JPS5913303A - 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 mainly composed of iron oxide.

A voltage nonlinear resistor (referred to as a μ-lower varistor) mainly composed of iron oxide (Fe, O,) is disclosed in, for example, Japanese Patent Publication No. 55-46044. This varistor is a so-called surface barrier type varistor, which is made of a sintered body containing rare earth oxides, calcium oxide, and iron oxide, an oxide semiconductor having barrier resistance, and a conductive film formed thereon. It is. This type of varistor has a small nonlinear coefficient α, but has a low rise voltage (vth) and small variation, so it is useful as a varistor for eliminating noise in a micromotor.

However, a varistor for this purpose is constructed by forming a plurality of silver electrodes on a ring-shaped sintered body and soldering the lead wires to each, but in this configuration, non-linear Coefficient α and rising voltage (v
th) will drop significantly.

On the other hand, there is a method disclosed in Japanese Patent Application Laid-open No. 55-9478, for example, which improves these drawbacks. This is a vapor phase deposition method (C
, V, D), and a silver electrode was further formed thereon. However, using the vapor phase deposition method itself is a factor that increases the cost of the varistor, and this tl.
This also causes variations in the characteristics of the Crab Norista, so it cannot be said to be a preferable solution.

Therefore, the present invention provides excellent voltage-
The object of the present invention is to provide a varistor having current characteristics and low rising stain pressure.

Another object of the present invention is to provide a varistor with small variation in rising stain pressure.

A further object of the present invention is to provide a varistor whose characteristics do not deteriorate due to processing such as soldering.

That is, the gist of this invention is that
j 70-96 molti, Cpa a01-10 molti, Sn
0. This varistor is characterized in that an electrode mainly composed of silver is formed on the surface of a sintered body made of 3 to 20 molten metal.

Here, the reason why the composition is limited to the above-mentioned composition range is as follows.

That is, rejOs is less than 7Q mol%, CaO is 10
When the molar ratio is exceeded and SnO exceeds 20 molar, the nonlinear coefficient α becomes small. On the other hand, Fe, O.

exceeds 96 molt, CaO is less than 1 molt, B11o
.

This is because if it is less than 6 molar, the change in rising stain pressure (Δvth) before and after soldering to the silver electrode becomes large.

Hereinafter, this invention will be explained in detail according to examples.

Example 1 F'e, O, cacoR, and SnO were used as raw materials and were weighed and mixed so as to obtain a sintered body having the composition ratio shown in Table 1. ? The mixed raw material C was calcined at 1000 tons, and a molded product was fired at 1250 to 1500°C for 2 hours.

The obtained sintered body is a disk with a diameter of about 10 mm and a wall thickness of 1 wt. A paste made by adding silver powder, glass frit, and fess was screen printed on both sides of this disk, and a paste of 800
Baking was carried out under the conditions of t'' and 30 minutes.

The voltage value V+ when a current of 1 mA and 10 fflA is applied to the sample thus obtained using a constant current power supply.
mA and VsomA were measured respectively. Further, the rising voltage (v th) was determined from the value at VlomA. In addition, the nonlinear coefficient α was determined using the following formula.

In addition, the sample was immersed in a 260 ± 20'c solder tank and soldered.
, find the nonlinear coefficient α, and find its rate of change Δvth.

Δα was measured for each. Measurement of each characteristic is shown in Table 81.

Note that the items marked with * in Table 1 are outside the scope of this invention, and all others are within the scope of the invention.

Further, the comparative example shows the results of similarly measuring the characteristics of a system containing La and O, which are types of rare earth oxides, instead of Snug.

As is clear in this example, according to the Fe, O, -CaO-day system according to the present invention, Δvtb
.

A varistor with small variations in both Δα and whose characteristics hardly change even after soldering has been obtained.

Example 2゜Example 1. For 100 samples having composition No. 3 in Example 1, a silver electrode was formed by baking in the same manner as in Example 1, and the average value (i) and variation (σ) of the rise voltage (vth) and nonlinear coefficient α were measured. It was Tooshi in Table 2.

Table 2 On the other hand, Example 1. For each 100 pieces having the composition of the comparative example in
2, a silver electrode was baked on top of that, and the average value ('li) and variation (σ) of the rising pressure (vth) and the nonlinear coefficient a were similarly measured. It was as shown in the table.

Table 3 As is clear from Tables 2 and 3, according to the present invention, the front electrode is baked directly onto the sintered body without forming SSn0z in advance by vapor phase deposition. Even if formed, v
It was found that the patent holds that the variation in both th and α is small.

As is clear from the above explanation, Fe according to the present invention
, 01-Cao-8nO, type varistors have the characteristic that their characteristics change little even when soldered, and moreover, they do not require the formation of vapor-deposited electrodes, which were conventionally thought to have stable characteristics. , Burning has the advantage of being able to provide a small risk of variation in both vth and α with a silver electric kettle.

patent applicant Floor type company Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] ``A voltage nonlinear resistor comprising an electrode mainly composed of silver formed on the surface of a sintered body consisting of 70 to 96% sOs, 1 to 10% CaO, and 0.3 to 20% Sn. .