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

Abstract

The self-healing of Kirkendall voids (KVs) was observed on the interface between Sn and (111) oriented and nanotwinned Copper ((111)nt-Cu) during aging. Around 85 % of KVs healed up after 288 h aging, while the interfacial Cu3Sn intermetallic compound (IMC) layer decreased its thickness noticeably. This is mainly due to the high Cu diffusivity on (111) plane. In addition, the wettability of Sn on (111)nt-Cu was higher than those of conventional polycrystalline Cu (C-Cu) and (110) textured Cu ((110)Cu), since (111)nt-Cu was less prone to be oxidized during reflow. For (110)Cu, the IMC layer growth was restrained after reflowing and thermal aging, which is strongly related to the slow Cu diffusivity along the (110) plane.