Small-angle neutron scattering analysis in graphene reinforced Sn–Ag lead-free solder alloys

The addition of Graphene Nano Sheets (GNS) to Sn–Ag alloys presents a promising approach for enhancing lead-free solder materials, aiming to improve structural integrity and mechanical properties for electronic applications. In this study, we investigate the microstructural evolution and property enhancements in a Sn–Ag-GNS composite using Small-Angle Neutron Scattering (SANS), X-Ray Diffraction (XRD), and Electron Backscatter Diffraction (EBSD) techniques. SANS analysis indicates that the specific surface area of the Sn–Ag-GNS composite increased from 2.4 m²/g in the base Sn–Ag alloy to 3.2 m²/g with the addition of GNS—a 25% rise that reflects the introduction of additional interfaces by the graphene. Furthermore, the fractal dimension (Df) decreased from 3.0 to 2.7, pointing to the development of rougher and more intricate interfacial structures that can enhance crack resistance and overall toughness. Such a reduction in fractal dimension reflects increased interfacial roughness, which is known to promote crack deflection and tortuous crack paths, thereby enhancing energy dissipation and resistance to crack propagation. The incorporation of GNS also disrupts the initial crystallographic texture, leading to a more isotropic grain orientation, which in turn promotes uniform mechanical behavior in all directions. Together, these findings demonstrate that GNS significantly improves the microstructure of Sn–Ag alloys by introducing refined grain structures, enhanced interfacial complexity, and increased isotropy, which are microstructural features commonly associated with enhanced mechanical performance and reliability in Sn-based solder systems. This study underscores the potential of GNS-reinforced Sn–Ag alloys as high-performance, lead-free solder materials suitable for modern electronic applications.