JPH0812810B2 - Method of manufacturing voltage non-linear resistor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a voltage nonlinear resistor containing zinc oxide as a main component.

(Prior Art) Conventionally, the main component is zinc oxide, and Bi ₂ O ₃ , Sb ₂ O ₃ , Si
It is widely known that resistors containing a small amount of additives such as O ₂ , Co ₂ O ₃ and MnO ₂ exhibit excellent voltage nonlinearity. ing.

In this voltage non-linear resistor, when a surge current such as lightning is applied to the element, a flashover mainly along the side surface of the element, a so-called creeping flashover may occur and the element may be destroyed. It is general to provide a high resistance layer made of an Sb-Si compound or a Bi-Sb-Si-Zn compound.

(Problems to be Solved by the Invention) Since the raw material of the conventional voltage non-linear resistor has a crystalline structure, the grain boundary layer between ZnO particles is not uniform, resulting in variation in characteristics and deterioration in quality. In order to solve this problem, a technique in which at least one of the raw materials for the resistor has an amorphous structure is disclosed in Japanese Patent Laid-Open No. 59-903.

However, in the technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 59-903, at least one of the raw materials for the resistor has only an amorphous structure. When a three-component or four-component side high-resistance layer is provided, the adhesion between the resistor body and the side high-resistance layer deteriorates, and as a result, the characteristics fluctuate, the discharge withstand capability changes, and the life span becomes shorter. There were cases.

The object of the present invention is to solve the above-mentioned problems, improve various discharge withstand capabilities and electric charge life, reduce variations in characteristics, and also provide good adhesion between the resistor body and the lateral high-resistance layer on a voltage non-linearity. It is intended to provide a method for manufacturing a resistor.

(Means for Solving the Problems) A method for manufacturing a voltage nonlinear resistor according to the present invention is to provide at least a silicon compound, an antimony compound, and bismuth on a side surface of a voltage nonlinear resistor containing zinc oxide as a main component and containing at least a silicon component. In a method for producing a voltage non-linear resistor in which a mixture for a lateral high resistance layer made of a compound is applied and then fired, amorphous silica is used as a silicon component raw material of the resistor, and a silicon compound is used as a silicon compound in the mixture. It is characterized by using amorphous silica.

(Operation) In the above-described configuration, the present inventors have conducted various studies on the properties of each additive component of the resistor to be used and the properties of each component of the side surface high resistance layer, and as a result, in the resistor body and the side surface high resistance layer. By using amorphous silica as the Si component,
It has been found that various discharge withstand capabilities and electric charging life are improved and variations are reduced, and the adhesiveness between the resistor body and the side surface high resistance layer is also improved.

That is, among various additive components, particularly the Si additive component reacts with zinc oxide in the resistor body and the lateral high-resistance layer to generate zinc silicate (Zn ₂ SiO ₄ ). This zinc silicate plays an important role in improving the uniformity of the resistor body such as grain growth control of zinc oxide in the resistor body, and also in the side surface high resistance layer, preventing creeping flashover due to lightning surge application. .

When the Si-added component is crystalline, the reactivity with zinc oxide deteriorates, so that the distribution of zinc silicate becomes nonuniform, and the uniformity of the resistor body and the lateral high-resistance layer deteriorates.
Therefore, in the resistor body, internal penetrating breakdown is likely to occur due to the application of the switching surge, and the resistor is apt to cause thermal runaway during constant power application due to the reduction in varistor voltage due to the surge application and the deterioration of the service life. Further, in the side surface high resistance layer, a lightning surge is likely to cause a creeping flashover on the side surface of the resistor.

Also, if the Si additive component of the side surface high resistance layer is not the same amorphous material as that of the resistor body, the contraction balance between the resistor body and the side surface high resistance layer is broken by firing, and the side surface high resistance layer is peeled off. Since the side surface high resistance layer exhibits hygroscopicity, the side surface of the resistor is likely to have a flashover due to the application of surge. It is not preferable that the side surface high resistance layer exhibits hygroscopicity in terms of long-term reliability.

The method for producing the amorphous silica to be used is not particularly limited, but will be described later when the one obtained from the metathesis reaction of sodium silicate and the one obtained by the thermal decomposition of silicon tetrachloride are used. As is clear from the examples, the characteristics are good, which is preferable. The purity of SiO ₂ is 95% or more, and the average particle size is 10 μm.
The following is preferable.

