Surge Current Failure in Solid Electrolyte Tantalum Capacitors

Fast charging and discharging of solid tantalum capacitors causes breakdown by heating in the MuO2cathode instead of dielectric breakdown. It appears that localized regions of lower resistance and poor thermal contact to a heat sink allow very high temperatures to occur. These "hot spots" can then cause breakdown of the adjacent dielectric film and, eventually, loss of the capacitor. Temperature increases are detected by measuring the change of resistance of the MuO2cathode and by their effect on temperature sensitive paint. The hot spots tend to concentrate near the surface of the anode at the upper and lower shoulders. The heating effect of leakage current is negligible for these tests.