Abstract
Understanding the reliability of eutectic Sn-3.5Ag lead-free solders in high temperature packaging applications is of significant interest in power electronics for the next generation electric grid. Large area (2.5mm×2.5mm) Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates were thermally cycled between 5°C and 200°C. Sn crystal orientation and microstructure evolution during thermal cycling were characterized by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Comparisons are made between observed initial texture and microstructure and its evolution during thermal cycling. Gradual lattice rotation and grain boundary misorientation evolution suggested the continuous recrystallization mechanism. Recrystallization behavior was correlated with dislocation slip activities.
