Intermetallic evolution between Sn-3.5Ag-1.0Cu-xZn lead free solder and copper substrate under long time thermal aging (x: 0, 0.1, 0.4, 0.7)

Due to environmental concern regarding toxicity of lead-based solder, the lead-free solders were introduced as a replacing solder in microelectronics devices technology. In this study, the effects of 0.1, 0.4 and 0.7 wt% Zn additions on the intermetallic formation and thickness of Sn-3.5Ag-1.0Cu solder on Cu substrate after long time aging were investigated. The X-Ray Diffraction (XRD) analysis shown that there were Cu₆Sn₅, Cu₃Sn, β-Sn, CuZn and Ag₃Sn phase formed after sintering process. The morphology of the intermetallic was observed under Scanning Electron Microscope (SEM) and the elemental distribution was confirmed by Energy Dispersive X-ray (EDX). The intermetallic thickness increases as the aging temperature increases while the addition of zinc into the system has suppressed the intermetallic formation.