Modeling of condensation heating during Vapour Phase Soldering

Vapour Phase Soldering (VPS, also Condensation Soldering) is a reflow soldering method based on condensation heat transfer. The scientific approach for the description of the heat-transfer mechanism during VPS is not detailed deeply in the literature. This paper presents an approach for describing the heat transfer, which occurs during the condensation process. The presented model describes a solution for the film condensation heat transfer based on the classic Nusselt theory, also discussing other refined solutions based on the original formula. With an applied numerical model it becomes possible to simulate the heat transfer on the surfaces of the FR4 board, and it becomes possible to calculate the temperature of the printed circuit board during the process. In order to find the proper heat transfer coefficient, different solutions are investigated in parallel with measurement results. The results show an acceptable approximation of the measured data. The paper presents the models and the results of the calculations, also suggesting a general solution for defining the heat transfer coefficient for the reflow technology itself.