Microstructural evolution of Sn-rich Au-Sn/Ni flip-chip solder joints under high temperature storage testing conditions

摘要

In this study, we fabricated Sn-rich, Au-Sn flip-chip solder bumps by using a sequential electroplating method with Sn and Au. After reflowing, only a (Ni,Au)3Sn_4 intermetallic compound (IMC) layer was formed at the Au-Sn solder/Ni interface. During aging for up to 1000 h at 150 deg C, the solder matrix was transformed sequentially in the following order: (beta-Sn and eta-phase, eta-phase, eta-phase and epsilon-phase. The microstructure variation resulted from the preferential consumption of more Sn atoms within the solder matrix during aging.