One important aspect regarding process control is the regular control of the thermal stability of the time / temperature progression in the soldering process. To monitor this, temperature profiles following standardized procedures should be taken during regular production, and these profiles should be compared to a reference profile. Deviations should be noted and corrective action taken. To assure reproducible results of these measurements, special test boards with calibrated thermocouples should be used. These test boards are subject to measuring device monitoring. Board assemblies fitted with thermocouples are not suitable for this task, as they will age and cannot be calibrated if needed.