JPS643326B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a voltage nonlinear resistance element containing metallic zinc and a spinel-type crystalline antimony compound as starting materials in a sintered body mainly composed of zinc oxide. In recent years, with the rapid development of semiconductor devices and circuits such as ICs, transistors, and thyristors, and their applications, the use of semiconductor devices and circuits in measurement, control, communication equipment, and power equipment has become widespread, and these devices are becoming smaller and more sophisticated. Performance improvements are progressing rapidly. However, with such progress, the withstand voltage, surge and noise resistance of these devices and their parts cannot be said to be sufficient. For this reason, protecting these devices and components from abnormal surges and noise, or stabilizing circuit voltages, has become an extremely important issue. To solve these problems, there has been a demand for the development of an inexpensive voltage nonlinear resistance element that has extremely high voltage nonlinearity, high discharge capacity, and excellent life characteristics. Conventionally, voltage nonlinear resistance elements such as SiC varistors and Si varistors, Zener diodes, and the like have been used for these purposes. Recently, varistors have been developed that contain zinc oxide as a main component and add additives to it. The current-voltage characteristics of a varistor are generally expressed by the following relationship: I=(V/C). Here, V is the voltage applied to the varistor and I is the current flowing through the varistor. Further, C is a constant corresponding to the voltage when a given current is passed. α=1 is an ordinary resistor that follows Ohm's law, and it can be said that the larger α is, the better the nonlinearity is. Here, instead of expressing the varistor characteristics by C and α, it is expressed by the rising voltage V1mA at 1 mA and α. Conventionally used SiC varistors are made by baking SiC particles with a magnetic binder, and their nonlinearity is due to the voltage dependence of the contact resistance between the SiC particles.
Therefore, the C value can be controlled by changing the thickness in the direction of the current flowing through the varistor.
However, the nonlinear coefficient α is relatively small, ranging from 3 to 7.
Furthermore, it is necessary to perform firing in a non-oxidizing atmosphere.
On the other hand, since the nonlinearity of Si varistors is due to the P-n junction of Si, it is impossible to control the C value over a wide range. Zener diodes similarly utilize a P-n junction of Si, so they have extremely high voltage nonlinearity, but they also have the drawback of being difficult to make high-voltage devices, and having a low discharge withstand capacity and being susceptible to surges. Ceramic varistors containing zinc oxide as a main component and containing bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, etc. have recently been developed. These have the advantage that their nonlinearity is caused by the sintered body itself, so they exhibit symmetrical voltage-current characteristics and have very large nonlinearity. However, when a large impact current is applied, the difference between the rate of change in V1mA in the positive direction and the rate of change in the negative direction is large, and the change in the negative direction is particularly large. This is a major drawback in that symmetrical voltage-current characteristics cannot be maintained, that is, polarity occurs, and reliability cannot be guaranteed as an unstable element. In addition, products that do not contain bismuth oxide but contain nickel oxide and barium oxide, and products that contain rare earth elements and cobalt oxide have been developed.
Although the difference in the rate of change in A has become smaller, the voltage nonlinearity is smaller than that of a varistor containing bismuth oxide, and the surge suppression properties as a varistor are poor, which limits the range of use. However, an object of the present invention is to overcome the above-mentioned drawbacks of conventional voltage nonlinear resistance elements. In other words, it has essentially symmetrical voltage-current characteristics, has good surge suppression characteristics, has a high voltage nonlinear coefficient α, and maintains voltage-current characteristics that give users high reliability when applying large shock currents in practical use. None, and in order to satisfy the high voltage stability of V1μA that improves the charging life characteristics, the voltage nonlinearity depends on the sintered body itself, and the α value is as high as 60 or more.
It also has extremely small polarity characteristics, with a difference of 1% or less between the rate of change in the positive direction and the rate of change in the negative direction of V1mA when a large shock current is applied, and the voltage change rate at V1μA is 3% or less. An object of the present invention is to provide a method for manufacturing a voltage nonlinear resistance element with excellent performance. The details of the present invention will be explained below based on one embodiment. Example Bismuth oxide, cobalt oxide, manganese oxide, metallic zinc, and spinel-type crystal antimony compound are added to zinc oxide in the range of 0.001 to 10 mol %, respectively, and mixed thoroughly to form a disk with dimensions of 20 mmφ x 1 mmt. It was molded into a mold and sintered in air at a high temperature of over 1000℃. The antimony compound of spinel type crystal used here is prepared in advance as follows. Specifically, zinc oxide, aluminum oxide, and antimony oxide are mixed into a composition that forms spinel-type crystals, treated at a high temperature of 1300°C for 6 hours, and wet-pulverized. When electrodes were attached to both sides of the sintered sample and its properties were measured, the results shown in Table 1 were obtained.

[Table] In other words, Table 1 examines the characteristics when the thickness of the sintered body is fixed and the type of electrode is changed. It can be seen that the sintered body itself is a nonlinear element whose characteristics change depending on the thickness of the sintered body. Next, Fig. 1 shows the change in α value corresponding to V1mA when the sintering temperature and addition amount are changed. The sintering temperature, composition, and amount added of the samples are shown in Table 2. Curve 1 shows the largest α value among the embodiments of the present invention. Curve 2 is a comparative example and shows the characteristics when zinc oxide was not used as a starting material in the sample described above but all zinc oxide was used. Curve 3 is a reference example in which nickel oxide, barium oxide, etc. are added to zinc oxide without containing bismuth oxide.

