JPH03208304A - Zinc oxide varistor and manufacture thereof, and crystallized glass composition for coating - Google Patents

Abstract

PURPOSE:To provide a high reliability zinc oxide varistor by providing a crystallized glass side high resistance layer taking PbO as a chief ingredient including a specific amount of MoO3 on the side surface of a sintered product taking zinc oxide as a chief ingredient. CONSTITUTION:There is provided on the side surface of a sintered product 1 including zinc oxide as a chief ingredient a crystallized glass side high resistance layer 3 taking PbO as a chief ingredient including molybdenum oxide of 0.1-10.0% by weight reduced in the form of MoO3. Hereby, the crystallized glass taking PbO as a chief ingredient is promoted in its crystallization with the addition of MoO3 and improved in the strength of a coated film with the addition of SiO2, an is excellent in an electrostatic breakdown characteristic because of its good contact property with a sintered product and is limited to the minimum in its deterioration of voltage nonlineality upon its being sintered because of its high insulator. Thus, an excellent charging life time characteristic, high reliability zinc oxide varistor can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a zinc oxide varistor, a method for manufacturing the same, and a thermistor, which are mainly used in the electric power field.

The present invention relates to a crystallized glass composition used for coating oxide ceramics such as varistors.

Conventional technology ZnO is the main component, Bi2O: +, Coo, 5b20
．． +.

Cr203. Zinc oxide varistors, which contain several types of metal oxides such as Mn02, have large surge resistance and excellent voltage nonlinearity, and have recently been used as elements for gear press arresters, replacing conventional silicon carbide. It is well known that it is widely used in place of baristas.

Conventionally, a method for manufacturing a zinc oxide varistor has been disclosed, for example, in Japanese Patent Application Laid-Open No. 101002/1983, and the content of the preceding example is as follows. First, Bi2O3゜5b203. Cr2O+,
0.01 each of metal oxides such as Coo and MnO2
The raw material powder containing ~6.0 mol% was mixed and granulated, the granulated powder was pressurized and formed into a cylindrical shape, and heated in an electric furnace at 1200°C for 6 mol%.
Bake for an hour. Next, PbO
A glass paste consisting of 80% by weight of PbO-based glass frit containing 60% by weight of PbO, 20% by weight of feldspar, and an organic binder is printed on a screen printing machine for 5 to 500 m.
After coating at g/cm2, baking treatment is performed.

Both end faces of the element thus obtained are polished to form aluminum metallicon electrodes to obtain a zinc oxide varistor.

Problems to be Solved by the Invention However, since the zinc oxide varistor manufactured by the conventional manufacturing method uses the screen printing method, the thickness of the side glass layer is uniform and the variation in discharge withstand characteristics is small, but 1PbO Because it is a composite glass of glass frit and feldspar, it has low discharge withstand characteristics, and voltage nonlinearity decreases during glass baking processing.
It also had the disadvantage of deteriorating the charging life characteristics.

The present invention solves the above-mentioned conventional problems, and aims to provide a highly reliable zinc oxide varistor, a method for manufacturing the same, and a coating crystallized glass composition used for coating varistors and thermistors. It is something.

Means for Solving the Problems In the present invention, in order to solve the above-mentioned conventional problems, a sintered body mainly composed of PbO containing at least 0.1 to 10.0% by weight of MoO3 is added to the side surface of a sintered body mainly composed of ZnO. This structure has a side surface high-resistance layer made of crystallized glass as a component. Further, at least M OO is added to the side surface of the sintered body.
A glass paste consisting of crystallized glass mainly composed of PbO containing 0.1 to 10.0% by weight of 3 and an organic binder was applied at 10.0 to 150.0 μ/a+r and heated at 450°C.
Baking treatment is performed at a temperature range of ~650°C to form a high resistance layer on the side surface.

Furthermore, at least Moo for the side high resistance layer.

