JP3419285B2 - Manufacturing method of ceramic electronic components - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a ceramic electronic component such as a varistor element for the purpose of protecting an electric circuit from overvoltage.

[0002]

2. Description of the Related Art Conventionally, a varistor element has been disclosed in Japanese Patent Laid-Open No. 8-93.
As disclosed in Japanese Patent No. 973, ZnO is a main component,
A mixture obtained by mixing a ceramic raw material composed of auxiliary components such as Bi ₂ O ₃ and an organic binder is molded, and the molded body is embedded in a reaction inert powder such as aluminum oxide and placed in an electric furnace and fired. It was manufactured by

[0003]

According to this method, B
Although i ₂ O ₃ is prevented from being suddenly scattered during firing, a ceramic sintered body having a small number of pores can be obtained, but the scattering of Bi ₂ O ₃ is controlled only by filling the powder with a reaction inactive substance. Therefore, the electrical characteristics of the varistor element often vary due to the difference in the filling rate.

Therefore, an object of the present invention is to provide a ceramic electronic component having a small number of holes and a small variation in electric characteristics.

[0005]

To SUMMARY OF THE INVENTION To achieve this object, the present invention, the surface of the ceramic molded body containing a substance having a potential to be scattered during firing, said scattering material
Is heat-treated by bringing it into contact with a mixture of a powder reactive with respect to the powder and a powder inert with respect to the scattered substance , and the mixture is heated against the powder inert to the reaction.
The ratio of reactive powder is 0.5 to 20 wt%
In order to move to substances that have the potential to scatter during the heat treatment According to this method of reaction with the reactive powder, substantially constant amount toward the reactive powder of a ceramic molded body, a ceramic fired body It is possible to control the amount of the remaining substances that may scatter, and as a result, it is possible to provide a ceramic electronic component with little variation in electrical characteristics.

[0006]

The invention according to claim 1 of the embodiment of the present invention is anti-surface of the ceramic molded body containing a substance having a potential to be scattered during firing, with respect to the scattering substance <br / > response to応活with powder and the scattering substance in contact with an inert mixture of powders is intended to heat treatment, the
The mixture contains the reaction-active powder to the reaction-inactive powder.
The ratio of the powder is 0.5 to 20 wt%. According to this method, the amount of the substance that may remain in the ceramic sintered body and may be scattered can be controlled, so that a ceramic electronic component with less variation in electrical characteristics can be provided. can do.

[0007]

According to the second aspect of the present invention, SiO ₂ is used as the reactive powder. According to this method, it is possible to control the amount of the substance that remains in the ceramic sintered body and may be scattered. It is possible to provide a ceramic electronic component with less variation in electrical characteristics.

According to the third aspect of the invention, at least one of aluminum oxide, magnesium oxide, zinc oxide and zirconium oxide is used as the reaction-inert powder.
That is intended, according to this method, can be controlled in the amount of substances that have the potential to scatter remains in the ceramic sintered body, it is possible to provide an electric characteristic variation less ceramic electronic component.

According to a fourth aspect of the present invention, the ceramic compact is immersed in a powder mixture and heat-treated.
According to this method, the amount of the substance that may remain in the ceramic sintered body and may be scattered can be controlled, so that it is possible to provide a ceramic electronic component with less variation in electrical characteristics.

According to a fifth aspect of the present invention, the mixture of the ceramic compact and the powder is contained in a container, and then the container is heat-treated while rotating the container. Since the amount of the remaining substance having a possibility of scattering can be controlled, it is possible to provide a ceramic electronic component with less variation in electrical characteristics.

(Embodiment 1) First, 0 to 20 wt% of reactive SiO ₂ powder is added to a ceramic compact and aluminum oxide powder which is inert to reaction, and they are sufficiently mixed,
A powder mixture is obtained.

FIG. 1 is a cross-sectional view showing a state in which a ceramic compact is embedded in this powder mixture. The surface of the ceramic compact 1 is covered with the powder mixture 2 on the aluminum oxide plate 3. FIG. 2 shows a cross-sectional view of a general disk type zinc oxide varistor element.
And the silver electrodes 6 provided on both upper and lower surfaces of the sintered body 5.

First, an organic binder is added to and mixed with a ceramic material containing at least zinc oxide and bismuth oxide, and then 1 t / thickness so that the diameter is 10 mm and the thickness is 1.2 mm.
A disc-shaped ceramic molded body 1 was obtained by applying a pressure of cm ² . The ceramic molded body 1 thus obtained is heated to 500 ° C.
After debindering with, the powder mixture 2 was placed on an aluminum oxide plate 3 having a length of 150 mm, a width of 150 mm and a thickness of 2 mm as shown in FIG. 1, and 50 cc of the powder mixture 2 was placed thereon. Further, by placing 50 cc of the powder mixture 2, the ceramic molded body 1 was completely embedded in the powder mixture 2 and fired at 930 ° C. to obtain a sintered body 5. It should be noted that the ceramic molded bodies 1 were prevented from directly contacting each other during firing.

The purpose of covering the surface of the ceramic molded body 1 with the powder mixture 2 is to contain Bi ₂ O ₃ contained in the ceramic molded body 1.
At a temperature equal to or higher than its melting point (825 ° C.), a vapor pressure is suddenly increased to block evaporation, and Bi ₂ O ₃ in the ceramic molded body 1 reacts with SiO ₂ ,
Distribution of Bi ₂ O ₃ in the sintered body 5 that moves uniformly in each direction,
Further, it is to reduce the variation of Bi ₂ O ₃ of each sintered body 5.

