Design Considerations for Reliable High Temperature Operation of Wet Electrolytic Tantalum Capacitors

Wet electrolytic tantalum (Ta) capacitors have historically been utilized in a variety of applications which endure harsh ambient conditions. Thermal, electrical and mechanical stresses, though, pose significant challenges to reliable performance of these capacitors in such environments. Thermal stress can increase the internal pressure of the capacitors, as well as mechanically compromise some of the components of which the capacitors are comprised. Electrical stress, in the form of current flow due to applied voltage, can elicit hydrogen gas evolution, which further exacerbates the internal pressure issue, potentially embrittles Ta components, and degrades AC performance of the capacitors. Mechanical stress, resulting from shock and vibration for example, can jeopardize the internal mechanical integrity of the capacitors. This paper elaborates on these obstacles, and offers design approaches to reliably overcome them. Also presented are results of high temperature performance, predominantly up to 230°C, but also a mention of limited 245°C results, of wet Ta capacitors manufactured with proper attention paid to these concerns.