JPH10203865A - Production of ceramic resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a ceramic resistor having a uniform electrical properties and excellent tolerance in improved workability by suppressing the solidification of a slurry. SOLUTION: This process for the production of a ceramic resistor comprises the mixing of powdery materials composed mainly of zinc oxide and containing 3.0-40mol% of aluminum oxide (in terms of Al2 O3 ), 2.0-40mol% of magnesium oxide (in terms of MgO) and 0.1-1.0mol% of silicon oxide (in terms of SiO2 ), the granulation, molding and baking of the mixture and the application of an electrode on the product. Not more than 50mol% of the magnesium oxide powder is substituted with an acidic magnesium compound in the addition of the powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a ceramic resistor.

[0002]

2. Description of the Related Art Conventional resistors include a carbon-based resistor, a metal boride-based resistor, and a zinc oxide-based resistor.

A carbon-based material has a structure in which carbon powder is dispersed in a matrix made of Al ₂ O ₃ . This resistivity is several hundred Ωcm.

[0004] The metal boride system is a resistor which uses a sintered body composed of a metal boride and a non-reducing glass and has temperature characteristics, current-voltage characteristics, and withstand capability.

[0005] On the other hand, zinc oxide is mainly composed of ZnO,
Al ₂ O ₃ , MgO as essential components, SiO ₂ , Y
It is a sintered body containing a small amount of ₂ O ₃ , Sb ₂ O ₃ , NiO, CaO, SrO, BaO and the like. This resistivity is 10-1000Ω
cm, depending on the application equipment.
This resistor has excellent voltage linearity, temperature characteristics and resistance.

The mass production process of this resistor is performed by using ZnO, Al ₂
Raw material powder containing O ₃ and MgO as essential components is mixed by a disper mill, an organic binder is added, granulated by a spray dryer, molded by a mold, and the molded body is fired by an electric furnace. It is produced by attaching an electrode to the.

On the other hand, in the case of a zinc oxide type non-resistor, the pH, viscosity and water content of the slurry are adjusted so that the electrical characteristics of the resistor,
In particular, a patent with improved switching surge withstand capability
No. 109804 is disclosed.

[0008]

In the conventional method for manufacturing a zinc oxide-based resistor, the slurry is solidified during mixing and granulation of the raw materials because MgO is alkaline, impairing the workability and, furthermore, reducing the resistance of the resistor. There is a problem that causes the electrical characteristics to vary.

When the slurry solidifies, the stirring takes time and the nozzle holes are clogged, so that the slurry does not spray. In this case, the nozzle hole must be immediately dismantled and cleaned. If the washing is delayed, the slurry is more and more solidified and cannot be sent to the spray dryer. Therefore, the slurry is quickly reset after the treatment, and sprayed again according to the operation procedure from the beginning. Moreover, when this granulated powder is used, the component distribution of the sintered body becomes non-uniform, and the electrical characteristics such as the resistance value and the withstand amount of the resistor vary, resulting in defective products.

[0010] In view of the above, applying the technique of Japanese Patent Publication No. 7-109804 to lower the pH by adding acetic acid when mixing and granulating the slurry, the slurry solidification is improved with the zinc oxide type resistor. Was not done. This is due to the fact that the slurry temperature rises during the mixing to adjust the viscosity of the slurry and the acetic acid evaporates.

An object of the present invention is to provide a method of manufacturing a ceramic resistor having good workability.

Another object of the present invention is to provide a method for manufacturing a ceramic resistor having a large electric resistance without variation in electric characteristics.

[0013]

In order to achieve the above object, the present invention comprises zinc oxide as a main component, aluminum oxide of 3.0 to 40 mol% in terms of Al ₂ O ₃ , and magnesium oxide of MgO. 2.0 to 40 mol% in terms of, ceramic silicon oxide after mixing the powder as an essential component from 0.1 to 10 mol% in terms of SiO _2, granulation, molding, sintering and attached electrodes The present invention provides a method for producing a ceramic resistor, wherein a magnesium oxide powder added in the mixing step is replaced with an acidic magnesium compound in an amount of 50% or less in molar ratio. I do.

The present inventors have found that when an acidic magnesium compound such as magnesium acetate, magnesium oxalate or the like is used instead of the conventionally used MgO for the magnesium raw material powder, the solidification of the slurry during the mixing step is improved, and It has been found that the workability and the variation in the electrical characteristics of the resistor are improved. However, as described in the examples, it was found that the use of a totally acidic magnesium compound as the magnesium raw material powder deteriorated the resistance. When the amount of the acidic magnesium compound is large, the resistance is deteriorated because the resistance temperature coefficient of the resistor is converted to a negative value at 250 ° C. or higher. Then, when a partly acidic magnesium compound was added while leaving magnesium oxide, the withstand amount was improved.

