JPH0320883B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a voltage nonlinear resistor, which comprises adding electrodes to both sides of a sintered body made by adding glass frit to a zinc oxide varistor composition and firing it at a high temperature. It is something.

Conventional structure and its problems Traditionally, voltage nonlinear resistors were made mainly of silicon carbide, which was hardened with a porcelain binder.
SiC varistors have been widely used, but recently SiC varistors have been developed using so-called sintered bodies made of zinc oxide as a main component and metal oxides such as Bi ₂ O ₃ and Co ₂ O ₃ added, mixed, molded, and fired. Zinc oxide varistors have been produced and put into practical use.

The voltage-current characteristics of this type of voltage nonlinear resistor (hereinafter referred to as a varistor) are generally expressed by the following equation.

I=(V/C) where I is current, V is voltage, and C and α are constants. The characteristics of the varistor can be expressed by two constants, C and α. C is the voltage when the current is 1 ampere, which generally corresponds to the resistance value of a fixed resistor, and as a varistor, the voltage nonlinearity index α
It is desirable that it be as large as possible. The present inventors replaced C with currents of 10μA, 100μA, 1mA,...
Voltage at 100A V ₁₀ 〓 _A , V ₁₀₀ 〓 _A , V _1nA ,...
I am using V _100A .

Zinc oxide varistors have an extremely large α of 40 to 100, and are highly effective in voltage stabilization and surge voltage suppression, and are widely used to protect electronic devices. Recently, there has been an active movement to use zinc oxide varistors in high voltage, high energy fields such as lightning arresters.

However, the zinc oxide varistor used in lightning arresters and the like is constantly applied with high voltage and must absorb high energy such as lightning surges, so the shape of the zinc oxide varistor element becomes large. Zinc oxide varistor elements used to protect electronic devices usually have a diameter of 3 mm to 14 mm and a thickness of 0.5 to 2 mm, whereas zinc oxide varistor elements used in lightning arresters etc. have a diameter of 30 mm to 80 mm and a thickness of 3 mm to 14 mm. 30mm～
It is 50mm.

Since the zinc oxide varistors used in lightning arresters and the like are large in size, the required performance cannot be met using normal manufacturing methods for small devices.
Among the required performances, the charging life characteristics, pulse life characteristics, and discharge withstand characteristics are particularly important. As a measure to improve the energized life characteristics of conventional small zinc oxide varistor elements, (1) After applying glass to the sintered body,
The glass is diffused by heat treatment at 850℃. (2) Glassy additives such as boric anhydride (B ₂ O ₃ ) and barium oxide (BaO) are added and fired. (3) Add bismuth borosilicate glass or lead borosilicate glass and fire. (4) Bismuth oxide, boric anhydride,
Adding glass made of cobalt oxide and silver oxide,
Methods such as firing are used. However, when the above method is applied to a large-sized element, the element is large in method (1), so the diffusion does not reach the interior of the glass element, and stable performance cannot be obtained. In method (2), gelation of the slurry of the raw material mixture occurs, so a calcination step is required as a countermeasure, and the moldability is poor and cracks occur inside the device. moreover,
Discharge withstand capacity and pulse life deteriorate. Method (3) does not have any problems with the manufacturing process, but the lifespan of charging is a little poor.
The discharge withstand capacity and pulse life will also deteriorate. Method (4) also has no problems in the manufacturing process, but it has problems such as insufficient energization life, weak discharge capacity, and weak pulse life.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention seeks to provide a method for manufacturing a voltage nonlinear resistor that has excellent charge life characteristics, pulse life characteristics, and discharge withstand capacity even with large zinc oxide varistor elements. .

