The Performance of Small Heat Sinks for LSI Packages in Combined Natural and Forced Convection Air Flows

Cooling performances of small finned heat sinks were investigated in combined natural and forced air convection environment, and the way to use the data in designing a heat sink on a LSI package is explored. An experimental study was performed providing natural and forced air convection over the heat sink. Several heat sinks having different base areas, fin spacing and heights were tested. The test heat sink was heated up by an electrical heater to produce a specific heat flux on its base. The increase in fin temperature was measured by small thermocouples. In natural convection experiments, the effect of the supplied wattage on the temperature rise of the heat sink was examined. In forced convection experiments, a wind tunnel was used. The hear sink was set near the downstream end of the wind tunnel and a specific heat flux was applied to it. A correlation between the air velocity and the temperature rise of the heat sinks was developed. Furthermore, the results are reduced to non-dimensional expressions to facilitate the design of small heat sinks.