Investigation into the strength of β-Sn/α-CoSn3 and Co/α-CoSn3 interfaces with Ni-doped α-CoSn3 using first-principles calculations

Abstract

The strength of Pb-free solder/Co-Ni alloy joints was investigated using first-principles calculations. The adhesion work was computed, revealing that the inclusion of Ni in the α-CoSn₃ phase reduced the adhesion work for both β-Sn/α-CoSn₃ and Co/α-CoSn₃ systems. Tensile and shear simulations further demonstrated distinct differences in the mechanical properties between β-Sn/α-(Co,Ni)Sn₃ and Co/α-(Co,Ni)Sn₃ systems. The results demonstrate that Co/α-(Co,Ni)Sn₃ exhibited superior tensile and shear strength. The analysis suggests that failure in β-Sn/α-(Co,Ni)Sn₃ structures was more likely to originate either at the interface or near the β-Sn region, as opposed to within the α-(Co,Ni)Sn₃ phase for the Co/α-(Co,Ni)Sn₃ structures. This observation is consistent with predictions made by Griffith’s fracture theory. Additionally, the valence electron density map illustrates the electron transfer under varying tensile strains.