Microstructure and shear properties of interconnect interface between multi-phase heterogeneous SnBi eutectic alloy and Cu substrate

The microstructures of the interconnect interfaces between Sn58Bi eutectic alloy and Sn53Bi3Cu3Zn2Ag2Sb multiphase alloy and Cu substrate, as well as the strength of the interconnect joints were systematically studied after 1008 h thermal aging at 70℃. Compared with the unmodified Sn58Bi alloy, the addition of alloying elements inhibited the coarsening of the organization and the growth of intermetallic compound (IMC) at the interconnect interface. At the same time, the Cu₃(Sn, Zn) phase in the upper part of the IMC and twinned Cu in the substrate can contribute to enhanced the mechanical properties of the interconnect joints. Compared to their respective shear strengths after reflow, the strength of the modified Sn53Bi3Cu3Zn2Ag2Sb/Cu interconnect joints increased by 22.3 %, while the strength of the Sn58Bi/Cu interconnect joints decreased by 18.3 % after thermal aging. This study indicate that alloying modification can effectively improve the shear strength of interconnect joints during aging, thus improving interconnect reliability.