Surge Current Testing of Resin Dipped Tantalum Capacitors

Resin dipped solid tantalum capacitors subjected to fast switch-on surges from a low impedance source have a low but significant instantaneous failure rate similar to that for metal cased tantalum capacitors. This failure is affected by external circuit conditions, by capacitor construction and by various applied stresses. The mechanism progresses through several stages. For the initial stage the voltage seems of more importance than the current. The high current availability is necessary for the second stage to appear. The effect of over voltage and thermal stresses and of the presence of moisture have been studied together with the effects of capacitor leakage current and ESR.