US20170023306A1

US20170023306A1 - Layered heat pipe structure for cooling electronic component

Info

Publication number: US20170023306A1
Application number: US14/806,018
Authority: US
Inventors: Irad Stavi; Gideon (Genady) YAMPOLSKY
Original assignee: COMPULAB Ltd
Current assignee: COMPULAB Ltd
Priority date: 2015-07-22
Filing date: 2015-07-22
Publication date: 2017-01-26
Also published as: WO2017013649A1

Abstract

A structure for transferring heat from a heat producing element to a heat sink includes a first layer including a first flat heat pipe array of a substantially parallel and adjacent heat pipes for conveying heat substantially along a first array axis and configured to be thermally coupled to the heat producing element. A second layer includes a second flat heat pipe array of substantially parallel and adjacent heat pipes for conveying heat substantially along a second array axis. The first flat heat pipe array and the second flat heat pipe array partially overlap and are in thermal contact. The first array axis and the second array axis form a nonzero angle, so that the second flat heat pipe array extends beyond the first flat heat pipe array. The second flat heat pipe array is configured to be thermally coupled to the heat sink.

Description

FIELD OF THE INVENTION

The present invention relates to cooling of electronic components. More particularly, the present invention relates to a layered heat pipe structure for cooling an electronic component.

BACKGROUND OF THE INVENTION

Computer systems and other electronic systems and components generate heat during their operation. However, the performance of those systems and components is adversely affected by overheating. Therefore, such systems include arrangements for generating heat.
Heat removal may be either active or passive. Active cooling may utilize forced convection, e.g., as provided by a fan, pump, or blower. Such active cooling is often unsuitable for portable or compact electronic systems. Passive cooling based on heat conduction and natural convection and radiation (e.g., fins) is often insufficient to transfer large heat loads away from electronic components.
Heat pipes and vapor chambers may enable efficient and effective passive heat transfer. Heat pipes and vapor chambers utilize evaporation and condensation of a working fluid (e.g., water, acetone, alcohol, or another suitable fluid that is liquid at the ambient temperature) that is sealed inside to transfer heat from a source of heat to a cooler periphery. A heat source in the form of a heat-producing element to be cooled, such as an electronic component, may be thermally connected to part of (e.g., a part close to the center) of the heat pipe or vapor chamber. The heat-producing element may heat the working fluid at the region of the connection and vaporize the fluid. The process of evaporation of the liquid absorbs heat. The vapor may migrate to a cooler periphery of the heat pipe or vapor chamber. At the cooler periphery, the vapor condenses back into liquid form, releasing heat to the environment. The condensed liquid is then transferred back to the location of the heat-producing component. For example, the heat pipe or vapor chamber may enclose a wick or other structure that conducts the condensed liquid by capillary action to the heat-producing element. In some cases, the heat pipe or vapor chamber may rely on gravity, an inertial (e.g., centripetal) force, or another mechanism to conduct the condensed liquid to the heat-producing element.
A heat pipe or vapor chamber may be considered to be a passive device since no additional power, other than the heat that is generated by component to be cooled, is typically required to operate the device.
Heat pipes are configured to transfer heat along an axis of the heat pipe primarily in a single dimension. (Heat transfer in other directions may result from conduction by the casing of the heat pipe, or external radiative and convective effects that are unrelated to the primary heat transfer function of the heat pipe by the internal processes of evaporation, migration, and condensation.) Vapor chambers are planar devices that are configured distribute heat in two dimensions. Thus, a vapor chamber is typically more effective than a heat pipe in passively dissipating heat.

