Abstract
In this study, the evolution of grain structures in Cu/Sn-3.5Ag/Cu-xZn (x=0 or 15 wt%) microbumps and SAC305/Cu-xZn solder joints was investigated. Due to the small size of microbumps, impingement of interface IMCs easily occur. In a Cu/Sn-3.5Ag/Cu (wt%) microbump, the grain orientation of combined intermetallic compounds (IMCs) tends to be homogenous and closely-grouped, allowing cracks to more easily propagate. In order to examine the grain evolution of Cu-Sn IMCs, EBSD analysis was applied to microbumps and conventional-sized solder joints. Replacing the Cu substrate with Cu-Zn causes the grain orientation of Cu-Sn IMCs to become more random and dispersed, which may hinder crack propagation. It is thus expected that the reliability of Zn-doped microbumps and solder joints is superior to that of Cu substrate joints. © 2014 Elsevier B.V.