Formation Mechanism of high Ni content (Cu, Ni)6Sn5 in Cu/Sn/Ni microbump for solid state aging

Due to its low cost, the Cu/Sn/Ni microbump is the most widely used structure in electronic packaging. Recent studies have characterized the evolution of the microstructure and phase formation in this system, and a unique (Cu,Ni)
6
Sn
5
phase has been discovered with a high Ni content. However, there has been debate over the formation mechanism of this phase. This study builds a model of the formation mechanism of (Cu,Ni)
6
Sn
5
and provides direct proof.