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Microwave Processing of Tantalum Capacitor Anodes*

  • R. J. Lauf (a1), C. Hamby (a1), C. E. Holcombe (a1) and W. F. Vierow (a2)

Abstract

Porous tantalum anodes were sintered at temperatures from 1600 to 1900°C using a conventional high-vacuum furnace as well as both 2.45 GHz fixed-frequency and 4-8 GHz variable-frequency microwave furnaces. Various insulation and casketing techniques were used to couple the microwave power to the tantalum compacts. Several types of tantalum powder were used to assess the effect of microwave processing on sintered surface area and impurity levels.

Some microwave sintered anodes have an unusual surface rippling not seen on conventionally fired parts. The rippling suggests that a microscopic arcing or plasma might have been generated. Two important effects could be exploited if this phenomenon can be controlled. First, the effective tantalum surface area could be increased, yielding higher capacitance per volume. Second, surface impurities might be cleaned away, allowing the formation of a better dielectric film during the anodization process and, ultimately, higher working voltage.

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Work supported by the U.S. Department of Energy, Office of Energy Research, under contract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc.

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1. Holcombe, C. E. and Dykes, N. L., “Microwave Sintering of Titanium Diboride,” J. Mat. Sci. 26, 3730–38 (1991).
2. Bible, D. W., Lauf, R. J., and Everleigh, C. A., “Multikilowatt Variable Frequency Microwave Furnace,” Mat. Res. Soc. Symp. Proc., Vol. 269 (1992).
3. Holcombe, C. E. and Dykes, N. L., “Importance of ‘Casketing’ for Microwave Sintering of Materials,” J. Mat. Sci. Lett. 2, 425–8 (1990).
4. Bible, D. W., Oak Ridge National Laboratory, personal communication (1992).

Microwave Processing of Tantalum Capacitor Anodes*

  • R. J. Lauf (a1), C. Hamby (a1), C. E. Holcombe (a1) and W. F. Vierow (a2)

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