Numerical and experimental study on surge current limitations of wire-bonded power diodes

摘要

Forward surge currents are considered both experimentally and numerically for wire bonded silicon free wheeling diodes. Measurements indicate that the destruction threshold is not given by the onset of intrinsic conductivity. Instead the failure signature indicates a purely temperature driven destruction mechanism caused by the limited ruggedness of the front side contact against excessive heating. The dependence of the surge current limit on pulse width is investigated for different diode types both experimentally and in theoretical models. The transient thermal behaviour is important for a quantitative analysis of the surge current leading to a good understanding of experimental data. A simple analytical formula for the maximum surge current is derived. The failure mode is studied in more detail via a finite element simulation. Finally the influence of higher junction temperatures on the surge current is discussed.