JPS6015128B2 - Manufacturing method of voltage nonlinear resistor element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a voltage nonlinear resistor element containing Zn○ as a main component.

Conventional methods for insulating the side surfaces of this type of voltage nonlinear resistance element (hereinafter referred to as element) whose main component is Zn○ include applying an epoxy-based organic substance to the side surface of the element after firing, or insulating it before firing the element. Various inorganic compounds were applied to the side surfaces of the device and then fired, and after firing, an insulating coating was formed which became a glassy or crystalline insulator for insulation.

However, the former method has the disadvantage that the adhesion between the applied epoxy-based organic material and the element body is poor, and as a result, moisture is adsorbed to the element, resulting in significant deterioration of characteristics and weakening of short-wave tail resistance.

Furthermore, since there is a difference in thermal expansion between the element body and the epoxy resin, there is a drawback that the epoxy resin coated on the side surfaces of the element cracks due to thermal shock, causing deterioration. In the latter method, it is necessary to match the shrinkage rates of the element body and the side insulating material during firing. For this purpose, the compression molded element is first fired to shrink the element to some extent, and then an inorganic compound or a mixture thereof is applied to the side surface of the element which has been fired for the first time, and the main firing is performed to form an inorganic insulating side film. . In this case, it is necessary to perform the baking twice. However, since it is not preferable for the electrical properties of the device to cause full shrinkage through primary firing, the shrinkage rate of the side insulating material made of an inorganic compound and that of the device must be matched as much as possible.
Furthermore, there is a phenomenon in which Bi203 evaporates from the element body during firing. This causes non-uniformity in the grain boundary layer concentration of Bj203, which is responsible for the nonlinearity of the Qin body, and liquid phase competition due to the liquid phase of Bi203 causes variations in the grain growth rate of Zn peach crystals, resulting in voltage fluctuation. There is a drawback that linearity decreases. Furthermore, both methods have the disadvantage that considerable technology and equipment are required to make the side insulating film uniform to the required thickness.

In view of the above-mentioned drawbacks, the object of the present invention is to form an insulating film having dense and uniform crystal grains and good adhesion to the element body, and to reduce the deterioration of the element characteristics and reduce the voltage non-linear characteristics. An object of the present invention is to provide a method for manufacturing a voltage nonlinear resistor element without any steps.

According to the present invention, the above object can be achieved by placing antimony oxide, bismuth oxide, and silicon oxide in a container used for firing, and placing a molded body containing Zn○ as a main component in the same container and firing at the same time. achieved.

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an embodiment to which the method of manufacturing a voltage nonlinear resistor element of the present invention is applied.

In FIG. 1, a pedestal 14 made of a heat-resistant ceramic material is placed on the bottom of an alumina sheath (firing container) 12. On this pedestal 14, a millet body 18 which is compression-molded and mainly composed of Zn◯ is placed with a layer of bedding powder 16 interposed therebetween. Bedding powder 1
6 prevents the pedestal 14 and the body 18 from being welded together. Further, a coating agent 20 is applied to the inner surface of the sheath 12 to form a side insulation coating on the element body 18. The top of the sheath 12 is provided with a lid 22 that is homogeneous to the sheath 12. Pedestal 14
The material is preferably alumina or a zinc oxide sintered plate. In particular, a zinc oxide sintered plate is desirable since it is the same as the main component of the element body and does not impair the properties of the sintered element. Bed powder 16
For example, alumina powder, powdered powder of Zn○ elements, or powder obtained by pre-pulverizing Zn○ elements is used. A component similar or the same as that of the Znd element is required more strongly than in the case of the pedestal. Note that if the pedestal 14 is made of the same material as the base body 18, the bedding powder 16 may be omitted. Further, the coating agent for forming the side insulation coating may be applied to a part or the entire inner surface of the sheath 12 and the bottom surface of the lid 22. In FIG. 2, an auxiliary member 24 of the same quality as the sheath 12 and lid 22 is placed upright along the inner surface of the sheath 12, and a coating agent 20 is applied to the inner surface (or both the inner and outer surfaces) of the auxiliary member 24. ing.

The upper surface of the element body 18 is masked with a bedding powder 26 and a shielding member 28 to prevent formation of an insulating film. Note that the coating agent is not only applied to the sheath 12 or the auxiliary member 24, but also
In short, the purpose can be sufficiently achieved simply by arranging it near the element 18. The auxiliary part 24 shown in the embodiment of FIG. 2 has a mechanical strength 3 sufficient to withstand being put in and out of the firing container, and is thin-walled because there is little risk of thermal deformation due to multiple firings. It is relatively inexpensive.

