JPH05275211A - Zinc oxide varistor and its manufacture and coating crystallized glass composite - Google Patents

Abstract

PURPOSE:To improve discharge withstand current rating characteristics and charge lifetime characteristics by forming a side face high resistance layer made of a specific crystallized glass on the side face of a sinter consisting mainly of ZnO. CONSTITUTION:The side face of a sinter 1 consisting mainly of ZnO has a side face high resistance layer 3 made of crystallized glass consisting mainly of PbO containing 0.1-5.0wt% of V2O2. The high resistance layer 3 is of PbO- ZnO-B2O3-V2O5 crystallized glass or PbO-ZnO-B2O3-SiO2-V2O5 crystallized glass: a glass paste consisting of this crystallized glass and an organic binder is applied 10.0-100.0mg/cm<2> and baked in a temperature range of 450-600 deg.C to form a side face high resistance layer 3. This process can provide excellent discharge withstand current rating characteristics and charge lifetime characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc oxide varistor mainly used in the electric power field, a method for producing the same, and a crystallized glass composition used for coating an oxide ceramic such as a thermistor or a varistor.

[0002]

2. Description of the Related Art ZnO as a main component and Bi ₂ O ₃ , Co
Zinc oxide varistor, which contains metal oxides such as O, Sb ₂ O ₃ , Cr ₂ O ₃ , and MnO ₂ as a secondary component, has a large surge withstand capability and excellent voltage non-linearity. It is well known that the conventional silicon carbide varistor has been widely used as an element for the device.

Conventionally, as a method for producing 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, ZnO as a main component is mixed with Bi ₂ O ₃ and Sb.
_{2 O 3, Cr 2 O 3} , CoO, a raw material powder of metal oxides such as MnO ₂ were added respectively 0.01 to 6.0 mol% mixture, granulating, pressing the granulated powder into a cylindrical shape Formed, and fired in an electric furnace at 1200 ° C. for 6 hours.

Next, a glass paste containing 80% by weight of a PbO-based glass frit containing 60% by weight of PbO, 20% by weight of feldspar and an organic binder was screened on the side surface of the obtained sintered body. 5 to 500 mg / in printing machine
After applying cm _2, apply baking treatment. Both end faces of the element thus obtained are flat-polished to form aluminum metallikon electrodes to obtain a zinc oxide varistor.

[0006]

However, since the zinc oxide varistor according to the above-mentioned conventional manufacturing method uses the screen printing method, the side glass layer is formed to have a uniform thickness, and the variations in discharge withstand voltage characteristics are small. However, since it is a composite glass of PbO-based glass frit and feldspar, it has the drawbacks of low discharge withstand characteristics, reduced voltage nonlinearity during glass baking treatment, and deteriorated voltage life characteristics.

The present invention solves the above-mentioned conventional problems by providing a highly reliable zinc oxide varistor and a method for manufacturing the same.
Furthermore, it is an object of the present invention to provide a crystallized glass composition for coating which is generally used for oxide ceramics.

[0008]

In order to solve the above-mentioned conventional problems, the present invention includes at least 0.1 to 5.0% by weight of V ₂ O ₅ on the side surface of a sintered body containing ZnO as a main component. Pb
The structure has a side surface high resistance layer made of crystallized glass containing O as a main component. Further, a glass pace composed of a crystallized glass containing PbO as a main component containing at least 0.1 to 5.0% by weight of V ₂ O ₅ and an organic binder is 10.0 to 100.0 mg / on the side surface of the sintered body. cm ² applied, 4
The side surface high resistance layer is formed by baking in a temperature range of 50 to 600 ° C.

Furthermore, at least V for the lateral high-resistance layer is used.
Including ₂ O ₅ 0.1 to 5.0 wt% PbO-ZnO-B ₂
Provided is a crystallized glass composition for coating an O ₃ —SiO ₂ —V ₂ O ₅ -based oxide ceramic.

[0010]

According to the present invention, compared to the PbO-feldspar composite glass, the crystallized glass containing PbO as the main component is
Crystallization is promoted by the addition of V ₂ O ₅ , the strength of the coating film is improved by the addition of SiO ₂ , and the adhesiveness with the sintered body is also good, so the discharge withstand characteristic is excellent, and the insulating property is also high. In addition, it is possible to minimize the decrease in voltage nonlinearity during the baking process, and it is possible to obtain a highly reliable zinc oxide varistor that is excellent in the electric charge life characteristic.

