Microchips, particularly those for power electronics, get hot. If they get too hot they cease to function. The need: a scheme for removing heat from power microchips. One such scheme is sketched in Fig. E1.2. Its working principle is that of thermal conduction to fins from which heat is removed by convection. Four working principles are listed as follows: thermal conduction, convection by heat transfer to a fluid medium, evaporation exploiting the latent heat of evaporation of a fluid, and radiation, best achieved with a surface with high emissivity. The best solutions may be found by combining two or more of these, such as conduction coupled with convection (as in the sketch – an often-used combination). Consider both the case of long term, continuous-operation heat sinks and the case of short-term, intermittent heat sinks (with pause between operations for system to return to ambient temperature). Suggest designs for efficient heat sinks for these two cases.

Data From Fig E.1.2

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Substrate Connecting pins Chips- Heat sink Cooling fins Conduction FIGURE E1.2 A heat sink. Convection