Therefore, if the material of the auxiliary part 24 changes due to repeated use and the properties of the formed side insulation coating deteriorate, it can be easily replaced. Furthermore, since the comparatively expensive sheath 12 and lid 22 are not coated with the coating agent 20, material changes are reduced and can be used for multiple firings, so the internal volume of the sheath is large and small diameter elements can be used. The embodiment shown in FIG. 2 is suitable when firing a plurality of pieces. A method for manufacturing the voltage nonlinear resistor element of the present invention will be described below.

First, the element body 18 is made of Zn○ (91% by weight) and Sb203.
, Bi203, Co203, Cr203, Mn02, S
A mixture of i02 and the like (9% by weight) is added, thoroughly mixed, and then compression molded into a suitable shape. For example, look up 4 times in diameter.
The molded product is shaped into a cylinder with a thickness of about 3 centimeters. The coating agent contains Bi203 (5-6% by weight), Sb2 as starting materials.
03 (5-6 wt%) and Si02 (1-3 wt%
) and then thoroughly mixed with water to form a slurry. This coating agent is applied to the inner surface of the sheath 12 and the auxiliary member 24 of the firing container shown in FIGS. 1 and 2 and dried. Thereafter, the element 18 whose main component is Zn○ is placed in the sheath 12 and covered with a lid 22 to make it almost airtight. 100,000 to 14 in this sealed state
00ko○ (from the point of view of the electrical characteristics of the element, 1100qo~1
When fired at a temperature range of 30,000 ℃ (preferably
Part of the applied mixture in the container 2 or the compound produced by their reaction evaporates and scatters, and the inside of the container becomes an atmosphere of these metal oxides.
A high-resistance insulating film is formed on the surface of the element body 18 through a gas-solid phase reaction with the additive mixture and the like. In the above gas-solid phase reaction, Bi203, SQ03, Si coated inside the container
Of 02, SQ03 metamorphosed into SQ04 at 57,000 and became 9
Sublimation begins around 20 qo and becomes very active above 1000 qo.

Also, Bi203 melts at 820 points and the container is at 10,000 points.
When the temperature is 0 or more, an atmosphere with a high concentration of antimony oxide and bismuth oxide is filled. Although Si02 has a much higher melting point and a lower vapor pressure than other substances, it scatters due to the sublimation of SQ03 and the evaporation of Bi203, reaches the surface of the element body 18, and reacts. It is believed that. On the other hand, in the temperature range of 80,000 to 1,000 oo, Thai body 18 contracts by about 40% in volume ratio, and in addition to Zn0, Z~Si04,
Zn2Bi3SQ04 (pyrochlore), Zn2.8S
b. ．． Target (spinel), Bi203, 14Si203・
A crystal layer of Cr203 or the like is formed. On the surface of the element body, Bj203 contained therein begins to evaporate as the heating temperature rises, but the amount of evaporation is considerably suppressed by the Bi203 atmosphere generated within the firing container. Also SQ in the atmosphere
04, Bi203, and Si02 react with the element and form Z mountains on its surface. 33S. Town 04, Z & Si04 begins to be formed. At 1000 oo or more, Zn formed on the side of the element body
2.3bub small 6704 and Zn2Si04 and unreacted S
b204, Si02 is Zn2 diffusing from inside the element body.
Zn2.3Sb Misaki 704, Zn2Si04 reacts with ten
, Bi203 are formed.

These compounds are crystallized together with the element body 18. Sintering B
Since J203 exists in a liquid phase, it has the function of uniformly promoting the sintering reaction between the element body and the insulating coating phase that is being formed. As a result, an insulating film with a thickness of 40 to 50 r is formed, having minute and uniform crystal grains without pinholes. In the end, the coating formed on the side surface of the element body is Znbu i04, Z mountain. 33S
〇． This is the crystal phase of Z-04. FIG. 3 shows the results of examining the state of the insulating film formed on the surface of the element as described above using an X-ray microanalyzer.

Figures a and b are secondary electron images, and b is an enlarged image twice that of a. In the same figure, c, d, e, f, Zg, h are respectively Sb,
These are characteristic X-ray images of Si, Bj, Zn, Mn, and Co. From the figure and Fig. 5, the insulation coating is Z&. 3Sb. 6704,Zn
The main component is Buj04, and its thickness is approximately 40 mm.
It was found to be ~50 μm.

