Interfacial IMC evolution and mechanical performance of In-doped Sn58Bi solder joints subjected to isothermal aging

Purpose This study aims to restrain excessive brittle Bi-phase coarsening, segregation and the consequent mechanical reliability deterioration of Sn58Bi solder joints during high-temperature service, 0.3 Wt.% indium particles were doped into SnBi solder and the interfacial intermetallic compound (IMC) evolution and mechanical performance of SnBi-In solder joints subjected to isothermal aging were studied. Design/methodology/approach Sn58Bi solder containing 0.3 Wt.% In particles was prepared to fabricate Sn-based solder joints. Specimens underwent isothermal aging treatment up to 500 h. Comparisons on IMC layer thickness, Bi microstructure evolution and shear strength evolution were systematically characterized and measured for pristine and In-doped solder joints. Findings IMC thickness rises with aging time for two solders. In doping slightly accelerates Cu6(Sn,In)5 growth yet drastically restricts brittle Cu3Sn formation. It also mitigates Bi grain coarsening to acquire uniform microstructures. After 500 h aging, pure Sn58Bi shear strength falls from 34.7 MPa to 29.4 MPa, whereas In-modified joints maintain a shear strength of 32.5 MPa with better mechanical retention. Originality/value Minor In particle doping optimizes interfacial phase constitution and refines Bi microstructure during aging. It alleviates mechanical performance attenuation and improves the long-term structural and mechanical reliability of Sn58Bi low-temperature solder joints for electronic packaging applications.