The effect of fan-reliability and cooling-performance on electronic-chassis reliability

A tractable model for predicting the failure rates of electronic chassis cooled by fans with finite failure rates is developed. The model accounts for two regimes prior to electronics failure: the electronic chassis is operated at a temperature which occurs with a fan that is operational and the electronic chassis is operated at a temperature which occurs when the fan has failed. Fan failures alone do not constitute a failure of the chassis. Such a model applies where cooling fans are not actively monitored, and where their failure is noticed only during the maintenance associated with an electronic failure of the chassis, i.e., the model accounts for the fact that the electronics in general continues to operate for a period of time following a fan failure. The model directly applies to cost/benefit studies in electronics packaging, including the determination of the improvement in mean time between failures (MTBF) to be anticipated when a chassis is implemented with a cooling fan, and the determination of the performance benefit to be anticipated when fans are actively monitored and replaced upon failure.<
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