Novel approaches in the thermal management of electronics involving coupled electrical, thermal and CFD analysis.

摘要

With the increasing design complexities and reliability requirements, today's electronic design engineers rely significantly on software packages, often based on methods of Computational Fluid Dynamics, for the prediction of electronics operational temperature. In the early product design phases, numerical analysis is used to select a cooling strategy and refine a thermal design by parametric analysis. In the final design phase, detailed analysis is performed for reliability predictions. However, for a large class of electronics applications, progress in reliability prediction is currently hampered by the lack of accurate prediction methods. This is especially true for problems in which there is significant heat generation due to the flow of electrical currents in traces and conductors. The main difficulty comes from the fact that the majority of the heat is dissipated as a result of electrical current flow in various conductors. In order to predict temperatures accurately, the important mechanisms for heat generation and heat transfer must be adequately considered. The issue that complicates matters is that the amount of heat generated by the electric current is itself dependent on temperature, thus requiring an approach that considers the coupling between the electrical and thermal aspects of the model. This study is aimed at this class of electronics cooling applications. Its objective is to present a novel approach to the thermal management of electronic systems that focuses on the multi-physics nature of these problems by coupling electrical, thermal and CFD effects. The software package ElectroFlo is developed by the author for the thermal management of electronic devices using this methodology. The method is first used to predict the temperature rise resulting from the flow of electrical current in an embedded trace. Results show excellent agreement with the experimental data reported by the IPC researchers. Subsequently, a far more complex transient problem involving electrical current flow in a multi-layer board with connecting vias is studied. The results of these simulations demonstrate the effect of coupling the electrical and thermal solutions. It is shown that failure to recognize this effect would result in an inaccurate model prediction; the coupled analysis predicts failure, whereas the uncoupled analysis predicts acceptable temperature levels.