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HeatSink Fin Design Scheme for Enhanced Thermal and Aerodynamic Performance

IP.com Disclosure Number: IPCOM000012651D
Original Publication Date: 2003-May-19
Included in the Prior Art Database: 2003-May-19
Document File: 8 page(s) / 203K

Publishing Venue

IBM

Abstract

The modified fins at the leading edge of this heatsink design causes the stagnation pressure to be lowered at the fin tips due to smaller kinetic energy losses, which then translate into static pressure rises. Greater airflow velocities are also achievable, thus enhancing the heat transfer coefficients at the fin tip and surface area. The modifications to the fin edges can be incorporated at the vendor while the fins are machined.

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  HeatSink Fin Design Scheme for Enhanced Thermal and Aerodynamic Performance

*Main Idea

  IBM has recently introduced a high performance server that utilizes multichip modules that dissipate very high heat loads. Each multichip module consists of four microprocessor chips encased by a copper cap that serves to spread the heat load over an area of roughly 113 mm x 113 mm. The module is air cooled by a single aluminum alloy bonded-fin fan sink. For applications requiring the microprocessors to operate at higher frequencies, the aluminum heat sink, with its lower thermal conductivity, cannot provide sufficient cooling, therefore, a copper heat sink must be employed. However, copper alloys have the disadvantage of a significant weight penalty (density ~ 8.9 g/cm3), being 3.3 times heavier than aluminum (density ~ 2.7 g/cm3), and is significantly more costly to manufacture.

  A novel approach for an improved heat sink has been developed using a new natural graphite-based/epoxy composite material. This material has low density (~1.9 g/cm3) and anisotropic thermal conductivity (~370 W/m-K in two directions, ~ 7 W/m-K in the third direction). Bonded fin manufacturing methods have been developed to produce a heat sink that exploits the material's high thermal conductivity when used in combination with a copper spreader module, such as used in the IBM server. oConvective heat sink thermal performance approaching that of copper (e.g. 0.030 C/W) has been achieved at a fraction of copper's weight. Therefore, additional hardware required to allow the copper heat sinks to withstand shock and vibration standards, was not necessary with the lightweight graphite solution.

  However, further enhancement can be realized when modification are made to the cooling fins themselves. In particularly, if the leading edges of the heat sink's cooling fins are modified to minimize the static pressure losses which are inherent with most recent designs (i.e., flat cross-sectional area profiles at the leading edges of fins). Therefore, this invention details shape configurations which can lower static pressure losses due to these present cross-sectional area profiles, and as a result, enhance or improve thermal performance over present heat sink designs. In addition, these leading edge configurations lead to a more uniform static pressure distribution, especially, for impingement airflow, and thus a more efficient heat sink design.

  Figures 1-3 illus...