Reliability implications of component temperature in electronic systems

Three of the principal failure mechanisms in silicon devices are: (1) second breakdown of p-n junctions; (2) electromigration of aluminium metallisation; and (3) corrosion. All three phenomena are thermally activated and thus the predicted life of an electronic component, and hence that of the system which incorporates it, is progressively reduced as the operating temperature rises. Component failures can also be induced by electrical over-stress (EOS) resulting from transient voltage spikes or electrostatic discharge (ESD). The sensitivity of a devise to EOS or ESD is increased as the temperature rises and thus there is another reason for minimising the operational temperature of a system. The reliability of a system usually predicted using the method proposed in MIL handbook 217 which quantifies environmental and other factors so that systematic reliability calculations can be performed. The estimates based on MIL 217 are often pessimistic when compared with observed failure rates