JPH06140202A - Oxide resistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To avoid the release of a side insulation coating layer from a sintered body by prescribing a specific value to the mean surface roughness on the sintered body side containing at least titanium. CONSTITUTION:A mixture mainly comprising zinc oxide whereto titanium and nickel are respectively added is previously wet-mixed with one another and then dried up and granulated to be baked later. Next, when a Zn2TiO4 particle layer formed on a sintered body surface by the reaction during the baking step is removed by about 1-200mum using centerless processing step, the inside of the sintered body 1 in the mean surface roughness of 0.5 to 5mum is to be exposed. Next, the side of the sintered body 1 after removing this Zn2TiO4 particle layer is coated with a polyimide base insulating resin to be baked for the formation of a side insulation coating layer 2. Furthermore, the upper and lower ends of the sintered body 1 are polished to be flame-sprayed with aluminum for the formation of electrodes 3. Through these procedures, the bonding strength between the sintered body 1 and the side insulation coating layer 2 can be increased thereby enabling the title oxide resistor high in withstand voltage and hardly subjected to creeping discharge to be manufactured.

Description

Detailed Description of the Invention

[0001]

The present invention is mainly composed of zinc oxide,
The present invention relates to an oxide resistor suitable for absorbing switching surges such as circuit breakers.

[0002]

2. Description of the Related Art As an oxide resistor, a zinc oxide-based oxide resistor containing zinc oxide as a main component and titanium oxide or nickel oxide as a secondary component is known (Solid-State El.
ectronics Pergamon Press 6 , 111 (1963), US Patent No. 2
892988, U.S. Pat. No. 2933586). Such a zinc oxide based oxide resistor needs to have a dense sintered body in order to increase the amount of energy absorbed per unit volume. In order to obtain a dense sintered body, for example, titanium oxide is added as an auxiliary component. A zinc titanate (Zn ₂ TiO ₄ ) particle layer in which coarser particles are deposited than in the inside of the sintered body is formed on the surface of the sintered body to which titanium oxide is added. The zinc titanate particle layer has a higher resistance than the inside of the sintered body and acts as a side surface high resistance layer for preventing creeping discharge. However, when a side insulating coating layer is formed for the purpose of further effectively preventing creeping discharge and improving the withstand voltage, the coating layer forming substance is difficult to penetrate into the zinc titanate particle layer. There is a problem that the side insulating coating layer is easily peeled off from the sintered body.

[0003]

As described above, the conventional oxide resistor has a problem that the side surface insulating coating layer is easily separated from the side surface of the sintered body.

SUMMARY OF THE INVENTION An object of the present invention is to provide an oxide resistor having an improved adhesive strength between a sintered body and a side insulating coating layer, which is resistant to creeping discharge and excellent in withstand voltage, and a method for producing the same. .

[0005]

In order to achieve the above object, in the present invention, as a first invention, a side surface insulating coating layer is formed on a side surface of a sintered body containing zinc oxide as a main component and containing at least titanium. In the oxide resistor described above, the average surface roughness of the side surface of the sintered body is 0.5 to 5 μm. In a second aspect of the present invention, there is provided a method of manufacturing an oxide resistor in which a side surface insulating coating layer is formed on a side surface of a sintered body containing zinc oxide as a main component and containing at least titanium. A method for manufacturing an oxide resistor, comprising forming the side insulating coating layer after removing the zinc titanate particle layer.

[0006]

When the zinc titanate particle layer formed on the side surface of the sintered body is removed, the inside of the sintered body having an average surface roughness of 0.5 to 5 μm appears. Since the side surface of this new sintered body having an average surface roughness of 0.5 to 5 μm has a dense structure, it has excellent adhesive strength with the side surface insulating coating layer, and the side surface insulating coating layer from the sintered body has excellent adhesive strength. Peeling can be prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

With zinc oxide (ZnO) as a main component, titanium is 0.5 to 15 mol% as titanium oxide (TiO ₂ ) and nickel is 0.5 to 30 mol% as nickel oxide (NiO).
Add each and mix well thoroughly. After the obtained mixture is dried and granulated, it is formed into a ring of, for example, φ155 × φ51 × 35 mm and fired at 1200 ° C to 1500 ° C. ZnO is evaporated during this firing,

[0009]

