MULTIPURPOSE LEAD-FREE RELIABILITY PREDICTION MODEL

In this paper, an interconnection reliability prediction model capable of providing lifetime estimates for various material and structural combinations is presented. This model was first introduced in Pan Pacific conference in 2005. There, Engelmaier's model was re-calibrated for ceramic components assembled using lead-free solder on organic printed wiring boards, and the fatigue ductility coefficient was suggested to be replaced by a stress-dependent correction term. Since those days, the model has gained quite some popularity and both its validity and accuracy have been proven. Moreover, materials and interconnection types that the model is valid for have significantly been extended. Now, for example lead-free solder castellations, collapsible and non-collapsible lead-free BGA solder joints can be accounted for in the model. In this paper, a new use case to the list is introduced: attaching power devices to their heat sink. A new interpretation of distance to neutral point in case of one single solder joint is needed for that. The correction term has also developed since Engelmaier's days from constant value through logarithmic model to second-order polynomial shape. This paper summarizes this development in a user-friendly way that makes it easy for the practitioner to choose the right one for his specific purpose. Also, the expected accuracy of each approach is estimated. In addition to Engelmaier's model, where absolute lifetime predictions are looked for, a parallel relative, acceleration-factor-based reliability prediction model using Norris-Landzberg model is provided.