JPH0897012A - Electrode material for zinc oxide varistor - Google Patents

Abstract

PURPOSE: To enhance the characteristics of limited voltage ratio by a method wherein the electrode material, which is obtained by adding the glass frit, formed by adding an Al-containing watersoluble inorganic metal compound or Al salt of high class fatty acid in the state as it is or as a liquid, to electrode paste, is printed and baked on a zinc oxide varistor. CONSTITUTION: An Al-containing inorganic metal compound or Al salt of high class fatty acid is dissolved into water, the dissolved material is added to the raw material containing B2 O3 and SiO2 , of 15.0wt.% for each of them and the remainder consisting of PbO. After the above-mentioned materials have been mixed and pulverized, the mixture is dissolved in a platinum crucible at 1000 to 1500 deg.C, and the mixture is virified by quenching. Then, the vitrified material is finely powdered, and lead borosilicate glass powder (glass frit) is obtained. The prescribed quantity (5.0wt.%) of the glass frit is mixed to the vehicle (30.0wt.%), in which ethyl cellusose is dissolved, together with Ag powder (65.0wt.%), and the electrode material for zinc oxide varistor is manufactured. This electrode material is coated on both surfaces of the zinc oxide lead varistor sintered body in such a manner that diameter of 10mm is obtained, and a baking operation is conducted at 800 deg.C for ten minutes.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrode material for a zinc oxide varistor.

[0002]

2. Description of the Related Art Conventionally, as an electrode material used in a zinc oxide varistor, for example, Japanese Patent Application Laid-Open No. 62-290104 has been disclosed, the contents of which are as follows. 50.0-85.0% by weight of PbO and 1 of B ₂ O ₃
0.0-30.0% by weight, SiO ₂ 5.0-25.0
Lead borosilicate glass powder consisting of weight% (glass frit)
Was weighed 5.0% by weight, and the vehicle in which ethylcellulose was dissolved in butyl carbitol (30.0% by weight)
%) With Ag powder (65.0% by weight) to prepare a silver paste, which is used as an electrode material for a zinc oxide varistor.

[0003]

However, when the above-mentioned conventional zinc oxide varistor electrode material made of lead borosilicate glass is used for a zinc oxide varistor, the limiting voltage ratio characteristic and the surge current withstanding characteristic are not satisfactory. In addition, there is a problem that there is a large variation in characteristics. The present invention
It is an object of the present invention to solve the above conventional problems and to provide an electrode material for a zinc oxide varistor, which is used in a zinc oxide varistor and exhibits excellent reliability.

[0004]

In order to solve the above problems, the electrode material for zinc oxide varistor according to the present invention contains a water-soluble inorganic metal compound containing aluminum or an aluminum salt of a higher fatty acid as it is or as a liquid. The lead borosilicate-based glass frit thus prepared is contained in a silver paste.

[0005]

In the electrode material for zinc oxide varistor having this structure, the compound of aluminum, which is softer than Al ₂ O ₃ , is
It is finely crushed and uniformly mixed in the material. Also, since it is mixed uniformly by adding it as an aqueous solution,
The manufactured electrode becomes homogeneous, and when it is used as an electrode of a zinc oxide varistor, it is possible to improve the limiting voltage ratio characteristic and the surge current withstanding characteristic, and to obtain a zinc oxide varistor with small variations in these characteristics. .

[0006]

【Example】

(Embodiment 1) Hereinafter, the first embodiment of the present invention will be described in detail.

First, the adjustment of the glass frit added to the electrode material for zinc oxide varistor will be described. According to the composition table of (Table 1) below, an inorganic metal compound containing aluminum such as aluminum nitrate and aluminum hydroxide, or an aluminum salt of a higher fatty acid such as aluminum stearate, aluminum oleate, and aluminum lactate is dissolved in water, B ₂ O ₃ and SiO ₂ are added to a raw material in which each is 15.0% by weight and the rest is PbO, and the mixture is mixed and pulverized in a ball mill and then heated in a platinum crucible at 1000 ° C.
It was melted under the temperature condition of 00 ° C. and rapidly cooled to be vitrified.
This glass was roughly crushed and then finely crushed with a ball mill to obtain a lead borosilicate glass powder (glass frit).

