Published online by Cambridge University Press: 15 February 2011
This study was conducted in order to determine and understand the effect of substrate on eutectic In-Sn. Samples for mechanical testing were produced with either bare Cu or Ni on Cu substrates. Both the microstructure and the mechanical behavior are strongly dependent on substrate, with In-Sn on Cu having a non-uniform and irregular microstructure and In-Sn on Ni having a uniform, normal colony-based eutectic. Deformation is more uniform in the In-Sn on Ni, while it is concentrated along the length of the joint in the In-Sn on Cu. This is reflected in the different shapes of stress-strain curves between In-Sn on Cu and In-Sn on Ni. The stress exponents and activation energies for creep also vary with substrate. Creep deformation is governed by the In-rich γ phase for In-Sn on Cu and by the Sn-rich y phase for In-Sn on Ni. If In-Sn on Ni samples are aged, the microstructure coarsens and the mechanical behavior changes to resemble that of the as-cast In-Sn on Cu.