JPH0320884B2 - - 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 10 μA, 100 μA, 1 mA,...
Voltage at 100A V ₁₀ 〓 _A , V ₁₀₀ 〓 _A , V ₁ m _A ,...
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 equipment. 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 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 a sintered body, heat treatment is performed at 500°C to 850°C to diffuse the glass. (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) Methods such as adding glass made of bismuth oxide, boric anhydride, cobalt oxide, and silver oxide and firing the mixture have been adopted. 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.

Furthermore, the discharge withstand capacity deteriorates. Method (3) has no problems with the manufacturing process, but the energized life is a little short and the discharge withstand capacity is also low. Method (4) also has no problems in the manufacturing process, but it has problems such as insufficient energized life and weak discharge capacity.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, the present invention seeks to provide a method for manufacturing a voltage non-linear resistor that has excellent charge life characteristics and discharge withstand capacity even when using a large-sized zinc oxide varistor element.

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 zinc oxide varistor composition were studied, and the This is a zinc varistor element with improved charge life characteristics and discharge capacity. Specifically, bismuth oxide (Bi ₂ O ₃ ) 40 to 90 wt%, silica (SiO ₂ ) 5 to 25 wt%
%, boric anhydride (B ₂ O ₃ ) 10-30 wt%, and silver oxide (Ag ₂ O) 5-30 wt%.
After melting at 1000°C to 1250°C, cooling and finely pulverizing glass frit is added in an amount of 0.01 to 5 parts by weight to 100 parts by weight of the zinc oxide varistor composition, mixed and molded, and the molded product is temporarily heated at 850°C to 950°C. Voltage non-linearity characterized by providing electrodes on the sintered body obtained by applying a mixed paste of bismuth oxide, silica and antimony oxide to the side surface of the calcined body and firing at 1000°C to 1400°C. A method for manufacturing a resistor is provided.

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% and 5 to 30 wt% of silver oxide (Ag ₂ O) were blended and mixed, the mixture was placed in a platinum crucible, and heated to 1000℃.
After melting at ~1250℃, 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 pair is calcined at 850 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 way is shown in FIGS. 1 and 2 using a sintered body having a diameter of 33 mm and a thickness of 30 mm. Figure 1 shows the charging life characteristics,
FIG. 2 shows the discharge capacity characteristics. The charging life test
The sample was placed in a constant temperature bath at 130°C, and an AC voltage with a peak voltage equivalent to 95% of the sample's V _{1 mA} was applied between the electrodes of the sample, and the increase in leakage current was investigated. . On the other hand, in the discharge endurance test, the rate of change in V _{1 mA} of the sample was examined when a pulse current with a current waveform of 4 x 10 μS was applied twice. 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).
% was melted at 1200℃, then rapidly cooled, and the finely ground glass frit was mixed into a varistor composition (ZnO95.495mol%,
_{Bi2O3 0.5mol} %, _{Co2O3 0.5mol} %, _MnO2 0.5mol
%, _{Sb2O3 1.0mol} %, _{Cr2O3 0.5mol} %,
_SiO2 0.5mol%, NiO1.0mol%, _{Al2O3 0.005mol}
%) Mix by adding 0.1 part by weight to 100 parts by weight,
The molded body is calcined at 900°C, and on the side of the calcined body, 10 mol% of bismuth oxide (Bi ₂ O ₃ ), 70 mol% of silica (SiO ₂ ), and 20 mol% of antimony oxide (Sb ₂ O ₃ ) are added. The sides were coated with a high-resistance agent consisting of the following materials and fired at 1200℃. In addition, the conventional product has Bi ₂ O ₃ 58.4wt%, SiO ₂ 12.5wt%, B ₂ O ₃ 12.5wt%
%, CoO 8.3wt%, and Ag ₂ O 8.3wt%, and 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.

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

[Brief explanation of drawings]

FIG. 1 is a diagram showing a comparison between a product of the present invention and a conventional product in charge life characteristics, and FIG. 2 is a diagram showing a comparison between a product of the present invention and a conventional product in terms of discharge withstand characteristics.

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 30wt% of silver oxide (Ag ₂ O) and 5 to 30wt% of silver oxide (Ag 2 O) is melted at 1000°C to 1250°C, cooled and finely ground, and the glass frit is added at a concentration of 0.01 to 5% per 100 parts by weight of the zinc oxide varistor composition. Part by weight is added, mixed and molded, the molded body is calcined at 850°C to 950°C, a mixed paste of bismuth oxide, silica and antimony oxide is applied to the side of the calcined body, and the mixture is heated to 1000°C.
A method for manufacturing a voltage nonlinear resistor, comprising providing an electrode on a sintered body obtained by firing at ~1400°C. 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%.