  The mechanical properties of $\beta$-Sn single crystals have been
systematically investigated using a combined methodology of micropillar tests
and rate-dependent crystal plasticity modelling. The slip strength and rate
sensitivity of several key slip systems within $\beta$-Sn single crystals have
been determined. Consistency between the numerically predicted and
experimentally observed slip traces has been shown for pillars oriented to
activate single and double slip. Subsequently, the temperature-dependent,
intermetallic-size-governing behaviour of a polycrystal $\beta$-Sn-rich alloy
SAC305 (96.5Sn-3Ag-0.5Cu wt%) is predicted through a multi-scale homogenization
approach, and the predicted temperature- and rate-sensitivity reproduce
independent experimental results. The integrated experimental and numerical
approaches provide mechanistic understanding and fundamental material
properties of microstructure-sensitive behaviour of electronic solders subject
to thermomechanical loading, including thermal fatigue.
