Effect of Solder Structure on the In-situ Intermetallic Compounds growth Characteristics of Cu/Sn-3.5Ag Microbump

Abstract

Thermal annealing tests were performed in an in-situ scanning electron microscope chamber at 130 o C, 150 o C, and 170 o C in order to investigate the effects of solder structure on the growth kinetics of intermetallic compound (IMC) in Cu/Sn-3.5Ag microbump. Cu/Sn-3.5Ag(6 µm) microbump with spreading solder structure showed Cu 6 Sn 5 and Cu 3 Sn phase growths and then IMC phase transition stages with increasing annealing time. By the way, Cu/Sn-3.5Ag(4 µm) microbump without solder spreading, remaining solder was transformed to Cu 6 Sn 5 right after bonding and had only a phase transition of Cu 6 Sn 5 to Cu 3 Sn during annealing. Measured activation energies for the growth of the Cu 3 Sn phase during the annealing were 0.80 and 0.71eV for Cu/Sn-3.5Ag(6 µm) and Cu/Sn-3.5Ag(4 µm), respectively.