PbO-ZnO-B20 containing 0.1 to 10.0% by weight
3-5 i 02 - A crystallized glass composition for coating MoO3-based oxide ceramics is provided.

According to the present invention, compared to PbO-feldspar composite glass, crystallized glass containing PbO as a main component has a higher Mo
Crystallization is promoted by the addition of O3, and the strength of the coating film is improved by the addition of Si02, and the adhesion with the sintered body is good, so it has excellent discharge withstand characteristics, and also has high insulation properties, so it is easy to use during baking treatment. It becomes possible to minimize the decrease in voltage nonlinearity, and it is possible to obtain a highly reliable zinc oxide varistor with excellent charging life characteristics.

Examples Below, the zinc oxide varistor of the present invention and its manufacturing method,
Furthermore, the crystallized glass composition for coating will be explained in detail based on Examples.

First, BizOzo, 5
Add mol%, CO2O30.5 mol%, Mn020.5 mol%, 5b2031.0 mol%, Cr2O:io, 5 mol%, NiOO, 5 mol%, 5iOzO65 mol%, and add pure water, binder, and dispersant together with e.g. After thorough mixing and pulverization in a ball mill, the mixture was dried and granulated in a spray dryer to obtain a raw material powder. This raw material powder has a diameter of 40 mm.
It was compression molded to a size of 30 m and 30 m thick, and was degreased at a temperature of 500° C. or higher. After that, 1100℃～1
A sintered body was obtained by firing in a temperature range of 250°C.

On the other hand, the crystallized glass for coating is PbO and ZnO.

B2O3,S 102. A predetermined amount of MoO3 was weighed, mixed and pulverized using, for example, a ball mill, then melted in a platinum crucible at a temperature of 1000t to 1200'C, and rapidly cooled to vitrify. This glass was coarsely ground and then finely ground in a ball mill to obtain a glass frit. In addition, Pb was used as a sample for comparative study.

70.0% by weight, ZnO25.0% by weight, B 20
: ] Glass frit consisting of 5°0% by weight 80. OTK
Amount% Tolc stone (& Stone KA I S i: +os, N
a A IS i 30B, Ca A I 2S
i20Bf) Solid solution) A composite glass consisting of 20.0% by weight was prepared in the same process. The composition and glass transition point (
Tg) and linear expansion coefficient (α) are shown in Table 1 below.

(Left below) From Table 1, when the amount of PbO added is large, the coefficient of linear expansion (α
) becomes high and the amount of ZnO added is large, the glass transition point (Tg) becomes low and crystallization becomes difficult. Also, B
When the amount of 2O3 added is small, the glass transition point becomes high, and when the amount added exceeds 15.0% by weight, crystallization becomes difficult. Furthermore, as the amount of SiO2 added increases, the glass transition point tends to increase and the linear expansion coefficient tends to decrease. As the amount of MoO2 added increased, crystallization of the glass progressed. Also, PbO.

Systems with low B2O3 tended to become porous glass.

Next, 85% by weight of this glass frit and 15% by weight of an organic binder (a mixture of ethyl cellulose and butylcarpitol acetate) were thoroughly mixed in, for example, a three-roll mill to obtain a glass paste for coating. This coating glass paste is applied for 12 minutes using a curved screen printing machine, for example.
Printing was performed on the side surface of the sintered body using a screen of 5 to 250 meters. Here, the amount of coating glass paste applied was determined from the difference in weight of the sintered body after applying the paste and drying at 150° C. for 30 minutes. Further, the coating amount was adjusted by adding an organic binder, n-butyl acetate, to the coating glass paste. Thereafter, the coating glass paste was baked at a temperature of 350°C to 700°C to form a side high-resistance layer on the sintered body. Next, both end faces of this sintered body were flat-polished to form aluminum metallicon electrodes to obtain a zinc oxide varistor.

