Suntan Tantalum Capacitors Self-destruction and thermal runaway
Tantalum capacitors are under some conditions prone to self-destruction by thermal runaway. The capacitor typically consists of a sintered tantalum sponge acting as the anode, a manganese dioxide cathode, and a dielectric layer of tantalum pentoxide created on the tantalum sponge surface by anodizing. The tantalum oxide layer may have weak spots that undergo dielectric breakdown during a voltage spike. The tantalum then comes to direct contact with manganese dioxide and the leakage current causes a local heating; a chemical reaction then produces manganese(III) oxide and regenerates (self-heals) the tantalum oxide layer.
If the energy dissipated at the failure point is high enough, a self-sustaining exothermic reaction may occur, similar to the thermite reaction, with tantalum as fuel and manganese dioxide as oxidizer, destroying the capacitor and occasionally producing smoke and possibly flame.
