Polymer tantalum capacitors are expanding their market share in the commercial world because they offer superior electrical performance (primarily much lower ESR), have outstanding reliability, and display a more benign failure response than the incumbent MnO2-cathode tantalum capacitor technology. It is natural that engineers want to use this new technology in high-reliability applications.
However, a critical reliability assessment tool for MnO2-cathode tantalum capacitors – Weibull grading per MIL-PRF- 55365 – is often ineffective when applied to tantalum polymer capacitors. Because this well-established tool often proves ineffective, a new reliability assessment strategy is needed and has now been developed by KEMET.
The basic principles behind the Weibull grading technique are reviewed, as are the reasons why it is often ineffective when applied to tantalum polymer capacitors. Then a new reliability assessment strategy for polymer tantalum capacitors is described. Particular emphasis is placed on differences in the typical time-to-failure responses of tantalum polymer capacitors versus MnO2-cathode tantalum capacitors during this discussion. Finally, an example is given of a successful use of this new reliability assessment strategy in a real-world high-reliability application.