Critical Review of the Engelmaier Model for Solder Joint Creep Fatigue Reliability

A solder interconnect fatigue life model was developed by Werner Engelmaier in the early 1980s as an improvement upon the inelastic strain range-based Coffin-Manson model. As developed, the model provides a first-order estimate of cycles to failure for SnPb solder interconnects under power and thermal cycles. While the model has been widely adopted for SnPb solder joint reliability prediction, many issues that arise from simplifications in formulating input model parameters as well as from the complex physics of solder degradation challenge the model's ability to accurately estimate cycles to failure. Deficiencies with the model have been reported by a number of researchers. This paper reviews and summarizes the major issues with the Engelmaier model in its applicability to predict solder joint thermal fatigue life.