Formation and behavior of Kirkendall voids within intermetallic layers of solder joints

Abstract

The sub-micron void called "Kirkendall void" has been widely observed within intermetallic compound (IMC) layers in solder joints of semiconductor package interconnections that include both the first level interconnection for a silicon die to a substrate and the second level interconnection for the substrate to a PCB board. Based on many researches on Kirkendall void through a variety of variables, it has been demonstrated as a critical reliability risk within various binary and ternary IMC layers of solder joints in electronic packaging industry. Even, it is more crucial for fine pitch and high complexity in chip-scale electronic packaging. Hence, it is necessarily demanding to review the dependency and influence of critical variables for Kirkendall void formation and behavior in the basis of solid and solid-liquid state interdiffusion process, time and temperature-dependent kinetic process, and morphology and microstructure change of IMCs. Specifically, we reviewed the initial formation, growth and behaviors of Kirkendall void in: (1) short and long-term interfacial reaction by aging in different time and temperatures (2) multiple reflows with different peak temperature (3) annealing after reflow and (4) electromigration, within IMCs of solder joints. Probably, this study may serve as conceptually helpful references to the overall understanding of formation, growth and behavior of Kirkendall void in interfacial reaction of solder joints.