Simulation of reflow-based heat transfer on different thermocouple constructions

In this paper, the heating during reflow soldering for different thermocouple constructions is modelled in order to reveal possible variations originated from the constructions itself. K-type (Chromel-Alumel) thermocouples are investigated from the aspect of various physical constructions. The physical dimensions were measured with optical microscopy for several types of thermocouples. Based on those results, CAD geometry was realized for finite element analysis. The temperature dependence of the welded hot-spot was investigated in time domain with different uninsulated wire lengths close to the hotspot, insulation- and hot-spot radiuses. The effect of the various heat transfer coefficient values was also analyzed. The simulation results were also compared with validation measurements performed with a K-type thermocouple in a Vapour Phase Soldering (VPS) chamber.