Effect of multiple flip-chip assembly on the mechanical reliability of eutectic Au–Sn solder joint

Eutectic Au–Sn solder has widely been used for high temperature bonding since it enables fluxless soldering and provides mechanically stable solder joint. However, effect of multiple bonding process on the mechanical reliability has not been studied in detail. In this study, microstructure evolution of Au–Sn solder joint and its effect on mechanical reliability were systematically investigated. During the multiple reflow process, the eutectic phase gradually transformed into ζ phase, which resulted in loss of solderable area. The phenomenon turned out to be responsible for degradation of bonding strength of the solder joint.