[0011]

EXAMPLES 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 with reference to Examples.

First, for the total amount of ZnO powder, Bi
₂ O ₃ 0.5 mol%, CO ₂ O ₃ 0.5 mol%, MnO
₂ 0.5 mol%, Sb ₂ O ₃ 1.0 mol%, Cr ₂ O ₃
0.5 mol%, NiO 0.5 mol%, SiO ₂
0.5 mol% was added, thoroughly mixed with pure water, a binder, and a dispersant by, for example, a ball mill, pulverized, dried with a spray dryer and granulated to obtain a raw material powder. This raw material powder was compression molded into a size of 40 mm in diameter and 30 mm in thickness, and degreased at a temperature of 500 ° C. or higher. Then, it baked in the temperature range of 1100-1250 degreeC, and obtained the sintered compact.

On the other hand, the crystallized glass for coating is made of PbO, Z
A predetermined amount of nO, B ₂ O ₃ , SiO ₂ , and V ₂ O ₅ is weighed, mixed and crushed by, for example, a ball mill, and then mixed with platinum crucible 1
It was melted under a temperature condition of 000 to 1200 ° C. and rapidly cooled to be vitrified. This glass was roughly crushed and then finely crushed with a ball mill to obtain a glass frit. As a sample for comparison, PbO 70.0 wt%, ZnO 25.0
80.0% by weight of glass frit composed of 5.0% by weight of B ₂ O ₃ and feldspar (feldspar is KAlSi ₃ O ₈ , NaA
A composite glass composed of 10.0% by weight of 1Si ₃ O ₈ and CaAl ₂ Si ₂ O _{8 as} a solid solution was prepared in the same process.

Of the glass frit produced as described above,
The composition, glass transition point (Tg), linear expansion coefficient (α) and crystallinity are shown in the following (Table 1).

In Table 1, the glass transition point Tg
The linear expansion coefficient α was measured using a thermal analyzer. For crystallinity, observe the surface condition of glass with a metallographic microscope or electron microscope.
The mark indicates that no crystal was observed, and the mark indicates x.

[0016]

[Table 1]

When the amount of PbO added is larger than that shown in Table 1,
When the coefficient of linear expansion (α) becomes high and the amount of ZnO added is large, the glass transition point (Tg) becomes low and crystallization becomes easy. Further, when the added amount of B ₂ O ₃ is large, the glass transition point becomes high, and when the added amount exceeds 15.0% by weight, crystallization becomes difficult. Furthermore, the glass transition point tends to increase and the linear expansion coefficient tends to decrease as the amount of SiO ₂ added increases. Then, as the amount of V ₂ O ₅ added increased, the glass transition point decreased and crystallization of the glass proceeded. Further, in a system containing a small amount of PbO and B ₂ O _3, it was easy to form a porous glass.

Next, with 85% by weight of this glass frit,
15% by weight of an organic binder (a mixture of ethyl cellulose and butyl carbitol acetate) was sufficiently mixed with, for example, a three-roll mill to obtain a glass paste for coating. This coating glass paste was printed on the side surface of the sintered body using a screen of 125 to 250 mesh with a curved screen printer, for example.

Here, the coating amount of the coating glass paste was obtained from the difference in weight of the sintered bodies after the paste was coated and dried at 150 ° C. for 30 minutes. The coating amount was adjusted by adding an organic binder and n-butyl acetate to the coating glass paste. Then, the glass paste for coating was baked under a temperature condition of 350 to 700 ° C. to form a side surface high resistance layer on the sintered body.

Next, both end faces of this sintered body were flat-polished,
An aluminum metallikon electrode was formed 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, and 2 is a sintered body 1.
Electrodes 3 formed on both end surfaces of the sintered body 1 are side surface high resistance layers obtained by baking crystallized glass on the side surfaces of the sintered body 1.

Next, the following (Table 2) shows the appearance of the zinc fluoride varistor prepared by using the above-mentioned glass for coating (Table 1),

[0023]

[Outer 1]

The discharge withstanding characteristic and the charging life characteristic are shown.
Here, the coating amount of the glass paste for coating is 50 mg / cm.
The viscosity of the paste was controlled to be ² . The baking treatment condition is 550 ° C. for 1 hour. here,
The number of samples is n = 5 for each lot.

