Board-Mounted Electronic Component Transient Thermal Behavior: CFD Prediction Versus Measurement

Numerical predictive accuracy is investigated for transient component heat transfer using a Computational Fluid Dynamics (CFD) code dedicated to the thermal analysis of electronic equipment. The test cases are based on a single Printed Circuit Board (PCB)-mounted, 160-lead PQFP component, analyzed in still-air, and both 1 and 2.25 m/s forced airflows. Three types of transient operating conditions are considered, namely (i) component dynamic power dissipation in fixed ambient conditions, (ii) passive component operation in dynamic ambient conditions, and (iii) combined component dynamic power dissipation in varying ambient conditions. Benchmark criteria are based on component junction temperature and component-PCB surface temperature, measured using thermal test dies and infrared thermography respectively. Using both nominal component/PCB geometry dimensions and material properties, component junction temperature is found to be accurately predicted for component dynamic power dissipation, in both fixed and varying ambient air temperature conditions. The results suggest that CFD analysis could play an important role in providing critical boundary conditions for component electrical and thermo-mechanical behavior analyses. However, caution is stressed on the use of heat transfer predictions for multi-component board applications.