Further, as a mixture for forming the lateral high-resistance layer, amorphous silica, a bismuth compound, and an antimony compound are used as Si.
_{O 2, Bi 2 O 3,} Sb 2 O 3 SiO 2 70~95 mol% in terms of, preferably
80 to 90 mol%, Bi ₂ O ₃ 1 to 15 mol%, preferably 3 to 10
Mol%, Sb ₂ O _{3 3 to} 20 mol%, preferably 5 to 15% It is preferable to add a zinc compound in an amount of 150 mol% or less, preferably 80 mol% or less, calculated as ZnO by external distribution, if necessary. The average particle size of the whole is preferably 10 μm or less. And
The thickness of the side surface high resistance layer is preferably 30 to 150 μm.

Here, a bismuth compound, an antimony compound, and a zinc compound are specified as the composition of the mixture for the lateral high-resistance layer, but each compound may be any oxide as long as it changes to an oxide at 1000 ° C or lower, preferably 800 ° C or lower. Specific examples thereof include oxides, carbonates, nitrates and hydroxides, with oxides being most preferred.

(Example) In order to obtain a voltage nonlinear resistor containing zinc oxide as a main component, first, a zinc oxide raw material adjusted to a predetermined particle size and Bi ₂ O ₃ , Co ₂ O ₃ , and MnO ₂ adjusted to a predetermined particle size were prepared. , Sb ₂ O ₃ , Cr ₂ O ₃ , Si
A predetermined amount of an additive such as O ₂ or NiO is mixed. On this occasion,
In the present invention, amorphous silica having an average particle size of 10 μm or less is used as the SiO ₂ source material. A predetermined amount of an aqueous polyvinyl alcohol solution or the like is added to these raw material powders, preferably mixed by a disper mill, and then preferably granulated by a spray dryer to obtain a granulated product. After granulation, molding pressure 80
It is formed into a predetermined shape under 0 to 1000 kg / cm ² . And the molded body is kept at a temperature rising / falling speed of 50 to 70 ° C / hr and a holding time of 800 to 1000 ° C 1
Preliminary firing is performed under the condition of about 5 hours.

In addition, the temperature rising / falling rate of the molded product before calcination is 10 to 100 ° C / hr.
It is preferable that the binder is scattered and removed by heat treatment at 400 to 600 ° C. for 1 to 10 hours.

The element body of the present invention means a molded body or a degreased body obtained by heat-treating the molded body under the above conditions.

Next, a side surface high resistance layer is formed on the side surface of the calcined body that has been calcined. In the present invention, a side surface high resistance layer mixture paste obtained by adding a predetermined amount of a bismuth compound, an antimony compound, a silicon compound, etc., as an organic binder, ethyl cellulose, butyl carbitol, n-butyl acetate, etc. to a thickness of 60 to 300 μm is prepared. Apply to the side of the calcined body. The mixture paste may be applied to the element body. At this time, in the present invention, amorphous silica having an average particle diameter of 10 μm or less is preferably used as the silicon compound. Next, set this to 40 ~ 60
C./hr, 1000 to 1300.degree. C., preferably 1100 to 1250.degree. C., main firing under conditions of 3 to 7 hours. A glass paste prepared by adding ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to glass powder is applied on the lateral high-resistance layer to a thickness of 100 to 300 μm, and the temperature rising / falling rate is 100 in air. It is preferable to form the glass layer by heat treatment under the conditions of ~ 200 ° C / hr and 400-600 ° C holding time of 0.5-2 hours.

After that, both end surfaces of the obtained voltage nonlinear resistor are
Polishing is carried out with water, preferably oil, with an abrasive corresponding to # 400 to 2000 such as ₂ O ₃ or diamond. Next, after cleaning the polished surface, electrodes are provided, for example, by spraying, on the polished both end surfaces by, for example, aluminum or the like to obtain a voltage non-linear resistor.

Hereinafter, the results of actually measuring various characteristics of the voltage nonlinear resistor within and outside the range of the present invention will be described.

Example 1 V _{1 mA} = 47 mm in diameter and 20 mm in thickness prepared by the method described above
In order to investigate the influence of the state of silicon in the resistor body and the mixture for the lateral high resistance layer on the characteristics in a voltage non-linear resistor of 210 to 230 V / mm, both of the present invention using amorphous silica Sample Nos. 1 to 8 within the range and Comparative Examples Nos. 1 to 4 which do not satisfy the scope of the present invention in any point are prepared,
Reduction rate of varistor voltage after application of lightning surge (Δ
V _1mA ), lightning surge withstand destruction rate, switching surge withstand destruction rate,
The ratio of leakage current and the hygroscopicity of the side surface high resistance layer were measured.

