An experimental study of the thermal processes relevant to infrared solder reflow



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An experimental system has been built to replicate, as closely as possible, the radiative and convective conditions during the infrared solder reflow process. Experiments were performed to measure the transient thermal response of modules for different module array configurations, under combined radiative and convective conditions. Numerical predictions have been obtained to i) identify and quantify the heat transfer mechanisms responsible for the transient thermal response of a center module within different array configurations and ii) to determine the level of modeling sophistication necessary to develop a detailed numerical model that can predict the thermal response of the card assembly. A comparison of the center module's thermal response in a uniform height array and in an array with different module heights illustrates the the module's sensitivity to shading. The predictions and measurements show the general need to incorporate the radiative exchange analysis which includes module-to-module radiative interactions and detailed evaluation of view factors. The predicted heat transfer mechanisms associated with the center module's thermal response shows that, for the case considered here, radiation is the dominant mode of heat transfer and is influenced by i) shading of the module's sides from the infrared panel heaters and ii) radiative exchange with neighboring modules. The convective cooling rate, although smaller than the radiative heating rates for the results presented here, increases with Reynolds number due to increasing convection coefficients. Radiative and conductive heat transfer rates through the gap separating the module and the card are small