JPH03181102A - Manufacture of nonlinearly voltage-dependent resistor - Google Patents

Abstract

PURPOSE:To manufacture a non-linear voltage resistor of good electric characteristics such as the surge discharge proof quantity with a high yield by applying the specified quantity of paste for high-resistance side-face layers uniformly on the side faces of an element with the water absorption thereof after calcination kept within the specified range. CONSTITUTION:An element is calcined for example with the temperature raised and lowered by 30-100 deg.C per hour and the holding time 120-130 minutes to make the water absorption after the calcination 1.0X10<-2>-4.0X10<-1>%. High-resistance layers are formed on the side faces of the calcined element. That is, mixture paste, consisting of the specified quantity of Bi2O3, Sb2O3, ZnO, and SiO2 and ethyl cellulose, butyl carbitol, and n-butyl acetate as organic binders added thereto, for the high-resistance side-face layers is applied to the side faces of the calcined element to 200-300mum thickness. The element, to the side faces of which the mixture paste is applied, is baked for example at 1,000-1,300 deg.C for several hours with the temperature raised and lowered by 20-100 deg.C per hour. Both end faces of a non-linear voltage resistor are abraded with an abrasive such as SiC aid Al2O3 and electrodes made of Al, etc., are formed on the end faces by thermal spraying to obtain a non-linear voltage resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a voltage nonlinear resistor containing zinc oxide as a main component.

(Prior Art) Voltage nonlinear resistors containing zinc oxide as a main component are widely used in lightning arresters and surge absorbers for the purpose of voltage stabilization or surge absorption because of their excellent nonlinear voltage-current characteristics. This voltage nonlinear resistor is made by adding metal oxides such as bismuth, antimony, cobalt, manganese, etc., which exhibit low voltage nonlinearity, to the main component zinc oxide, mixing, granulating, and molding. The sintered body is fired, an inorganic insulating material is coated on the side surface of the calcined body to form a high-resistance layer on the side, and then the sintered body is fired, and electrodes are attached to both end faces of the sintered body.

In the conventional method described above, in order to obtain good electrical characteristics as a voltage nonlinear resistor, an inorganic insulating material (hereinafter referred to as It is known that it is necessary to uniformly coat a side surface of an element body for a voltage nonlinear resistor to a predetermined thickness with a high resistance agent (hereinafter referred to as a side surface high resistance agent).

(Problem to be solved by the invention) However, it is difficult to uniformly apply the side high resistance agent to the side surface of the element body at a predetermined thickness, and it is difficult to uniformly apply the side high resistance agent to the side surface of the element body at a predetermined thickness. If this is not possible, there are problems in that the incidence of insulation defects in the resulting voltage nonlinear resistor increases and electrical characteristics such as lightning surge discharge resistance deteriorate.

The purpose of the present invention is to solve the above-mentioned problems, increase the adhesion strength of the side high resistance agent, and further uniformly apply it to a predetermined thickness, resulting in a non-linear voltage with excellent insulation resistance and lightning surge discharge resistance. It is an object of the present invention to provide a method for manufacturing a voltage nonlinear resistor that can produce resistors with a high yield.

(Means for Solving the Problems) The method for manufacturing a voltage nonlinear resistor of the present invention includes adding Bi, Sb, Co, Mn, etc. to the main component, zinc oxide, which causes the fired body to exhibit voltage nonlinearity after firing. At least one kind of metal oxide additive is added, mixed, granulated, and molded, and then calcined to have a water absorption rate of 1, OX 10-2 after calcining.
~4.0X10-'% preferably 5. OX 10-2~
2.0 x 10-'%, and is characterized by main firing after providing a high resistance layer on the side surface.

(Function) In the above-described configuration, the present inventors have realized that by controlling the water absorption rate of the calcined body before coating, it is possible to control the amount of coating on the side surface of the element body of the side high resistance element, and to reduce the coating amount. It has been found that the variation can be reduced and the thickness of the coating film can be made uniform. That is, the water absorption rate of the calcined body is 1.0X10-2 to 4.0X1.
By limiting the amount to 0-'%, in the subsequent process of applying the side surface high resistance agent, the amount of the side surface high resistance agent applied to the side surface of the element body can be controlled and made uniform without variation.