Structure of the Invention In order to achieve this object, as a manufacturing method of the voltage nonlinear resistor of the present invention, the constituent materials and amount of glass frit added to the oxide varistor composition were studied, and zinc oxide, which is particularly suitable for high voltage and high energy fields, was studied. The varistor element has improved charging life characteristics, pulse life characteristics, and discharge withstand capacity. Specifically, bismuth oxide (Bi ₂ O ₃ ) 40-90 wt%, silica (SiO ₂ ) 5-25 wt%, boric anhydride (B ₂ O ₃ ) 10-90 wt%.
A glass composition consisting of 30 wt%, silver oxide (Ag ₂ O) 5 to 30 wt%, and antimony oxide (Sb ₂ O ₃ ) 2 to 30 wt% was melted at 1000°C to 1250°C, cooled, and finely pulverized glass frit was obtained. Zinc oxide barista composition 100
0.01 to 5 parts by weight are added to the parts by weight, mixed and molded, the molded body is calcined at 850°C to 950°C, and a mixed paste of bismuth oxide, silica, and antimony oxide is applied to the side of the calcined body. Coated, 1000℃~1400℃
The present invention provides a method for manufacturing a voltage nonlinear resistor, characterized in that an electrode is provided on a sintered body obtained by firing the resistor.

Description of examples The present invention will be described below with reference to Examples.

First, bismuth oxide (Bi ₂ O ₃ ) 40-90 wt%, silica (SiO ₂ ) 5-25 wt %, boric anhydride (B ₂ O ₃ )
10 to 30 wt%, silver oxide (Ag ₂ O) 5 to 30 wt%, and antimony oxide (Sb ₂ O ₃ ) 2 to 30 wt% are blended and mixed, and the mixture is placed in a platinum crucible and heated at 1000°C to 1250°C.
After melting, it is poured into water, rapidly cooled, and pulverized in a pot mill to make glass frit.

On the other hand, zinc oxide (ZnO) 85-98.5 mol%, bismuth oxide (Bi ₂ O ₃ ) 0.01-5 mol%, cobalt oxide (Co ₂ O ₃ ) 0.01-5 mol%, manganese oxide (MnO ₂ )
0.01~5mol%, antimony oxide (Sb ₂ O ₃ ) 0.02~
10mol%, chromium oxide (Cr ₂ O ₃ ) 0.01-5mol%,
A mixture of 0.02 to 10 mol% of silica (SiO ₂ ), 0.02 to 10 mol% of nickel oxide (NiO), and 0.001 to 0.05 mol% of aluminum oxide (Al ₂ O ₃ ) (hereinafter referred to as a varistor composition) is prepared, and this varistor The glass frit is added to 100 parts by weight of the composition.
0.01 to 5 parts by weight are added, mixed and molded, and the molded body is calcined at 850°C to 950°C. On the side of the calcined body, 5 to 20 mol% of bismuth oxide (Bi ₂ O ₃ ) and silica (SiO ₂ ) 60-90mol% ammothine _oxide ( _Sb2O3 )
Apply a side high resistance agent consisting of 10 to 30 mol%,
Electrodes are attached to both sides of the cylindrical sintered body obtained by firing at 1000°C to 1400°C by metal spraying.

A comparison of the characteristics of the inventive example and the conventional example made in this manner is shown in FIGS. 1, 2, and 3 using a sintered body having a diameter of 33 mm and a thickness of 30 mm. FIG. 1 shows the charging life characteristics, FIG. 2 shows the pulse life characteristics, and FIG. 3 shows the discharge endurance characteristics. In the energized life test, the sample is placed in a constant temperature bath at 130°C, and the sample is placed between the electrodes of the sample.
An AC voltage having a peak voltage corresponding to 95% of V _{1 nA} was applied, and the increase in leakage current was investigated. The pulse life characteristics are determined by applying a current waveform of 8× to the sample.
Pulses of 20 μS and a current peak value of 5000 A were repeatedly applied to examine the rate of change in V _{1 nA} of the sample. On the other hand, in the discharge withstand test, a pulse current with a current waveform of 4 x 10 μS is
The rate of change in V _1nA of the sample when the voltage was applied twice was investigated.
In the figure, A shows the characteristics of the present invention, and B shows the characteristics of the conventional product.

