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Abstract: This study forms composite solders by adding 0.5–3wt% of Ni particles in situ to Sn–3.5wt%Ag lead-free solder. Cu/solder/Cu specimens are prepared by dipping two Cu rods into a solder bath to produce a solder joint. Some of the joint specimens are retained in the as-soldered condition, while the others are aged at 150°C for 100, 200, 400, or 500h, respectively. The experimental results reveal that the addition of Ni to the molten Sn–Ag solder leads to the formation of in situ Ni3Sn4 dispersoids. The adhesive strength of the joint is found to increase with increasing Ni content in the as-soldered specimens. In general, the strength of the thermally processed specimens reduces as the thermal storage time increases. The Sn–Ag–0.5wt%Ni joints show a mixture of ductile and brittle fracture, whereas the joints containing more than 1wt% of Ni show mainly brittle fracture with solder residue at the exposed (Cu,Ni)6Sn5 IMC layer. [Copyright &y& Elsevier]

In this study, various amounts of Ni particles were added in situ to Sn–3·5 wt-%Ag lead free solder to form new composite solders. Copper substrates were then dipped into these solders and aged at 150°C for 0, 25, 225, or 1000 h. The microstructure and microhardness of the as solidified solder and the aged solder/copper couples were investigated. Experimental results revealed that the addition of Ni particles increased the microhardness of the composite solder. Ni additions of less than 3 wt-% yielded a microstructure of β-Sn grains surrounded by a eutectic mixture of Ag3Sn and a Sn rich matrix. An intermetallic compound of Ni3Sn4 particles was dispersed throughout the eutectic. For 5 wt-%Ni addition, the Ni3Sn4 phase and the remaining Ni particles were agglomerated. In the case of copper substrate dipped with a thick layer of composite solder, water quenched and then aged at 150°C, the induced (Ni, Cu)3Sn4 particles coarsened and agglomerated. Additionally, the intermetallic (Cu, Ni)6Sn5 compound layer formed at the solder/Cu interface thickened with increasing Ni content. [ABSTRACT FROM AUTHOR]