Further, as a lead borosilicate glass of the conventional example, Pb is used.
A lead borosilicate glass powder containing 70.0% by weight of O and 15.0% by weight of B ₂ O ₃ and SiO ₂ was prepared in the same manner. Further, as a comparative study example, Al ₂ O ₃ was used as a glass raw material.
A lead borosilicate glass frit added in the form of was also prepared by the same method. The glass transition point (Tg) of the glass produced as described above is shown in (Table 1) below. Here, the glass transition point (Tg) was measured using a thermal analyzer.

Next, a predetermined amount (5.0% by weight ratio) of this lead borosilicate glass powder was weighed, and a vehicle (30.0% by weight ratio) in which ethyl cellulose was dissolved in butyl carbitol.
%) And kneaded with Ag powder (65.0% by weight) to prepare an electrode material for zinc oxide varistor.

In order to evaluate the zinc oxide varistor electrode material produced as described above, bismuth oxide (Bi ₂ O ₃ ),
Cobalt oxide (Co ₂ O ₃ ), manganese oxide (Mn
O ₂ ), nickel oxide (NiO), titanium oxide (Ti
0.5 mol% of O ₂ ) and antimony oxide (Sb ₂
O ₃ ), chromium oxide (Cr ₂ O ₃ ) 0.1 mol%, Al ₂ O ₃ 0.005 mol%, and the balance zinc oxide (Z
Zinc oxide varistor sintered body (diameter 13 m)
m, thickness 1.5 mm) on both surfaces to have a diameter of 10 mm, baked at 800 ° C. for 10 minutes, soldered with lead wires, and then resin-molded to obtain a sample.

The limiting voltage ratio characteristic (V _50A / V _1mA ) and surge current withstanding characteristic of the sample thus obtained are shown in the following (Table 2). Here, V _1mA was measured using a DC constant current power source, and V _50A was measured by applying a current having a standard waveform of 8/20 μs and a peak value of 50A. In addition, the surge current withstand characteristic has a standard waveform of 8/20 μs and a peak value of 2500.
The impact current of A is applied twice in the same direction.

[0012]

[Outer 1]

The rate of change of was measured. The number of samples is 20 in each lot. The limiting voltage ratio characteristic (V _50A / V
_1mA ) is the better the closer the value is to 1.0, and

[0014]

[Outside 2]

The smaller the absolute value of the change amount, the better. And the smaller the variation value in parentheses in the table, the better.

[0016]

[Table 1]

[0017]

[Table 2]

First, from (Table 1) and (Table 2), a limiting voltage ratio characteristic and a surge current of a water-soluble inorganic metal compound containing aluminum and an aluminum salt of a higher fatty acid, which are added when a lead borosilicate glass is manufactured. Consider the effect on the withstand characteristics.

As shown in (Table 1) and (Table 2), a water-soluble inorganic metal compound containing aluminum such as aluminum nitrate or aluminum hydroxide as a glass raw material in the electrode material, or aluminum stearate or aluminum oleate. Aluminum salts of higher fatty acids such as aluminum lactate are converted into Al ₂ O ₃ and the total amount is 1.
In the composition system in which 0 × 10 ⁻⁴ wt% or more is added, the conventional sample No. Although the limiting voltage ratio characteristic is improved as compared with Example 1, a large amount of aluminum was added.
It can be seen that the surge current withstand characteristic deteriorates in the composition system exceeding 0% by weight. Since the water-soluble inorganic metal compound containing aluminum and the aluminum salt of higher fatty acid are softer than Al ₂ O _3, they are sufficiently crushed and uniformly dispersed in the glass raw material. When a glass frit produced using this raw material is used as an electrode material for a zinc oxide varistor, variations in characteristics such as limiting voltage ratio characteristics and surge current withstand characteristics are obtained compared with those added to the glass raw material in the form of Al ₂ O _3. Becomes smaller.

Further, when the water-soluble inorganic metal compound containing aluminum used in the above examples was added to the glass raw material in the form of an aqueous solution, the sample No. As shown in Nos. 15 to 16, the characteristic variation becomes smaller. Further, even if an aluminum salt of a higher fatty acid is dissolved in an organic solvent such as alcohol and added in a liquid form, No. It was confirmed that the same effect as 17 was obtained.

(Second Embodiment) The second embodiment of the present invention will be described in detail below.

First, a predetermined amount of a higher fatty acid aluminum salt such as aluminum stearate, aluminum oleate, or aluminum lactate is added to the conventional electrode material (silver paste) for zinc oxide varistor used in Example 1. When these were added, those with a small addition amount were dissolved in an organic solvent or the like and added as a liquid. Each composition is according to (Table 3).

