JPH0524648B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method of manufacturing a surface reoxidation type semiconductor ceramic capacitor. [Prior Art] Surface reoxidation type semiconductor ceramic capacitors are generally manufactured by the following steps. For example, after mixing raw materials containing BaTiO ₃ as a main component, a binder and the like are added, kneaded, extruded into a sheet, and the resulting sheet is punched out to obtain a disc-shaped molded body. A plurality of the above molded bodies are piled up and packed in pods, fired in the atmosphere, and then the obtained sintered body is heat treated in a reducing atmosphere to obtain semiconductor porcelain. The semiconductor ceramic is heat-treated again in the atmosphere to re-oxidize the surface to obtain a surface-reoxidized semiconductor ceramic. A surface reoxidation type semiconductor ceramic capacitor is obtained by forming Ag electrode layers at mutually opposing positions on both principal surfaces of the surface reoxidation type semiconductor ceramic capacitor. In the surface reoxidation type semiconductor ceramic capacitor manufactured by the above manufacturing method, depending on the degree of oxygen supply to the surface of the semiconductor ceramic and the conditions of the heat treatment temperature when the semiconductor ceramic is heat-treated in the atmosphere again, the semiconductor ceramic The degree of oxygen diffusion in the surface layer portion of the
Characteristics such as these are greatly affected and fluctuate. From this point of view, conventionally, in order to prevent the degree of oxygen diffusion from varying among individual semiconductor porcelains, a firing sheath made of a refractory material such as alumina or zirconia was placed directly on top of the firing pod, or a setter made of the above refractory material was used. It was common practice to pack the semiconductor porcelain flatly so that they did not overlap each other, and then stack these pods in multiple stages and heat-treat them in the atmosphere. [Problems to be Solved by the Invention] However, in the above conventional manufacturing method, semiconductor porcelain was packed flat on a refractory firing pod or setter and heat-treated so that they did not overlap each other. The number of semiconductor ceramics that could be processed per unit was small, and both thermal efficiency and processing efficiency were low. In addition, in order to increase the throughput per pod, heat treatment of multiple layers of the above semiconductor porcelain is being considered, but the characteristics vary widely among semiconductor porcelains, resulting in an increase in dielectric loss and a decrease in insulation resistance. I couldn't deny it. An object of the present invention is to provide a manufacturing method capable of solving the above-mentioned conventional problems and efficiently obtaining a surface reoxidation type semiconductor ceramic capacitor without increasing variation in characteristics or deteriorating characteristics. There is a particular thing. [Means for Solving the Problems] The present invention involves mixing raw materials for semiconductor porcelain, molding the resulting molded product, firing it in the air, heat-treating it in a reducing atmosphere, and then heat-treating it again in the air. In the method for producing a surface reoxidation type semiconductor ceramic capacitor, the surface reoxidation type semiconductor ceramic capacitor is formed by reoxidizing the surface and forming a pair of electrode layers on the surface of the obtained surface reoxidation type semiconductor ceramic. At this time, plate-shaped spacers of the same size or larger than the semiconductor porcelain to be heat-treated are prepared, and the semiconductor porcelain and the spacers are alternately stacked so that the semiconductor porcelain is sandwiched between the spacers. It is characterized by being heat-treated in the state. Note that the spacer is preferably formed of a refractory obtained by firing alumina, zirconia, magnesia, or a mixed composition thereof. [Function] In the method for manufacturing a surface reoxidation semiconductor ceramic capacitor of the present invention, as described above, both sides of the semiconductor ceramic are sandwiched between the spacers,
Since the semiconductor ceramics and the spacers are alternately stacked and the heat treatment for reoxidation is performed in this state, heat conduction and oxygen diffusion to each semiconductor ceramic is uniform. [Example] Next, examples of the surface reoxidation type semiconductor ceramic capacitor of the present invention will be described together with comparative examples. First, BaTiO ₃ 92 mol%, CeO ₂ 5 mol%,
Mix raw material powder for semiconductor porcelain with a composition ratio of 3 mol% TiO ₂ , 7 wt % methyl cellulose as a binder, and 10 wt % glycerin as a plasticizer.
% aqueous solution was added and extruded into a sheet with a thickness of 0.6 mm. Next, the sheet was punched out into a disk shape of 10 mmφ, and the resulting molded body was packed in an alumina porcelain firing sheath, and then fired in the air at 1300°C to obtain a sintered body. Next, the sintered body was packed into a firing pod again and heat treated at 1000° C. for 2 hours in a reducing atmosphere containing 10 vol% H ₂ and 90 vol% N ₂ to obtain semiconductor porcelain. After this, using the semiconductor porcelain obtained above, Examples 1 to 4 and Comparative Example 1 shown in Table 1 were prepared.
A heat treatment was performed again at 900° C. for 2 hours in the air under the conditions of 3 to 3 to obtain a surface reoxidation type semiconductor porcelain. Ag electrode material paste was applied in a circular shape of 6 mm diameter to both main surfaces of the surface reoxidation type semiconductor porcelain obtained above.
A surface reoxidation type semiconductor ceramic capacitor sample was obtained by baking at 800°C for 10 minutes. 500 capacitor samples each obtained in this way
For each piece, capacitance C [nF], dielectric loss tan δ [%], and insulation resistance IR after applying a voltage of 50 V DC for 15 seconds at a measurement frequency of 1 KHz and a measurement voltage of 0.1 V.
[MΩ] was measured, and the average value and variation (3σ/
x) and the throughput per pod, that is, the throughput ratio, were determined and the results are shown in Table 2. Examples 1 to 4 of the present invention as shown in Table 2
All of the samples obtained in this procedure had the same characteristics in terms of capacitance, dielectric loss, and insulation resistance as the sample obtained by the conventional flat-packing method shown in Comparative Example 1. The variation was smaller than that of the samples obtained in 2 and 3. In addition, in terms of the throughput per pod, the throughput was more than seven times that of the conventional flat packing method. In the above embodiments, alumina or zirconia was used as the spacer, but the present invention is not limited thereto. Various selections can be made except for the composition. Furthermore, by adjusting the vacancy of the spacer, it is also possible to adjust the degree of oxygen supply to the surface of the semiconductor ceramic.

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〔Effect of the invention〕

According to the present invention, as shown in the results of the above examples, surface reoxidation type semiconductor ceramic capacitors can be efficiently manufactured without increasing variation in characteristics or deteriorating characteristics.

Claims (1)

[Claims] 1. Mix the raw materials for semiconductor porcelain and then form it.
The obtained compact is fired in the air, heat-treated in a reducing atmosphere, and then heat-treated again in the air to re-oxidize the surface, and a pair of electrode layers is formed on the surface of the surface-reoxidized semiconductor porcelain obtained. In the method for manufacturing a surface reoxidation type semiconductor ceramic capacitor, when the semiconductor ceramic is heat-treated in the atmosphere again, a plate-shaped spacer of the same size or larger than the semiconductor ceramic is prepared, and the A method for manufacturing a surface reoxidation type semiconductor ceramic capacitor, characterized in that the semiconductor ceramics and the spacers are alternately stacked so that the semiconductor ceramics are sandwiched between the spacers, and heat-treated in this state.