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Method for a porous heatsink for cooling low-end microprocessors and chipsets under buoyancy-induced flows

IP.com Disclosure Number: IPCOM000019856D
Publication Date: 2003-Oct-01
Document File: 4 page(s) / 112K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a porous heatsink for cooling low-end microprocessors and chipsets under buoyancy-induced flows. Benefits include improved functionality, improved thermal performance, improved performance, and improved reliability.

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Method for a porous heatsink for cooling low-end microprocessors and chipsets under buoyancy-induced flows

Disclosed is a method for a porous heatsink for cooling low-end microprocessors and chipsets under buoyancy-induced flows. Benefits include improved functionality, improved thermal performance, improved performance, and improved reliability.

Background

         Chipsets and local area network (LAN) controllers conventionally use natural convection from the bare die for cooling. Heat dissipation is solely dependent on buoyancy-induced convection (natural convection). The hot air in proximity to the heated die rises up due to its lower density. The warm air is replenished by the inflow of cold (denser) air. The rate of heat transfer is governed by temperature difference between the heated surface and the ambient air.

         Inadequate cooling can cause overheating and processor failure. Using a heatsink adds cost and is sometimes not possible because adequate space is not available.

General description

         The disclosed method is a light, low cost, efficient porous heatsink for a low-power microprocessor or chipset die that relies on buoyancy-induced convection for cooling.

         The disclosed method uses a fibrous metal foam to create a porous structure. It is light weight and low cost. The simplicity of the method has potential for widespread application.

         The key elements of the method include:

•         Fibrous metal foam (porous medium) heatsink

•         Die

•         Solder thermal interface material (TIM)as interface material between the die and heatsink

•         Buoyancy-induced (natural) convection cooling without fans

Advantages

         The disclosed method provides advantages, including:

•         Improved functionality due to providing buoyancy-induced (natural) convection cooling without fans

•         Improved thermal performance due to improved cooling because of the porous medium

•         Improved performance due to the porous structure’s low weight

•         Improved reliability due to reduced device failure because of improved cooling

Detailed description

The disclosed method proposes the use of a fibrous metal foam (porous medium), which is placed on top of the heated die. High porosity metal foams are potentially excellent candidates for high heat transfer. These foams provide extended surface area, serving as fins. The foam enhances the heat transfer coefficient due to local thermal dispersion caused by circulation eddies that occur in the wake of flow past the fibers. This air movement in turn reduces the thermal resistance from junction-to-ambient air (if placed on bare die) or case-to-ambient air (if placed on an integrated heatsink).

         The disclosed method can be implemented using the following steps:

1. Apply a thin layer of solder paste on the bare die or the integrated heatsink.

2. Put the piece of metal foam on top of the die and heat spreader.

3. Apply a simple load on top of the porous heatsink.

4. Put the entire assembly in a reflow oven to reflow the solder.

5. Remove the load from the...