FIG. 1 shows a sectional view of a zinc oxide varistor according to the present invention obtained as described above. In FIG. 1, 1 is a sintered body mainly composed of zinc oxide, 2 is an electrode formed on both end faces of the sintered body 10, and 3 is obtained by baking crystallized glass on the side surface of the sintered body 1. It is a high-resistance layer on the side surface.

Next, Table 2 below shows the appearance, V,..., A/V of the zinc oxide varistor manufactured using the coating glass shown in Table 1.
IQIIAI Indicates discharge capacity characteristics and charging life characteristics. At this time, the coating amount of glass paste for coating was 50μ/
The viscosity of the paste was controlled so that it was al. Furthermore, the baking treatment conditions were 550° C. and 1 hour. here,
The number of samples is n=5 for each lot. Also, V+, ^+
VIO#A was measured using a DC constant current power supply. The discharge withstand characteristics were determined by applying an impact current of 4/10 μs twice in the same direction at 5 minute intervals, and stepping up from 40 kA. Furthermore, the charging life characteristics are as follows: ambient temperature 130℃2
The test was carried out under the condition that the charging rate was 95% (AC, peak value), and the time until the leakage current reached 5 mA (peak value) was measured.

(Left below) From Table 2, the linear expansion coefficient of the coating glass is 65XIO-
When smaller than 7/℃ (Gl, G5.Gi-8 glass)
It can be seen that when the temperature exceeds 90×10 −7 /° C. (G4 glass), the glass tends to peel off easily, and cranks tend to occur. It is thought that the samples in which cracks and glass peeling occurred have low discharge withstand characteristics because the insulation of the side high-resistance layer is poor. Further, the linear expansion coefficient of the coating glass is 65X1. O-7 to 90 x 10-7/'C
Glass with poor crystallinity (G8 glass) even in the range of
They tend to crack easily and have low discharge withstand characteristics. This is considered to be because the coating film strength of crystalline glass is higher than that of amorphous glass. Furthermore, the addition of ZnO does not significantly affect the electrical properties and reliability of the zinc oxide varistor, and is useful for lowering the glass transition point among the physical properties of glass. In addition, PbO-ZnO, which is an example of prior literature
- When using B2O3, feldspar composite glass,
It can be seen that although the charging life characteristics are at a practical level, the discharge withstand characteristics are low.

Next, the amount of M o O3 added will be considered. first,
In any composition system in which the amount of MoO3 added is 0.1% by weight or more, the voltage nonlinearity is improved, and the charging life characteristics are also improved accordingly. This is MoO
This is thought to be because adding 0.1% by weight or more of 3 increases the insulation resistance of the coating film. On the other hand, M
o When the amount of O3 added is higher than 1000% by weight, the discharge durability characteristics are low. This is thought to be because the glass tends to become porous due to its poor fluidity during the baking process. Therefore, for the side high resistance layer of zinc oxide varistor (7
) PbO-ZnOB2O3S io2 In MoO3-based crystallized glass, at least M o O3 is 0.1 to
A necessary condition is that the composition contains 10.0% by weight.

From the above results, the composition of the coating crystallized glass is PbO
is 50.0 to 75.0% by weight, and ZnO is 10.0 to 30% by weight.
．． 0 wt%, B2O3 5.0-10.0 wt%, Si
O2 is 0-15.0% by weight, MoO3 is 0.1-10.
It can be seen that the range of 0% by weight is optimal. Further, for use in a side surface high resistance layer of a zinc oxide varistor, it is necessary that the coefficient of linear expansion is within the range of 65 to 90 x 10-7/'C.

Next, the amount of glass paste to be applied was examined using 016 glass shown in Table 1, which is an example of the present invention. The results are shown in Table 3 below. Here, the amount of glass paste applied is 1
．． 0-300. The viscosity of the paste and the number of applications were controlled using Ovrg/crl. From Table 3, when the coating amount is less than 10.0mg/cm2, the strength of the coating film is low, and when the coating amount is more than 1.50.0cm2/al, the glass may flow or Since pinholes are likely to occur in the battery, discharge durability characteristics are poor. Therefore, it can be seen that the optimum amount of glass paste to be applied is in the range of 10.0 to 150.0 mg/cl.

