High-Performance Air-Cooled Heat Sinks for Power Packages

Abstract

Compact heat exchangers have been designed for spot-cooling of high-power electronic components (power transistors of TO-2xx type and the like) by extending the limits of air-cooling through the use of novel heat sink configurations and impingement flow arrangement with attention given to meet noise requirements. Experiments have been conducted to test and compare the thermal performance and pressure drop characteristics of two narrow channel heat sinks, a woven wire screen and a porous metal fibre structure. Thermal resistance measurements were made both for steady-state and transient conditions using the MOSFET’s source-gate voltage as TSEP to obtain the peak junction temperature. The effects of heat sink structure, mass-flow rate of air and component power dissipation have been investigated. Measured heat sink-to-ambient thermal resistances varied from 0.53 to 0.20 K/W for air velocities between 4 and 21 m/s, yielding average areal and volumetric heat transfer coefficients from 150 to 280 W/m²K (based on the total surface area) and from 0.14 to 0.53 W/cm³K, respectively, corresponding to maximum removable base plate heat flux of 12 W/cm². Obtained results demonstrate that confined ducting of high-velocity laminar air-flows through compact structures of these types, combined with central feeding of air, provides greatly improved thermal performance compared to conventional forced air cooling schemes taking up considerably larger volumes.