Microstructures of Pb-Free Solder Joints by Reflow and Thermo-Compression Bonding (TCB) Processes

Differences in microstructures of lead-free solder joints, Sn-Ag-Cu (96.5 wt./3.0 wt./0.5 wt.% SAC-305), made by two different semiconductor packaging processes such as reflow and TCB are discussed. Despite the enormous potential for TCB solder bonding process in microelectronic packaging, there has been few studies regarding the comparative analysis on electro-migration (EM) failure mechanism for the reflow process. We have systematically examined the EM-derived failures of the reflow and TCB-processed solder joints and demonstrated a process-structure-property linkage. This study also includes the analysis performed using generalized spherical harmonics (GSH) representation, a statistical and quantitative measure of material crystallographic informatics, which is novel in this field as to analyzing solder joint microstructures.