Thermal Effects During Infrared Solder Reflow—Part I: Heat Transfer Mechanisms

An experimental study has been conducted to reveal the relevant heat transfer mechanisms which exist within an infrared reflow oven. Simulated card assemblies are used and their transient thermal responses, induced by combined radiative and convective heating, are measured. A simple numerical model is developed with which relevant heat transfer mechanisms are identified and quantified. The study shows that radiative and mixed convective heat transfer processes induce a variety of system thermal responses. Model predictions, which incorporate measured forced convection heat transfer coefficients and accurate descriptions of surface-to-surface radiative exchange, are in excellent agreement with experimental data for cases where the thermally induced buoyancy forces within the oven air are relatively small. The results of the experimental and analytical study provide guidelines for the development of more sophisticated models of the infrared reflow process.