摘要
The effect of Sn orientation on thermomigration was investigated in Cu/Sn2.3Ag/Ni microbumps with diameter of 20 μm. Results showed that anisotropic diffusion of Cu in Sn grains affected both formation rates and locations of Cu 6 Sn 5 intermetallic compounds (IMCs). Rapid growth of Cu 6 Sn 5 IMCs at the cold-end 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 Cu 6 Sn 5 IMCs near the grain boundary inside the solder.