A Study on Heatsink Cooling Fan Lifetime Evaluation

SUMMARY & CONCLUSIONSA fan has both electronic and mechanical parts, and it can fail electronically, mechanically, or due to a combination of both modes. The electronic parts include control circuitry, motor, and its electronic components; the mechanical parts of a fan include bearing, lubricant, shaft, fan blades or propeller/ impeller, and fan housing.To have a full understanding of fan reliability, all possible failure mechanisms and failure modes should be considered and for estimation of reliability metrics (L
10
, MTTF) dominant failure mechanisms need to be used. Observations from field failures of some marginal fans that have occurred at customer locations are used here and the Weibull plot shows a shape parameter of ~6, indicating a strong wear out but there was not enough spread in the data to give confidence in the results.It has been established that majority of fans fail due to failure of mechanical parts, driven by bearing failures and the reliability of the bearing is a function of the lubrication system too. In this work, different failure mechanisms for field failures were further investigated and understanding of customer application stresses that lead to early degradation of lubricant system were studied. Potential failure modes of fan bearings, their causes and failure mechanisms have been summarized in this study; analyses of both failed fans and surviving fans from customers were undertaken along with failure analysis of fans with similar operational hours from different customer sites. Construction analyses of existing fans were undertaken to improve the design for next generation of fans.