Electroforming of stacked thyristor diodes for long-term reliability - involves application of excessive current pulse to one chip of stack which has weak point with e.g. uncompensated surface charges

摘要

A predetermined forming pulse of current is applied to the anode (18) and cathode (20). The pulse waveform is such that for a limited time, the weak point (22) under a passivation coating (16) in the vicinity of one thyristor chip (12) is thermally overloaded to the extent that the p-n junction (14) is shorted by a melting channel (24). The other chips which have no such weak point are not overloaded or shorted in the same way. The forming current is set at a level considerably higher than that of the current pulse to be expected in normal operation. ADVANTAGE - Blocking voltage can be adjusted and probability of failure in long-term operation reduced significantly.