Investigations on Electrolytic Capacitors to Improve Reliability under Assembly-Level Impact Conditions

Electrolytic capacitors are of great importance in modern power electronics due to their ability to withstand high voltages for PFC (power factor correction) applications. Solid capacitors, such as ceramic chip capacitors, are not able to achieve this purpose.One of the most common failure modes of electrolytic capacitors is dielectric breakdown, which may lead to internal short-circuits when the capacitor is being charged under high-voltage. Although protection features in the control circuit may be implemented, the voltage fluctuations during the short may still results in failures of other sensitive components in the circuit. Diagnosing such failures is difficult because the functional parameters of the capacitor return to normal following breakdown.One of the dominant reason for dielectric breakdown of electrolytic capacitors is repeated mechanical impact, such as drop loading and vibration, which the jelly-rolled structure of electrolytic capacitors are sensitive to. Repeated mechanical stress may also results in accumulative internal damage to the capacitor and trigger dielectric breakdown over time.The research presented in this paper involves both non-destructive inspection techniques and root cause analysis approaches to analyze typical dielectric breakdown of the capacitor after industry-standard assembly-level drop tests. Based on the failure mode, several measures are proposed to improve the drop reliability of the capacitor in the power electronics. The feasibility of those measures is also analyzed.In summary, we have proposed a potential mitigating strategy to protect power electronics against impact (drop and vibration, etc.) applications, such as high-power portable converters, chargers and electric vehicles