JPS62179701A - Screening of durability characteristics of nonlinear resistance element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to determining the quality of withstand characteristics with extremely little damage in a nonlinear resistor whose main component is zinc oxide, which is used, for example, in an overvoltage protection device that protects a power system. The present invention relates to a method for selecting withstand characteristics of non-linear resistors that can be determined.

[Technical background of the invention and its problems]

A voltage nonlinear resistor is generally called a varistor, and its excellent nonlinear voltage-current characteristics are utilized to make it widely used in lightning arresters and surge absorbers for the purpose of voltage stabilization or surge absorption.

A typical example is the recently developed zinc oxide varistor. The main component is zinc oxide, to which a small amount of oxides such as bismuth, antimony, cobalt, manganese, chromium, etc. are added, mixed, granulated, molded, and then fired at high temperature in air to form a sintered body. It is constructed by attaching electrodes. Its non-linear resistance properties are very good, and the sintered body consists of a grain boundary layer formed by zinc oxide particles and additives surrounding them. It is believed that this is due to the interface between

Furthermore, these non-linear resistors have extremely excellent withstand characteristics to absorb large currents generated by lightning strikes and the like.

However, since non-linear resistors containing zinc oxide as a main component are manufactured by mixing zinc oxide with fine powders of many metal oxides, molding the mixture, and then firing it, the fine structure tends to be non-uniform. That is, internal defects such as voids and cracks occur due to imbalance of components due to insufficient mixing. It is known that if a non-linear resistor has defects such as voids and cracks due to the presence of these components, the withstand characteristics will be inferior.

Typical methods for detecting the presence or absence of internal defects in nonlinear resistors include ultrasonic echo testing and X-ray radiography, but these methods cannot detect large voids or cracks. Even if it could be detected, there was a risk of missing small objects, which caused reliability problems. In addition, deviations in component distribution could hardly be detected and were not useful for selecting tolerance characteristics.

[Purpose of the invention]

The present invention has been developed in view of the above-mentioned needs, and provides a method for selecting the withstand characteristics by applying energy of 1/3 or less of the withstand limit value of the element, and determining pass/fail based on the temperature distribution on the element surface. aim at something.

[Summary of the invention]

In order to achieve this object, the present invention is a method for selecting the withstand characteristics of the non-linear resistor 3, by applying energy of 1/3 or less of the withstand limit value that does not leave any damage to the element and measuring the temperature distribution on the surface of the element. It is characterized in that it compares with a predetermined allowable temperature pattern to judge whether it is good or bad and then selects it.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIG.

1/1 of the energy obtained by carrying out a tolerance limit test on the non-linear resistor 1 to be measured using a large number of elements of the same shape.
Power supply 4 with energy of 3 or less using a 2 ms rectangular pulse wave
It was applied from The element generates Joule heat, the temperature rises instantly, and infrared rays are emitted from the surface. This infrared rays are photographed by an infrared imaging device 2. A microcomputer 3 is connected to the infrared imaging bag w2, into which data for determining the quality of the withstand characteristics is inputted, so that the pass/fail determination can be made instantaneously.

FIG. 2 shows the applied energy and the degree of damage.

1. The rate of change (V2 Va) of □ (terminal voltage when a current of 0.1 mA flows through the non-linear resistor 1) is shown here.
l is vo before energy is applied, the value v2 of 1 mA is Vo after energy is applied, and the value of □+aA. According to this, it can be seen that below the withstand limit value of 173, the value of vo, 1mA does not change and there is no damage.

In addition, Fig. 3 shows the relationship between the temperature distribution on the element surface and the applied energy, which was obtained for a large number of elements with the same shape.
Two directions, Y-Y', are shown. The solid line A shows the heat generation pattern when an energy of 475, which is the average withstand limit value, is applied, and the broken line B shows the heat generation pattern when the same energy <113 is applied.

According to this, it can be seen that even if the applied energy is 1/3 or less of the withstand limit value, the pattern remains the same even if the absolute value of heat generation changes. In this way, energy is increased step by step for a large number of elements, and the heat generation pattern on the surface until the element breaks is image-processed and stored in a microcomputer.Heat generation pattern of so-called defective products that break down below a certain withstand value. was determined and stored in a microcomputer.

Next, approximately ⅓ of the energy limit was applied to determine the temperature distribution on the element surface, and then the energy that actually caused the element to break was determined. This was done for a large number of elements to confirm whether the heat generation pattern used to screen out defective elements was appropriate and to make corrections.

As a result, it has become possible to accurately select defective elements by determining the heat generation pattern of the element when energy of 173 or less is applied.

FIG. 4 shows the variation in tolerance limit values of elements selected by the present invention and elements selected by the conventional X-ray transmission method. This shows that extremely reliable selection was performed according to the present invention.

[Effects of the Invention] As described above, according to the present invention, devices with poor withstand characteristics can be selected with little damage to the devices.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an apparatus for carrying out the resistance selection method according to the present invention, and Fig. 2 shows the applied energy and the degree of damage.
3 is a diagram showing the relationship between applied energy and temperature distribution on the surface of the element, and FIG. 4 is a diagram showing the withstand characteristics of elements selected by the present invention and the conventional method. 1...Non-linear resistor 2...Infrared imaging device 3
... Microcomputer 4 ... Power supply agent
Patent Attorney Nori Chika Ken Yudo Hirofumi Mitsumata Figure 1 Lagoon V,, 37 (X Tolerance Limit I) Figure 2 W Castle (Kanfu Pitou-ki)

Claims (1)

[Claims] In a method for selecting withstand characteristics of a non-linear resistor whose main component is zinc oxide, energy of 1/3 or less of the withstand limit value of a non-linear resistor element is applied to determine the temperature distribution on the surface of the element and a predetermined tolerance. A method for selecting withstand characteristics of a non-linear resistor, which comprises comparing the temperature pattern to determine the quality of an element and selecting it.