The In–48Sn eutectic alloy has emerged as a favorable solder for flexible electronic devices, owing to its low operating temperature. However, the low strength of In–48Sn eutectic alloy compared with that of other commercial solders affects the product life and limits its use in the device applications. Herein, we studied the effects of xCu addition (x = 1.0, 2.0, and 8.0 wt %) on melting temperature, phase segregation, and mechanical properties of In–Sn alloy. The results revealed that the melting temperatures of the In–Sn–Cu (ISC) alloys were close to that of eutectic In–Sn alloy (115 °C) due to the ternary reaction in the ISC alloys. In addition, the initial solidification temperature of the η-(Cu,In,Sn) compound took place below 400 °C, and partial solid-transformation to ternary τ-Cu₂In₃Sn occurred in the temperature range 83–78 °C, owing to the diffusion of Cu-atoms and consumption of the β-In₃Sn phase in the new ISC alloys. The phase segregation affected the phase fraction in the ISC matrix and the mechanical properties of ISC alloys. Furthermore, the In–Sn-1.0Cu alloy exhibited the highest elongation of 74%, which was more than twice that of In–48Sn alloy. Simultaneously, the In–Sn-8.0Cu alloy presented the highest tensile strength of approximately 17.0 MPa, which was 1.5 times that of the In–48Sn alloy.

In-48Sn共晶合金由于其较低的工作温度而已成为柔性电子设备的理想焊料。但是，与其他商用焊料相比，In-48Sn共晶合金的低强度会影响产品寿命并限制其在器件应用中的使用。在这里，我们研究了添加xCu（x = 1.0、2.0和8.0 wt％）对In-Sn合金的熔化温度，相偏析和力学性能的影响。结果表明，由于ISC合金中的三元反应，In-Sn-Cu（ISC）合金的熔融温度接近共晶In-Sn合金的熔融温度（115°C）。此外，η-的初始固化温度（铜，铟，锡）化合物发生低于400℃，和部分固变换到三元τ-Cu系₂在₃的Sn发生在温度范围83-78℃，由于铜原子的扩散和消费β-在₃在新的ISC合金Sn相。相分离影响了ISC基体中的相分数和ISC合金的机械性能。此外，In-Sn-1.0Cu合金的最高伸长率达到74％，是In-48Sn合金的两倍以上。同时，In-Sn-8.0Cu合金的最高拉伸强度约为17.0 MPa，是In-48Sn合金的1.5倍。