LAUSR

The fragility of Au80Sn20 eutectic solder is the major bottleneck of its application, which origins from the coarse primary ζ′-phase and the intrinsic brittleness of irregularly eutectic structure. To tackle this problem, various solidification processes have been adopted in this work, and the influence of those processes on phase composition and eutectic microstructure is studied. The results show that simply increasing the cooling rate does not prevent the formation of detrimental ζ′-Au5Sn phases, although the resulting eutectic morphology changes from dendritic to isometric. Applying magnetic field into rapid solidification can effectively remove the primary ζ′-Au5Sn phases, which is attributed to the fission of primary crystal nucleus during the fast eutectic nucleation course. The alloys through magnetic-field-induced rapid cooling exhibit a superior room-temperature compressive property, and the fracture stress and strain reach up to 1456.7 MPa and 64% respectively. Our finding on the effect of cooling rate and magnetic field on solidification not only sheds light on future research direction but also provides practical guidance to the engineers in solder industry.