Effect of Different Concentrations of Co Doping on the Properties of η′‐Cu6Sn5 and Ni3Sn4: First‐Principles Study

In the field of electronic packaging, Ni 3 Sn 4 ‐based and η′‐Cu 6 Sn 5 ‐based compounds are common Sn‐based intermetallic compounds into which doping of other appropriate elements has been widely studied. Herein, the structural stability, mechanical properties, and electronic structures of (Ni,Co) 3 Sn 4 and η′‐(Cu,Co) 6 Sn 5 are systematically investigated using first‐principles calculations. By comparing the heat of formation of the doped and undoped intermetallic compounds, it is found that the doped Ni 3 Sn 4 structure has a higher heat of formation and a less stable structure, while the doped η′‐Cu 6 Sn 5 structure has a lower heat of formation and a more stable structure. The doped Ni 3 Sn 4 exhibits an increasing bulk modulus ( B ) and Young's modulus ( E ), and the doped η′‐Cu 6 Sn 5 exhibits a gradually increasing bulk modulus ( B ). These findings suggest that doping improves the rigidity and elastic deformation properties of the two intermetallic compounds. And yet the anisotropy of both intermetallic compounds is decreasing as doping concentration increases. According to the calculations of the electronic structures, the doped (Ni,Co) 3 Sn 4 structure and the doped η′‐(Cu,Co) 6 Sn 5 structure exhibit stronger metallicity. In addition, stronger Co–Sn ionic bonds are formed in the doped Ni 3 Sn 4 and η′‐Cu 6 Sn 5 structures. This suggests that the doped Ni 3 Sn 4 and η′‐Cu 6 Sn 5 structures are harder.