Life model for tantalum electrolytic capacitors with conductive polymers

Tantalum electrolytic capacitors have been on the market for more than half a century, in a range of applications. However, the most common design uses MnO2 as the electrolyte, which can be thermodynamically unstable and, upon failure, can damage the circuit. To mitigate this risk, an alternative to the MnO2 electrolyte was developed using conductive polymers. Compared to MnO2, polymer Ta capacitors are more resilient to surge current, have a lower equivalent series resistance, and are ignition-free. However, polymer electrolytes are susceptible to degradation at high temperature and humidity. This paper presents an experimental study of polymer Ta capacitors from two different manufacturers, tested under six different environmental conditions, and characterized electrically at intervals during those tests. A time-to-failure model was developed to predict the degradation as a function of temperature and humidity.