Failure mechanisms of solder interconnects under current stressing in advanced electronic packages

The pursuit of greater performance in microelectronic devices has led to a shrinkage of bump size and a significant increase in electrical current. This has resulted in a high current density and accompanying Joule heating in solder interconnects, which places great challenges on the reliability of advanced electronic packages. A review of current stressing-induced failures of solder interconnects is thus timely. This review is devoted to five types of physical failure mechanisms occurring in high current density applications, which include electromigration (EM), Joule heating-induced failures, interfacial reactions, stress-related damage, and thermomigration (TM). In practice, some of these failure mechanisms are mixed together so that the real root cause cannot be easily detected and understood. Reliability designers need to be well informed to evaluate the electrical characteristics, thermal characteristics and mechanical strength for solder interconnects in advance. This review summarizes recent progress and presents a critical overview of the basis of atomic transport, diffusion kinetics, morphological evolution, and numerical simulation. Special emphasis is on the understanding of the interactions of EM with other failure mechanisms. Aside from the review of the current status of knowledge, the remaining challenges as well as future directions are also discussed.