The atomic-scale structure, stability, and bonding characteristics of Ag(224)/Ag3Sn(002) interfaces based on the first-principles calculation

Ag3Sn plays a connecting role in the bonding between a Sn-based solder and an Ag substrate due to its excellent connectivity performance. Therefore, it is particularly important to explore the Ag3Sn/Ag interface. The binding energies, interfacial energies, wetting behaviors, electronic structures, and interfacial bonding properties of fourteen Ag(2̄2̄4)/Ag3Sn(002̄) interfaces were investigated by using the first-principles calculation. The layer spacing convergence results show that an eight-layered Ag(2̄2̄4) surface and a nine-layered Ag3Sn(002̄) surface are enough thick to be chosen for the interface models. The calculated results showed that the surface energies are 0.91 , 0.91–0.96, and 0.70–0.75 J/m2 for the Ag(2̄2̄4) surface, Ag3Sn(002̄) surface I, and Ag3Sn(002̄) surface II, respectively. It is shown that the interface I (A-Sb) configuration is the most stable structure with the largest adhesion work and the smallest interface energy. The calculation results for the contact angle indicated that the interface I (A-Sb) configuration exhibits good wettability. The density of states and electron difference density were calculated for the four most representative interfacial configurations. In addition, the results showed that the main bonding characteristic of the interface I (A-Sb) configuration is composed of Ag–Sn and Ag–Ag covalent bonds.