JPS6364887B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a grain boundary insulated semiconductor ceramic capacitor.

Barium titanate-based materials and strontium titanate-based materials contain at least one kind of valence control elements such as rare earth elements, Nb, Sb, and Bi,
Semiconductor porcelain can be obtained by firing in a neutral or reducing atmosphere. By applying a metal or a compound thereof, such as copper, bismuth, manganese, lead, etc., to the surface of such semiconductor porcelain to make the grain boundaries of the porcelain an insulator, and heat-treating the surface,
It is known that a grain boundary insulated semiconductor ceramic capacitor can be obtained by making the grain boundaries an insulator and further forming electrodes on both main surfaces of the semiconductor ceramic.

This type of semiconductor ceramic capacitor is characterized by a larger apparent dielectric constant than conventional ceramic capacitors.

Conventionally, when manufacturing this type of semiconductor porcelain capacitor, a metal or a compound thereof is applied to make the crystal grain boundaries of the porcelain an insulator, and the semiconductor porcelain is stacked vertically or horizontally and placed in a box. It was placed in a furnace and heat treated to make the grain boundaries an insulator.

However, with the above method, there are temperature differences due to heat treatment depending on the position inside the box, and differences in the atmosphere inside the furnace occur depending on the evaporated metal or compound, resulting in variations in the characteristics of semiconductor ceramic capacitors. However, the variation was large. Furthermore, semiconductor porcelain tends to weld together,
The yield rate of non-defective products was also poor.

The present invention aims to solve the various problems described above, and provides a method for manufacturing a grain boundary insulated semiconductor ceramic capacitor with small variations in characteristics and high yield.

That is, the gist of this invention is to mix semiconductor porcelain obtained by firing in a neutral or reducing atmosphere with powder of a metal or its compound that makes the crystal grain boundaries of this semiconductor porcelain an insulator. This method is characterized by heat treatment in a neutral or oxidizing atmosphere while stirring at room temperature, thereby converting grain boundaries into insulators.

Semiconductor porcelain obtained by firing in a neutral or reducing atmosphere includes barium titanate-based semiconductor porcelain, strontium titanate-based semiconductor porcelain, composite semiconductor porcelain mainly composed of barium titanate and strontium titanate, and titanate-based semiconductor porcelain. There are composite semiconductor porcelains mainly made of strontium and calcium titanate.

Metals or compounds thereof that are mixed with semiconductor porcelain and stirred to make the crystal grain boundaries of semiconductor porcelain insulators include bismuth, copper, lead, manganese, iron,
There are powders of metals such as boron or compounds such as their oxides.

Semiconductor porcelain is mixed with powder of metal or its compound and heat treated in a neutral or oxidizing atmosphere while stirring, and the heat treatment temperature is 950 to 1300.
It should be within the range of ℃. If the temperature is lower than 950° C., the metal or its compound will not be sufficiently diffused, and therefore the apparent dielectric constant will not increase and the insulation resistance will not improve. Furthermore, when the temperature exceeds 1300°C, the metal or its compound evaporates rapidly, resulting in a decrease in capacity.

An example of a method for mixing and stirring semiconductor porcelain and powder of a metal or its compound is, for example, a method in which semiconductor porcelain and powder of a metal or its compound are placed in the same container and the container is rotated or moved back and forth and left and right. There is.

This invention will be described in detail below with reference to Examples.
A mixture consisting of 99.5 mol% SrTiO ₃ and 0.5 mol% Y ₂ O ₃ was calcined at 1150° C. for 2 hours, and then a binder was added and granulated to form a disk with a diameter of 4.3 mm and a thickness of 0.5 mm. Next, the molded product was pre-fired in air at 1150°C for 2 hours, and further fired at 1460°C for 3 hours in a reducing atmosphere consisting of 90% nitrogen and 10% hydrogen to give a diameter of 3.5mm and a thickness of 0.4mm. A strontium titanate semiconductor porcelain of mm was obtained.

