Microstructure refinement, thermal stability and mechanical properties improvements of Sn-3.0Ag-0.5Cu-xSb

Abstract

This study systematically elucidates the effects of antimony (Sb) additions (0, 0.5, and 1.5 wt%) on the microstructure, thermal stability, wettability, and mechanical performance of SAC305 solder alloys at both bulk and solder joints. The results demonstrate that incorporating 1.5 wt% Sb leads to significant microstructure refinement as evidenced by a 66 % reduction in crystallite sizes of β-Sn phase through Synchrotron X-ray Diffraction. Synchrotron micro-XRF mapping analysis further confirmed a uniform distribution of Sb within the matrix phase, which contributes to enhanced grain refinement. Additionally, Sb addition reduces the interfacial intermetallic compound (IMC) layer thickness by 9 %, enhancing joint reliability. The undercooling values were also reduced with increasing Sb content, indicating improved thermal stability. The growth restriction factor (Q) was calculated, and the results demonstrated that the Q value increased from 13.82 to 15.62 with 1.5 wt% Sb addition highlighting Sb’s role as an effective grain refiner. Mechanical testing confirmed that Sb additions enhance the mechanical performance of both bulk solder and solder joints primarily through solid solution strengthening mechanisms. By employing advanced synchrotron-based characterization techniques to quantitatively correlate Sb-induced microstructure refinement with improved mechanical and thermal properties, these findings contribute to a deeper understanding that is crucial for optimizing reliability in electronic packaging systems while providing new insights into the role of Sb in optimizing the performance and reliability of SAC305 solder alloys.