Interfacial Reactions of Sn-58Bi and Sn-9Zn Lead-Free Solders with Au/Ni/SUS304 Multi layer Substrate

The liquid/solid interfacial reactions of Sn-58Bi (SB) and Sn-9Zn (SZ) lead-free solders with Au/Ni/SUS304 multilayer substrates have been investigated in this study. In the SB/Au/Ni/SUS304 couple, only the Ni3Sn4 phase with needle-like grains was formed at the SB/Au/Ni/SUS304 interface. The Ni5Zn21 phase with a column structure was formed at the SZ/Au/Ni/SUS304 interface. The thickness of both intermetallic compounds (IMCs) increased with increasing reaction temperature and time. Meanwhile, the growth mechanism of these two IMCs is seen to follow a parabolic law and is diffusion controlled.