Mechanical properties of Sn–Ag lead-free solder alloys based on the dendritic array and Ag3Sn morphology

The aim of this experimental investigation is to evaluate the tensile properties of as-cast Sn–Ag alloys as a function of both the resulting secondary dendritic arm spacings and the morphology of the Ag3Sn IMC (intermetallic compound). This comparative experimental investigation was carried out with a view to assess the application of Sn–Ag alloys as alternative solder materials. A directional water-cooled solidification apparatus was used to obtain the as-cast samples. The resulting microstructures, ultimate and yield tensile strengths and elongation of Sn–2 wt.% Ag and Sn–3.5 wt.% Ag alloys were experimentally determined and compared with the corresponding results of the traditional Sn–40 wt.% Pb solder alloy. It was found that the Sn–Ag alloys examined comply with the compromise between compatible mechanical strength and environmental protection.

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► Dendrite array and Ag3Sn IMC affect the mechanical behavior of Sn–Ag alloys.
► Combined fiber-like Ag3Sn/tertiary dendritic arms seems to increase the elongation.
► Tertiary dendritic arms affect both UTS and YS results in a Sn–3.5 wt.% Ag alloy.