A high-performance Sn–Sb–Cu alloy processed by pressure heat treatment: microstructure, thermal and mechanical properties

Abstract

Here, we present a notable achievement in the development of Sn-5.5Sb-0.7Cu (SSC-557) alloy by employing pressure heat treatment (PHT) during the casting process. The resultant SSC-557-PHT alloy exhibits remarkable mechanical properties and demonstrates superior thermal characteristics. In comparison to the commonly utilized SSC-557 alloy, the SSC-557-PHT alloy demonstrates a substantial increase in both yield strength (YS) ~ 90.5% and ultimate tensile strength (UTS) ~ 86.8% at room temperature (RT), while preserving its ductility. The remarkable strength properties exhibited by the SSC-557-PHT alloy can be attributed to various factors. First, the alloy benefits from the reinforcement of fine-grain structure, thereby augmenting its overall mechanical performance. Moreover, the formation of a heterogeneous structure and the reduction in size of Cu₆Sn₅ and SbSn IMCs contribute significantly to the enhanced strength characteristics. These refined structures effectively serve as sources of dislocation and obstacles, thereby further enhancing the mechanical strength of the alloy. Furthermore, differential scanning calorimetry (DSC) analysis was conducted, revealing notable changes in thermal behavior after the application of pressure heat treatment (PHT). Specifically, the peak temperature decreased from 243.7 to 235.4 °C, the pasty range narrowed from 6.2 to 4 °C, and the undercooling decreased from 9.1 to 3.2 °C. These findings highlight the positive impact of PHT on the alloy’s thermal characteristics, making it more suitable for practical applications. The results obtained in this study are expected to contribute significantly to closing the existing knowledge gap regarding the performance characteristics of recently developed solder alloys when subjected to PHT.