Aluminum oxide reacts with zinc oxide,
3. To form sub-compound crystal grains and increase electric resistance.
0-40 mol% is added. Magnesium oxide increases the electrical resistance and converts the temperature coefficient of resistance to positive.
0-40 mol% is added. Silicon oxide is added in an amount of 0.1 to 10 mol% in order to enhance the sinterability of the molded body. Others
Yttrium oxide, antimony oxide, nickel oxide, calcium oxide,
Strontium oxide, barium oxide, etc. are added. It is desirable to add a small amount of calcium oxide, strontium oxide, and barium oxide in order to improve the resistance. Antimony oxide and nickel oxide improve electrical characteristics. The firing temperature is suitably between 1100 and 1300 ° C. This firing converts magnesium acetate and magnesium oxalate to magnesium oxide.

[0016]

Embodiments of the present invention will be described below.

Example 1 The composition of the raw material powder was Al ₂ O ₃ 11.
0 mol%, 5.5 mol% of MgO, and magnesium acetate (MgCH ₃ COO) ₂₀ which replaces this MgO.
6 types of 0, 3.0, 4.0, 5.5 mol%, SiO ₂ 2.
0 mol%, the remaining amount was ZnO. An organic binder and an antifoaming agent together with these raw material powders were sequentially charged into a disper mill and stirred to form a slurry. The solids concentration of the slurry is 65
%, Sample slurry pH 6.2-9.8, viscosity 25Pa.
s. After the completion of mixing, the slurry was immediately stored in a slurry tank and granulated by a spray dryer.

This granulated powder was molded in a mold having a diameter of 50 mmΦ and a thickness of 11 mm. The molded body was kept at a temperature between 350 and 550 ° C. for 1 hour to remove the binder. Next, this was placed in an electric furnace and calcined while maintaining the temperature at 1150 to 1270 ° C. for 4 hours. Finally, both surfaces of the sintered body were polished, and aluminum was sprayed to attach electrodes.

Table 1 shows the solidification of the slurry of the six types of resistors.
The yield and resistance of the resistors were compared.

[0020]

[Table 1]

The clogging of the nozzle hole is caused by the number of times when a slurry of 100 kg is granulated, the rejection rate of the electric resistance is a percentage of the resistance value outside the acceptable range, and the energizing time is 39Ω.
This is the time until thermal runaway occurs when 3.5 A alternating current is passed through the resistor. The amounts of magnesium oxide, magnesium acetate, and the pH of the slurry are also shown.

In Examples 1 and 2, the number of times of clogging of the nozzle holes is smaller than in Conventional Example 1, and the rejection rate of electric resistance is low. On the other hand, the number of times of clogging of the nozzle holes is larger than in Comparative Examples 1 to 3, and the rejection rate of the electrical resistance is higher, but the energization time is longer. It can be seen that the example is superior in productivity to the conventional example and has a higher tolerance than the comparative example.

Example 2 A resistor was produced in the same manner as in Example 1 except that magnesium oxalate (MgC ₂ O ₄ ) was used as the raw material powder of acidic magnesium. The solid content of the slurry is 62-65%, and the pH of the sample slurry is 6.5-9.5.
8. The viscosity was 23 to 25 Pa · s.

Table 2 compares the amount of magnesium oxide, the amount of magnesium oxalate, the pH of the slurry, the clogging of the nozzle hole, the rejection rate of the electrical resistance, and the energizing time of the six types of resistors.

[0025]

[Table 2]

In Examples 1 and 2, the number of times of clogging of the nozzle holes is smaller than in Conventional Example 2, and the rejection rate of the electric resistance is low. On the other hand, the number of times of clogging of the nozzle holes is larger than in Comparative Examples 4 to 6, and the rejection rate of the electrical resistance is higher, but the energization time is longer.

[0027]

According to the present invention, since the solidification of the slurry is small, the workability is good, and since the resistance of the resistor is large, the breakage during operation is small, and both the workability and the electrical characteristics are improved. Are better. In addition, since the component distribution of the sintered body is highly uniform, the electrical characteristics do not vary.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiichi Yamada 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shigeru Tanaka 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Ken Takahashi 7-1-1, Omika-cho, Hitachi City, Ibaraki Pref. Hitachi, Ltd. Hitachi Research Laboratory

Claims (1)

[Claims] 1. Zinc oxide as a main component, aluminum oxide is 3.0 to 40 mol% in terms of Al ₂ O ₃ , magnesium oxide is 2.0 to 40 mol% in terms of MgO, and silicon oxide is After mixing powder having an essential component of 0.1 to 10 mol% in terms of SiO ₂ , in a method of producing a ceramic resistor for granulation, molding, firing, and electrode attachment, the molar ratio of the magnesium oxide powder is adjusted. A method for producing a ceramic resistor, comprising adding an amount of 50% or less by substituting with an acidic magnesium compound in (1).