The self-healing of Kirkendall voids on the interface between Sn and (1 1 1) oriented nanotwinned Cu under thermal aging

•A self-healing of Kirkendall voids on the Sn/(111)nt-Cu interface was observed during thermal aging.•Around 85 % volume shrinkage of KVs was calculated.•Faster Sn diffusion over Cu in interfacial Cu6Sn5 IMC layer attributed to the Cu3Sn IMC layer decrease around KVs.•Sn showed a higher wettability on (111)nt-Cu over other Cu sheets.•Interfacial IMC layer grew slower on (110)Cu film compared with other Cu sheets.