Study on morphology and interface relationship between Ag3(Sn, In) and Cu6(Sn, In)5

The morphology, orientation and growth relationships of the intermetallic compounds (IMCs) Ag3(Sn, In) and Cu6(Sn, In)5 at the Sn-3.5Ag-0.5Bi-8.0In solder/Cu substrate interface were investigated. The Ag(Sn, In) at the interface is "flower-like". However, when the reflow parameters were changed and the cooling rate was increased, Ag3(Sn, In) had difficulty in nucleation. A preferential orientation relationship between the Ag3(Sn, In) phase and the Cu6(Sn, In)5 substrate was established. An angle of 35° existed between the adjacent Ag3(Sn, In) grains and Cu6(Sn, In)5 grains. In addition, coincident mismatch relationships were found between specific crystallographic planes of Ag3(Sn, In) and Cu6(Sn, In)5. The (001) crystallographic plane of Ag3(Sn, In) and the (0001) crystallographic plane of Cu6(Sn, In)5 have a mismatch of 12.23% and are more likely to form a coherent interface.