The microstructural behaviours of solder joints during thermomechanical stresses are still not fully understood, and the thermomechanical reliability of solder joints remains a research area for scientists. In many cases, the solder material is modelled as a homogeneous material in Finite Element-based lifetime estimation calculations, while the microstructural effects are neglected. The development of virtual lifetime estimation methods is required; these methods should involve grain structure and therefore provide accurate results for a variety of test cases under thermomechanical loading. This paper presents a meso-scale analysis of lead-free SAC305 solder polycrystals using DAMASK modelling of the grain structure of the solder material and emulating mechanical loading while investigating the mechanical response of the polycrystal. Our finding is that the orientations and grain sizes of the solder polycrystal have significant effects on the mechanical parameters, and these microstructural parameters could not be neglected, because the impact of these also has a very relevant impact on the estimated lifetimes.