JP2800341B2 - Method for manufacturing voltage non-linear resistor element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistor having a high resistance layer formed on a side surface of a sintered body mainly composed of zinc oxide and exhibiting voltage non-linearity itself. The present invention relates to a method for manufacturing an element.

2. Description of the Related Art Conventionally, zinc oxide has been used as a main component, and bismuth,
A resistor having a high voltage non-linearity obtained by adding an oxide such as manganese as an additive, molding, and firing is called a zinc oxide varistor, and is used as a voltage stabilizing element, a surge absorbing element, a lightning arrestor, and the like. Widely used.

When this zinc oxide varistor is used as a power surge arrester, one of the required characteristics is a discharge withstand characteristic.
This is defined as 4/10, as specified in JEC-187-1973.
This is the maximum value of the peak current that the element can withstand when a shock current of μs is applied twice at 5 minute intervals.

Conventionally, as a method of manufacturing a power surge arrester, SiO ₂ , Zn ₇ Sb
A mixture of ₂ O ₁₂ , Bi ₂ O _3, etc. is applied and sintered to form a high resistance layer (Japanese Patent Application Laid-Open No. 56-69804).
_{b 2 O 3, Bi 2 O} 3, the mixture is placed consisting of SiO ₃ etc., air - a method of forming a high-resistance layer on the side surfaces of the arrester element by solid phase reaction (JP-B 60-15128 Patent Publication) Hitoshigachi Had been.

Problems to be Solved by the Invention However, in the above method, in the former case, the size of the particles in the high-resistance film after sintering is not uniform, or the produced film may be porous, In some cases, the adhesion between the lightning arrester and the high-resistance film is not always sufficient.
In the latter case, the uniformity of the formed film thickness may not be good. If the adhesion between the high-resistance layer and the lightning arrester is not sufficient, a surge current leaks between the lightning arrester and the high-resistance layer, and the characteristics of the high-resistance layer, which should be originally possessed, are not sufficiently satisfied. Limit value may decrease. In addition, if the thickness of the high resistance film is not uniform, a surge current flows selectively in a thin portion of the film, which causes a decrease in the limit value of the discharge withstand amount.

The present invention is intended to solve such a problem. By forming a high-resistance thin film having high uniformity and a uniform thickness on the varistor element side surface on the side of the varistor element, the voltage non-linearity excellent in discharge withstand characteristics can be obtained. It is an object of the present invention to provide a resistor element.

Means for Solving the Problems In order to achieve this object, a method for manufacturing a voltage non-linear resistor element according to the present invention comprises the steps of: An SiO ₂ thin film or a Si ₃ N ₄ thin film is formed on the surface behind the varistor element by a sputtering method or a sputtering method.

According to this method, SiO ₂ with excellent thermal shock resistance and insulation properties
Since a thin film or Si ₃ N ₄ thin film can be formed on the side surface of the varistor element with uniform thickness and good adhesion to the varistor element, it can sufficiently withstand a strong electric field due to surge current application and heat generation of the varistor element. That is, it is possible to obtain a voltage non-linear resistor element having excellent discharge withstand characteristics.

Examples Hereinafter, the production method of the present invention will be described in detail based on examples.

First, oxides such as bismuth, cobalt, manganese, antimony, and chromium are added to zinc oxide powder in an amount of 0.3 mol% to 1.5 mol% based on the total amount, sufficiently pulverized and mixed, and then granulated. A powder was made. This raw material powder has a diameter of 40
mm, thickness of 30mm, formed in air, 700 ° C ~ 9 in air
After sufficiently decomposing the binder at a temperature of 00 ° C, the binder was sintered in air at 1200 ° C to obtain a zinc oxide varistor body.

A high resistance film of SiO ₂ was formed on the side surface of the varistor element body thus obtained by using a plasma CVD method. The specific manufacturing method is described below. That is, as shown in FIG. 2, a jig 5 rotatable up and down of the varistor element body 4 is provided.
After heating the varistor element 4 in advance at a temperature of 300 ° C. using infrared rays, the reaction chamber 6 is rotated slowly.
Passed through. Here, the film thickness was controlled by the time required to pass through the reaction chamber 6. The internal volume of the reaction chamber 6 is about 65 liters, and the reaction gas is introduced into the reaction chamber 6 at a flow rate of 30 (ml / min) of SiH ₄ gas and 800 (ml / min) of N ₂ O gas. The valve 8 was controlled and introduced, and the gas pressure in the reaction chamber 6 during film formation was 1 T
orr. was controlled by a main valve 9 to a vacuum pump (not shown). The discharge electrode 7 for generating plasma is a plane of 40 cm square and uses a 13.56 MHz high frequency power supply.
500 (W) power was applied. The film formation rate on the varistor element body 4 under the above conditions was about 150 (ml / min). The film thickness was changed under these conditions, and four types of samples were prepared. Both ends of the sample thus manufactured were polished to form aluminum spray electrodes, and a varistor element was manufactured. FIG. 1 shows a schematic view of the varistor element thus manufactured. Table 1 below shows the thickness of the SiO ₂ thin film of the prepared sample.

