JPH0648665B2 - Method for manufacturing grain boundary insulated semiconductor ceramic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a grain boundary insulation type semiconductor ceramic capacitor using a plated electrode as an electrode.

(Prior Art) Conventionally, as a method for manufacturing this type of grain boundary insulating type semiconductor ceramic capacitor, there is one described in Japanese Patent Application Laid-Open No. 57-30310.

This method for manufacturing a grain boundary insulating type ceramic capacitor was devised to use a low-cost plated electrode as an electrode of a grain boundary insulating type semiconductor ceramic capacitor instead of the silver electrode used so far.

Specifically, a semiconductor porcelain mainly composed of strontium titanate is coated with a diffusing agent prepared by mixing a grain boundary insulating agent composed of bismuth, copper, lead, boron and the like and glass powder, and thermally diffused. After insulating the grain boundaries, plating electrodes are formed on both main surfaces by electroless plating.

(Problems of Prior Art) However, in the above-described method for manufacturing a grain boundary insulating type semiconductor ceramic capacitor, since there is a step of applying a diffusing agent in which a grain boundary insulating agent and glass powder are mixed, the number of steps is reduced. More and more costly.

Also, due to variations in the diffusion energy of the diffusing agent caused by variations in the amount of the diffusing agent applied and the heat distribution during heat treatment, or changes in the diffusion degree of the glass powder due to the presence or absence of the portion coated with the diffusing agent, the capacitor There was a case where the capacity of the capacitor varied and the characteristics were deteriorated.

Further, due to the unevenness of the diffusion energy, the diffusing agent intervenes unevenly between the particles, so that the bonding strength varies and the transverse strength is weak, and defects such as cracks may occur in the plating process.

Therefore, the present invention has been made to solve the above-mentioned problems, and even if a plating electrode is used as an electrode of a grain boundary insulation type semiconductor ceramic capacitor, it has the same electrical characteristics and reliability as a silver electrode, and high resistance. It is an object of the present invention to provide a method for manufacturing a grain boundary insulation type semiconductor ceramic capacitor which can reduce cracks and cracks in the plating process due to bending strength.

(Means for Solving Problems) A method for manufacturing a grain boundary insulating type semiconductor ceramic capacitor according to the present invention includes a step of preparing a semiconductor ceramic, a grain boundary for insulating the semiconductor ceramic and the grain boundary of the semiconductor ceramic. 1% by weight with respect to the insulating agent and this grain boundary insulating agent
-100% by weight of glass powder is mixed with a diffusing agent and heat-treated with stirring to insulate the grain boundaries of the semiconductor porcelain. And a step of forming a plated electrode.

(Operation) According to the method for producing a grain boundary insulating semiconductor ceramic capacitor of the present invention, the semiconductor ceramic is mixed with the grain boundary insulating agent and the diffusing agent composed of the glass powder, and heat treated while stirring. Since the grain boundaries are insulated, the amount of the diffusing agent applied and the heat distribution during the heat treatment are made uniform, and variations in diffusion energy are eliminated.

Further, since there is no portion where the diffusing agent is not applied, the degree of diffusion of the glass powder does not change.

(Example) Below, the manufacturing method of the grain boundary insulation type semiconductor ceramic capacitor of this invention is explained in detail.

First, a mixture of SrTiO ₃ (99.0 mol%) and Y ₂ O ₃ (1.0 mol%) was calcined at 1150 ° C. for 2 hours, and then a binder was added to granulate the mixture to a diameter of 1.0 mm and a thickness of 0. It was molded into a 4 mm disk shape. Then, the molded product molded into a disc shape is
Pre-baking was performed at 100 ° C. for 2 hours, and then baking was performed at 1430 ° C. for 3 hours in a reducing atmosphere composed of NH 3 to obtain a semiconductor porcelain.

Next, a diffusing agent, which is a mixture of Bi-Pb-Cu-B-based glass powder and Bi ₂ O ₃ -PbO-CuO in the proportions shown in Table 1, was added to the semiconductor porcelain at 1.5% by weight. Was weighed so that

Next, this diffusing agent is put together with 1000 semiconductor porcelains in a cylindrical box, and this box is rotated in a furnace to mix the semiconductor porcelain and the diffusing agent in the box and agitate in an oxidizing atmosphere. Medium heat treatment was performed at 1120 ° C. for 1 hour to insulate the grain boundaries of the semiconductor porcelain.

Next, a plating resist was applied to the end surface of the semiconductor porcelain after the heat treatment, and then nickel plating electrodes were formed on the main surface of the semiconductor porcelain by electroless plating to obtain a grain boundary insulation type semiconductor porcelain capacitor.

For the grain boundary insulation type semiconductor ceramic capacitors obtained in this way, the capacitance (nF), standard deviation, welding rate (%), bending strength (kg), crack / chip failure rate (%) and dielectric loss (%) Was measured, and the results are shown in Table 1.

In Table 1, Nos. 1, 5, 7, and 11 are out of the scope of the present invention, and Nos. 6 and 12 are grain boundary insulation type semiconductor ceramic capacitors manufactured by a conventional manufacturing method for comparison. .

Further, in Table 1, the grain boundary insulating agent A is Bi ₂ O ₃ -PbO-Cu.
The composition is O and the weight ratio is 40:40:20, and the grain boundary insulating agent B is B
The composition is i ₂ O ₃ -PbO-CuO and the weight ratio is 90: 2: 8.

Further, in Table 1, glass powder C is Bi ₂ O ₃ -PbO-CuO.
-B ₂ O ₃ composition has a weight ratio of 30: 30: 10: 30, and glass powder D has a Bi ₂ O ₃ -PbO-CuO-B ₂ O ₃ composition weight ratio of 25:20:30. .

As is clear from Table 1, the addition amount of glass powder is 1% by weight with respect to the grain boundary insulating agent as in Sample Nos. 1 and 7.
When it is smaller, when the addition amount of the glass powder is larger than 100% by weight with respect to the grain boundary insulating agent as in Sample Nos. 5 and 11, or when it is produced by the conventional manufacturing method as in Sample No. 6. Compared to any of the above cases, the variation in capacitance is small and the bending strength is large. In addition, since the defective rate of cracks and chips is low, the non-defective rate is high.

In the description of the present invention, the nickel-plated electrode is formed by electroless plating, but the present invention is not limited to the nickel-plated electrode, and a copper-plated electrode or the like may be used.

Furthermore, when performing the heat treatment while mixing the semiconductor porcelain and the diffusing agent and stirring, the method of putting the semiconductor porcelain and the diffusing agent in the box and performing the heat treatment while rotating was shown, but not limited to this. Alternatively, the heat treatment may be performed while moving the box back and forth or left and right.

(Effects of the Invention) As described above, if the method for manufacturing a grain boundary insulating semiconductor ceramic capacitor of the present invention is used, the diffusion energy of the diffusing agent becomes uniform and the grain boundaries can be stably insulated. Further, this makes it possible to reduce the variation rate of the electrostatic capacitance of the capacitor or the defective rate of cracks, chips, etc., so that the reliability of the grain boundary insulation type semiconductor ceramic capacitor can be improved.

Claims (1)

[Claims] 1. A step of preparing a semiconductor porcelain, a grain boundary insulating agent for insulating the grain boundaries of the semiconductor porcelain, and the grain boundary insulating agent, and 1% by weight based on the grain boundary insulating agent.
-100% by weight of glass powder is mixed with a diffusing agent and heat-treated with stirring to insulate the grain boundaries of the semiconductor porcelain. A method of manufacturing a grain boundary insulation type semiconductor ceramic capacitor comprising the step of forming a plated electrode.