JP2532493B2 - Electrode forming method for voltage non-linear resistor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a voltage non-linear resistor containing zinc oxide (ZnO) as a main component to which an additive is added so that the sintered body itself has voltage non-linearity. The present invention relates to an electrode forming method.

Conventional technology Conventionally, the main component is ZnO, and Bi ₂ O ₃ , Co ₂ O ₃ , S
_{b 2 O 3, MnO 2,} Cr 2 O 3, TiO 2, Al 2 O 3, minor as an additive component a metal oxide such as SiO ₂ was added, obtained by firing at a high temperature sintered body, It exhibits remarkable voltage non-linearity and is widely used as a voltage stabilizing element and a surge absorbing element.

Conventionally, this type of voltage non-linear resistor is manufactured by adding the necessary additives to the main component ZnO, mixing, molding, and then sintering at high temperature, and then Ag powder on the facing surface. Was applied in the form of paste and baked at about 500 to 900 ° C. to form electrodes.

Problems to be Solved by the Invention However, additives (for example, Bi ₂ O ₃ , Co ₂ O ₃ , MnO ₂ , Sb ₂ O ₃ , Cr ₂ O _{3) in which} the sintered body itself has voltage nonlinearity are disclosed. )
When a mixture containing ZnO added as a main component is formed and sintering is started, the solid-phase reaction of ZnO and each component is gradually performed up to around 800 ° C, and the temperature is increased to around 800 to 900 ° C. When
The liquid phase reaction centered on Bi ₂ O ₃ suddenly started at 1000 ℃
In the vicinity, a solid solution component of Bi ₂ O ₃ is formed in the grain boundary layer with ZnO particles, and the liquid phase sintering is completed. However, in general, in order to improve the grain boundary density and promote the grain growth of ZnO grains, 1200 to 1300
The sintering temperature has been raised to around ℃. Therefore,
Above 1000 ° C, solid solution components centering on Bi ₂ O ₃ tend to evaporate and scatter. This phenomenon occurs as the compact shape becomes smaller and the electrode facing surface distance becomes smaller. However, it is remarkable when viewed from the sintered body.

Thus, in the conventional method, evaporation of the solid solution component,
Since it is easy to scatter, the sintered density of the sintered body is lowered, and the electrode is formed after the sintered body is formed, which is disadvantageous in terms of workability.

Moreover, in order to increase the sintering density of the voltage nonlinear resistor whose main component is ZnO, molding by isostatic pressing,
Various attempts have been made, such as firing in an atmosphere and sintering by hot pressing, but all of them require large-scale production equipment and are complicated to apply.

The present invention solves such a problem by making electrode baking during the sintering process of a voltage non-linear resistance element, and evaporating solid solution components such as Bi ₂ O ₃ during the sintering process. It is an object of the present invention to provide an electrode forming method for a voltage non-linear resistor capable of suppressing scattering.

Means for Solving the Problems In order to solve this problem, the electrode forming method of the present invention comprises forming a mixture composed of ZnO as a main component and an additive exhibiting voltage nonlinearity, After pre-sintering at a temperature of ~ 1000 ° C and applying Pt powder in a paste form on the opposing surface, baking of the Pt powder is performed during the sintering process of the pre-sintered compact, and the electrode is Are formed. Further, as a preferred embodiment, the Pt powder has an average particle diameter of 0.5 to 0.7 μm.

Action According to this structure, Pt is extremely inert to other elements due to its properties, does not affect the sintered body of the voltage nonlinear resistor, and also depends on the particle size of Pt powder. However, Pt powder starts to sinter at 800-1000 ℃, and 1200-1
Since the sintering is completed at 300 ° C., evaporation and scattering of solid solution components such as Bi ₂ O ₃ generated during the sintering process of the voltage nonlinear resistance element can be physically suppressed. In addition, since O ₂ is released from Pt during the sintering process of Pt powder, O ₂ is diffused and held under a constant pressure inside the sintered body of the voltage nonlinear resistor. The sintered body under the Pt electrode will lead to better results. From these facts, it is possible to improve the sintering density of the sintered body in the voltage nonlinear resistor. Further, since the electrodes are formed at the same time during the sintering process, it is very advantageous in terms of productivity.

Examples Hereinafter, examples of the present invention will be described.

First, a mixture of the mixture to first main component ZnO, molding, Stated presintering, Bi ₂ with respect to the total amount of ZnO powder
O ₃ 0.5 mol%, Co ₂ O ₃ 0.5 mol%, MnO ₂ 0.5 mol%, Sb ₂
Add O ₃ at 1.0 mol% and Cr ₂ O ₃ at 0.5 mol% and mix well. After that, a small amount of PVA (polyvinyl alcohol) solution was added, kneading and granulation were performed, and 32 ^# (μm)
After passing through a sieve of about 10 mm, fill a mold of about 17 mmφ,
A molding having a molding thickness of about 1.0 mm was obtained at a molding pressure of 400 to 800 kg / cm ² , and pre-sintering was performed in air under various conditions as shown in Table 1 below. Also, at that time Bi ₂ O
Table 1 shows the results of the differential thermal analysis of the amount of solid solution components such as ₃ evaporated and scattered (binder disappearance was eliminated).

