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Qualification testing programs have been developed for assessing the reliability of commercial grade discrete semiconductors for use in office business machines. These programs include accelerated stresses of high temperature storage (HTS) and high temperature reverse bias (HTRB) for 1000 hours, and a sequence test of thermal cycle and thermal shock followed by storage at 85Â°C and 85% RH (85/85) for 1000 hours. Both hermetic and plastic encapsulated parts have been tested more than 15 million part hours. HTRB and 85/85 are about twice as effective as HTS in identifying potentially unreliable parts. Plastic packaged semiconductors are inherently capable of withstanding 85/85 for 1000 hours without parameter degradation. The value of qualification testing against the 85/85 environment is demonstrated by the observed correlation of machine failure rates in the field with the relative humidity in the use environment. The observed failure rate of plastic parts is not more than 3.2 times that of hermetic parts. Plastic parts are capable of reliable operation, but the marked differences in reliability between different vendors and between different part types from the same vendor require increased process and materials control in order to achieve the potential of which plastic parts are capable.