Hermetically Sealed 230°C MnO2 Tantalum Capacitors

Hermetically Sealed 230°C MnO2 Tantalum Capacitors
Written By: T. Zednicek | M. Biler | J. Petrzilek | I. Pinwill

Abstract:
Certain electronic applications, such as oil and gas exploration drilling, are continuously demanding ever higher operating temperatures. Recently operating temperature requirements have increased from 200°C to 230°C with an increased operating life from hours to one thousand hours and beyond. This need is linked with the continuous development of oil drilling heads and sensors and their use for deeper drilling or drilling in more difficult geological conditions. Capacitors with high capacitance value are a common part of the electronic boards used in these applications, but over 125°C/175°C, available capacitor choice is very limited. Tantalum SMD capacitor technology has proved its reliability in operation up to 175°C and there is a limited choice of special designs up to 200°C. Long life wet tantalum capacitors up to 200°C are available from multiple sources, or up to 230°C with reduced operational life from a single source. Hermetically sealed MnO2 tantalum capacitors have demonstrated their ability to offer unique long life stability at 230°C combined with solid, stable and robust design. [1]. The next testing and development presented in this paper discusses the basic behavior of the solid hermetically sealed MnO2 tantalum capacitor above 200°C. A certain type of “wear out” has been observed in a longer exposure at 230°C depending on applied voltage. Nevertheless, the basic capability of the capacitor meets the “best in class” requirement for 230°C 1000hours continuous operating life with 50% voltage derating. The paper discusses and summarizes the “wear out” phenomenon observed at temperatures above 200°C on these capacitors and impact of different voltage derating to operational life at 230°C.
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