JP2819731B2 - Zinc oxide varistor, method for producing the same, and crystallized glass composition for coating oxide ceramic - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a zinc oxide varistor mainly used in the field of electric power, a method for producing the same, and a crystallized glass composition for coating an oxide ceramic such as a thermistor and a varistor. .

Conventional technology Zinc oxide varistors containing ZnO as a main component and metal oxides of various types including Bi ₂ O ₃ , CoO, Sb ₂ O ₃ , Cr ₂ O ₃ , and MnO ₂ as sub-components have a large surge withstand capability. It is well known that it has been widely used in recent years as an element for a gapless arrester instead of a conventional silicon carbide varistor.

Conventionally, as a method for manufacturing a zinc oxide varistor, for example, Japanese Patent Application Laid-Open No. 62-101002 has been disclosed. The contents of the above-mentioned prior art are as follows. First, the main component Zn
O is mixed with a raw material powder in which metal oxides such as Bi ₂ O ₃ , Sb ₂ O ₃ , Cr ₂ O ₃ , CoO, and MnO ₂ are added in an amount of 0.01 to 6.0 mol%,
Granulate, press and form this granulated powder into a columnar shape,
Bake at 1200 ° C for 6 hours. Next, a glass paste made of a PbO-based glass frit containing 60% by weight of PbO, 80% by weight of a PbO-based glass frit, 20% by weight of feldspar, and an organic binder was applied to a side surface of the obtained sintered body by a screen printing machine. 5-500 mg / cm ²
After the application, a baking treatment is performed. The both end faces of the element thus obtained are polished in a plane, an aluminum metallikon electrode is formed, and a zinc oxide varistor is obtained.

However, since the zinc oxide varistor according to the conventional manufacturing method uses a screen printing method, the thickness of the side glass layer is uniformly formed, and the zinc oxide varistor has the advantage of having a small variation in discharge capability. Since it is a composite glass of a PbO-based glass frit and feldspar, it has a drawback that the discharge withstand capability is low, the voltage non-linearity is reduced during the glass baking treatment, and the charge life is deteriorated.

Accordingly, an object of the present invention is to provide a highly reliable zinc oxide varistor, a method for producing the same, and a crystallized glass composition for coating an oxide ceramic which can be generally used for an oxide ceramic.

Means for Solving the Problems In the present invention, in order to solve the above-mentioned conventional problems, at least NiO is 0.5 to 5.0 on the side surface of the sintered body containing ZnO as a main component.
It has a configuration in which a side surface high-resistance layer made of crystallized glass containing PbO as a main component is contained by weight%. PbO containing at least 0.5 to 5.0% by weight of NiO on the side surface of the sintered body
A glass paste composed of crystallized glass having a main component and an organic binder of 10.0 to 150.0 mg / cm ^{2 is} applied, and 450 ° C. to 60 ° C.
The baking treatment is performed in a temperature range of 0 ° C. to form a high resistance side surface layer.

Further, at least NiO of 0.5 to 5.
0 and provides a _{PbO-ZnO-B 2 O 3} -SiO 2 -NiO -based oxide crystallized glass composition for a ceramic coating comprising by weight%.

According to the action present invention, compared with PbO- feldspar-based composite glass, crystallized glass as a main component PbO is crystallized accelerated by the addition of NiO, the strength of the coating film is improved by the addition of SiO ₂ Also, because of its good adhesion to the sintered body, it has excellent discharge withstand characteristics, and because of its high insulation properties, it is possible to minimize the decrease in voltage non-linearity during the baking process. An excellent high reliability zinc oxide varistor can be obtained.

EXAMPLES Hereinafter, the zinc oxide varistor of the present invention, the method for producing the same, and the crystallized glass composition for coating will be described in detail based on examples.

First, 0.5 mol% of Bi ₂ O _3, 0.5 mol% of Co ₂ O _3, 0.5 mol% of MnO ₂ , Sb ₂ O ₃
Mol%, Cr ₂ O ₃ 0.5 mol%, NiO 0.5 mol%, SiO ₂ 0.
5 mol% was added, and the mixture was thoroughly mixed and pulverized with, for example, a ball mill together with pure water, a binder, and a dispersant, and then dried and granulated with a spray drier to obtain a raw material powder. This raw material powder is compression-formed to a size of 40mm in diameter and 30mm in thickness, and 500 ℃
Degreasing was performed under the above temperature conditions. Then 1100 ℃ ~ 12
It was fired in a temperature range of 50 ° C. to obtain a sintered body.

On the other hand, the crystallized glass for coating is PbO, ZnO, B ₂ O ₃ , SiO ₂ , Ni
After a predetermined amount of O was weighed and mixed and pulverized by, for example, a ball mill, it was melted in a platinum crucible at a temperature of 1000 ° C. to 1200 ° C., rapidly cooled, and vitrified. The glass was roughly pulverized and then finely pulverized with a ball mill to obtain a glass frit.
In addition, 70.0% by weight of PbO, ZnO 2
Glass frit 8 consisting of 5.0% by weight and 5.0% by weight of B ₂ O ₃
Feldspar 0.0% by weight (feldspars are KAlSi ₃ O ₈ , NaAlAi ₃ O ₈ , CaAl ₂ Si ₂
A composite glass composed of 20.0% by weight (solid solution of O ₈ ) was prepared in the same process.

