Strength-enhanced Sn–In low-temperature alloy with surface-modified ZrO2 nanoparticle addition

Abstract

Low-temperature packaging is essential for the widespread use of flexible electronic devices, and Sn–In eutectic alloys have attracted considerable attention because of their low melting temperatures. However, these alloys have a lower strength compared with other types of solder alloys. This study aimed to investigate the effect of adding nanoparticles on the mechanical strength of Sn–In eutectic alloys while keeping their melting temperature unchanged. ZrO2 nanoparticles coated with NiO (NiO/ZrO2 nanoparticles) were utilized to strengthen Sn–In eutectic alloys with a high dispersity. Sn–In composite alloys reinforced with NiO/ZrO2 nanoparticles were fabricated, and tensile strength evaluation and microstructure observations were conducted. The experimental results showed that the addition of nanoparticles to the Sn–In eutectic alloys did not change their melting behavior. The tensile strength of the Sn–In composite alloys reinforced with NiO/ZrO2 nanoparticles increased by up to 35.6%, which was attributed to grain refinement and dispersion strengthening. Even after thermal aging at 60 ºC, the Sn–In composite alloys reinforced with NiO/ZrO2 nanoparticles showed a 1.11 times higher ultimate tensile strength than that of the non-aged, non-reinforced eutectic alloy, despite grain coarsening. This was attributed to the contribution of dispersion strengthening. These results indicate that the addition of NiO/ZrO2 nanoparticles is an effective method to improve the strength of low-melting-temperature alloys.