[Table] As can be seen from the following, varistors containing bismuth oxide and metallic zinc as a starting material are characterized by a large α value over a wide range of V1mA. Next, Table 3 shows a comparison of polar characteristics. In other words, Table 3 shows the shock large current characteristics,
The DC load characteristics and temperature/humidity cycle characteristics are expressed as the rate of change in the positive direction and the rate of change in the negative direction of V1mA, and were compared with those of a conventional voltage nonlinear resistance element of this type. All elements used in Table 3 had the same geometry. This is an example shown for a device with V1mA=200V. Conventional ZnO
The data of the varistor does not contain metal zinc as a starting material from the composition of the example of the present invention.

[Table] From the values in Table 3, it can be seen that the values of the varistor obtained by the manufacturing method of the present invention are much better than those of the conventional varistor. The impact current characteristics are
V1 when 500A surge current is applied 10000 times
It looks at the rate of change in the mA value in the positive and negative directions.
This study investigated the stability of varistors as surge absorption elements, which are their main use. DC load characteristics are
V1m after applying a load of 2W for 500 hours continuously at 85℃
The rate of change of A was investigated. It can be seen that conventional varistors deteriorate significantly at high temperatures. The temperature/humidity cycle characteristics were determined by examining the rate of change after 100 cycles of a 2W load in an atmosphere from -40°C to 85°C and 95% RH. In addition, the polarity of the zinc oxide shown as a reference example (curve 3) in Figure 1 with nickel oxide, barium oxide, etc.
The absolute value of the difference between the rate of change in the positive direction and the rate of change in the negative direction is 4 to 5%. The voltage nonlinear resistance element obtained by the manufacturing method of the present invention not only has excellent nonlinearity but also has extremely small polarity characteristics. This is very important in terms of maintaining symmetrical voltage-current characteristics, and these life characteristics and stability guarantee high reliability as an element. This is particularly important from a practical standpoint. Although oxides were used as additives such as bismuth oxide, cobalt oxide, manganese oxide, etc. in the above embodiments, it goes without saying that the additives are not necessarily limited to oxides as long as they become oxides at high temperatures in air. The optimal point of sintering temperature varies slightly depending on the amount of additives added, but at temperatures below 1000°C, sintering becomes insufficient and it is difficult to exhibit the stability characteristics shown in Table 2. The upper limit of the sintering temperature is determined by the degree of sintering, that is, the temperature at which the sintered body does not deform or expand. According to the inventor's experimental results, the most effective addition amount of metallic zinc is in the range of 0.001 to 10 mol%, as is clear from the impact current characteristics shown in Figure 2. The most effective amount of the antimony compound added to the type crystal is in the range of 0.001 to 10 mol%, as is clear from the temperature/humidity cycle characteristics shown in FIG. In both cases, in the range of less than 0.001 mol% or more than 10 mol%, the rate of change in V1mA in the negative direction becomes negative, and the stability is comparable to that of the conventional one. In addition, in the present invention, other additives other than the above-mentioned additives may be added to the zinc oxide in advance, or may be diffused into the sintered body, or an appropriate combination of these methods may be used. As detailed above, according to the present invention, metal zinc, zinc oxide, aluminum oxide, zinc oxide, zinc oxide, zinc oxide, aluminum oxide, etc. A voltage nonlinear resistor that contains an antimony compound in the form of a spinel type crystal made of antimony, has extremely high nonlinearity, has very good polar characteristics, is extremely simple to manufacture, and has stable characteristics. A method for manufacturing an element can be provided.

[Brief explanation of drawings]

Figure 1 shows the difference between an embodiment of the present invention and a conventional reference example.
FIG. 2 is a curve diagram showing a comparison of changes in α value corresponding to V1 mA, FIG. 2 is a curve diagram showing shock current characteristics, and FIG. 3 is a curve diagram showing temperature/humidity cycle characteristics.

Claims (1)

[Claims] 1. A method for manufacturing a voltage nonlinear resistance element whose main component is zinc oxide and whose sintered body itself has voltage nonlinear characteristics. A method for producing a voltage nonlinear resistance element, characterized in that it contains an antimony compound as a starting material. 2. The method for manufacturing a voltage nonlinear resistance element according to claim 1, wherein the content of metallic zinc and the antimony compound of the spinel type crystal is 0.001 to 10 mol%, respectively. 3. The voltage nonlinear resistance element according to claim 1 or 2, wherein the sintered body is made of zinc oxide, metallic zinc, and an antimony compound of spinel type crystals, with at least bismuth oxide added thereto. manufacturing method. 4 Claims characterized in that the sintered body is made of zinc oxide, metallic zinc, and an antimony compound in the form of spinel-type crystals, with the addition of a small amount of one or more metal oxides such as cobalt oxide and manganese oxide. A method for manufacturing a voltage nonlinear resistance element according to any one of Items 1 to 3.