(The following is a blank space.) Next, using the 016 glass shown in Table 1, which is an example of the present invention, the baking treatment conditions of the glass paste were investigated. The results are shown in Table 4 below. Here, the viscosity was controlled so that the amount of glass paste applied was 50.0 .mu./al. In addition, the baking treatment of glass paste is 350 to 700℃.
The test was carried out in air at a temperature range of 1 hour for a holding time of 1 hour.

As a result, when baking treatment is performed at a temperature lower than 450℃,
Since the glass paste is not sufficiently melted, the discharge resistance characteristics are low, and when baking treatment is performed at a temperature higher than 650° C., the voltage ratio is significantly lowered and the energized life characteristics are deteriorated. Therefore, it can be seen that the temperature range of 450 to 650°C is optimal for the baking treatment conditions for glass paste.

(The following is a blank space) 19- In addition, in this example, PbO-PbO-Zn0-B203
-, PbO-ZnO-B2O35102-M2O34
and a five-component crystallized glass for coating have been described, but as the sixth component, a trace additive that further promotes the crystallization of the glass, such as A I 203. Even if S n 02 or the like is added, the effects of the present invention will not change. Furthermore, in the above embodiment, ZnO was used as a substance that lowers the glass transition point.
was used, but it goes without saying that it can be replaced with other substances. Furthermore, in this example, the P bo ZnOB2O3S i 02M0O3-based coating crystallized glass of the present invention was used for the zinc oxide varistor as a representative example of the oxide ceramic; It can be applied in exactly the same way to any oxide ceramics, such as capacitors, positive characteristic thermistors, and metal oxide-based negative characteristic thermistors.

Effects of the Invention As described above, according to the present invention, at least 0.1 to 10 of MoO3 is added to the side surface of the sintered body containing zinc oxide as a product.
．． PbO-ZnO-B203S i 02 containing 0% by weight
By baking the crystallized glass for MOO3-based oxide ceramic coating at a temperature of 450 to 650° C., a zinc oxide varistor with excellent discharge durability characteristics and energized life characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a zinc oxide varistor according to an embodiment to which the manufacturing method of the present invention and the crystallized glass for coating of the present invention are applied. 1... Sintered body, 2... Electrode, 3...
... Side high resistance layer.

Claims (6)

[Claims] (1) The main component is PbO, which contains zinc oxide as the main component and contains at least 0.1 to 10.0% by weight of molybdenum oxide in the form of MoO_3 on the side surface of the sintered product, which has varistor properties. A zinc oxide varistor with a high-resistance side layer made of crystallized glass. (2) Side high resistance layer is PbO-ZnO-B_2O_3-
The zinc oxide varistor according to claim 1, comprising MoO_3-based crystallized glass. (3) Side high resistance layer is PbO-ZnO-B_2O_3-
The zinc oxide varistor according to claim 1, comprising SiO_2-MoO_3-based crystallized glass. (4) At least MoO_3 is applied to the side surface of the sintered body which is mainly composed of zinc oxide and has varistor properties.
．． A glass paste consisting of crystallized glass whose main component is PbO containing 1 to 10.0% by weight and an organic substance is 10.0 to 1% by weight.
A method for producing a zinc oxide varistor, in which 50.0 mg/cm^2 is applied and baked in a temperature range of 450°C to 650°C. (5) The linear expansion coefficient of crystallized glass is 65 to 90 x 10^
The method for manufacturing a zinc oxide varistor according to claim 4, wherein the temperature is -^7/°C. (6) PbO50.0-75.0% by weight, ZnO10.
0 to 30.0% by weight, B_2O_35.0 to 15.0% by weight, SiO_20 to 15.0% by weight, MoO_30.
A crystallized glass composition for coating consisting of 1 to 10.0% by weight.