Experiments on behaviour of power silicon PN junctions under reverse bias voltage at high temperature

By suitable change of the junction-base (heatsink) thermal resistance for commercially available power diode dice, it has been found out that at high temperature internal overheating is induced at the junction edge by the surface component of the reverse current. To change the junction-base thermal resistance, thin aluminium pellets of different dimension or shape have been used, which were pressed between the silicon die and base for a good thermal and electric contact. The surface component of reverse current as a non-negligible source of dissipated power, localized at the junction periphery, can produce hot spots followed by device failure. Due to the effect of the surface component on the junction temperature distribution over the junction area, the maximum permissible operation temperature has specified values up to 200°C for standard recovery junctions and up to 150°C for fast recovery junctions.