Interfacial Reactions between Lead-Free Solders and the Multilayer Au/Ni/SUS304 Substrate

Abstract

Abstract Interfacial reactions between Sn, Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC) and an Au/Ni/SUS304 stainless steel (SUS304) substrate were conducted using the reaction couple technique at 240, 255 and 270 °C for 1 – 5 h. In the earliest stage of the reaction, only the Ni 3 Sn 4 phase was formed on the Sn/Au/Ni/SUS304 interface. As the reaction time increased to 4 h, the Ni layer was gradually consumed and the Ni 3 Sn 4 phase detached from the interface. Meanwhile, the Sn reacted with the SUS304 to form the FeSn 2 phase. In the SAC/Au/Ni/SUS304 reaction couple, both Ni 3 Sn 4 and Cu 6 Sn 5 phases were formed on the interface. When the reaction time exceeded 4 h, the Ni 3 Sn 4 phase disappeared; the Cu 6 Sn 5 phase was spread over the SUS304 surface and the FeSn 2 phase was formed on the SUS304 surface. The growth of intermetallic compounds can be described by the parabolic law and the reactions were diffusion-controlled.