The zinc oxide varistor electrode material obtained by the above method was applied to the zinc oxide varistor used in Example 1 above and evaluated in the same manner. The results are shown in (Table 4).

[0024]

[Table 3]

[0025]

[Table 4]

First, from (Table 3) and (Table 4), the influence of the water-soluble inorganic metal compound containing aluminum or the aluminum salt of higher fatty acid on the limiting voltage ratio characteristic and the surge current withstanding characteristic is examined. As shown in (Table 3) and (Table 4), a water-soluble inorganic metal compound containing aluminum and an aluminum salt of a higher fatty acid were converted into Al ₂ O ₃ form with respect to the above-mentioned conventional electrode materials. In the composition system in which the total amount is 5.0 × 10 ⁻⁵ wt% or more, the conventional sample No. Although the limiting voltage ratio characteristic is improved as compared with No. 1, in a composition system in which a large amount of aluminum is added and exceeds 5.0 × 10 ^-2 % by weight, Sample No. As can be seen from Nos. 2 and 3, the surge current withstand characteristic deteriorates.

Further, according to the method of this embodiment, the sample No. Characteristic variations such as the limiting voltage ratio characteristic and the surge current withstanding characteristic are smaller than those of Al ₂ O ₃ such as 2 to 4 added to the electrode material.

Since the silver paste is based on an organic solvent (butyl carbitol) in the above examples, a higher fatty acid salt was used, but when the silver paste is based on water, The present invention can be similarly carried out using the water-soluble inorganic compound salt as used in Example 1.

Further, from the above results, zinc oxide varis
Water-soluble inorganic metallization containing aluminum for electrode material
Compound, or the amount of higher fatty acid aluminum salt added,
Al ₂O₃5.0 × 10 in total when converted to^-Five~ 5.0
× 10^-2It can be seen that the composition of wt% is optimal.

Further, in Examples 1 and 2 above, the lead borosilicate glass content in the electrode material for zinc oxide varistor was 5.
Only the case of 0% by weight was described, but 1.0 to 30.
If it is 0% by weight, the effect of the present invention remains unchanged. Further, although lead borosilicate glass was used in Examples 1 and 2,
Co ₂ O ₃ in the glass _{composition, MgO, Y 2 O 3,} Sb 2 O 3,
It was confirmed that the effect of the present invention was not changed even when lead borosilicate glass containing an oxide such as MnO ₂ was used.

As a sintered body for evaluation, ZnO, Bi
₂ O ₃ , Co ₂ O ₃ , MnO ₂ , NiO, Sb ₂ O ₃ , Cr ₂ O
_{Although a} zinc oxide varistor of the system consisting of ₃ , ₃ Al ₂ O ₃ was used, Pr ₆ O ₁₁ , CaO, BaO, MgO, K ₂ O, Si
Even if the electrode material for a zinc oxide varistor according to the present invention is applied to a zinc oxide varistor containing O ₂ etc., the effect remains the same.
Furthermore, it was confirmed that the same effect can be obtained by using these oxides in combination.

[0032]

INDUSTRIAL APPLICABILITY As described above, an electrode material prepared by adding a glass frit prepared by adding a water-soluble inorganic metal compound containing aluminum or an aluminum salt of a higher fatty acid as it is or as a liquid to an electrode paste is used. By printing and baking on a zinc oxide varistor, it is possible to obtain a zinc oxide varistor which is excellent in limiting voltage ratio characteristics and surge current withstanding characteristics and has small characteristic variations.

Claims (6)

[Claims] 1. An electrode material for a zinc oxide varistor, wherein a water-soluble inorganic metal compound containing aluminum is added. 2. An electrode material for a zinc oxide varistor, which has a glass frit to which a water-soluble inorganic metal compound containing aluminum is added. 3. An electrode material for a zinc oxide varistor, which comprises a glass frit to which a water-soluble inorganic metal compound containing aluminum is added in the form of an aqueous solution. 4. An electrode material for a zinc oxide varistor, which is obtained by adding an aluminum salt of a higher fatty acid. 5. An electrode material for a zinc oxide varistor, which has a glass frit added with an aluminum salt of a higher fatty acid. 6. An electrode material for a zinc oxide varistor, comprising a glass frit obtained by dissolving an aluminum salt of a higher fatty acid in an organic solvent and adding it in a liquid form.