From Table 1 above, the need for pre-sintering is solved as follows. That is, as is clear from Table 1, Bi ₂ O in the weight of the compact with respect to the pre-sintering temperature and the compacting pressure.
Looking at the relationship between the amount of evaporation and scattering such as ₃ , the pre-sintering temperature up to 1000 ℃ is almost negligible regardless of the molding pressure. However, up to 700 ° C, the sintering reaction of the molded body composed mainly of ZnO as a mixture does not occur, and when the paste of Pt powder described below is applied and dried, the shape retention of the molded body deteriorates and it becomes practical. Not suitable. Also, the pre-sintering temperature is 1100
At temperatures above ℃, as mentioned above, the amount of solid solution components, mainly Bi ₂ O ₃ , evaporated and scattered cannot be ignored. Therefore, the pre-sintering temperature needs to be in the range of 800 to 1000 ° C.

Next, the production of Pt powder paste, the sintering of the pre-sintered compact, and the electrode formation will be described. First, Pt
The powder paste is prepared by using polyvinyl butyral resin 3w as a binder for 100 wt% of black fine Pt powder.
t%, 2.1 wt% of dibutyl phthalate as a plasticizer, and 23 wt% of butyl acetate as a solvent are thoroughly mixed and kneaded with a liquor machine, and then the kneading effect is further enhanced by using a three-stage roller to form a paste. It was made. Then above
On the opposing surface of the molded body pre-sintered at a temperature of 800 to 1000 ° C, the above Pt powder prepared in a paste form by a screen printing method was applied so as to have a desired electrode diameter, Dry. Then, the pre-sintered, Pt paste-coated and dried compact is fired at 1200 to 1300 ° C. As a result, as shown in FIG. 1 and FIG.
As a result, a voltage non-linear resistor including Pt electrodes 2 formed by baking on both surfaces of the sintered body 1 during the sintering process is obtained.

The following Table 2 shows the average particle size of Pt powder is 0.4 to 1.0 μm.
Of Pt paste that has been changed in the above range at a temperature of 800 to 1000 ° C above (molding pressure is 400 kg / c
was applied to m ^2), dried, shows the sintered density of the voltage nonlinear resistor when Sintered, a voltage nonlinear index α is the performance of the voltage nonlinear resistor at 1300 ° C., 1 hour . Here, when measuring the sintered density, the Pt electrode was omitted. Also,
Generally, the index α is I = (V / C) ^α The higher the value of α, the better the performance of the voltage nonlinear resistor.

With the addition of the explanation in Table 2, the sintered body density and the non-linear index α are almost the same when the presintering temperature is in the range of 800 to 1000 ° C., rather, the average particle diameter of the Pt powder is rather small. Dependent. When the average particle size is 0.4 μm or less, when the paste is prepared, the particle size is small, so that aggregation easily occurs, the paste is easily gelated, and the surface is not practical. On the other hand, when the average particle size is in the range of 0.5 to 0.7 μm, there is no problem that the paste preparation is not practical, and the sintered body density and the nonlinear index α showing the performance of the voltage nonlinear resistor are the same as those of conventional products. It is extremely large in comparison. The reason is that the sintering start temperature of Pt powder is 800
Temperature rises to ~ 1000 ° C, and the Pt electrode is sufficiently densified by baking at 1300 ° C for 1 hour, which suppresses evaporation and scattering of solid solution components such as Bi ₂ O ₃ generated during the sintering process. Therefore, the sintered body density and the nonlinear index α are increased. Furthermore, if the average particle size of Pt powder is 0.8 μm or more, the sintering start temperature of Pt powder will be 1000 ° C. or more, and sufficient sintering cannot be achieved by baking at 1300 ° C. for 1 hour. Is more advantageous than the conventional method,
Sintered body density and non-linear index α are only slightly improved compared to conventional products.

In addition, in the above-mentioned examples, as an additive for expressing voltage non-linearity, only some kinds and combinations thereof are shown, but the effect of the present invention is not limited to a non-linear resistor whose main component is ZnO. However, it is applicable and is not limited by the type of additive that causes nonlinearity or the combination thereof.

EFFECTS OF THE INVENTION The present invention is configured as described above, and Pt
The powder starts to sinter at approximately 800-1000 ℃, 1200-130
Since the sintering is completed at 0 ° C, evaporation of solid solution components such as Bi ₂ O ₃ generated during the sintering process of the voltage nonlinear resistance element,
Since the scattering is physically suppressed and O ₂ is released from Pt during the sintering process of Pt powder, O ₂ diffuses under a constant pressure with O ₂ inside the sintered body of the voltage nonlinear resistor. Since it is held, the sintered body under the Pt electrode leads to a better result, and from these, the sintered density of the sintered body in the voltage nonlinear resistor can be improved. Further, since the evaporation and scattering of solid solution components such as Bi ₂ O ₃ generated during the sintering process can be suppressed, the voltage nonlinear index α can be increased. Further, since the electrodes are formed simultaneously during the sintering process, the productivity is high and the manufacturing apparatus may be simple. Therefore, there is an advantage that it can be reasonably applied to a small amount and a wide variety of products.

[Brief description of drawings]

FIG. 1 is a top view showing a voltage nonlinear resistor obtained by the method of the present invention, and FIG. 2 is a front view of the same. 1 ... Sintered body, 2 ... Pt electrode.

Claims (2)

(57) [Claims] 1. A mixture composed of ZnO as a main component and an additive exhibiting voltage non-linearity is molded to obtain 800-1000.
After pre-sintering at a temperature of ° C and applying Pt powder in a paste form on the opposing surface, baking the Pt powder during the sintering process of the pre-sintered compact to form an electrode A method of forming an electrode of a voltage non-linear resistor, comprising: 2. The method for forming an electrode of a voltage non-linear resistor according to claim 1, wherein the Pt powder has an average particle diameter of 0.5 to 0.7 μm.