The composition, glass transition point (Tg), and coefficient of linear expansion (α) of the glass frit prepared as described above are shown in Table 1 below.

As shown in Table 1, when the added amount of PbO is large, the linear expansion coefficient (α) becomes high, and when the added amount of ZnO is large, the glass transition point (Tg) becomes low and crystallization becomes easy. Also, B ₂ O ₃
When the addition amount is small, the glass transition point increases, and when the addition amount exceeds 15.0% by weight, crystallization becomes difficult.
Further, as the amount of added SiO ₂ increases, the glass transition point tends to increase, and the coefficient of linear expansion tends to decrease. Then, as the amount of NiO added increased, crystallization of the glass progressed. Further, in a system containing less PbO and B ₂ O ₃ , a porous glass was easily formed.

Next, 85% by weight of this glass frit and 15% by weight of an organic binder (a mixture of ethyl cellulose and butyl carbitol acetate) were sufficiently mixed, for example, by a three-roll mill to obtain a glass paste for coating. This coating gul paste is coated with a curved screen printing machine for 125
Printing was performed on the side surface of the sintered body using a screen of 250250 mesh. Here, the application amount of the glass paste for coating was determined from the difference in weight of the sintered body after the paste was applied and dried at 150 ° C. for 30 minutes. The coating amount was adjusted by adding an organic binder and n-butyl acetate to the glass paste for coating. Thereafter, the glass paste for coating was baked at a temperature of 350 ° C. to 700 ° C. to form a high-side resistance layer on the sintered body. Next, both end surfaces of the sintered body were polished to form an aluminum metallikon electrode to obtain a zinc oxide varistor.

FIG. 1 shows a sectional view of the zinc oxide varistor according to the present invention obtained as described above. In FIG. 1, 1 is a sintered body containing zinc oxide as a main component, 2 is an electrode formed on both end surfaces of the sintered body 1, and 3 is a crystallized glass on a side surface of the sintered body 1 by baking crystallized glass. It is a side surface high resistance layer obtained.

Next, Table 2 below shows the appearance, V _{1 mA} / V _{10 μA} , discharge withstand _voltage characteristics, and charging life characteristics of zinc oxide varistors prepared using the coating glass of Table 1. Here, the viscosity of the paste was controlled so that the coating amount of the coating glass paste was 50 mg / cm ² . The baking condition is 55
0 ° C., 1 hour. The number of samples was n = 5 for each lot. V _1mA and V _{10 μA} were measured using a DC constant current power supply. In addition, the discharge withstand characteristics show that a shock current of 4/10 μS is 5
It was applied twice in the same direction at minute intervals, and stepped up from 40 kA. And, the charging life characteristics are as follows: ambient temperature 130 ℃,
The test was performed under the conditions of a power application rate of 95% (AC, peak value).
The time to reach mA (peak value) was measured.

From Tables 1 and 2, when the coefficient of linear expansion of the coating glass is smaller than 65 × 10 ^-7 / ° C (G1, G5 glass), the glass is easily peeled and exceeds 90 × 10 ^-7 / ° C. In the case of (G4 glass), cracks are more likely to occur. It is considered that the sample in which these cracks and glass peeling have low discharge withstand characteristics because the insulating property of the side high-resistance layer is poor. Even if the linear expansion coefficient of the coating glass is in the range of 65 × 10 ⁻⁷ / ° C. to 90 × 10 ⁻⁷ / ° C., the glass with poor crystallinity (G8 glass) can be easily clutched, and the discharge withstand capacity can be improved. Characteristics are low. This is presumably because crystalline glass has a higher coating film strength than amorphous glass. In addition, the addition of ZnO depends on the electrical characteristics of the zinc oxide varistor,
It does not significantly affect the reliability and helps to lower the glass transition point even during the physics of glass. In addition, Pb
_{O-ZnO-B 2 O 3} , in the case of using the composite glass feldspar, voltage application life characteristic is it can be seen that a lower discharge withstand current rating characteristic is a practical level.

Next, the amount of NiO added will be considered. First, in the composition system in which the addition amount of NiO is 0.5% by weight or more, the voltage non-linearity is improved in any of the composition systems, and the charging life property is accordingly improved. This is considered to be because the addition of 0.5% by weight or more of NiO increases the insulation resistance of the coating film. On the other hand, when the addition amount of NiO is more than 5.0% by weight, discharge withstand characteristics are low. This is considered to be because the fluidity of the glass during the baking process is poor, and the glass tends to be porous. Therefore, in the PbO—ZnO—B ₂ O ₃ —SiO ₂ —NiO-based crystallized glass for the side surface high resistance layer of the zinc oxide varistor, it is a necessary condition that the composition system contains at least 0.5 to 5.0% by weight of NiO. .

