Reflow soldering process simulation: a simplified model

Established models of temperature development during reflow soldering have used general purpose, finite difference (FD) or computational fluid dynamics modelling tools to create detailed representations of both the product and the reflow furnace. Such models have been shown to achieve a high degree of accuracy, but are complex to generate and analysis times are long. With the move to adopt lead free soldering technology, and the consequently higher reflow process temperatures, optimisation of the reflow profile will gain a renewed emphasis. This paper will report a model of the process which uses simplified representations of both the product and the process which achieves an accuracy comparable with more detailed models. In order to establish an accurate representation of the specific reflow furnace being simulated, a reflow logger is used to make measurements of the temperature and level of thermal convection at each point along the length of the furnace for a small number of carefully chosen reflow profiles. The behaviour for any other reflow profile may then be extrapolated from these measurements.