Small-angle neutron scattering analysis in Sn-Ag Lead-free solder alloys: A focus on the Ag₃Sn intermetallic phase

This study addresses the critical need for lead-free solder alternatives in electronic manufacturing by investigating the microstructural characteristics of Sn-Ag solder alloys, focusing on the Ag₃Sn intermetallic phase. Utilizing Small-Angle Neutron Scattering (SANS), the study explored the phase interface and grain structure within Sn-Ag alloy to identify attributes that influence mechanical stability and performance. The research was structured around a comprehensive SANS analysis, complemented by Electron Backscatter Diffraction (EBSD) to expose the morphology and orientation of crystalline phases within the material. The investigation revealed distinct scattering patterns indicative of a multi-phase structure with a homogeneous distribution of fine Ag₃Sn precipitates within a β-Sn matrix. EBSD data confirmed these findings, showing a wide range of grain sizes and a random orientation distribution that matches theoretical models for polycrystalline materials. Notably, the SANS data uncovered a specific size distribution of the Ag₃Sn phase, which was characterized by a sharp interface contrast against the β-Sn matrix, pivotal for understanding the solder's mechanical properties. Interpretation of the SANS and EBSD data sets suggests that the Sn-Ag alloy's performance is significantly influenced by the dispersion and morphology of the Ag₃Sn phase. The presence of nanoscale Ag₃Sn structures, exhibiting a needle-like surface, implies a material optimized for mechanical reinforcement, which is essential for robust electronic connections. The integrated approach offers a novel perspective on the nano structural arrangement of lead-free solders, contributing to the advancement of safer, more reliable electronic materials. The findings have significant implications for the development of next-generation electronic components, reinforcing the transition to environmentally benign manufacturing processes.