The composition of the tested resistors is Bi ₂ O ₃ , Co ₃ O ₄ , and Mn.
_{O 2, Sb 2 O 3,} Cr 2 O 3, NiO each 0.1 to 2 _{mole%, Al (NO 3) 3} · 9
0.001 to 0.01 mol% of H ₂ O, 0.01 to 0.3 wt% of bismuth borosilicate glass containing silver, 2 mol% of SiO ₂ , balance ZnO
And Regarding the amorphous silica used,
1A is used according to FIG. 1A, B is used according to FIG. 1B, and B is used according to FIG. 1B. ) Is C,
In addition, amorphous silica glass and quartz and cristobalite as conventional products having a crystalline structure were used with the average particle sizes shown in Table 1. Furthermore, the mixture other than the silicon compound for the side surface high resistance layer has an average particle size of 5 μm as a bismuth compound.
m of bismuth oxide, and the antimony compound used was antimony oxide having an average particle size of 3 μm. The mixture for the side surface high resistance layer is composed of SiO ₂ 85 mol%, Bi ₂ O ₃ 5 mol%, Sb ₂
A ternary system containing 10 mol% O ₃ was used. The results are shown in Table 2.

In Table 2, ΔV _1mA is the current waveform of 8 / 20μs.
The varistor voltage (V _1mA ) drop rate after the KA current was repeatedly applied 10 times, and the lightning surge withstand breakdown rate was 100KA, 11
The ratio of the breakdown after applying the pulse current of 0KA and 120KA twice with the current waveform of 4/10 μs and then breaking is shown. In addition, the switching surge withstand breakdown rate is the ratio of the breakdown after the current of 1000A, 1100A, 1200A is repeatedly applied 20 times with the current waveform of 2ms.
The ratio of the leakage current was calculated from the current ratio I ₁₀₀ hours / I ₀ hours after 100 hours of application of electricity immediately after application of electricity at an ambient temperature of 130 ° C and an electricity application rate of 95%. Furthermore, the hygroscopicity of the side surface high resistance layer is that the element is immersed in the fluorescent flaw detection liquid at a pressure of 200 kg / cm ² for 24 hours and then the moisture absorption state is inspected. Some are shown as x.

From the results shown in Table 2, the sample Nos. 1 to 8 of the present invention using amorphous silica as the silicon raw material in the resistor and the high resistance layer.
Are comparative examples Nos. 1 to 4 which do not satisfy the present invention in any point.
It was found that various characteristics were good as compared with. Further, among the present invention, various characteristics are further improved by using those obtained by utilizing the metathesis reaction of sodium silicate or those obtained by utilizing the thermal decomposition reaction of silicon tetrachloride as the amorphous silica. Therefore, it is preferable. Furthermore, if the same type of amorphous silica used in the resistor and the high-resistance layer is used, the shrinkage balance of the resistor body and the side high-resistance layer due to firing will match, as described above, and therefore various characteristics will be further improved. It can be seen that it becomes good and preferable.

(Effects of the Invention) As is clear from the above description, according to the method for manufacturing a voltage nonlinear resistor of the present invention, amorphous silica is used as the silicon component in the mixture for the resistor body and the lateral high-resistance layer. By using it, it is possible to improve various discharge withstand capability and electric charging life, reduce the variation in characteristics, and to improve the hygroscopicity of the lateral high-resistance layer and to ensure good adhesion between the resistor body and the high-resistance layer. A linear resistor can be obtained.

It was also confirmed that good characteristics can be obtained for the limiting voltage.

[Brief description of drawings]

1 (a) to 1 (c) are flow charts showing an example of a method for producing amorphous silica used in the present invention.

Claims (2)

[Claims] 1. A voltage for applying a mixture for a lateral high-resistance layer comprising at least a silicon compound, an antimony compound, and a bismuth compound to the side surface of a voltage non-linear resistor containing zinc oxide as a main component and at least a silicon component, and then firing. In the method for manufacturing a non-linear resistor, a voltage non-linear resistor characterized by using amorphous silica as a silicon component raw material of the resistor and using amorphous silica as a silicon compound in the mixture. Manufacturing method. 2. The voltage nonlinear resistor according to claim 1, wherein the amorphous silica is one obtained by a metathesis reaction of sodium silicate or one obtained by a thermal decomposition of silicon tetrachloride. Production method.