Enhancement of the mechanical strength of Sn-3.0Ag-0.5Cu/Ni joints via doping minor Ni into solder alloy

In this study, the Ni-doped solder alloy led to joints with improved shear performance and Sn-3.0Ag-0.5Cu-0.1Ni/Ni joint showed the highest strength. The mechanical response under shear testing depended on the microstructure of the solder zone. Doping minor Ni into the solder ball modified the evolution of the solder microstructure, leading to (Cu,Ni)6Sn5 precipitation in the solder zone and consequently strengthening the Ni-doped joints. Additionally, the pre-existence of Ni in the solder alloy is necessary for triggering the precipitation of (Cu,Ni)6Sn5 particles in solder.