Due to the ever-increasing demands on the power density of electronic assemblies, the soldering of THT components is a major challenge. The more thermal mass in the PCBs is connected to the THT pins, the more difficult it is to achieve IPC-compliant solder hole fill. The design and layout of solder joints has an important influence on the subsequent solderability of electronic assemblies. In order to mitigate these challenges, profound investigations on the model based optimization of the THT-soldering process were conducted in the research project "SmartSelective" at the FAU Erlangen-Nürnberg.