[0025]

[0026]

[Outside 2]

Was measured using a DC constant current power supply. As for the discharge withstand voltage characteristic, an impact current of 4/10 μS is applied twice in the same direction at intervals of 5 minutes, and the step is increased from 40 kA to visually check whether there is an abnormality in the appearance, and if necessary, use a metallurgical microscope. It was investigated using.

Here, in the table, ∘ indicates that no abnormalities were observed in the sample after the predetermined current was applied twice, Δ indicates 1 to 2 pieces, and x indicates 3 to 5 pieces. Indicates that an abnormality was found in the. Further, the life characteristics of charging were performed under conditions of an ambient temperature of 130 ° C. and a charging rate of 95% (AC, peak value), and the time until the leakage current reached 5 mA (peak value) was measured. Also,

[0029]

[Outside 3]

The applied voltage life is shown as an average value of 5 pieces. Number of samples above,

[0031]

[Outside 4]

Unless otherwise specified, the discharge withstand voltage test method and the voltage application life characteristic evaluation method are the same for the following examples.

[0033]

[Table 2]

From (Table 1) and (Table 2), when the linear expansion coefficient of the coating glass is less than 65 × 10 ⁻⁷ / ° C. (G
(1, G5 glass), the glass is easy to peel off, 90 × 1
It can be seen that when it exceeds 0 ⁻⁷ / ° C. (G4 glass), cracks are likely to occur. It is considered that the samples in which cracks and glass peeling occurred have low discharge withstand characteristics because the side surface high resistance layer has poor insulation.

The linear expansion coefficient of the coating glass is 65 to
Even in the range of 90 × 10 ⁻⁷ / ° C., glass having poor crystallinity (G8 glass) is likely to be cracked and has low discharge withstand characteristic. This is considered to be because the strength of the coating film of crystalline glass is higher than that of amorphous glass.

Further, the addition of ZnO has no great influence on the electrical characteristics and reliability of the zinc oxide varistor, and is useful for lowering the glass transition point among the physical properties of glass. Further, the prior art example in which _{PbO-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 V ₂ O ₅ added will be considered.
First, in the composition system in which the added amount of V ₂ O ₅ is 0.1% by weight or more, the voltage non-linearity is improved in any composition system, and accordingly, the life span characteristic is also improved. this is,
By adding V ₂ O _{5 in an amount} of 0.1% by weight or more, V ₂ O ₅ is slightly diffused on the side surface of the sintered body during the glass baking treatment, and ZnO
It is considered that this is because the resistance of the particles increases.

On the other hand, when the added amount of V ₂ O ₅ is more than 5.0% by weight, the discharge withstand characteristic is low. It is considered that this is because the flowability of the glass during the baking process is poor and the glass tends to become porous. Accordingly, PbO-ZnO-B ₂ for side high-resistance layer of a zinc oxide varistor O ₃ -SiO ₂ -V ₂ O ₅
In the crystallized glass, at least V ₂ O ₅ is 0.1 to
It is a necessary condition that the composition system contains 5.0% by weight.

From the above results, the composition of the crystallized glass for coating is 55.0 to 75.0% by weight of PbO and 1% of ZnO.
0.0-30.0 wt%, B ₂ O ₃ 5.0-10.0 wt%, SiO ₂ 0-15.0 wt%, V ₂ O ₅ 0.1
It can be seen that the range of up to 5.0% by weight is optimal. Further, for the side surface high resistance layer of the zinc oxide varistor, it is necessary that the coefficient of linear expansion be within the range of 65 to 90 × 10 ^-7 / ° C.

Next, the coating amount of the glass paste was examined using the G16 glass of the present invention (Table 1). The results are shown in (Table 3) below. At this time, the coating amount of the glass paste was 1.0 to 300.0 mg / cm ² , and was controlled by the viscosity of the paste and the number of coatings. At this time, when the coating amount is less than 10.0 mg / cm ² , the strength of the coating film is low, and when the coating amount is more than 100.0 mg / cm ^2, glass flows or pinholes occur. Is likely to occur, resulting in poor discharge withstand characteristics. Therefore, it is understood that the optimum application amount of the glass paste is in the range of 10.0 to 100.0 mg / cm ² .