## EQU1 ## The reaction of ZnO + TiO ₂ → Zn ₂ TiO ₄ causes zinc titanate (Zn ₂ Ti
O ₄ ) A particle layer is formed. This ZnTiO ₄ particle layer is constituted by layering Zn ₂ TiO ₄ particles having a diameter of 1 to 10 μm, and the layer thickness changes depending on the firing conditions. The Zn ₂ TiO ₄ particle layer is removed by, for example, centerless processing. Here, the Zn ₂ TiO ₄ particle layer is 200
If firing is performed under firing conditions such that the sintered body is formed with a thickness of μm or more, the variation in the electric resistance characteristics of the sintered body becomes large, and stable characteristics cannot be obtained.
_{2 When} the thickness of the TiO ₄ particle layer is 1 μm or less, Zn ₂
TiO ₄ particle layer sufficiently without further removing the side insulation co - thickness of Zn ₂ TiO ₄ particle layer to be removed since it is possible to obtain a bonding strength between the coating layer and the sintered body 1
Approximately 200 μm is desirable. Thus, as shown in FIG. 1, a polyimide-based insulating resin, for example, is applied as a side surface insulating coating for preventing a creeping discharge when a high voltage is applied to the side surface of the sintered body 1 from which the Zn ₂ TiO ₄ particle layer is removed. Then, the baked side insulating coating layer 2 is formed. Further, the upper and lower end surfaces of the sintered body 1 were polished, and aluminum was sprayed on the polished surface to form the electrode 3 to obtain an oxide resistor A.

[0010] In addition to the oxide resistor A of this example for comparison, without removing the Zn ₂ TiO ₄ particle layer 4, as shown in FIG. 2, the side surface insulation co on the Zn ₂ TiO ₄ particle layer 4 -The coating layer 2 was formed and the oxide resistor B was manufactured. Also Z
Side insulating coating layer 2 only with n ₂ TiO ₄ particle layer 4
Oxide resistor C and Zn as shown in FIG.
An oxide resistor D as shown in FIG. 4 in which the side surface of the sintered body 1 was exposed, in which the ₂ TiO ₄ particle layer 4 was removed and the side insulating coating layer 2 was not formed, was also manufactured. Impulse voltage of 8 × 20μs was applied from 5kV / cm for multiple lots of these 4 kinds of oxide resistors with different lateral states.
A test was conducted to find the average withstand voltage by examining the probability that creeping discharge did not occur when the voltage was increased by 0.5 kV / cm and applied. Next, the operation will be described.

Table 1 shows the average withstand voltage when an impulse voltage of 8 × 20 μs was applied to the oxide resistor A according to this example and the oxide resistors B, C, and D having different side states. A distribution diagram of the withstand voltage of A, B, C and D is shown in FIG. In FIG. 5, the horizontal axis represents the withstand voltage [kV / cm] and the vertical axis represents the distribution.

[Table 1]

As shown in Table 1, the average withstand voltage is highest in the oxide resistor A of this embodiment, and decreases in the order of the oxide resistors B, C and D. Since Zn ₂ TiO ₄ has a higher resistance than the inside of the sintered body, the withstand voltage of the oxide resistor C is higher than that of the oxide resistor D. The withstand voltage of the oxide resistor B in which the side surface insulating coating layer 2 is formed on the Zn ₂ TiO ₄ particle layer 4 is higher than that of the oxide resistor C, but there is not much difference. On the other hand, the withstand voltage of the oxide resistor A according to the embodiment in which the Zn ₂ TiO ₄ particle layer 4 is removed and then the side surface coating layer 2 is formed is much higher than the other resistors. Further, as shown in FIG. 5, the oxide resistor A has little variation in withstand voltage and is uniform in quality.

From the side surface of the sintered body 1, Zn ₂ TiO ₄
Removing the particle layer 4 to expose the side surface of the sintered body having a dense structure excellent in adhesive strength with the polyimide resin, and applying the polyimide resin to the side surface of the sintered body to form the side insulating coating layer 2. by.

In the above embodiment, zinc oxide, titanium oxide, and nickel oxide were added as raw materials for the sintered body. This is because nickel is solid-dissolved in zinc oxide and zinc titanate to increase the resistivity. However, it has been confirmed that the same effect can be obtained even if cobalt oxide or the like is used as long as it can form a solid solution with zinc oxide and zinc titanate.

Furthermore, in the above embodiments, oxides were used as starting materials for titanium and nickel, but any material may be used as long as it can be converted into an oxide by firing, and the same effect can be obtained even if it is a carbide or the like. Needless to say.

As described above, according to this embodiment, since the adhesive strength between the sintered body 1 and the side insulating coating layer 2 is increased, the side insulating coating layer 2 can be prevented from peeling off from the sintered body 1. It is possible to manufacture an oxide resistor having excellent voltage. Another embodiment of the present invention will be described below with reference to FIG.

