US20150129174A1

US20150129174A1 - Component reachable expandable heat plate

Info

Publication number: US20150129174A1
Application number: US14/076,589
Authority: US
Inventors: Robert J. Monson; Kent Katterheinrich; Yung-Cheng Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-11-11
Filing date: 2013-11-11
Publication date: 2015-05-14

Abstract

Some embodiments of the invention provide a heat plate system that includes a closed vessel having at least one flexible surface. The flexible surface allows the vessel to come into intimate contact with heat-generating components (e.g., integrated circuits) residing at varying heights above the floor of a module (e.g., an avionics module). In some embodiments, the material may allow the heat plate to expand in response to absorbing heat, so that it may mold itself around the contours of different heat-generating components, increasing the surface area contact between the heat plate and the components, and increasing the heat plate's ability to conduct heat away from the components.

Description

FIELD OF INVENTION

This invention deals generally with heat transfer, and more particularly with heat plates and/or heat pipes used in transferring heat away from one or more heat-generating components.

BACKGROUND

Proper thermal management is critical to the successful operation of many types of devices. In this respect, modern jet aircraft include numerous types of devices which generate significant heat during operation, including avionic electronics, radar and directed-energy systems. As an example, avionics components commonly use integrated circuits (hereinafter called “chips” for convenience) for computing applications which can generate significant heat during operation.
Various techniques are known for transferring heat away from devices and/or their components during operation, to keep the devices functioning properly. For example, heat plates are commonly used to transfer heat away from the tops of the chip(s) in an avionics module toward the module's edge (e.g. to one or more side walls). Often a thermal interface transfers heat from the edge to a chassis, which is often a cooled component in which the module resides.
Heat plates commonly employ heat pipe technology. A heat pipe is a closed vessel which stores fluid in two states, or phases (i.e., liquid and gas), and which makes use of changes between the states to transfer heat. In some heat pipes, a volume of liquid is stored in the heat pipe at a given temperature, and then a vacuum is imposed in the vessel. The vessel is then sealed, so that the pressure level within the vessel causes some of the liquid to change to a gaseous state. The two-phase system inside the vessel remains at equilibrium, meaning that the boiling point and condensation point of the fluid in the vessel are at approximately the system's temperature. If heat is then absorbed at a particular location on the vessel, the heat causes liquid stored at that location to boil and be converted to gas, the heat being transferred to the gas, and pressure in the system increasing. A pressure increase causes the condensation point to increase as well, so that condensation begins occurring almost immediately at a different location in the heat pipe, typically where it is coolest, so that heat is transferred from the gas within the vessel to the external environment near the cool location. The liquid which results from this condensation transfers from the cool location back to the heated region (e.g., via a wick, one or more micro-grooves, and/or other mechanism(s)) so that the evaporation-and-condensation cycle can begin again.
Within a heat pipe, heat is transferred at approximately sonic speed from a heated location to a cooled location. As such, if a heat pipe is long enough to transfer heat a sufficient distance away from a heated location of a component, the heat pipe can effectively cool the component, without the need for any auxiliary pumping or moving parts.
FIG. 1 depicts the operation of an example conventional heat pipe 100. In this example, water is the fluid within the closed vessel that is used to transfer heat, although any of numerous materials could alternatively be used. In the example of FIG. 1, evaporator region 105 is heated, such as by a component (e.g., a chip, not shown in FIG. 1) which generates heat during operation. This heat causes water near evaporator region 105 to be turned to vapor. The heat transfers through the vapor to condenser region 110, which is a cooled location in heat pipe 100. Heat is then transferred to the external environment, causing the water at to be converted back to liquid, and this liquid is transferred by wick 115 (e.g., via capillary action) to evaporator region 105.

SUMMARY

The inventors have appreciated that employing heat plates to cool the numerous types of devices and components used in modern applications can present challenges. Components on modern jet aircraft serve as an illustrative example. On a modern jet aircraft, there may be dozens of different avionics modules, each having chips disposed at different locations within the module. In modules in which chips are attached to the module floor, different chips may be at different heights. To provide proper thermal management for all types of modules, a different heat plate may need to be separately configured to properly accommodate the location and height of the chips therein. In this respect, a heat plate is generally designed to come into intimate contact with the chips in a module so as to effectively transfer heat away, without applying so much pressure that any chip's operation is affected. As such, preparing a heat plate for use with a module usually involves configuring the plate to reach each of its chips at a particular height with great specificity. This is difficult to accomplish using conventional fabrication techniques.
One conventional approach to overcoming these difficulties is to employ a conformable, compressible thermal interface layer between each chip and the heat plate. In this approach, a thermal interface typically sits atop each chip, and contacts the heat plate when the heat plate is lowered into the module in which the chip resides. Because the thermal interface is conformable, the heat plate need not be configured to accommodate varying chip heights with great specificity. However, thermal interfaces are notoriously poor at conducting heat away from a chip, because they are typically made from materials which are highly conformable but not very thermally conductive. For example, many thermal interfaces cause about a 50% loss in thermal conductivity when compared with direct contact between a chip and a heat plate.
The inventors have recognized that other conformable materials which are more thermally conductive could be used in a thermal interface layer. For example, silver or copper pastes are both conformable and thermally conductive. However, the use of pastes can make module assembly problematic, because applying a paste on a set of chips having varying heights so that the paste atop each chip reaches the same height can be difficult. In addition, pastes are messy, and can therefore make module maintenance difficult.
In contrast to conventional approaches, some embodiments of the invention provide a heat plate system which includes a closed vessel having at least one flexible surface. The flexible surface allows the vessel to come into intimate contact with heat-generating components of varying heights. In some embodiments, the heat plate may be expandable during use (e.g., in response to being heated). As such, the heat plate may mold itself around the contours of different heat-generating components, increasing the surface area contact between the heat plate and the components, and increasing the heat plate's ability to conduct heat away from the components. In some embodiments of the invention, a heat plate may interface directly with one or more of the module's side walls, and/or a cooling mechanism. As a result, heat is transferred to the external environment via the module's periphery rather than through its cover, which may provide greater control and effectiveness with respect to thermal management than conventional approaches allow.
The foregoing is a non-limiting summary of the invention, some embodiments of which are defined by the attached claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

FIG. 1 is a symbolic representation of the operation of a conventional heat pipe or heat plate, according to the prior art;

FIG. 2 is a perspective view of a heat plate, implemented in accordance with some embodiments of the invention, for use with an example module;

FIG. 3 is a side view showing a heat plate, implemented in accordance with some embodiments of the invention, installed in a module; and

FIG. 4 is a side view of a heat plate, implemented in accordance with some embodiments of the invention, illustrating the heat plate's flexibility and expandability.

DETAILED DESCRIPTION

Some embodiments of the invention provide a heat plate system which includes a closed vessel having at least one surface that is pliable and/or flexible, allowing the vessel to come into close contact with contoured surfaces of heat-generating components of varying heights, and enabling effective heat transfer away from those components. In some embodiments of the invention, a heat plate may be expandable, such as upon the absorption of heat, so as to increase the component surface area with which the heat plate system comes into contact, and thereby improving thermal conductivity. In addition, some embodiments of the invention may provide a heat plate system for use with heat-generating components residing in a module housing which is designed to conduct heat to the housing's peripheral walls and/or a cooling mechanism, rather than to the housing's cover, to provide greater control and effectiveness with respect to heat transfer than conventional systems provide.
FIG. 2 depicts an example heat plate system 205 that is designed for use with module 220. Module 220 includes components which generate heat during operation, and may be an avionics module, or any other suitable type of module. In the example shown in FIG. 2, module 220 includes four heat-generating components, namely integrated circuits 210A, 210B, 210C and 210D. It should be appreciated, however, that embodiments of the invention may be employed with modules having any suitable number of heat-generating components, which may or may not include integrated circuits.
In module 220, components 210A-210D reside on module floor 225. It should be appreciated, however, that embodiments of the invention are not limited to being used with components residing on the floor of a module, and may be used with components in any suitable location. For example, components may be elevated above a module floor, reside within a recess within a module's floor, be attached to one or more of the module's side walls, and/or reside in any other suitable location(s).
In module 220, periphery walls 215 define a cavity in which components 210A-210D reside. As explained further below, in some embodiments of the invention, one or more of walls 215 may contact, or otherwise be thermally coupled to, one or more external cooling components. For example, one or more of walls 215 may contact components through or over which cooling fluid (which may comprise any suitable gas and/or liquid) flows. It should be appreciated, however, that embodiments of the invention are not limited to being used in conjunction with modules having walls which contact external cooling components.
Arrow 230 in FIG. 2 indicates that example heat plate 205 is designed to be introduced into the cavity defined by walls 215 from above. However, it should be appreciated that the invention is not limited to being implemented in this manner, and that heat plate 205 may be introduced in to or on to a module in any suitable manner. For example, heat plate 205 may be injected, fed or introduced into a cavity in any other suitable way.
FIG. 3 is a side view (specifically, viewed along line 301 in FIG. 2) which shows heat plate 205 having been introduced into the cavity defined by walls 215. In the example shown in FIG. 3, the dimensions of heat plate 205 approximate those of the cavity into which it is introduced, such that it contacts walls 215 when in use. However, it should be appreciated that the invention is not limited to such an implementation, and that a heat plate may take any suitable shape, which may or may not coincide with the shape of a cavity into which it is introduced. As one example, heat plate 205 could alternatively be designed to come into contact with one or more of side walls 215 (e.g., one or more walls in contact with a cooling element) but not all of the side walls.
In the example shown in FIG. 3, bottom surface 315 of heat plate 205 comes into contact with the top surfaces 310B, 310C of components 210B, 210C, respectively, when introduced, although component 210B is taller than component 210C. In this respect, in some embodiments of the invention, heat plate 205 is at least partially formed of a flexible, pliable material which allows bottom surface 315 to come into intimate contact with components of varying heights. Any of numerous materials may be used. In some embodiments, it may be desirable to employ a material or materials which exhibit sufficient flexibility to allow the heat plate to come into intimate contact with components at varying heights within a module, a tensile strength and/or tensile modulus that is sufficient to allow for stretching with minimal risk of rupture during operation, and good heat transfer capability. Materials having suitable physical properties include Kapton® polyimide film (which exhibits a tensile strength of approximately 231 Mpa and Young's modulus of approximately 2.5 GPa at room temperature), aluminum foil (which exhibits a tensile strength of 330 Mpa and Young's modulus of 70 GPa at room temperature), and gold foil (which exhibits a tensile strength of 330 Mpa and Young's modulus of 120 MPa at room temperature), although the inventors have recognized that in certain applications it may be advantageous to employ materials having dielectric or non-conductive properties so that the surface of the heat plate which contacts electrical components (e.g., circuits) does not interfere with their operation. Thus, in certain applications, Kapton® polyimide film may exhibit more suitable physical properties than aluminum or gold foil. A moisture barrier layer (not shown in FIG. 3), which may be formed of, for example, rubber, flexible glass, and/or any other suitable material(s)), may be used to prevent vapor from transmitting through the bottom surface of the heat plate if Kapton® polyimide film is used.
In the example shown in FIG. 3, heat plate 205 conducts heat from the top surfaces 310B and 310C of components 210B and 210C, respectively, to cooled regions 305 which contact walls 215. More specifically, fluid within heat plate 205 proximate top surfaces 310B and 310C is heated and converts to a vapor state, and the heat transfers through the vapor to cooled regions 305 and then through walls 215 to the external environment. The fluid then converts back to a liquid state, and is transferred back to locations proximate top surfaces 310B and 310C (e.g., by a wick, not shown), so that it may transfer additional heat generated by components 210B and 210C away from the components.
In some embodiments, the material(s) from which heat plate 205 is formed may allow it to expand as it absorbs heat generated by module components, so that as heat is generated, bottom surface 315 is forced into more intimate contact with the components, increasing the surface area of heat plate 205 across which heat may be conducted. FIG. 4 illustrates this capability. In FIG. 4, heated generated by component 210A causes heat plate 205 to expand, forcing regions 415 and 420 of heat plate 205 to bend along the edges of component 210, in contrast to FIG. 3, in which a lack of heat generated by component 210 leaves regions 315 and 320 of heat plate 205 largely undeformed. By expanding when heat is absorbed, heat plate 205 forces regions into intimate contact with heat-generating components and provides an efficient heat transfer mechanism.
Heat plate 205 may employ any of numerous types of fluids to perform heat transfer. The inventors have observed that fluids which transition without difficulty between liquid and vapor phases, and which expand when entering the vapor phase, may prove advantageous in certain applications. Examples of fluids exhibiting these characteristics include water, alcohol and paraffin. However, it should be appreciated that any suitable fluid(s) may be used, as embodiments of the invention are not limited in this respect.
It should also be appreciated that numerous advantages may flow from the example arrangements shown in FIGS. 2-4. For example, a heat plate formed of one or more materials that enable the heat plate to expand as heat is absorbed enables the heat plate to expand to a volume at which heat transfer may be more effectively performed than in conventional arrangements. In addition, a heat plate designed to transfer heat to one or more side walls of a module, where cooling components may be located, may provide a more effective mechanism than conventional arrangements which rely on transfer or heat to the module's cover.
It should further be appreciated that the implementation examples described above are intended to be illustrative rather than limiting, and that numerous variations on these examples are possible. For example, embodiments of the invention may be used to transfer heat away from any suitable component(s), which may or may not include an integrated circuit. In addition, embodiments of the invention may be used in conjunction with any suitable collection of components, which may or may not include or comprise a functional module such as an avionics module. The collection of components may be of any suitable size and include any suitable quantity of components. Embodiments of the invention are not limited in this respect.
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
Various aspects of the present invention may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in this application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.
Also, the invention may be embodied as a method, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.
Use of ordinal terms such as “first,” “second,” “third,” etc. in the claims to modify a claim element does not by itself connote any priority, precedence or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claimed element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
Also, the phraseology and terminology used herein is used for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

Claims

What is claimed is:

1. An apparatus for use with a module comprising components which generate heat during operation, each of the components having a component surface, the apparatus comprising:

a closed vessel adapted for installation within the module to conduct heat away from the components, the closed vessel storing a fluid in a liquid state and a gaseous state, the vessel comprising at least one vessel surface adapted to contact the component surface of each component, the at least one vessel surface being at least partially formed of a material exhibiting a Young's modulus of at least 120 MPa and a tensile strength of at least 231 MPa at room temperature.

2. The apparatus of claim 1, wherein the material exhibits a Young's modulus of approximately 2.5 GPa at room temperature.

3. The apparatus of claim 2, wherein the material is a polyimide film.

4. The apparatus of claim 1, wherein the material is non-conductive or dielectric.

5. The apparatus of claim 1, wherein the material exhibits a tensile strength of approximately 330 MPa at room temperature.

6. The apparatus of claim 5, wherein the material comprises at least one of an aluminum foil and a gold foil.

7. The apparatus of claim 1, wherein the component surface of each of the components resides at a different height above a floor of the module, and wherein the vessel surface comes into contact with substantially the entirety of each component surface when installed in the module.

8. The apparatus of claim 1, wherein the material accommodates expansion of the fluid in response to absorbing heat generated by the plurality of components.

9. The apparatus of claim 1, wherein the module comprises side walls extending orthogonally from a floor of the module, and wherein the closed vessel is adapted to conduct heat generated by the components to at least one of the side walls.

10. The apparatus of claim 1, wherein the fluid comprises one or more of water, alcohol and paraffin.

11. The apparatus of claim 1, in combination with the module.

12. The apparatus of claim 1, wherein the module is an avionics module.

13. The apparatus of claim 1, wherein the plurality of components comprise at least one integrated circuit.

14. A method for use in a system comprising a module having components which generate heat during operation, each of the components having a component surface, the method comprising an act of:

(A) employing a closed vessel to conduct heat away from the components, the vessel being adapted for installation within the module and storing a fluid in a liquid state and a gaseous state, the vessel comprising at least one vessel surface adapted to contact the component surface of each component, the at least one vessel surface being at least partially formed of a material exhibiting a Young's modulus of at least 120 MPa and a tensile strength of at least 231 MPa at room temperature.

15. The method of claim 14, wherein the material exhibits a Young's modulus of approximately 2.5 GPa at room temperature.

16. The method of claim 15, wherein the material is a polyimide film.

17. The method of claim 14, wherein the material is non-conductive or dielectric.

18. The method of claim 14, wherein the component surface of each of the components resides at a different height above a floor of the module, and wherein the act (A) comprises causing the vessel surface to come into contact with substantially the entirety of each component surface.

19. The method of claim 14, wherein the module comprises side walls extending orthogonally from a floor of the module, and wherein the act (A) comprises conducting heat generated by the components to at least one of the side walls.

20. The method of claim 14, wherein the plurality of components comprise at least one integrated circuit.