The above results show that the product of the present invention contains 50wt% bismuth oxide (Bi ₂ O ₃ ), 10wt% silica (SiO ₂ ), 20wt% boric anhydride (B ₂ O ₃ ), and 20wt% silver oxide (Ag ₂ O).
%, antimony oxide (Sb ₂ O ₃ ) 15wt% was melted at 1200℃ and then rapidly cooled, and the finely ground glass frit was mixed into a varistor composition (ZnO 95.495mol%,
_{Bi2O3 0.5mol} %, _{Co2O3 0.5mol} %, _MnO2 0.5mol
%, _{Sb2O3 1.0mol} , _{Cr2O3 0.5mol} %, _SiO2 0.5mol
%, NiO 1.0 mol%, Al ₂ O ₃ 0.005 mol%), 0.1 part by weight is added to 100 parts by weight, mixed and molded, the molded body is calcined at 900℃, and the side surface of the calcined body is Bismuth oxide (Bi ₂ O ₃ ) 10mol%, silica (SiO ₂ )
The side surfaces were coated with a high resistance agent consisting of 70 mol% and 20 mol% of antimony oxide (Sb ₂ O ₃ ) and fired at 1200°C. In addition, the conventional product has Bi ₂ O ₃ 58.4wt%,
_SiO2 12.5wt%, _{B2O3 12.5wt} %, CoO8.3wt%,
It is a glass composition containing 8.3 wt% of Ag ₂ O, and the other conditions are the same as the products of the present invention.

When the amount of glass frit added is less than 0.01 part by weight, the improvement effect on the charged life characteristics disappears;
If it exceeds 1 part by weight, the discharge withstand capacity will deteriorate. Furthermore, if Bi ₂ O ₃ in the glass frit is less than 40 wt%, vitrification becomes difficult, and if it exceeds 90 wt%, the voltage nonlinearity index α of the device becomes poor. Next, _SiO2 is 5wt%
If it is less than 25 wt%, the life of the device will be shortened, and if it exceeds 25 wt%, the discharge withstand capacity will be poor. moreover,
If B ₂ O ₃ is less than 10 wt%, the voltage nonlinearity index α will be poor, and if it exceeds 30 wt%, the discharge withstand capacity will be poor. If Ag ₂ O is less than 5 wt%, the charging life characteristics will be poor, and if it exceeds 30 wt%, the discharge withstand capacity will be poor. Further, when Sb ₂ O ₃ was less than 2 wt%, the pulse life characteristics deteriorated, and when it exceeded 30 wt%, vitrification became difficult.

Effects of the Invention As described above, the present invention can greatly improve the charge life characteristics, pulse life characteristics, and discharge withstand characteristics of large-sized zinc oxide varistor elements, and has great practical effects.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a comparison between the inventive product and the conventional product in terms of energization life characteristics, Figure 2 is a diagram showing the comparison between the inventive product and the conventional product in terms of pulse life characteristics, and Figure 3 is the discharge withstand characteristic. FIG. 2 is a diagram showing a comparison between a product of the present invention and a conventional product.

Claims (1)

[Claims] 1. Bismuth oxide (Bi ₂ O ₃ ) 40-90 wt%, silica (SiO ₂ ) 5-25 wt%, boric anhydride (B ₂ O ₃ ) 10-90 wt%.
A glass composition consisting of 30 wt%, silver oxide (Ag ₂ O) 5 to 30 wt%, and antimony oxide (Sb ₂ O ₃ ) 2 to 30 wt% was melted at 1000°C to 1250°C, cooled, and finely pulverized glass frit was obtained. Zinc oxide barista composition 100
0.01 to 5 parts by weight are added to the parts by weight, mixed and molded, the molded body is calcined at 850°C to 950°C, and a mixed paste of bismuth oxide, silica, and antimony oxide is applied to the side of the calcined body. Coated, 1000℃~1400℃
1. A method for manufacturing a voltage nonlinear resistor, which comprises providing an electrode on a sintered body obtained by firing the resistor. 2 The composition of the zinc oxide varistor composition is zinc oxide (ZnO) 85 to 98.5 mol%, bismuth oxide (Bi ₂ O ₃ ) 0.01 to 5 mol %, and cobalt oxide (Co ₂ O ₃ ).
0.01~5mol%, manganese oxide ( _MnO2 ) 0.01~
5mol%, antimony oxide (Sb ₂ O ₃ ) 0.02-10mol
%, chromium oxide ( _Cr2O3 ) 0.01-5mol%, _silica ( _SiO2 ) 0.02-10mol%, nickel oxide (NiO)
0.02-10mol% aluminum _oxide ( _Al2O3 )
The method for manufacturing a voltage nonlinear resistor according to claim 1, wherein the content is 0.001 to 0.05 mol%.