ABSTRACT
The life of tin-lead (Sn-Pb) or Pb-free solder joints is limited by the fatigue damage that accumulates in solder materials. Accelerated testing provides distributions of failure times whose relevance to service life is determined by extrapolation to use conditions based on the appropriate acceleration factors (AFs). Because AFs are defined as the ratio of life under test and use conditions, their determination requires up-front predictions of solder joint lives under both sets of conditions. Such models are also of use for reliability analysis of circuit boards at the design stage. While a variety of life prediction models have been developed for near-eutectic Sn-Pb assemblies, to this author’s knowledge, such models are not currently available for Pb-free soldered assemblies. The development of life prediction models requires a detailed understanding of failure modes, an adequate constitutive model that captures the thermomechanical behavior of Pb-free solders in electronic assemblies, and a reliability database that is needed for the empirical correlation of failure times under test and field conditions.
