Thermal performance of air-cooled hybrid heat sinks for a low velocity environment

Experimental procedures were used to compare thermal performance characteristics for similar shaped air-cooled heat sinks manufactured from metallic and non-metallic materials. The heat sink geometry was designed and optimized with the intent of cooling a single die which is dissipating 100 watts in a desktop, workstation environment. One of the heat sinks was fabricated by bonding a copper base to a machined, graphite fin structure which has a uni-directional thermal conductivity of 800 W/m C. At 183 air velocity of 150 linear feet per minute (lfm) and an estimated pressure loss of less than 0.039 inches of water, the measured sink-to-air thermal resistance was 0.53 C/W for this copper/graphite hybrid design. Measured junction-to-sink thermal resistances were less than 0.20 C/W when a commercially available land grid array package was used to directly attach a copper heat sink to a 0.50"/spl times/0.50"/spl times/0.015" thermal test chip. Measured heat sink thermal resistances were in relatively good agreement with predicted heat sink resistance values for sea level atmospheric conditions. A modeling simplification technique is presented which allows the numerical computational time to be reduced by at least 50 percent for heat sink optimization studies. Numerical computational techniques were used to estimate the effect of reduced air density on heat sink performance for high altitude, low air velocity environmental conditions.<>