Surge Step Stress Testing ( SSST ) of Tantalum Capacitors

A misunderstanding of the failure mechanism of tantalum capacitors has created the fear of using these capacitors in high current applications. A capacitor depends on the dielectric as an insulative material and the plates as a conductive material. If the current was the trigger mechanism for failure, then the plates should be suspect throughout the life of the capacitor. This is not the case as the failures with this capacitor are normally related to initial power-on occurrences. As such, the failure mechanism is most likely the breakdown of the dielectric when exposed to a specific critical strain for the first time. The high available current ensures that the failure does not heal itself, but breaks down the dielectric so catastrophically that the dielectric loses most of its insulative properties. This Surge Step Stress Test (SSST) is intended to identify the critical stress level of any batch of capacitors to give some predictability to the power-on failure mechanism.