A benchmark study of computational fluid dynamics predictive accuracy for component-printed circuit board heat transfer

The application of computational fluid dynamics (CFD) analysis for the thermal design of electronic systems has the potential to enable accurate solutions to be generated and quickly assessed. With the use of validated numerical models, numerical analysis can also be used to provide useful insights into heat transfer processes which could otherwise be difficult to characterize experimentally. However, the capabilities of the CFD tool need to be carefully evaluated so as to provide a degree of confidence in prediction accuracy, thereby minimizing the need to qualify thermal designs. Such an evaluation is presented in this paper, which represents the culmination of a benchmark study by Rodgers et al. [1999]. This overall study assesses the predictive accuracy of a commercial CFD code for both natural and forced convection heat transfer of single- and multicomponent printed circuit boards (PCBs). Benchmark criteria were based on both component junction temperature and component-PCB surface temperature profiles. In the context of the overall study, this paper brings these analyses together to provide a more comprehensive assessment of CFD predictive accuracy for component junction temperature. Additionally the validated numerical models are used to further investigate the sensitivity of component heat transfer to convective environment, both natural and forced, component position relative to the PCBs leading edge, impact of upstream aerodynamic disturbance, and the representation of PCB FR4 thermal conductivity. The significance of the listed variables is quantified by analyzing predicted component energy balances. Qualitative descriptions of the fluid flow fields obtained using a novel paint film evaporation technique are also provided in this study. Both analyses yield new insights of the heat transfer processes involved and sources of numerical error.