Here, the water absorption rate after calcination is 1.0X10-2 to 4.0X
The water absorption rate is limited to 10-1% because it is 1.0X10-"
If it is less than %, it becomes difficult for the side high resistance agent to adhere to the side surface of the element body, resulting in deterioration of electrical characteristics. In addition, the water absorption rate is 4.0X1
If it exceeds 0-'%, the amount of high-resistance agent applied on the side surface will exceed the specified amount and the variation in the amount applied will become large, resulting in areas where the chemical reaction of the side surface agent is insufficient during the final firing, and the electrical characteristics will deteriorate. descend. This is also because the electrical characteristics of the element itself deteriorate after the final firing.

The water absorption rate of the above calcined body is 5. OX 10-2~2.0X1
When it is set to 0-'%, it is more preferable because the coating amount can be controlled to a predetermined amount and the variation in the coating amount can be significantly reduced, the incidence of insulation defects can be significantly reduced, and the lightning surge discharge resistance can be improved. .

In addition, in order to obtain a calcined body with a predetermined water absorption rate, the molding pressure in the molding process is 1000 kg/cm2, the holding time at this pressure is 30 seconds, and the calcining temperature is 920°.
C to 925°C, and the holding time at this temperature is 120 to 925°C.
When the water absorption rate after calcination is 130 minutes, the water absorption rate is 1. OX1
It is preferable because it can be controlled to 0-2 to 4.0×10-'%.

(Example) To obtain a voltage nonlinear resistor whose main component is zinc oxide,
First, zinc oxide raw material adjusted to a specified consistency, bismuth oxide, cobalt oxide, manganese oxide, adjusted to a specified particle size,
A predetermined amount of additives such as antimony oxide, chromium oxide, preferably amorphous silicon oxide, nickel oxide, boron oxide, silver oxide, etc. are mixed. In this case, silver nitrate or boric acid may be used instead of silver oxide or boron oxide, and preferably bismuth borosilicate glass containing silver may be used. Alternatively, the additive may be calcined at 800 to 1000°C, then pulverized and adjusted to a predetermined particle size, and the zinc oxide raw material may be mixed with the additive. At this time, a predetermined amount of polyvinyl alcohol aqueous solution or the like is added to these raw materials.

Next, deaeration is performed under reduced pressure, preferably at a vacuum level of 200 mm and 11 g or less, to reduce the water content of the mixed slurry to about 30 to 35-t%.
Further, it is preferable that the viscosity of the mixed slurry is 100±50 cP. Next, the obtained mixed slurry is fed to a spray dryer to obtain an average particle size of 50 to 150 μm, preferably 80 to 1 μm.
20 pm, and granulated powder having a moisture content of 0.5 to 2.0 wt%, more preferably 0.9 to 1.5 wt%.

Next, the obtained granulated powder is subjected to a molding process under a molding pressure of 1
000 kg/cm2 into a predetermined shape.

Then, the element body (molded body) is raised and lowered at a temperature of 30 to 100'.
C/hr preferably 920-925°C1 holding time 1
Calcinate for 20 to 130 minutes and reduce the water absorption rate to 1.0X1 after calcining.
It is set at 0-2 to 4.0X10-'%. During this calcination, the pressure is preferably lower than atmospheric pressure, and preferably 1
Preliminary firing is performed under a condition of 000 torr or less. In addition, before calcining, the molded body was heated at a heating/cooling rate of 10 to 100°C/hr for 40 minutes.
It is preferable to scatter and remove the binder at 0 to 600°C for a holding time of 1 to 10 hours.

Next, a high resistance layer is formed on the side surface of the calcined body.

BizO,,5bz03. ZnO,5iO
A mixture paste for forming a side high resistance layer, which is prepared by adding organic binders such as ethyl cellulose, butyl calpitol, n-butyl acetate, etc. to a predetermined amount of Z, etc., is applied to the side surface of the calcined body to a thickness of 200 to 300 μm. The paste may be applied to the element body.

