Bi-induced voids at the Cu3Sn/Cu interface in eutectic SnBi/Cu solder joints

Transmission electron microscopy evidence was obtained to elucidate the mechanism for Bi-induced interfacial void formation in solder joints. After thermal aging, Bi segregated to the Cu3Sn/Cu to form fine particles on the interface in SnBi/Cu solder joints. Interfacial voids were found near the interfacial Bi particles.