JPS6028121B2 - Manufacturing method of voltage nonlinear resistor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing a voltage non-linear resistor, and an object thereof is to provide a method for manufacturing a Kanji non-linear resistor that has excellent limiting voltage characteristics and has very little variation in characteristics during manufacturing. It is something to do.

BACKGROUND ART Voltage nonlinear resistance elements (hereinafter referred to as varistors) are widely used in overvoltage protection elements and lightning arresters.

The voltage (V) - current (1) characteristic of a varistor is usually 1 = (
V no C) It is represented by Q.

However, C is a constant corresponding to resistance, and Q is called a voltage nonlinear index. Generally, the characteristics of a varistor are expressed by Q and the capacitance at a certain current (hereinafter referred to as varistor voltage).

Q is usually determined from voltage-current characteristics at 0.1 to lmA/. Further, for convenience, the varistor voltage is often expressed as a terminal voltage (V, mA) when a current of 1 mA flows. As a varistor, the varistor voltage is within an appropriate range (usually tens to hundreds of volts per skin thickness), and the larger the Q value, the more desirable it is. , the limiting voltage ratio that represents the protection performance of the element (usually the voltage Vx^ at XA and the varistor voltage V,
The smaller the value (expressed as a ratio to m^), the better. Widely used varistors include SIC varistors, which are made by agitating carbonized porcelain and raw materials at high temperatures, and Zn○ varistors, which exhibit voltage nonlinearity due to the aggregates themselves consisting mainly of zinc oxide (bulk voltage nonlinearity). Are known.

However, when considered as an overvoltage protection element or earth protector,
The Z varistor is superior to the Holihu C varistor in almost all of the above-mentioned characteristics, and the Zn0 varistor is now mainly used. Outside of Zn0 balis, main component Znuni, bismuth oxide (Bi203),
It is obtained by adding and mixing a small amount of cobalt oxide (C 03), manganese oxide (M 2), etc., molding, and scaling at a temperature within the range of 1000 to 140 pi. The Zn0 varistor made in this way is similar to the subordinate SIC
While the barista's Q was 3-7, it was 30-50.
Since it can provide much more than that, it has become the mainstream of overvoltage protection elements. Among the above-mentioned characteristics, an important characteristic for an overvoltage protection element is the limiting voltage ratio, and it is desired that this characteristic be as good as possible. On the other hand, when considered from a production standpoint, variation in characteristics during production is one of the important issues.

Since Zn○ is a semiconductor ceramic that is extremely sensitive to the outer structure, small differences in its composition cause large differences in properties. Therefore, one important issue is how to make it smaller and produce it. In view of this situation, the present invention aims to provide a method for manufacturing a voltage non-linear resistor that has an excellent limiting voltage ratio and less variation in characteristics during manufacturing.Examples thereof will be described in detail below.

Example 1 Z or Zno shown in Table 1 and additives were placed in an alumina crucible and fired at 1100°C for 2 hours.

Further, grain boundary layer forming component additives having the same composition shown in Table 2 were placed in another alumina crucible and heated at 110 pi for 30 minutes. Next, the ratio of Zn○ and Bi203 is 99:1.
Zn○ or ZNO containing additives and grain boundary layer forming component additives were mixed at a ratio of It was baked in air for 2 hours. After polishing both sides of the obtained screen structure, aluminum traverse electrodes were provided and the electrical properties were measured. Table 3 shows the results. For comparison, Table 3 shows the combined compositions of A-8 and B-1, in which Zn0 and all additives were mixed together without individual temporary burning treatment as in this example. , shows the results when molding was performed.
This shows that the sample obtained by the method of this example has a large Q and a small limiting separation ratio. Table 1, Table 2, Table 3, and Figure 1 also show the variation in Q of the 100 samples obtained by this example and the results obtained by the method of the comparative example for the combination composition of A-8 and B-1. 100 of the sample
This shows the variation in the Q characteristics of .

Furthermore, FIG. 2 shows a comparison of variations in the limiting voltage ratio, and FIG. 3 shows a comparison of variations in V and m^/bar. It can be seen from this that the variations in the characteristics of the samples obtained in this example are much smaller than those obtained by conventional simultaneous mixing, molding, and firing. Example 2 Next, the effects of the firing temperature of Zn○ or Zn○ and additives, and the firing temperature of grain boundary layer forming component additives on the characteristics were investigated.

Samples were prepared using the same procedure as in Example 1, changing the firing conditions for samples with a combination of compositions A-8 and B-1, and the characteristics were measured. The results are shown in FIG. From this, it is found that the firing temperature of Z or Zn0 and additives to form Zn○ grains is preferably 1000 to 1400 pm, and the firing temperature of additives forming grain boundary layer formation components is 900 to 130 pm. Recognize. Example 3 Next, cooling conditions for additives were studied.

In the method of Example 1, for the sample with the combination of compositions A-8 and B-1, the additive to be the grain boundary layer forming component was added to 110%
After 30 minutes of anaerobic formation in a pyrotechnic furnace, the material was poured into a furnace at a rate of 20 pm, and then suddenly taken out into the air at room temperature, cooled, and a sample was prepared to measure its electrical properties. did.
The results are shown in Table 4. This shows that the properties of the grain boundary layer forming component additives are better when they are rapidly cooled. Table 4 Example 4 Next, in the composition of the combination of A-8 and B-1, the effect of the ratio of Z and Bi203 was investigated.

