JPH02164006A - Zinc oxide type varistor - Google Patents

Abstract

PURPOSE:To obtain a zinc oxide type varistor with a large surge resisting amount of sintering a mixture whose main component is zinc oxide, and sub- compoents are bismuth oxide, chromium oxide, etc., and further containing a predetermined amount of boron silicide. CONSTITUTION:Raw material powder is formed whose main component is zinc oxide, and sub-components are bismuth oxide, chromium oxide, etc., and further to which at least 0.05-0.5mol% boron silicide, when converted to the form of SiB6, is added. Next, this raw is compression molded, then sintered, and further glass paste 3 is applied to the side surface of the sintered body 1 and baking treatment is carried out. Both end surfaces of thus obtained sintered body are polished to form flame sprayed electrodes of 2 of Al. Namely, boron silicide suppresses the growth of zinc oxide grains as conventional silicon oxide, and moreover the bulk specific gravity thereof is high and grinding proceeds uniformly, and has good dispersibility so that voids are scarcely produced. Thus, a zinc oxide type varistor with a large surge resisting amount can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a zinc varistor with excellent surge resistance characteristics.

Conventional technology Zinc oxide type varistors have a large surge current capacity and excellent voltage non-direction properties, and the low voltage type elements are widely used as surge absorbers, and the high voltage type elements are widely used as gapless arrester elements.

Conventionally, zinc oxide type varistor elements are based on the oxidation profile (Z) of the main component.
nO), bismuth oxide (Bi, O,), ammonium oxide>
(Sb, O,), # conversion: r HaN) (Go, O
, ) e Manganese oxide (MnO, ), silicon oxide (Si
n, ), etc., add an appropriate binder, wet-pulverize with a ball mill, etc., and then granulate and mold 0w8. Manufactured through a gambling process. Oxide tEi for arresters
When manufacturing a type varistor, the varistor voltage (vll, /l111) per unit thickness is generally 200 V or more.

Necessary for downsizing and cost reduction. Among the above-mentioned additives, silicon oxide (Sin) is particularly known as a substance that suppresses grain growth of zinc oxide and improves temperature characteristics and charge life characteristics. It is an essential component of the material.

Problems to be Solved by the Invention However, when silicon oxide (Sin) is used as an additive to increase the varistor voltage (v++y") per unit thickness of an oxidized surface-shaped varistor, other additives Even if a material with a significant bulk specific gravity and long settling time is used, it will not be sufficiently crushed, resulting in voids in the sintered body, which is one of the most important characteristics of an 8-il zinc varistor. The problem was that the surge #*C2m5 square wave current application test) was low. In addition, if silicon oxide (f9i0.) is added at 1 mo/l/% or more in order to increase the pressure of the material, the viscosity of the pulverized raw material slurry increases significantly, making granulation difficult and causing problems. was.

The present invention is intended to solve these conventional problems, and its main purpose is to significantly improve the surge resistance of zinc oxide type varistors.It also aims to prevent gelation of slurry, which is a manufacturing problem. The purpose is to

Means for Solving the Problems The present invention solves the above conventional problems by using taro as a main component, zinc oxide, and as subcomponents of bismuth oxide, antimony oxide, and cobalt oxide. Boron silicide in manganese oxide, chromium oxide, etc. is at least 0.06 in 5in6 form.
It is characterized in that it is added at ~5.0 moA/.

Function According to the present invention, boron silicide replaces conventional silicon oxide (
Similar to Sin,), it has the effect of suppressing the growth of concentrated zinc particles, and also has a high bulk specific gravity, allows for uniform pulverization, and has good dispersion and aggregation, so voids occur in the am body (<, extremely It is possible to obtain a zinc oxide type varistor having high A surge 1 withstand characteristics.

EXAMPLES Hereinafter, the lead oxide type varistor according to the present invention will be described in detail based on examples.

First, add bis-v-suo, ts-e:/L'X, a-7:/timo71.0-f to the powder of zinc a-chloride for each total amount.
=A/%.

Cobal oxide l-0.5 mo/l/π, manganese oxide 0.5
Mo μ%, chromium oxide 0.5 moN, boron silicide in 5iB6 (7) form 0, 0.01, 0.05 respectively
゜0.1.1.0.5.0, 10.0 mo/%/7 kinds of raw material powders were added with pure water so that the solid content ratio was about 60 wt. (Polyvinyl μAcor A/) was added to 0.6 weight based on the solid content,
Put the whole thing in a ball mill with zirconia boulders, and
A slurry was obtained by grinding for a time. In addition.

The average particle size of the boron silicide used was 3.0 μm. These six types of sprays were dried with a spray dryer and granulated to create raw material powder. This raw material powder was pressed into a shape with a diameter of 4ON and a thickness of 30fi using a fire, and sintered at 1000°C in air. Glass paste was applied to the side surface of this sintered body and baked at 500°C. Both end faces of the sintered body thus obtained were polished,
A sprayed aluminum electrode was formed. Figure 1 shows the zinc oxide type varistor obtained as described above, where 1 is a sintered body;
2 is a sprayed aluminum electrode, and 3 is an overcoat layer on the side surface of the fired fiNf*1, which is formed by baking glass, plasma spraying alumina, etc.

