This research uses finite element analysis to investigate the impact of different solder joint sizes on the mechanical aspects. Specifically, a three-dimensional model of a leadless solder joint for surface mount components was created in simulation software. The study analyses lead-free solder joint thermo-mechanical properties, such as maximum stress and strain. The simulation results indicate that the solder joints parameters significantly influence the thermo-mechanical behaviour during temperature cycling tests. The highest stress is observed at the interface between the solder and pad on the large-size solder joint, while the lowest stress (118MPa) is recorded when employing a small-size solder joint. This research contributes to a better understanding the thermo-mechanical characteristics of different solder joint parameters under temperature cycling conditions.