Microstructure evolution and properties of rapidly solidified Au-20Sn eutectic solder prepared by single-roll technology

The current chip-level Au-Sn solder production process is very complex, to simplify the process while improving the quality of the solder, Au-20Sn solder ribbon was prepared by single-roll rapid solidification technology. The microstructure evolution, composition distribution, phase composition, melting characteristics, wettability and mechanical properties of the solder were studied. The rapidly solidified Au-20Sn solder alloy consisted of a small amount of primary ζ′-Au5Sn dendrites and eutectic structure (ζ′-Au5Sn+δ-AuSn). The microstructure was refined and the components were evenly distributed, while no new phase was formed during the annealing. With Sn element diffused into the δ-AuSn phase from the ζ′-Au5Sn phase, the ζ′-Au5Sn phase was decomposed and the δ-AuSn phase grew up and distributed in the matrix. After rolling, the δ-AuSn phase was elongated along the elongation direction of the ribbon, and the elements were further segregated. Ultimately, compared to the cast-rolling Au-20Sn solder, the melting range was narrower, and the wettability and the shear strength of the solder joint improved.