[0041]

[Table 3]

Next, the conditions for baking the glass paste were examined using the G16 glass of the present invention (Table 1). The results are shown in (Table 4) below. At this time, the viscosity was controlled so that the coating amount of the glass paste was 50.0 mg / cm ² . Further, the baking treatment of the glass paste was performed in the air in the temperature range of 350 to 700 ° C. for a holding time of 1 hour.

As a result, when the baking treatment is carried out at a temperature lower than 450 ° C., the glass paste is not sufficiently melted so that the discharge withstand characteristic is low, and when the baking treatment is carried out at a temperature higher than 600 ° C., the voltage ratio is remarkably lowered. , The charging life characteristic deteriorates. Therefore, the baking treatment condition of the glass paste is 450-
It can be seen that the temperature range of 600 ° C. is optimum.

[0044]

[Table 4]

In this embodiment, PbO-ZnO-B is used.₂
O₃-V₂O_Five, PbO-ZnO-B₂O₃-SiO₂-V₂
O_FiveCrystallized Glass for Coating of 4 and 5 Component Systems
As mentioned above, as the sixth component, it promotes further crystallization of glass.
Advancing trace additives such as Al ₂O₃, SnO₂Etc.
Even if added, the effect of the present invention does not change.

Further, ZnO was used as the substance for lowering the glass transition point in the above embodiment, but it is needless to say that it can be replaced with other substances.

Further, in this embodiment, as a typical example of oxide ceramics, zinc oxide varistor is used in the PbO-type of the present invention.
ZnO—B ₂ O ₃ —SiO ₂ —V ₂ O ₅ based crystallized glass for coating was used, but strontium titanate varistor, barium titanate based capacitors and positive temperature coefficient thermistors, and metal oxide negative electrodes were used. It can be applied to any oxide ceramic such as a characteristic thermistor.

[0048]

As described above, according to the present invention, at least V ₂ O ₅ is added to the side surface of the sintered body containing zinc oxide as a main component.
_{PbO-ZnO-B 2 O 3} -SiO containing 1 to 5.0 wt%
By baking at a temperature of ₂ -V ₂ O ₅ based oxide crystallized glass ceramic coating of the 450 to 600 ° C., discharge withstand current rating characteristics, is possible to obtain an excellent ZnO varistor voltage application life characteristics it can.

[Brief description of drawings]

FIG. 1 is a sectional view of a zinc oxide varistor according to an embodiment to which the manufacturing method of the present invention and the coated crystallized glass of the present invention are applied.

[Explanation of symbols]

 1 Sintered body 2 Electrode 3 Side high resistance layer

Claims (6)

[Claims] 1. At least 0.1% by weight of vanadium oxide in the form of V ₂ O _{5 on} the side surface of a sintered body containing zinc oxide as a main component and having varistor characteristics by itself. A zinc oxide varistor having a lateral high-resistance layer made of crystallized glass containing PbO as a main component. 2. A side high-resistance layer is _{PbO-ZnO-B 2 O 3} -
The zinc oxide varistor according to claim 1, which is made of V ₂ O ₅ type crystallized glass. 3. The lateral high-resistance layer comprises PbO—ZnO—B ₂ O ₃ —
Zinc oxide varistor according to claim 1, wherein comprising a SiO ₂ -V ₂ O ₅ based crystallized glass. 4. 0.1 to 5.0% by weight of at least vanadium oxide in the form of V ₂ O _{5 on} the side surface of the sintered body having zinc oxide as a main component and the sintered body itself having varistor characteristics. A glass paste composed of crystallized glass containing PbO as a main component and an organic substance is applied in an amount of 10.0 to 100.0 mg / cm ² ,
A method for producing a zinc oxide varistor, which comprises performing a baking process in a temperature range of 450 to 600 ° C. 5. The method for producing a zinc oxide varistor according to claim 4, wherein crystallized glass having a coefficient of linear expansion of 65 to 90 × 10 ⁻⁷ / ° C. is used. 6. PbO 55.0 to 75.0% by weight, Zn
O 10.0-30.0% by weight, B ₂ O ₃ 5.0-1
5.0% by weight, SiO _{2 0 to} 15.0% by weight, V ₂ O ₅
A crystallized glass composition for coating comprising 0.1 to 5.0% by weight.