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Incoming test screening should avoid other longer duration transients that may be potentially damaging. For example, the smallest DO-35 Zener diodes made by MCC can still typically absorb or withstand peak pulse power (PPP) transients up to 3 or 4W for 8.3ms. Higher or lower PPP at 25°C will be further dictated by shorter or longer pulse widths (tw) respectively. This is typically determined by the classic Wunsch-Bell curve of “PPP = K/√ tw”, where K is a constant dictated by the effective size of pn junction semiconductor devices. Transients can be generated by poor contact to the Device Under Test (DUT) by some test equipment designs when uncontrolled high compliance voltages may be briefly generated while trying to force a desired programmed level of test current. Therefore precautions are also necessary in test equipment selection or maintenance of electromechanical features (test clip contacts as one example) where poor electrical continuity may occur. If the DUT has tarnished leads from other prior high temperature testing such as HTRB or burn-in operations, then leads should be cleaned prior to testing.