From the above results, the composition of the crystallized glass for coating is PbO
55.0-75.0% by weight, ZnO 10.0-30.0% by weight, B ₂ O ₃
5.0 to 10.0 weight%, SiO ₂ is 0 to 15.0 wt.%, NiO is 0.5
It can be seen that the range of 5.0% by weight is optimal. Further, for the side surface high resistance layer of the zinc oxide varistor, the linear expansion coefficient needs to be in the range of 65 to 90 × 10 ⁻⁷ / ° C.

Next, the application amount of the glass paste was examined using the G16 glass of Table 1 which is an example of the present invention. The results are shown in Table 3 below. At this time, the application amount of the glass paste was 1.0
〜300.0 mg / cm ^2, which was controlled by the viscosity of the paste and the number of applications. In this case, if the coating amount is less than 10.0 mg / cm ^2, the strength of the coating film is low, also the coating amount is 150.0m
When the amount is more than g / cm ² , the glass tends to flow and pinholes are easily generated, so that the discharge capability is poor. Therefore, it is understood that the optimal amount of the glass paste applied is in the range of 10.0 to 15.0 mg / cm ² .

Next, using the G16 glass shown in Table 1 as an example of the present invention, the baking conditions of the glass paste were examined. The results are shown in Table 4 below. At this time, the viscosity was controlled so that the application amount of the glass paste was 50.0 mg / cm ² . Further, the baking treatment of the glass paste was performed in air at a temperature range of 350 to 700 ° C. with a holding time of 1 hour. As a result,
When the baking treatment is performed at a temperature lower than 450 ° C, the glass paste does not melt sufficiently, resulting in low discharge withstand characteristics. Getting worse. Therefore, it is understood that the optimal temperature range for the baking treatment of the glass paste is 450 to 600 ° C.

_{Incidentally, PbO-ZnO-B 2 O} 3 in the present embodiment -NiO, PbO-ZnO
-B ₂ O ₃ —SiO ₂ —NiO 4 and 5 component system crystallized glass has been described. As the sixth component, a trace additive that further promotes crystallization of the glass, for example, Al ₂ O ₃ , Even if SnO ₂ or the like is added, the effect of the present invention does not change. Further, as the substance for lowering the glass transition point, Zn
O was used, but of course it could be replaced with other substances. Further, in this embodiment, as a typical example of oxide ceramics, it was used _{PbO-ZnO-B 2 O 3} -SiO 2 -NiO -based coating for crystallized glass of the present invention zinc oxide varistor, strontium titanate The present invention can be applied to any oxide ceramic, such as a varistor of a system, a barium titanate-based capacitor or a positive temperature coefficient thermistor, and a metal oxide type negative temperature coefficient thermistor.

Effects of the Invention As described above, according to the present invention, P containing at least 0.5 to 5.0% by weight of NiO on the side surface of a sintered body containing zinc oxide as a main component
By baking at a temperature of the oxide crystallized glass ceramic coating of _{bO-ZnO-B 2 O 3} -SiO 2 -NiO system 450 to 600 ° C., discharge withstand current rating characteristic was excellent voltage application life characteristics A zinc oxide varistor can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zinc oxide varistor according to an embodiment to which the production method of the present invention and the crystallized glass for coating of the present invention are applied. 1 ... sintered body, 2 ... electrode, 3 ... side surface high resistance layer.

Claims (6)

(57) [Claims] 1. PbO containing zinc oxide as a main component and containing at least 0.5 to 5.0% by weight of nickel oxide as NiO on a side surface of a sintered body having a varistor characteristic. Oxide varistor having a high-side resistance layer made of crystallized glass. 2. The zinc oxide varistor according to claim 1, wherein the side surface high resistance layer is made of a PbO—ZnO—B ₂ O ₃ —NiO crystallized glass. 3. A side surface high resistance layer is _{PbO-ZnO-B 2 O 3} -SiO 2 -Ni
The zinc oxide varistor according to claim 1, which is made of an O-based crystallized glass. 4. PbO containing zinc oxide as a main component and containing at least 0.5 to 5.0% by weight of nickel oxide in NiO form on the side surface of the sintered body itself having varistor characteristics. A method for producing a zinc oxide varistor, in which a glass paste composed of crystallized glass and an organic substance is applied at 10.0 to 150.0 mg / cm ² and baked at a temperature in a range of 450 ° C. to 600 ° C. 5. The crystallized glass has a coefficient of linear expansion of 65 to 90 × 10 ^−7.
The method for producing a zinc oxide varistor according to claim 4, wherein the temperature is / C. 6. PbO from 55.0 to 75.0 wt%, ZnO 10.0 to 30.0 wt%, B ₂ O ₃ 5.0 to 15.0 wt%, SiO ₂ from 0 to 15.0 wt%, the oxide ceramic coating of NiO 0.5 to 5.0 wt% Crystallized glass composition.