Homogeneous (Cu, Ni)₆Sn₅ intermetallic compound joints rapidly formed in asymmetrical Ni/Sn/Cu system using...

Homogeneous (Cu, Ni)₆Sn₅ intermetallic compound (IMC) joints were rapidly formed in asymmetrical Ni/Sn/Cu system by an ultrasound-induced transient liquid phase (TLP) soldering process. In the traditional TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system consisted of major (Cu, Ni)₆Sn₅ and minor Cu₃Sn IMCs, and the grain morphology of (Cu, Ni)₆Sn₅ IMCs subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the joints. However, in the ultrasound-induced TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system only consisted of the (Cu, Ni)₆Sn₅ IMCs which exhibited an uniform grain morphology of rounded shape with a remarkably narrowed Ni concentration gradient. The ultrasound-induced homogeneous intermetallic joints exhibited higher shear strength (61.6 MPa) than the traditional heterogeneous intermetallic joints (49.8 MPa).