Failure analysis of high power white LEDs

Moisture-induced silver reactions have been identified as a fast degradation mechanism in commercial plastic packaged white LEDs, that passed a standard incoming lot inspection but resulted all degraded at the switching-on after mounting on the final boards. The source of the contaminant (Sulphur) is not explained by any part of the available history of the devices in the lot. Anyway, each one of three possible scenarios depicts a reliability issue that escaped the process monitors and reached the shelf.