Microstructural and mechanical analysis of Cu/Sn/Cu microbump by doping Ni and Zn into Cu substrate

This study investigated the reaction between Cu-18Ni-18Zn substrate and Sn-3.5Ag solder under various reflow times. Microstructural analysis revealed that the traditional scallop-type Cu
6
Sn
5
in Cu/Sn/Cu system was replaced by layer-type (Cu,Ni)
6
(Sn,Zn)
5
, and Cu
3
Sn was eliminated. Moreover, the introduction of Ni and Zn led to more diverse grain orientation and refined grains. Shear test showed that Cu-18Ni-18Zn/Sn-3.5Ag/Cu-18Ni-18Zn samples exhibited higher strength than Cu/Sn-3.5Ag/Cu samples, showing 32% and a 111% increase in shear strength for 150 seconds and 300 seconds reflow process, respectively. In summary, the Cu-18Ni-18Zn/Sn-3.5Ag/Cu-18Ni-18Zn system is a promising choice for advanced electronic packaging in the near future.