Effect of Sn grain orientation on growth of Cu-Sn intermetallic compounds during thermomigration in Cu-Sn2.3Ag-Ni microbumps

Abstract

The effect of Sn orientation on thermomigration was investigated in Cu/Sn2.3Ag/Ni microbumps with diameter of 20 mu m. Results showed that anisotropic diffusion of Cu in Sn grains affected both formation rates and locations of Cu6Sn5 intermetallic compounds (IMCs). Rapid growth of Cu6Sn5 IMCs at the coldend interface was observed when the c-axis of Sn grains was parallel to the temperature gradient. In addition, diffusion of Cu atoms was blocked by a Sn grain with a high angle between the Sn c-axis and the thermal gradient, resulting in formation of Cu6Sn5 IMCs near the grain boundary inside the solder. (C) 2018 Elsevier B.V. All rights reserved.