Two-dimensional mapping of the mechanical properties of Pb-free solders for reliability optimisation

The development of thermomechanical models of Pb-free solders is more complex than Pb-Sn solders as a result of the higher reactivity and processing temperature that leads to the presence of stiff and angular intermetallics in the microstructure. In this paper, nanoindentation was explored for its potential to characterize mechanically the complex microstructure of Pb-free solder joints. Hardness and elastic modulus of the various micro-phases in a Sn-Ag-Cu/Cu solder joint were characterized at 25°C and averages obtained from nanoindentation maps composed of 100 to 200 indentations. The possibility to map mechanical property gradients across the various solder joint interfaces has been suggesting to be useful in extending the available data for constitutive models used in reliability simulations of Pb-free solders