SnPbInBiSb high-entropy solder joints with inhibited interfacial IMC growth and high shear strength

The rapid advancements in microelectronic devices towards miniaturization and multifunctionality have led to an increasing demand for solder joints that exhibit enhanced mechanical properties and reliability. This study focuses on investigating the high-shear strength of SnPbInBiSb/Cu high-entropy solder joints. The analysis encompasses the microstructure evolution, interfacial reactions, and shear behavior of these solder joints after reflowing at 180 °C. The study reveals the formation of very thin intermetallic compound (IMC) layers, specifically Cu₆Sn₅ and Cu₃Sn, at the SnPbInBiSb/Cu interface with an average thickness of about 1.04 μm following a 10min reflow. Transmission electron microscopy (TEM) analysis illustrates the presence of nanoscale precipitates of InSn₃ or Sn₃Sb phases dispersed within the Cu₆Sn₅ IMC. The high mixing entropy of the SnPbInBiSb solder contributes to the suppression of the interfacial IMC growth rate during the reflow process. Notably, the shear strength and fracture behavior of the SnPbInBiSb high-entropy solder joints are significantly influenced by the thickness of the interfacial IMC. In particular, solder joints reflowed at 180 °C for 10 min exhibit a high shear strength of 102.4 MPa with a ductile fracture mode.