Cooling High-Powered Silicone Chips Timothy L. Hoopman of the 3M Corporation described a novel method for cooling high-powered-density silicone chips (D. Cho et al., eds., Microchanneled Structures in DCS, Vol. 19: Microstructures, Sensors, and Actuators, ASME Winter Annual Meeting, Dallas, Texas, November 1990). This method involves etching microchannels in the back surface of the chip. These microchannels typically have hydraulic diameters of 10 µ to 100 µwith length-to-diameter ratios of 50-1,000. Microchannel center-to-center distances can be as small as 100 µ, depending upon geometry.
Design a suitable microchannel cooling system for a 10-mm x 10-mm chip. The microetched channels are covered with a silicone cap as shown in the schematic diagram. The chip and cap are to be maintained at a temperature of 350 K and the system has to remove a heat flux of 50 W/cm2. Explain the reason why microchannels, even in laminar flow, produce very high heat transfer coefficients. Also, compare the temperature difference achievable with the microchannel design with a conventional design using water-forced convection cooling in a channel covering the chip surface.