Next, the element body coated with the mixture paste on the side surface is subjected to main firing at a heating/lowering rate of 20 to 100' C/hr, 1000 to 1300 DEG C., preferably 1050 DEG to 1250 DEG C., for 13 to 7 hours. In addition, a glass paste made by adding ethyl cellulose, butyl calpitol, n-butyl acetate, etc. as an organic binder to glass powder is applied to the above-mentioned side high-resistance layer.
00~300μm thickness, heating and cooling rate 5 (1~200'C/hr, 400~900°C1) in air.
It is preferable to enhance the glass layer by heat treating it for a holding time of 0.5 to 4 hours.

After that, both end faces of the obtained voltage nonlinear resistor were bonded to SiC,
8f 203. Diamond etc. 11400~#200
Polishing is performed using water, preferably oil, as the polishing liquid with a polishing agent equivalent to 0. Next, after cleaning the polished surfaces, electrodes made of aluminum or the like are provided on both polished end surfaces by, for example, thermal spraying to obtain a voltage nonlinear resistor.

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

According to the method described above, Bit (1+ 1.0 mol%,
CO: 1040.5 mol%, MnO20.5 mol/L/%
, 5bzO3 1.0 mol%, CrzOi 0.5 mol%
, 0.5 mol% of Ni, 2030.005 mol% of Al, 1 to 2 mol% of 5iOz, and the balance is ZnO, and 0.1w of bismuth borosilicate glass is added as an extra.
t% was added and calcined at 900 to 925°C for 1 to 5 hours to obtain a calcined body with a diameter of 55 mm and a thickness of 25 mm. After measuring the water absorption rate of the obtained calcined body, a side high resistance layer paste having a predetermined composition was applied to the side surface of the element body. Thereafter, the average value and dispersion of the coating amount were measured for each of a plurality of test specimens (n = 20). The results are shown in Table 1. Thereafter, voltage nonlinear resistors of the present invention examples and comparative examples shown in Table 1 having the above-mentioned shape and a varistor voltage (VImA) of 200 V/mm were prepared by main firing. In addition, the water absorption rate was measured and determined according to JIS R2205.

Finally, the insulation failure rate and lightning surge discharge breakdown rate of the obtained voltage nonlinear resistor were measured, and the results are shown in Table 1. Here, the insulation defect occurrence rate is measured using a super insulation meter in accordance with JIS C1303, and is 1.0.
Those with a resistance value of X10'MΩ or more are accepted, and this number a and 1. OX It was determined by the formula of resistance value 100 less than 10'MΩ. The lightning surge discharge withstand breakdown rate is determined by applying a 120 KA current twice with a current waveform of 4/10 μs, and determining the number of items that do not break down as acceptable (m), and the number of items that break down as being defective (n). It was calculated using the formula x ioo.

-1-n From the results in Table 1, samples No. 3 to 7 of the present invention using calcined bodies having a predetermined water absorption rate are comparative sample No. 1 which does not satisfy the present invention in terms of water absorption rate. ~2 and 8~9
Compared to the above, the coating amount is preferably 1.2 to 1.8 g/piece, and the variation in coating amount σ□ is also 0.03 to 0.0.
5, and as a result, it was possible to reduce the incidence of insulation defects and the breakdown rate of lightning surge discharge capacity. Moreover, the coating films of samples Nos. 3 to 7 of the present invention all had extremely small thickness deviations.

(Effects of the Invention) As is clear from the above description, according to the present invention, the water absorption rate of the calcined body after calcination is reduced to 1.0×10 −
By setting it to 2 to 4.0 x 10-'%, the paste for the side high resistance layer can be uniformly applied to the side surface of the element body in a predetermined amount,
As a result, a voltage nonlinear resistor having good electrical characteristics such as surge discharge resistance can be obtained with a high yield.

Claims (1)

[Claims] 1. At least one kind of metal oxide additive such as Bi, Sb, Co, Mn, etc., which causes voltage nonlinearity to appear in the fired body itself after firing, is added to the main component zinc oxide, and the mixture is mixed, granulated, and molded. After that, it is calcined and the water absorption rate after calcining is 1.0×
10^-^2 to 4.0 x 10^-^1%, a high resistance layer is provided on the side surface, and then main firing is performed.