JPH0779041B2 - Method for manufacturing voltage non-linear resistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a voltage non-linear resistor containing zinc oxide as a main component, and particularly to electrical resistance such as surge withstand capability and electric charge life characteristic. It is intended to effectively improve various characteristics.

(Prior Art) A voltage non-linear resistor useful for protecting electric systems and electric devices is preferably obtained by granulating a mixture of zinc oxide as a main component and various additives, It is general that the powder is pressure-molded into a desired shape, for example, using a press die, then fired under appropriate processing conditions, and then an electrode is attached to the powder.

However, with the voltage nonlinear resistor manufactured according to the conventional method, it is difficult to secure a predetermined quality over a certain lot even when processed under the same conditions, and the productivity is inevitably reduced.

In this respect, for example, Japanese Examined Patent Publication No. 62-45681 discloses a technique for producing a non-linear resistor, in which the treatment atmosphere in the firing process is a bismuth oxide atmosphere of 0.05 to 50 mmHg.

(Problems to be Solved by the Invention) By simply applying the technique disclosed in the above publication, it is difficult to avoid variations in quality although characteristics tend to be improved, and products with good quality are obtained. There was a disadvantage that you could not get stable.

It is an object of the present invention to propose a manufacturing method which solves the above-mentioned conventional problems and is advantageous in securing various electrical characteristics and stable quality.

(Means for Solving the Problems) The inventors have conducted various experiments and studies to stably manufacture a voltage non-linear resistor having good electric characteristics, and as a result, It has been found that it is extremely effective to adjust the partial pressures of antimony oxide, bismuth oxide, and oxygen within appropriate ranges.

The present invention is based on the above findings.

That is, according to the present invention, a raw material powder containing zinc oxide as a main component is mixed with an additive containing bismuth oxide and antimony oxide, preferably granulated and pressure-molded, and then fired to produce a voltage non-linear resistor. On the side of the object to be fired
Apply an oxide paste to a thickness of 100-300μm, and apply this to a bismuth oxide with a partial pressure of 0.1-30mmHg, 0.1-50mmHg
And a firing method in an atmosphere of antimony oxide and oxygen of 150 mmHg or more.

(Operation) When manufacturing a voltage nonlinear resistor, adjust the partial pressures of bismuth oxide, antimony oxide, and oxygen during firing to 0.1 to 30 mmHg, 0.1 to 50 mmHg, and 150 mmHg or more, respectively. Electrical characteristics are improved,
Moreover, the reason why a certain quality can be ensured is that voltage nonlinearity develops in the grain boundary phase in the voltage nonlinear resistor, but the bismuth oxide phase and spinel phase (reaction of zinc oxide and antimony oxide that form the grain boundary phase Bismuth oxide partial pressure in the firing atmosphere, antimony oxide partial pressure,
It is considered that the partial pressure of oxygen plays an important role.

Specifically, the partial pressure of bismuth oxide and antimony oxide is 0.1 m.
If it is less than mHg, bismuth oxide and antimony oxide are diffused into the air from oxygen, while the partial pressure of bismuth oxide is 30 mmHg.
It is considered that bismuth oxide and antimony oxide are diffused in the device, and the distribution of bismuth oxide and antimony oxide in the device becomes nonuniform when the partial pressure of antimony oxide exceeds 50 mmHg. In addition, the oxygen partial pressure
It is considered that these grain boundary phases are not stabilized below 150 mmHg.

Therefore, a voltage nonlinear resistor having stable electrical characteristics and good quality can be provided only when the three conditions of bismuth oxide partial pressure, antimony oxide partial pressure, and oxygen partial pressure are satisfied within a specific range in the firing atmosphere. Of.

The specific manufacturing procedure according to the present invention will be described below.

Borosilicate containing a main material of zinc oxide adjusted to a predetermined particle size and an additive made of bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, silicon oxide, nickel oxide, etc. adjusted to a predetermined particle size and preferably silver Mix a predetermined amount of bismuth glass. Next, a predetermined amount of an aqueous solution of polyvinyl alcohol and a predetermined amount of an aluminum sulfate solution as a source of aluminum oxide are added to these raw material powders. This mixing operation preferably uses an emulsifier.

Next, vacuum degassing is preferably performed at a vacuum degree of 200 mmHg or less to obtain a mixed sludge. The water content of the mixed slurry is 30-35wt%
The viscosity of the mixed slurry is preferably 100 cp ± 50.

