Enhancement mechanism of Te doping on microstructure, wettability and mechanical properties of Sn–Bi-based solder

Sn–Bi-based solder alloys have sparked tremendous research interest towards the development of low-temperature interconnecting materials in multi-level packaging interconnections electronic devices. Nevertheless, the research speed of solder is elusive to match well with the rapid development of integrated circuit design and manufacturing, which leads to the slow renewal course of electronic products. In the pursue for more effective modification strategies, Te was selected to be doped into Sn58Bi–1Sb (SBS) solder. As expected by the design, Te existed in the solder matrix in the form of solid solution and intermetallic compound simultaneously. To our satisfaction, Te enormously improved both the tensile strength and plasticity of the SBS solder. This largely circumvents the negative correlation between strength and plasticity during the modification process. Additionally, Te element significantly optimized the thermal properties, wettability, and creep resistance of SBS solder. Many tiny Bi particles embedded in Sn phase and strengthened the SBST solder matrix as the second phase. More strikingly, numerous Bi twin crystal structures were observed in the Sn58Bi–1Sb1Te (SBST) solder matrix, which occurred in Sn–Bi-based solder matrixes first time. The Bi phase twin represents preferable deformation ability of Bi phase and the plasticity of the solder matrix. It indicated that the doping of Te comprehensively enhanced the performance of SBS solder and may opened new horizons to the design route of alloying modification for Sn–Bi-based solder.