was obtained in this voltage region.

On the other hand, according to bulk type varistors, if you want to obtain a low voltage 1\ristor, you have to make the thickness thinner, but the thinner the varistor, the less the nonlinear coefficient tends to be. There is also a characteristic upper limit. Furthermore, when the thickness is reduced, the mechanical strength decreases, resulting in poor manufacturing yields. However, according to the present invention, the varistor is based on contact between semiconductor porcelain and an electrode mainly made of copper, so there is no processing problem associated with the above-mentioned bulk type varistor, the yield is good, and mass production is possible. We can provide excellent baristas.

Patent applicant Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] (1) A voltage nonlinear resistor characterized by forming an electrode mainly made of copper on the surface of strontium titanate-based semiconductor ceramic.