2Figure 4A,
B shows the results of line analysis using an x-ray microanalyzer of the element fired in this example. However, for example, No.ZnlOK shown in the upper right of the figure represents a full scale of 10 kcps (kilocount per second) of zinc. It can be seen that in the side insulating coating portion (b) of FIG. It can be seen from Figure B that Si and Bi are present in the film. Note that m indicates a mold portion. Its thickness is about 40-50 Buddhas. The spinel formed on the side of the element melts Co, Mn, and Cr present in the element, and Zn2Si04 melts Co, Mn, and Cr present in the element.
It can be seen that the spinel and Zn2Si04 formed on the surface during firing are sufficiently reacting with the element body since Mn is solidified. Furthermore, as is clear from the X-ray diffraction diagram of the coating shown in FIG. 5, the insulating coating is made of Zn2.33S. 67
04 (spinel), Zn2Si04 is the main component, Sp in the figure is spinel (Zn2.3Sb ship 704
), and the official one is zinc silicate (Znbui04).

FIG. 6 shows the electrical characteristics of elements when the element bodies were manufactured in a firing furnace with different mixing ratios of SQ03, Bi203, and Si02.

In the figure, × indicates △VimA/VimA, and 0 indicates discharge withstand capacity (4×
10rS twice). Bi203, Sj02
It can be seen that the discharge withstand capacity decreases as the amount of . According to this embodiment, SQ03, Bi203, and Si
Apply the mixture of 02 as a coating agent into the container for marriage, and
By manufacturing a device by firing the Zn○ element body in an atmosphere of Q03 and Bi203, Bi20 is removed from the Z element body.
Since 3 is difficult to evaporate, it is effective in manufacturing a voltage non-linear resistor element having non-linear voltage-current characteristics with good electrical characteristics such as discharge withstand capacity.

Since the Bi203 atmosphere promotes the formation of an insulator, it has the effect of easily forming a high-resistance insulating layer on the side surface of the device within the device firing temperature range. This insulating layer has better electrical properties such as corona resistance and arc resistance than when coated with epoxy resin, and has the same properties as those coated with an inorganic side coating and fired. There are benefits to be gained. Further, since scattering of Bj203 from the ZnO element body is suppressed, it is effective to manufacture a homogeneous element. Therefore, there is an effect of obtaining an insulating coating having good adhesion between the grain body and the insulating coating and having dense and uniform crystal grains free of pithoholes. Since it is only necessary to sinter the Znq element body 18 in a metal oxide atmosphere within the element firing temperature range, there is less need to consider the shrinkage rate of the element body and the inorganic surfacing agent compared to a method in which an inorganic surfacing agent is applied. This has the effect of making it easy to obtain a high-resistance side insulator. Furthermore, since the temporary mounding process of the element body can be omitted, the manufacturing process can be simplified, which contributes to cost reduction. As is clear from the above description, according to the present invention, by firing a Zn○ element body in a mixed atmosphere of bismuth oxide, antimony oxide, and silicon oxide, a dense and uniform A voltage nonlinear resistor element that has crystal grains, forms an insulating layer with good adhesion to the element body, has little deterioration of element characteristics, increases voltage nonlinearity, and also improves other electrical characteristics. You can get it.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a method for manufacturing a voltage nonlinear resistor element, which is an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a method for manufacturing a voltage nonlinear resistor element, which is an embodiment of the present invention. Other applied explanatory diagrams, Fig. 3, are state diagrams of the insulating layer formed by an X-ray microanalyzer, a and b in the same figure are secondary electron images, and c, d, e, f, g, and h in the same figure are respectively Sb, Si, Bi,
Characteristic X-ray images of Zn, Mn and Co, Figures 4A and 4B
is a line analysis diagram of an x-ray microanalyzer, Figure 5 is an X-ray diffraction diagram of an insulating coating, and Figure 6 is a diagram of the relationship between changes in the mixing ratio of Sb203, Bi203, and Si02 and the electrical characteristics of the element. be. 12...Sheath, 18...Body, 20...Linting agent, 2
2... Lid, 24... Auxiliary member. Figure 1 Figure 2 Figure 3 Figure 3 Figure 4 Figure 5 Figure 4 Figure 6

Claims (1)

[Claims] 1. When firing a voltage nonlinear resistor containing zinc oxide, antimony oxide, bismuth oxide, and silicon oxide are placed in a container, and at the same time as the firing, a side insulating film is formed by a gas-solid reaction. A method of manufacturing a voltage nonlinear resistor element, characterized in that: