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Vapor-augmented heat spreader device

Vapor-augmented heat spreader device description/claims

This application is a nonprovisional of U.S. Application No. 60/893,801, entitled “Vapor Augmented Heat Spreader” and filed 8 Mar. 2007, the disclosure of which is hereby incorporated by reference in its entirety.

This application relates to cooling devices and, more particularly, to a vapor-augmented heat spreader including condensate and vapor grooves, wherein the capillary force generated by the vapor grooves is lower than the capillary force generated by the condensate grooves.

As electronic components and devices decrease in size while increasing in operational speed, generated heat becomes a major obstacle to improving performance in electronic devices and systems. The demand for increased performance continues in spite of the continuing need to decrease the size of the semiconductor forming the electronic component. As the size of the semiconductor decreases, the resulting heat flux (heat transfer per unit area, q) increases. The increase in heat flux poses a different challenge to cooling products than a mere increase in total heat, since an increase in heat flux causes overheating on a different time and length scale, which could then lead to electronics failure.

In an attempt to address this problem, a range of solutions has been employed. For example, a metallic lid has been placed on top of the semiconductor to function as a heat spreader. In addition, vapor chambers have been used to enhance the heat spreading effect. While these solutions are somewhat effective, problems still remain. The metallic lid utilizes a conductive mechanism for heat transport; consequently, it needs to be sufficiently thick to ensure appropriate heat spreading. Increased lid thickness, however, results in a semi-finite heat-transfer behavior. Thus, a thicker heat spreader may cause localized, transient overheating. Vapor chambers, although an improvement over the metallic lid, do not maintain dimensional tolerance under the high vapor pressure generated when the vapor chamber is integrated with the electronics and subjected to the high-temperature reflow processes (e.g., in the context of the vapor chamber operating in the format of a vapor-chamber lid). In addition, vapor chamber wick selection is problematic—the appropriate wick needs to be chosen to both enable a high condensate flow rate and maintain sufficient capillary pressure to overcome the effect of gravity. This becomes more of a problem as the thickness of the vapor chamber is reduced in an effort to replace the function of the metallic lid. Thus, it would be desirable to provide a heat dissipation device that overcomes these and other problems of vapor chambers and metallic lids.

The present invention is directed toward a vapor-augmented heat spreader device including vapor and condensate channels selectively formed into a pair of fluid transfer elements to enable the selective increase of the device's in-plane thermal spreading ability. Each set of channels may be spaced to form crests configured to provide sufficient joint area to minimize resistances to through-plane heat flow, as well as to ensure an appropriate pressure rating. In one embodiment of the invention, the heat spreader device includes a lower panel and an upper panel. Each panel is generally planar, including a top surface and a bottom surface. The lower panel has condensate channels formed into its top surface, while the upper panel has vapor channels formed into its bottom surface (i.e., the channels are formed on generally opposing interior surfaces). The channels formed into the upper and lower panels are spaced apart such that a plurality of crests is created. With this configuration, when the bottom surface of the upper panel is brought into mechanical contact with the top surface of the lower panel, the crests function as pillars, supporting the sheet against high pressures existing within the device. Optionally, the crests may be selectively joined (e.g., via welding) to create crest joints. In operation, the device may be evacuated and charged with a vaporizable liquid, which is then sealed inside to create a heat-pipe environment.

The dimensions or shape of the condensate channels may differ from the dimensions or shape of the vapor channels such that the condensate channels can generate a higher capillary force than the vapor channels. For example, the condensate channels may possess dimensions smaller than those of the vapor channels. Alternatively, the condensate channels may possess a shape differing from that of the vapor channels (e.g., the condensate channels may include sharper corners than the vapor channels). The lower panel, furthermore, may include a multi-wick structure, in which wicking power increases with decreasing distance to an evaporation region. The multi-wick structure may also define a boiling-enhanced, multi-wick structure to promote evaporation and minimize boiling superheat.

FIG. 1 illustrates a perspective view of a vapor-augmented heat spreader in accordance with an embodiment of the invention.

FIG. 2A illustrates an exploded view of the vapor-augmented heat spreader taken along line A-A of FIG. 1.

FIG. 2B illustrates a cross sectional view of the vapor-augmented heat spreader taken along line A-A of FIG. 1, showing an embodiment including edge joint connections.

FIG. 3 illustrates a cross sectional view of the vapor-augmented heat spreader taken along line A-A of FIG. 1, showing an embodiment including a folded joint connection.

FIG. 4 illustrates a cross sectional view of the vapor-augmented heat spreader taken along line B-B of FIG. 1, further showing joints around a charging tube.

FIG. 5 illustrates a plan view of the interior surface of the lower sheet of FIG. 1, showing a groove structure formed into the lower sheet in accordance with an embodiment of the invention.

FIG. 6 illustrates a plan view of the interior surface of the upper sheet of FIG. 1, showing groove structure formed into the upper sheet in accordance with an embodiment of the invention.

• Provisional Patent
• Utility Patent

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