Hierarchical thermal analysis of large IC modules

This paper presents a new approach to hierarchical thermal modeling using libraries of parametrized sub-models. It is demonstrated how to efficiently create thermal sub-models based on a parametrized model reduction technique. These sub-models are then used for fast simulation of complex parts using a hierarchical modeling building methodology that nests sub-models within sub-models. As an example of such a model parametrized thermal sub-models of a GaAs power cell, an integrated GaAs microwave power amplifier and an InP optical modulator are generated. A complete module is then built by attaching these sub-models to detailed models in a hierarchical manner, creating a thermal model of the entire system. This methodology allows a quick thermal analysis to be performed of very large systems. The thermal sub-models are small in size, boundary condition independent, have very short simulation times, and predict with high accuracy (better then 2% error) all internal temperatures. Finally, the optical modulator model is used as example of the computational efficiency of the methodology. Although an absolute speed-up is difficult to define two cases were provided with gains of around 30 to 40 times calculated. System memory requirements were also reduced by a factor of three.