JPH02241004A - Manufacturing method of zinc oxide type varistor - 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 Field of Industrial Application The present invention relates to a method for manufacturing a high-performance zinc oxide type varistor for protecting semiconductor electronic components and the like from surges.

BACKGROUND ART Conventionally, when firing a disc-shaped zinc oxide type varistor, a molded body 2 of powder mainly composed of zinc oxide, which produces varistor properties when fired, is placed in a box-shaped pod 1 with a single bottom. Firing was performed in stacks or in bulk.

Problems to be Solved by the Invention However, when the conventional firing pods 1 with a single bottom are used, the heat capacity of the firing furnace, or when the pods 1 are stacked and fired, the lower or upper pods After firing, the varistor voltage per unit thickness of the element placed in the upper part of pod 1 and the element placed in the lower part of pod 1 is affected by its own heat capacity (Vz flA/m+)
There was a problem that a difference occurred in i[.

The present invention solves the above-mentioned conventional problems, and is an oxidation method that can stabilize the varistor voltage (Vt In^/wm) value of the element in the pod by reducing the influence of heat capacity from the firing furnace or pod. The object of the present invention is to provide a method for manufacturing a zinc-type varistor.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a zinc oxide type varistor of the present invention has a bottom with a double structure of two layers, upper and lower, and a space between the upper and lower bottoms. A firing pod connected to a furnace is used, and a zinc oxide type varistor is placed on the top of the firing pod for firing.

Effect: By the above method, the gas in the furnace is sufficiently circulated through the space between the upper and lower bases of the double structure, so that the firing of the zinc oxide type varistor placed on the upper base of the firing pod can be performed easily. It is less affected by the heat capacity of the firing furnace, and even when firing pods are stacked, it is less affected by the heat capacity of the lower or upper tiered pods; This reduces the occurrence of differences in varistor voltage values between parts.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view for explaining a method of manufacturing a zinc oxide type varistor according to an embodiment of the present invention.

In FIG. 1, a molded body 11 of powder mainly composed of zinc oxide, which exhibits varistor properties when fired, has a thickness of 1.2 mm.
The varistor voltage (V 111A/
m ) value is approximately 200 V. The baking pod 12 has a height of 50 m, a length and a width of 150 cm, and a wall thickness of 7 plates. The lower bottom pod 3 for firing is arranged so that the bottom of the pod 12 is double mm, and has a height of 20 m, a vertical and horizontal length of 150 am, and a wall thickness of 7 mm. A pair of side walls are removed to allow communication with the inside of the furnace so that gas in the furnace can be sufficiently circulated between the bottom of the firing pod 12 and the bottom of the firing pod 12. In this structure, the molded body 11 is placed on the bottom 12a of the baking pod 12, which is the upper bottom of the double structure, and the pod unit consisting of the baking pod 12 and the bottom baking pod 13 is, for example, divided into two stages. The openings of the uppermost firing pods 12 are sealed by pods 1114 each having a length, width, and length of 150-1 and a thickness of 7 cm.

The operation of the above configuration will be explained. The pods 12, which were stacked in two layers and each with the formed body 1 placed on the upper bottom (bottom 2a of the sintering pod 2), were heated at a heating rate of 200°C/h.
Keep temperature 1300℃, keep time 1h, cooling rate 20
The compact 11 was fired under firing conditions of 0° C./h in a firing furnace having a length, width, and height of approximately 300 rxxr and a furnace wall thickness of approximately 50 m. For comparison experiments, we prepared two pods with the same shape, one with a wall thickness of 5m, and another with a wall thickness of 10all.As shown in Figure 2, we also prepared a conventional pod with a single bottom and a wall thickness of 10all. A molded body 11 having a length of 5 m+, a length of 71111, and a length of 10 m was prepared and fired under the same firing conditions. Electrodes containing silver as a main component were baked on both sides of the sintered body obtained by this method, and the varistor voltage (V 1 mA/m ) of the zinc oxide type varistor element in each sac was measured0Table 1
And Table 2 shows that the elements fired in 20 stacks are
Number the varistor voltage (V 1 mA/
The results of measuring m) values are shown.

Table 1: Firing conditions and varistor voltage It can be seen that the thinner the wall thickness of the pod, the smaller the difference in the varistor voltage (Vl n^/Sono) value of each sintered body within the same pod. In the conventional case where the bottom of the pod is single, there is a large difference in the varistor voltage (vl n^/,,) value of each sintered body in the sintered body, especially in the bottom pod of Table 2. This is thought to be due to the fact that the heat capacity of the sheath and the firing furnace affect the properties of the sintered body. Therefore, the wall thickness of the pod is made thinner, and the structure is designed to allow sufficient gas circulation in the furnace between the upper bottom 12a of the firing pod 12 and the lower bottom 13b of the lower bottom pod 13, as shown in FIG. This is desirable.

In the examples, the molded bodies were stacked and fired, but it goes without saying that the same effect can be obtained even if they are stacked in bulk.

Effects of the Invention As described above, according to the present invention, the furnace has a double structure with two upper and lower bottoms, and the gas in the furnace can be sufficiently circulated through the space between the upper and lower bottoms. By using a firing pod with a structure that communicates with the inside, the influence of heat capacity from the firing furnace or firing pod is reduced when firing zinc oxide type varistors, making it possible to produce elements with stable varistor voltage values. can do.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a firing pod for explaining a method for manufacturing a zinc oxide varistor according to an embodiment of the present invention, and FIG. 2 is a perspective view of a firing pod for explaining a conventional method for manufacturing a zinc oxide varistor. It is a perspective view of a pod. 11... Molded body, 12... Saya for firing, 12a...
- Upper bottom, 13... Lower bottom pod for firing, 13a... Lower bottom, 14... pod lid. Agent Yoshihiro Morimoto Figure 11 - Molded body t2---' Armpit floor size f2a - Single layer bottom ta---'tr

Claims (1)

[Claims] 1. We use a firing pod that has a double bottom structure with two upper and lower layers, and the space between the upper and lower bottoms communicates with the inside of the furnace.
A method for manufacturing a zinc oxide type varistor, which comprises placing a zinc oxide type varistor on the upper bottom of the firing pod and firing the zinc oxide type varistor.