Advances in electronic component miniaturization have progressed faster than reductions in power dissipation.  This results in higher power dissipation on a typical board.  Current typical average power densities of 0.1 W/cm2 (over an entire board) are predicted to grow to as high as 1.0 W/cm2 within a few years.  Such high power densities require designers to consider active cooling options.  Many alternative cooling options have been considered to solve the thermal problem.  One option is forced convection cooling with an internal flow.  A typical internal flow configuration is to vacuum braze a fin structure between aluminum plates.  The printed wire boards are then mounted to both sides of this heat sink structure.  The coolant, either gas of liquid, is then passed through the finned cavity.  For air-cooled modules, significant design data are available in the literature.  A comparison of predicted heat transfer performance obtained from simulation is made against recent experimental data on air cooled boards to validate the model.  For liquid cooled systems, the available design data are largely proprietary.  An experimental program aimed at measuring the performance of liquid cooled systems is described and preliminary data are presented.
 

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