In FIG. 1, 1 is a zinc oxide varistor element body,
2 is an SiO ₂ thin film and 3 is an electrode.

For comparison, as a conventional device, instead of a SiO ₂ thin film, SiO ₂ , Zn ₇ Sb ₂ O ₁₂ , B
A sample (sample 5) was prepared by thinly coating an insulating material in which i ₂ O ₃ was mixed at an appropriate ratio, performing heat treatment, and forming an electrode in the same manner as described above.

Varistor element thus obtained (Samples 1 to 5)
Then, an impact current of 4/10 μs was applied twice at 5 minute intervals, and the limit value of the peak current that the element could withstand was measured.

The results are shown in Table 2 below. In Table 2, the mark x indicates the current value at which the element was destroyed.

From Table 2, it can be seen that the discharge withstand capability of the element coated with the SiO ₂ thin film on the side surface of the varistor element is significantly superior to that of the element coated with nothing or the element coated with insulating material by heat treatment. Recognize. Further, in this experiment, although the discharge withstand capacity increased as the thickness of the SiO ₂ thin film increased, the characteristics were sufficiently improved even in a device having a thickness of 10 μm as compared with the conventional example.

In this experiment, the SiO ₂ thin film was composed of SiH ₃ gas and N ₂
It was produced by the plasma CVD method using O gas, but this is not limited to the plasma CVD method, such as a low pressure CVD method, a normal pressure CVD method, etc.
The SiO ₂ thin film can be produced by other chemical vapor deposition methods or physical vapor deposition methods such as sputtering, and can be applied to the device of the present invention.

Here, even if a high-resistance film was formed by using a Si ₃ N ₄ thin film instead of the above-mentioned SiO ₂ thin film, the same effect as in the above example could be obtained. Table 3 below shows the film thickness of the prepared Si ₃ N ₄ thin film. Here, the sample preparation conditions were as follows: the reaction gas was SiH ₄ gas: 30 (ml / min), N ₂ gas: 800 (ml / min), and the film formation rate on the varistor element: about 50 ( nm / min), except that the conditions were all the same as in the above example.

Here, the sample 6 is the same as the sample 1 of the above embodiment. Table 4 shows the results of applying the same impact current to these samples and measuring the limit value of the peak current that the device can withstand. Table 4 also shows, for reference, the measurement results obtained using the above-described sample 5 for comparison.

As shown in Table 4 above, even when a Si ₃ N ₄ thin film is used, excellent discharge capability can be obtained.
In particular, in the case of the Si ₃ N ₄ thin film, even if the device has a thickness of 2.0 μm, the characteristics are sufficiently improved as compared with the conventional example. Further, this Si ₃ N ₄ thin film can also be produced by a plasma CVD method using a SiH ₃ gas and an NH ₃ gas.
Of course, it can also be manufactured by other chemical vapor deposition methods such as a chemical vapor deposition method, or a physical vapor deposition method such as sputtering.

Effects of the Invention According to the present invention, Si having excellent thermal shock resistance and insulation properties is provided.
An O ₂ thin film or Si ₃ N ₄ thin film can be formed on the side surface of the varistor element with a uniform thickness and good adhesion to the varistor element. It is possible to obtain a voltage non-linear resistor element that can sufficiently withstand, that is, is excellent in discharge withstand characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a voltage non-linear resistor element manufactured by the manufacturing method of the present invention, and FIG. 2 is a view showing an example of a thin film forming method in the manufacturing method of the present invention. 1 ...... zinc oxide varistor element, ₂ ...... SiO 2 thin film, 3 ......
Electrode, 4 ... Zinc oxide varistor element, 5 ... Rotable jig, 6 ... Reaction chamber, 7 ... Discharge electrode, 8 ... Gas introduction valve, 9 ... Main valve to vacuum pump.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01C 7/02-7/22

Claims (1)

(57) [Claims] 1. A thin film of SiO ₂ or a thin film of Si ₃ N ₄ is formed on a side surface of a varistor element by a CVD method or a sputtering method while sandwiching and rotating the varistor element mainly composed of zinc oxide. A method for manufacturing a voltage non-linear resistor element.