Next, the obtained mixed sludge is supplied to a spray dryer to have an average particle size of 50 to 150 μm, preferably 80 to 120 μm, and a water content of 0.
Granulate 5 to 2.0 wt%, more preferably 0.9 to 1.5 wt%.

Next, the granulated powder obtained is subjected to a molding pressure of 80 in the molding step.
It is molded into a specified shape under 0 to 1000 kg / cm ² . Then, the molded body is preliminarily fired at a temperature rising / falling speed of 50 to 70 ° C./hr at 800 to 1000 ° C. and a holding time of 1 to 5 hours to remove the binder by scattering.

Then, an insulating coating layer is formed on the side surface of the calcined body that has been calcined. This insulating coating layer is made up of a specific amount of bismuth oxide, antimony oxide, silicon oxide, zinc oxide, etc.
It is made of an oxide paste to which butyl and the like are added, and this is applied to the side surface of the calcined body in a thickness of 100 to 300 μm.

Next, this is heated up and down at a temperature of 30 to 60 ° C / hr and a processing temperature of 1000 ° C to 1
300 ° C, more preferably 1100-1250 ° C, holding time 2-7
Time and the partial pressure of bismuth oxide in the treatment atmosphere
The main firing is performed under the conditions of 0.1 to 30 mmHg, preferably 2.0 to 20 mmHg, antimony oxide partial pressure of 0.1 to 50 mmHg, preferably 5 to 35 mmHg, and oxygen partial pressure of 150 mmHg or more, preferably 160 mmHg or more.

Here, the atmosphere at the time of firing can be appropriately adjusted by using pellets or spread powder containing these components or by using those gas media. The order to measure the partial pressure sampling a fixed amount of the sintering atmosphere to obtain the partial pressure of _{Bi 2 O 3, Sb 2 O} 3 by quantifying the _{Bi 2 O 3, Sb 2 O} 3 amount contained therein The oxygen partial pressure is measured by an oxygen meter.

On the above-mentioned insulating coating layer, glass powder was added as an organic binder to ethyl cellulose, butyl carbitol, and acetic acid.
Apply a glass paste with butyl etc. to a thickness of 100-300 μm, and further raise and lower the temperature in air at 100-200 ° C / hr, 4
It is more preferable to provide a glass layer obtained by heat treatment at a temperature of 00 to 600 ° C. for 0.5 to 2 hours.

And finally, polish both end faces of the obtained element body smoothly,
An aluminum electrode is provided on the surface by thermal spraying.

(Example) According to the present invention, a voltage non-linear resistor having a diameter of 47 mm and a thickness of 20 mm having the composition shown in Table-1 was manufactured under the conditions shown in Table-2, and various electrical characteristics of each element obtained were investigated. The voltage non-linearity index α in Table 2 was calculated from the values of V ₁ mA and V ₁₀₀ μA based on I = KV ^α (I: current, V: voltage, K: proportional constant), and the lightning surge withstand destruction rate (%) Is the breakdown rate after 100 kA and 120 kA currents are repeatedly applied 20 times with a current waveform of 4/10 μs, and the switching surge withstand breakdown rate (%) is 1000 A and 1200 A current waveform of 2 ms At 20
The percentages of breakdown when applied repeatedly are shown. The leakage current ratio is calculated from the current ratio I ₁₀₀ hours / I ₀ hours immediately after the power is applied 100 hours after the power is applied to the obtained device under an ambient temperature of 130 ° C. I asked.

As is clear from Table 2, it is confirmed that the voltage nonlinear resistors (Sample Nos. 1 to 12) manufactured according to the present invention have good electrical characteristics and stable quality. It was

(Effects of the Invention) According to the present invention, it is possible to stably manufacture a voltage non-linear resistor having excellent electrical characteristics such as surge withstand capability and voltage application life characteristic.

Claims (1)

[Claims] 1. A raw material powder containing zinc oxide as a main component is mixed with an additive containing bismuth oxide and antimony oxide, pressure-molded, and then fired to produce a voltage non-linear resistor. Applying an oxide paste on the side surface, a partial pressure of 0.1 to 30 mmHg of bismuth oxide, 0.1 to 50 mmHg of antimony oxide and 150 mmHg or more of the voltage nonlinear resistor characterized by firing in an atmosphere of oxygen Production method.