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 Ag 3 Sn 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 Ag 3 Sn 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 Ag 3 Sn 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 Ag 3 Sn phase. The presence of nanoscale Ag 3 Sn 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. • Utilized Small-Angle Neutron Scattering (SANS) and Electron Backscatter Diffraction (EBSD) to comprehensively investigate the microstructural properties of Sn-Ag lead-free solder alloys • Provided detailed characterization of the Ag3Sn intermetallic phase, revealing its morphology, size distribution, and dispersion within the β-Sn matrix. • Employed Guinier and Porod analysis to derive quantitative parameters from SANS data, offering insights into the material's specific surface area and fractal dimensions. • The SANS analysis uncovered a homogeneous distribution of fine Ag3Sn precipitates within the β-Sn matrix