In this paper, the effect of soldering technique and thermal shock test were investigated on SAC 305 solder joints, produced by 2 different solder methods, which are the most common solder materials used for through-hole reflow soldering (THRS) and multiwave soldering techniques. The solder joints were subjected to different cycle numbers up to 5000 thermal shock tests with 2 different thermal profiles of −30/+110 °C and −40/+125 °C. Microstructural properties of the tested joints were examined with the focus on intermetallic layer thickness and crack formation/propagation. The thickness of the scallop-shaped Cu6Sn5 intermetallic layer was increased with increasing cycle number for both THRS and multiwave joints, but the thickening was more effective for the THRS joints. Cracks typically formed at the solder alloy–plated-through-hole (PTH) barrel and the solder alloy–pin interfaces and propagated along grain boundaries and precipitations of an intermetallic compound.