After this, Bi ₂ O ₃ 24% by weight, Pb ₃ O ₄ 24% by weight,
A mixed powder consisting of 2% by weight of CuO was weighed so that the dry weight was 20% by weight of the semiconductor porcelain.

1,000 pieces of the semiconductor porcelain described above and the mixed powder were placed in a cylindrical box, and the box was rotated in a furnace to mix and stir the semiconductor porcelain and the mixed powder in the box, and the mixture was heated for 1,100 minutes in an oxidizing atmosphere. Heat treatment was performed at ℃ for 1 hour.

The welding rate of the semiconductor ceramics after the heat treatment was 0%.

Next, a silver paste was printed and coated on both main surfaces of the semiconductor porcelain in a size of 3.0 mm in diameter on one side and 2.5 mm in diameter on the other side, and baked at 800°C for 30 minutes to obtain a semiconductor porcelain capacitor.

The average value of the capacitance of the obtained semiconductor ceramic capacitor was 2100PF, and the standard deviation was 48PF.

As a comparative reference example, the welding rate, capacitance, and standard deviation thereof were similarly measured for a semiconductor ceramic capacitor made by a conventional method.

The semiconductor ceramic capacitor was produced as follows. That is, for the semiconductor porcelain obtained in the above example, 24% by weight of Bi ₂ O ₃ , 24% by weight of Pb ₃ O ₄ ,
A metal oxide paste consisting of 2% CuO and 50% varnish by weight is applied, and this is placed horizontally inside the box.
It was placed in a furnace and heat treated at 1100°C for 1 hour in an oxidizing atmosphere.

The welding rate of the semiconductor porcelain after heat treatment was 17.0%.

When electrodes were formed on this semiconductor ceramic in the same manner as in the above-mentioned example to produce a semiconductor ceramic capacitor, the average value of the capacitance was 2010PF, and its standard deviation was 180PF.

As is clear from the above examples, according to the present invention, welding of semiconductor ceramics does not occur, and the standard deviation of capacitance is also good. This is thought to be due to the fact that during heat treatment, the metal or its compound diffuses evenly into the grain boundaries of the semiconductor porcelain, and furthermore, the conversion of the grain boundaries into insulators is promoted throughout the semiconductor porcelain placed inside the box. be done.

The above-mentioned embodiments are merely examples of the present invention, and the present invention is not limited thereto. For example, for semiconductor porcelain, barium titanate-based ceramics or composites of strontium titanate-based ceramics may be used. Of course, similar results can be obtained with semiconductor ceramics and the like.

Claims (1)

[Claims] 1. Semiconductor porcelain obtained by firing in a neutral or reducing atmosphere and a powder of a metal or its compound that turns the crystal grain boundaries of this semiconductor porcelain into an insulator are mixed and stirred. A method for manufacturing a grain boundary insulated semiconductor ceramic capacitor, which is characterized in that the grain boundaries are made into an insulator by heat treatment in a neutral or oxidizing atmosphere. 2. The method for manufacturing a grain boundary insulated semiconductor ceramic capacitor according to claim 1, wherein the semiconductor ceramic obtained by firing in a neutral or reducing atmosphere is barium titanate semiconductor ceramic. 3. The method for manufacturing a grain boundary insulated semiconductor ceramic capacitor according to claim 1, wherein the semiconductor ceramic obtained by firing in a neutral or reducing atmosphere is a strontium titanate semiconductor ceramic. 4. Grain boundary insulation according to claim 1, wherein the semiconductor porcelain obtained by firing in a neutral or reducing atmosphere is a composite semiconductor porcelain mainly composed of barium titanate and strontium titanate. A method for manufacturing type semiconductor porcelain capacitors. 5. Grain boundary insulation according to claim 1, wherein the semiconductor porcelain obtained by firing in a neutral or reducing atmosphere is a composite semiconductor porcelain mainly composed of strontium titanate and calcium titanate. A method for manufacturing type semiconductor porcelain capacitors. 6. The method for manufacturing a grain boundary insulated semiconductor ceramic capacitor according to claim 1, wherein the heat treatment is performed at a temperature range of 950 to 1300°C.