Then, a silver paste having a diameter of 7 mm was applied to the obtained sintered body 5 as shown in FIG. 2 and then baked at 800 ° C. to form a silver electrode 6 to obtain a zinc oxide varistor element.

Table 1 shows SiO ₂ for Al ₂ O ₃ powder.
And the weight loss of the sintered body 5 with respect to the ceramic compact 1 (proportional to the amount of Bi ₂ O ₃ scattered) and the varistor voltage V _1mA (voltage at a current of 1 mA) (standard deviation / average value) Shows the relationship.

[0018]

[Table 1]

(Embodiment 2) Zinc oxide powder that is inactive with the ceramic compact 1 is reacted with SiO that is reactive.
Add 0 to 20 wt% of ₂ powders and mix well to obtain a powder mixture.

FIG. 3 is a cross-sectional view in which the powder mixture 2 and the ceramic molded body 1 are put into a cylindrical sheath 11. FIG. 4 is a perspective view of this cylindrical sheath 11.

First, the ceramic molded body 1 produced by the same method as in (Embodiment 1) is debindered at 500 ° C., and then provided on a cylindrical sheath 11 having a diameter of 7 cm and a length of 10 cm as shown in FIG. Input from the input port 12 with a diameter of 2 cm,
Further, 100 cc of the powder mixture 2 is charged to obtain the state shown in FIG. Next, the cylindrical sheath 11 is fired at 930 ° C. while rotating at 0.5 r / min, and then the powder mixture 2 and the sintered body 5 are taken out from the cylindrical sheath 11, separated by a sieve, and the sintered body 5 is removed. Got

Here, the purpose of rotating the cylindrical sheath 11 at the time of firing is to make the contact opportunities between the ceramic compact 1 and the powder mixture 2 uniform, and to diffuse oxygen sufficiently during firing to improve electrical characteristics and life characteristics. To obtain an excellent sintered body 5.

The sintered body 5 thus obtained has an extremely small Bi concentration distribution both inside the sintered body 5 and between the sintered bodies 5, and has a small variation in characteristics.

Table 2 shows the amount of SiO ₂ added to the ZnO powder, the weight loss of the sintered body 5 with respect to the ceramic compact 1 (proportional to the amount of Bi ₂ O ₃ scattered), and V _1mA (at a current of 1 _mA ). The relation of the variation (standard deviation / average value) of voltage is shown.

[0025]

[Table 2]

In the first embodiment, aluminum oxide powder was used as the reaction-inert powder, but zirconium oxide and zinc oxide, which are stable with the ceramic compact 1 at the firing temperature, and powders obtained by mixing them are not used. Any active powder will do.

The same applies to the aluminum oxide plate 3 and the cylindrical sheath 11, and any material may be used as long as it is a stable substance with the powder mixture 2 and the compact 1 at the firing temperature.

The shape of the sintered body 5 is not limited to the disk type, and the same effect can be obtained with a molded body of any shape such as a laminated body in which internal electrodes and ceramic layers are alternately laminated.

Further, the mixing ratio of the reactive powder is preferably as large as possible within the range where the basic characteristics of the sintered body 5 (for example, non-linearity in the varistor) are not deteriorated. The ratio is 0.5w
t% to 10 wt% is suitable.

Further, although the varistor has been described as an example in the present embodiment, the same effect can be obtained in other ceramic electronic parts such as capacitors and thermistors.

[0031]

As described above, according to the present invention, it is possible to control the amount of a substance that has a possibility of scattering in the ceramic sintered body, and as a result, it is possible to provide a ceramic electronic component with less characteristic variation. Become.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a firing process of a ceramic molded body according to an embodiment of the present invention.

FIG. 2 is a sectional view of a zinc oxide varistor element according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining a firing process according to an embodiment of the present invention.

FIG. 4 is a perspective view of a sheath according to an embodiment of the present invention.

[Explanation of symbols]

1 Ceramic molded body 2 powder mixture 3 Aluminum oxide plate 5 Sintered body 6 silver electrode 11 Cylindrical pod 12 slot

Continuation of the front page (56) Reference JP-A-8-31616 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01C ^7/ 02-7/22

Claims (5)

(57) [Claims] 1. A surface of the ceramic molded body containing a substance having a potential to be scattered during firing, said scattering material
Intended to heat treatment in contact with a mixture of anti <br/>応不active powder against reactive powder and the scattering substance against
And said mixture is based on said reactive inert powder
A method for manufacturing a ceramic electronic component, wherein the proportion of reactive powder is 0.5 to 20 wt% . As wherein reactive powder, a manufacturing method of a ceramic electronic component according to claim 1 using SiO _2. As 3. A reaction inert powder, aluminum oxide, magnesium oxide, zinc oxide, among zirconium oxide, a manufacturing method of a ceramic electronic component according to claim 1 using at least one type. 4. The method for producing a ceramic electronic component according to claim 1 , wherein the ceramic compact is immersed in a powder mixture and heat-treated. 5. The method for producing a ceramic electronic component according to claim 1 , wherein the mixture of the ceramic compact and the powder is placed in a container and then heat treated while rotating the container.