In this work, formation and evolution of microstructures in CuSn/Pt bonding were investigated after 320 °C reflow process as well as after high temperature storage test at 150 °C. Sputtered thin film platinum on silicon wafer and high purity platinum sheet were applied as contact metallizations for electroplated copper-tin based bonding metallurgy. As bonded microstructure showed PtSn4 intermetallic compound growth at the Pt/Sn interface, and both Cu6Sn5 and Cu3Sn phases formed at the Cu/Sn fiinterface. Both hexagonal and monoclinic Cu6Sn5 were found to coexist after 1000 h high temperature storage test. Platinum was discovered to dissolve into the Cu6Sn5 phase during soldering process and form (Cu, Pt)6Sn5 intermetallic compound exhibiting hexagonal allotropy. Meanwhile, under annealing, monoclinic Cu6Sn5 phase layer without platinum was observed to form between (Cu, Pt)6Sn5 grains and tin. Thermodynamic analysis was performed in order to reason the effects of Pt on the phase equilibria and phase stabilities. Results show that platinum has a significant impact on the stability of hexagonal Cu6Sn5.
|Number of pages||11|
|Journal||Journal of Materials Science: Materials in Electronics|
|Publication status||Published - 16 Jul 2018|
|MoE publication type||A1 Journal article-refereed|