Figure 2 shows the change in viscosity of the raw material slurry over time.

Here, the viscosity was measured using a rotational viscometer. Also.

For comparison, when silicon oxide (Sin2) was used as an additive, a slurry was prepared under the same manufacturing conditions even though it was busy, and the viscosity was measured for comparison. Now, as a method for drying and granulating slurry, a spray dryer is generally used when producing one product. In order to dry and granulate using a spray blower, the slurry paste must be 300 to 50%
It is necessary that it is 0009!1 or less. As shown in Fig. 2, when using 1 mo/L' koto weakened silicon,
The viscosity increased rapidly in 6 hours and was dried with a spray dryer.
It becomes impossible to carry out granulation. Furthermore, 5mo/I/CX
When using silicon oxide, the initial MIE is already 50ocp.
I confirmed that it was over 8. On the other hand, when boron silicide of 1 mo/L'% and 5 moA/% is used as the starting material, it can be seen that almost no thickening phenomenon of the slurry is observed in either case. Therefore, when boron silicide is used as an additive, granulation using a spray dryer becomes possible over a long period of time.

It can be seen that it is extremely convenient for processing raw materials for Daizo.

Next, the initial characteristics of the sintered body are shown in Table 1 below.

Here, V and V are 1 using a DC constant current power supply.
Measurements were made with a thickness of 10 μm. In addition, the slope control 1 pressure characteristic has a waveform of 8/2゜μS.
, was measured using an impulse with a current peak value of 5000 μm. And v! I2. /IM has a boron silicide content of 0.06 mol% or more and 2007/ff or more.
This value is suitable as a material for an arrester element, and when 6 mol % is added, the pressure can be increased to about 300 V/m. And 6 mol%
It can be seen that when more boron silicide is added, the limiting solder pressure ratio deteriorates rapidly. On the other hand, when silicon oxide is used as an additive, the slurry viscosity increases even though the pressure is increased in the same machine, so the addition is limited to 1 mol%, and V...
/m is 225 V 711M (!: Natsuta.

(Margin below) Next, a surge resistance test was conducted on the above sample.

The trial condition is 2! A rectangular wave current of Is, 300 μm was applied at 2 minute intervals until the device was destroyed. The results are shown in Table 2 below. The line in the table is the average number of square wave current applications that the element withstood without breaking (number of samples: 51 m each),
and the distribution range (highest value - minimum range).

(Left below) From Table 2, the amount of boron silicide added is O, OS ~ 6.
It can be seen that the surge 1lft/dragon characteristic is about 2 to 2.6 times higher than that of the conventional silicon oxide type in the range of Mo/L/%, and the performance is significantly improved. It can also be seen that the dispersion (distribution range) of the characteristics of Surge 1 has become narrower, and the compatibility of the element has also improved. This is thought to be because boron silicide has good dispersibility and pulverization progresses uniformly, which reduces the occurrence of defects such as voids inside the 6,41 tubes. but,
6. In a system in which boron silicide is added in excess of Omo/I/, the surge rate decreases. This is because the ballista Ka: (V,,,7m) of Ugly ILC has risen,
It is thought that the amount of energy applied per unit volume increases, making it easier to rupture due to heat stress. Therefore.

The most preferable addition amount of boron silicide is 0.05 to 6.0 from the results of initial characteristics and surge performance characteristics tests.
It can be seen that it is monN%.

In addition, one invention Kj? - The basic material composition is ZnO.

BiO, SbO, Coo MnO, Or, O, 25
25 23 ・
Although the experiment was carried out with 2 systems, Ni was used to further improve the properties of the sintered body.
O, SnO, MgO, TiO, Mura05. Even if Mug20 or the like is added, the effects of the present invention will not change.

Effects of the Invention As described above, according to the present invention, zinc oxide is the main component,
Bismuth a, antimony oxide, cobalt chloride, manganese oxide,! Add chromium ROM etc. as a sub-layer, and further add at least boron silicide to the shape of SiB6 to 0.06.
By sintering a mixture containing ~5.0 MoJV%,
A zinc oxide varistor with high surge resistance and high varistor bottom pressure per unit thickness can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a zinc oxide varistor according to the present invention, and FIG. 2 is a diagram showing changes over time in the viscosity of raw material slurry for zinc oxide varistors according to a practical example of the present invention and a conventional example. 1... Sintered book, 2... Electrode, 3...
...Overcoat layer.

Claims (1)

[Claims] Zinc oxide is the main component, metal oxides such as bismuth oxide, antimony oxide, cobalt oxide, manganese oxide, and chromium oxide are subcomponents, and at least boron silisite is 0.05 to 5 in terms of SiB_6 form. Zinc oxide type varistor made by sintering raw material powder containing .00 mol%.