EBSD characterization of Ag3Sn phase transformation in Sn–Ag lead-free solder alloys: a comparative study before and after heat treatment

The phase transformation and microstructural evolution of Sn–Ag solder alloys under heat treatment, with a focus on the Ag 3 Sn phase, were investigated to address the need for reliable lead-free solder alternatives in electronic packaging. Initially, the solder alloy exhibited a fine eutectic structure with well-dispersed Ag 3 Sn particles and a polycrystalline grain structure devoid of any strong crystallographic texture. Following heat treatment, significant microstructural changes were observed, including the coarsening of the Ag 3 Sn phase and the development of a preferred grain orientation, suggesting recrystallization and grain growth. XRD analysis revealed a decrease in the intensity of the Sn phase peaks and an increase in the coarseness of the Ag 3 Sn peaks post-heat treatment, indicating phase evolution and redistribution of silver within the alloy. The EBSD results supported the SEM findings, showing elongation and growth of grains and a shift in texture. These changes imply that heat treatment can significantly alter the mechanical properties of Sn–Ag solders, particularly affecting creep resistance and hardness due to the evolution of anisotropic mechanical properties. The study provides essential insights into the selection and optimization of solder materials for high-reliability applications in the electronics industry.