In-depth investigation of multi-element alloying on the microstructure and mechanical properties of Sn7Sb/Cu joints

The rapid development of large-scale data exchange and high-power devices necessitates that interconnect joints with enhanced load-bearing capacity and mechanical stability under varying conditions. Traditional SAC and Sn5Sb interconnect materials fall short of meeting these stringent requirements. This study investigates novel multi-alloys SACN-2.7In, SACN-4Bi and SACN-5Bi by incorporating Ag, Cu and In or Bi into Sn7Sb0.05Ni (SN) to evaluate the microstructure and mechanical properties of SN alloys and the corresponding joints. The results indicate that alloying elements reduce the melting point and widen the melting range of solder alloys. The internal microstructure of SN/Cu joints consists of β-Sn matrix, (Cu,Ni) 6 Sn 5 and SnSb phases. SACN-2.7In/Cu joints form additional Ag 3 Sn and InSb phases, while SACN-4Bi/Cu and SACN-5Bi/Cu joints develop Ag 3 Sn and Bi phases. Multi-alloying results in thinner, flatter interfacial IMC layers and enhances mechanical properties, with increased shear strength and hardness. Tensile tests conducted at 25, 80, 120, and 160 °C under strain rates of 0.0001, 0.001, and 0.01 s -1 , which reveals SACN-2.7In's superior ultimate tensile strength over SN alloys. The alloying elements modify the second phase's type and quantity in the matrix, strengthening diffusion mechanisms and improving properties. The SnSb phase's solid solution enhances alloy plasticity, with deformation indices increasing above 120 °C. Among the tested alloys, SACN-2.7In emerges as the most promising candidate. These results under wide rate and temperature ranges tests provide a new connection solution for high-density and high-power packaging, addressing the traditional challenges of balancing strength and plasticity in solder materials and insufficient high-temperature stability.