Microstructure, corrosion behaviour and microhardness of a directionally solidified Sn-Cu solder alloy

Sn-Cu alloys are becoming interesting lead-free solder alternatives. However, little is known on the effects of the cooling rate during the solidification stage of the soldering process on the resulting microstructures of these alloys, as well as on the microstructure-properties relationships. Requirements such as the mechanical strength and the corrosion resistance are of prime interest in order to confirm such alternatives. In the present study, an interrelation of experimental results of a Sn-2.8 wt%Cu solder alloy, which include the cooling rate and the growth rate during solidification, the morphology of intermetallic particles, the segregation pattern and the resulting corrosion potential and rate, polarization resistance, capacitance and Vickers microhardness is developed. It is shown that the cooling rate plays an important role on the microstructure formation affecting significantly the resulting electrochemical behaviour and that coarser microstructural arrays have higher electrochemical corrosion resistance. (C) 2011 Elsevier Ltd. All rights reserved.