Reliability of Manganese Dioxide and Conductive Polymer Tantalum Capacitors under Temperature Humidity Bias Testing

Abstract

Despite being highly reliable under steady state operating conditions, manganese dioxide (MnO2) tantalum capacitors are prone to catastrophic exothermic failures under surge current conditions. Such failures can be mitigated by the use of conductive polymers in place of MnO2. However, these polymers are more susceptible to failure at elevated humidity levels. In this paper, the electrical performances of both MnO2 and polymer tantalum capacitors are compared by subjecting them to temperature humidity bias testing at 85°C and 85% RH. The test population consists of tantalum capacitors with two voltage ratings (50V and 16V). At each of these voltage ratings, two sets of tantalum capacitors, one each with MnO2 and conductive polymer electrodes, were tested. The voltage levels used to bias the capacitors were periodically increased in multiples of the rated voltage to accelerate degradation. The performance of the capacitors was tracked by monitoring their capacitance, dissipation factors and leakage currents, both in-situ and at room temperature. The degradation trends are discussed in light of the differences in voltage ratings and electrode types. These trends are also mapped to fundamental failure mechanisms within the capacitors.