The manufacturing conditions for the sample were the same as in Example 1. The results are shown in Table 5. From Table 5, the ratio of Zn0 and Bi203 is 99.
It can be seen that good characteristics are exhibited at a molar ratio of 9/0.1 to 97/30. From the explanations in Table 5 and above, it is clear that according to the method of the present invention, a varistor with better characteristics can be obtained.

The invented barista can mix, mold, and
The reason why the properties are better than that of fired products is thought to be as follows. First, Z0 is an n-type semiconductor with an excess of interstitial zinc, and therefore its specific resistance is lower as it is fired at a higher temperature. Therefore, as mentioned in the example, by pre-sintering Zn○ at a high temperature, the resistivity of ZNO decreases, and the Zn in the compact, which is a problem in the large current range, is reduced.
This is thought to be because the resistance of ○ is lower, so the voltage rise in the large current range is reduced. On the other hand, additives such as Co203 and MN02 form traps in Bj203, and the higher the trap density, the higher Q becomes.
In the method of the present invention, additive components that are thought to form traps are uniformly and sufficiently spaced out in Bj203 in advance, so that the resulting grain boundary layer contains traps uniformly and at a high density. Therefore, Q is considered to be large. In other words, if all the additives are mixed from the beginning and fired, the additive components that would prefer to enter the grain boundary layer will also enter into the Zn○, while the additive components that would be better to enter only into the Zn○ will also enter the Zn○. Since it penetrates into the Bi203, its uniformity is poor and its density is also insufficient. Therefore, it is considered that the characteristics deteriorate. It is also presumed that the variation in properties is due to variation in the distribution of such additives. In addition, the reason why it is better to rapidly cool Bi203 and additives is that when slowly cooling, the additive components that were molten in Bi203 at high temperatures during tentative scaling will precipitate out due to gradual cooling. This is thought to be due to the effect fading away.

Therefore, although this example shows only one example, it goes without saying that similar effects can be seen with any composition. In addition, in the method of the present invention, since the final reaction product is already produced in temporary phosphorus, there is no need to wait for a new reaction to occur in the firing after molding, and therefore it is not necessary to braze at a low temperature. I can do it.

In other words, in the conventional method, the light was not sufficiently lit at 1200 to 135 qo, but with the method of the present invention, it is 900 to 1150 qo. Competitive binding can be achieved with a low degree of fringe. Therefore, as shown in Fig. 2, even with the same composition and the same firing temperature, the varis voltage (V, m^/skin) is higher due to more competitive bonding than in the past.
A low value is obtained. Furthermore, regarding the types and amounts of components added to the ZnO legs, the object of the present invention is to
Since the additive components that are solid dissolved in Zn0 and are effective in improving properties are sufficiently dissolved in Zn0 particles in advance, it is natural that the additives should be those that are solid dissolved in Zn0 and effective in improving properties. , that is, C et al 03, Mh02, C also 03,
It is at least one of the peaks 203, Ga 203, etc., and the amount added is within the range where it can be dissolved as a solid solution in Zn0. As a grain boundary layer forming component, Bi208 contains at least 0.05 to 3
0 mol% Co203, 0.05-30 mol% Mn0
2, 0.05 to 10 mol% of SQ03, 0.1 to 70 mol% of Si02, and 0.1 to 30 mol% of Z pond may be added. As described in detail above, the method of the present invention was obtained by fully understanding and controlling the fine structure and formation reaction mechanism of Zn○ varistors, and enables the creation of high-performance overvoltage protection elements. This is effective for stable production.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 illustrate the effect of reducing variations in varistor characteristics by the method of the present invention.
FIG. 4 shows the optimum implementation conditions of the method of the present invention.

Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A ZnO grain component and an additive forming a grain boundary layer are separately calcined and pulverized, and the powders of both are mixed, molded, and fired. A method of manufacturing a voltage nonlinear resistor. . 2. As ZnO grain components, ZnO and at least one or more of cobalt, manganese, nickel, chromium, aluminum, and gallium are added and mixed in an amount within the solid solubility limit range of ZnO, and calcined to solidify into ZnO. At the same time, Bi_2O_3 and at least cobalt oxide are dissolved as grain boundary layer forming components in the form of Co_2O_3, 0.05
~30 mol%, manganese oxide converted to MnO_2 form 0.05 to 30 mol%, antimony oxide Sb_2O
0.05 to 10 mol% in terms of the form of _3, 0.1 to 70 mol% in terms of silicon oxide in the form of SiO_2, ZnO
2. The method for manufacturing a voltage nonlinear resistor according to claim 1, wherein one or more of 0.1 to 30 mol % of the above components are added, mixed, and calcined. 3 The calcination temperature of the ZnO grain component is 1000 to 1400°C, and the calcination temperature of the additive as a grain boundary layer forming component is 900°C.
The method for manufacturing a voltage nonlinear resistor according to claim 1 or 2, characterized in that the temperature is 1300°C to 1300°C. 4 When mixing ZnO grain components and grain boundary layer forming components, ZnO
The method for manufacturing a voltage nonlinear resistor according to claim 1, characterized in that 0.1 to 3 mol% of Bi_2O_3 is added to the components. 5. A method for manufacturing a voltage nonlinear resistor according to claim 1 or 2, which comprises calcining the grain boundary layer forming component and then rapidly cooling it to a temperature below room temperature from the calcining temperature. .