First-Principles calculations of structural, thermodynamic and electronic properties of intermetallic compounds in solder

First principles calculations have been performed to investigate the structural, thermodynamic and electronic properties of four common intermetallic compounds (IMCs) formed at the solder joints of electronic packages, namely, Cu₆Sn₅, Cu₃Sn, Ni₃Sn₄ and Ag₃Sn. The theoretical heat of formation of Cu₆Sn₅ is close to that of Cu₃Sn, both of them are overestimated relative to the experimental results. In addition, Ni₃Sn₄ has the lowest heat of formation among these IMCs. The curves of total DOS near the Fermi level for the IMCs are mainly dominated by the Sn-sp hybridization states, M (M=Cu, Ni, Ag)-sp hybridization states and M-d states. The complicated bonding states for Ni₃Sn₄ may caused by the position of the main peak of Ni-d states.