Investigated is the performance of composite spreaders, consisting of a top layer of porous graphite (⩾0.4mm), for enhanced cooling by nucleate boiling of FC-72 dielectric liquid, and a copper substrate (⩽1.6mm), for efficient spreading of the dissipated thermal power by the underling 10×10mm or 15×15mm high-power computer chips. The analysis assumes uniform thermal power dissipation by the chips and calculates the square surface area of the spreader, along with the spreading, boiling and total thermal resistances, the maximum chip temperature, and the removed thermal power from the spreader surface by saturation or subcooled nucleate boiling of FC-72 liquid. These performance parameters are determined as functions of the thickness of the copper substrate and the size of the underlying chip. When compared with those of copper and porous graphite spreaders of the same total thickness, 2.0mm, the performance of the composite spreaders is superior for cooling high-power computer chips. When cooled by nucleate boiling of 30K subcooled FC-72 liquid, the composite spreader removes 160.3W and 98.4W of dissipated thermal power by the underlying 10×10mm and 15×15mm chips, at total thermal resistances of 0.29 and 0.48°C/W. When the same spreader is cooled by saturation boiling of FC-72, the removed thermal power decreases to 85.6W and 53.4W, and the total thermal resistances also decrease to 0.12 and 0.20°C/W, respectively. Although the calculated surface temperatures of the chips are not uniform, the maximum temperatures are <71°C and the temperature differential across the chips is <8°C. For the same cooling condition, the calculated surface area of the copper spreaders, the total thermal resistance, and the maximum chip temperature are much higher, but the removed thermal powers from the surface of spreaders are much lower than with composite spreaders. The calculated surface areas of the porous graphite spreaders are smaller, the thermal powers removed from surface of these spreaders are much lower and both the total thermal resistance and the maximum chip temperature are higher than those with composite spreaders.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.