0.5 to 15 mol% of titanium as titanium oxide (TiO ₂ ) and 0.5 to 30 mol% of nickel as nickel oxide (NiO) containing zinc oxide (ZnO) as a main component.
Add each and mix well thoroughly. After the obtained mixture is dried and granulated, it is formed into a ring of, for example, φ155 × φ51 × 35 mm and fired at 1200 ° C to 1500 ° C. Zn ₂ TiO during firing
_{Since 4} particles are formed on the surface of the sintered body,
The Zn ₂ TiO ₄ particle layer on the outer surface is removed by, for example, centerless processing to make the average surface roughness 0.5 to 5 μm,
A side insulating coating layer is formed. The upper and lower end surfaces of the sintered body on which the side-surface insulating coating layer was formed were polished, and aluminum was sprayed on the polished surface to form electrodes to obtain an oxide resistor.

For comparison, the Zn ₂ TiO ₄ particle layer was removed by, for example, centerless processing, and the average surface roughness was 0.1.
A sintered body having a thickness of .about.0.5 .mu.m and a sintered body having a thickness of 5 to 20 .mu.m were prepared, and a side insulating coating layer and electrodes were similarly formed to obtain an oxide resistor.

8 × 20 μs for a plurality of lots of the oxide resistors of this example and the oxide resistors for comparison
A test was performed to determine the average withstand voltage by examining the probability that creeping discharge did not occur when the impulse voltage was increased by 5 kV / cm from 0.5 kV / cm in increments of 0.5 kV / cm. Next, the operation will be described. FIG. 6 shows the relationship between the average surface roughness on the side surface of the sintered body and the average withstand voltage. Here, the horizontal axis is logarithmic and the average surface roughness [μ
m] indicates the average withstand voltage [kV / cm] on the vertical axis.

As can be seen from FIG. 6, the average surface roughness is 0.5.
A high withstand voltage is obtained at ˜5 μm. If the average surface roughness is 5 μm or more, pores may be formed between the sintered body and the insulating coating layer, or cracks may easily occur in the insulating coating layer, resulting in adhesion between the sintered body and the insulating coating layer. The strength is reduced and the withstand voltage is reduced. Average surface roughness 0.5μ
If it is m or less, the adhesive area between the sintered body and the insulating coating layer is reduced, so that the adhesive strength is lowered and the withstand voltage is lowered.

In this example, zinc oxide, titanium oxide, and nickel oxide were added as raw materials for the sintered body, but this is because nickel is solid-dissolved in zinc oxide and zinc titanate to increase the resistivity. It has been confirmed that the same effect can be obtained even if cobalt oxide or the like is used as long as it can form a solid solution with zinc oxide and zinc titanate.

Further, although an oxide was used as a starting material for titanium and nickel in this embodiment, any material may be used as long as it is an oxide by firing, and the same effect can be obtained even if it is a carbide or the like. Needless to say.

As described above, according to this embodiment, by limiting the average surface roughness of the side surface of the sintered body to 0.5 to 5 μm, the adhesive strength between the sintered body and the side surface insulating coating layer is increased, and the high withstand voltage is increased. It is possible to provide an excellent oxide resistor.

[0024]

As described above, according to the present invention, the oxide resistor containing zinc oxide as the main component is sintered by setting the average surface roughness of the side surface of the sintered body to 0.5 to 5 μm. The adhesive strength between the body and the side-surface insulating coating layer is enhanced, and it is possible to provide an oxide resistor having a high withstand voltage that is unlikely to cause creeping discharge when a high voltage is applied.

Further, by removing the zinc titanate particle layer formed on the side surface of the sintered body and then forming the side insulating coating layer, the adhesive strength between the sintered body and the side insulating coating layer is increased, It is possible to provide an oxide resistor in which creeping discharge is less likely to occur and which has an improved withstand voltage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an oxide resistor showing an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional oxide resistor.

FIG. 3 is a sectional view of a conventional oxide resistor.

FIG. 4 is a sectional view of a conventional oxide resistor.

FIG. 5 is a withstand voltage distribution diagram of the present invention and a conventional oxide resistor.

FIG. 6 is a diagram showing the relationship between the average surface roughness on the side surface of the sintered body and the average withstand voltage.

[Explanation of symbols]

1 ... Sintered body, 2 ... Side insulating coating layer, 3 ... Electrode,
4 ... Zinc titanate particle layer

Claims (2)

[Claims] 1. An oxide resistor in which a side surface insulating coating layer is formed on a side surface of a sintered body containing zinc oxide as a main component and containing at least titanium, wherein an average surface roughness of the side surface of the sintered body is 0.5. An oxide resistor having a thickness of 5 μm. 2. A method of manufacturing an oxide resistor, wherein a side surface insulating coating layer is formed on a side surface of a sintered body containing zinc oxide as a main component and containing at least titanium, wherein the side surface of the sintered body is formed. A method for producing an oxide resistor, comprising forming the side insulating coating layer after removing the zinc titanate particle layer.