SUMMARY OF THE INVENTION

There is thus provided, in accordance with an embodiment of the present invention, a structure for transferring heat from a heat producing element to a heat sink, the structure including: a first layer including a first flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a first array axis and configured to be thermally coupled to the heat producing element; and a second layer including a second flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a second array axis, wherein the first flat heat pipe array and the second flat heat pipe array partially overlap and are in thermal contact, the first array axis and the second array axis forming a nonzero angle, so that the second flat heat pipe array extends beyond the first flat heat pipe array, the second flat heat pipe array configured to be thermally coupled to the heat sink.
Furthermore, in accordance with an embodiment of the present invention, the second array axis is substantially perpendicular to the first array axis.
Furthermore, in accordance with an embodiment of the present invention, thermal coupling between the first flat heat pipe array and the heat producing element includes a heat conducting plate.
Furthermore, in accordance with an embodiment of the present invention, the first array axis is configured to be substantially horizontal when the heat producing element is in operation.
Furthermore, in accordance with an embodiment of the present invention, the structure is configured such that the second array axis is substantially vertical when the heat producing element is in operation.
Furthermore, in accordance with an embodiment of the present invention, the first flat heat pipe array includes a central region that is configured to be thermally coupled to the heat producing element, and wherein the second flat heat pipe array overlaps an end region of the first flat heat pipe array.
Furthermore, in accordance with an embodiment of the present invention, the second layer includes two flat heat pipe arrays, each of the two flat heat pipe arrays overlapping and in thermal contact with a different end regions of the first flat heat pipe array.
Furthermore, in accordance with an embodiment of the present invention, an interface at the thermal contact between the second flat heat pipe array and the first flat heat pipe array includes a thermal interface material.
Furthermore, in accordance with an embodiment of the present invention, the thermal interface material includes a thermal adhesive.
There is further provided, in accordance with an embodiment of the present invention, an assembly including: a heat producing element; a heat sink; and a structure for transferring heat from the heat producing element to the heat sink, the structure including: a first layer including a first flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a first array axis from a first region of the at least one first flat heat pipe array that is thermally coupled to the heat producing element, to a second region of the first flat heat pipe array; and a second layer including at least one second flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a second array axis that forms a nonzero angle with the first array axis, the second flat heat array overlapping and in thermal contact with the second region of the first flat heat pipe array and thermally coupled to the heat sink.
Furthermore, in accordance with an embodiment of the present invention, the second array axis is substantially perpendicular to the first array axis.
Furthermore, in accordance with an embodiment of the present invention, the assembly includes a heat conducting plate, one face of which is in thermal contact with the heat producing element, and another face of which is in thermal contact with the first region the first flat heat pipe array.
Furthermore, in accordance with an embodiment of the present invention, an interface of thermal contact between the heat conducting plate and the heat producing element includes an uncured thermal interface material.
Furthermore, in accordance with an embodiment of the present invention, the heat producing element is held in a socket of a circuit board.
Furthermore, in accordance with an embodiment of the present invention, the assembly is configured such that the first array axis is substantially horizontal and the second array axis is substantially vertical when the assembly is operating.
Furthermore, in accordance with an embodiment of the present invention, the heat sink is configured to be passively cooled.
Furthermore, in accordance with an embodiment of the present invention, the heat sink includes a plurality of channels configured to produce an internal flow of air when heat is conveyed from the heat producing element to the heat sink and when the channels are substantially vertical.
Furthermore, in accordance with an embodiment of the present invention, a length of the at least one second flat heat pipe array is substantially equal to a length of the heat sink.
Furthermore, in accordance with an embodiment of the present invention, the first region of the first flat heat pipe array includes a central region of the first flat heat pipe array, the second region of the first flat heat pipe array includes an end region of the first flat heat pipe array.
Furthermore, in accordance with an embodiment of the present invention, the at least one second flat heat pipe array includes two flat heat pipe arrays, each of the two flat heat pipe arrays overlapping and in thermal contact with a different end region of the first flat heat pipe array.

BRIEF DESCRIPTION OF THE DRAWINGS

In order for the present invention, to be better understood and for its practical applications to be appreciated, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the invention. Like components are denoted by like reference numerals.

FIG. 1 schematically illustrates components of an assembly in which an electronic component is passively cooled by a layered heat pipe structure, in accordance with an embodiment of the present invention.

FIG. 2A schematically illustrates the assembly whose components are shown in FIG. 1.

FIG. 2B shows a schematic rotated view of the assembly shown in FIG. 2A.

FIG. 2C shows a schematic lateral cross section of the assembly shown in FIG. 2A.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.
Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,” “establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information non-transitory storage medium (e.g., a memory) that may store instructions to perform operations and/or processes. Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently. Unless otherwise indicated, us of the conjunction “or” as used herein is to be understood as inclusive (any or all of the stated options).
In accordance with an embodiment of the present invention, a layered heat pipe structure is configured to dissipate heat in two dimensions. Each layer of the structure includes one or more flat and substantially planar arrays of parallel and adjacent heat pipes. A face of each heat pipe array in each layer (after the first) of the layered heat pipe structure partially overlaps, and is in thermal contact with, the face of at least one heat pipe array of the previous layer. The layered heat pipe structure may be utilized to dissipate heat that is generated by a heat producing element. For example, the heat producing element may include an electronic component, such as a central processing unit (CPU), a graphics processing unit (GPU), or another element.
As used herein, a heat pipe is considered to be flat when two opposite sides of the heat pipe are substantially flat. The other sides of the heat pipe (e.g., that connect the opposite faces) are herein referred to as edges or ends of the heat pipe. A heat pipe array may be considered to be flat when the heat pipes of the array are flat heat pipes, when the heat pipes of the array are arranged substantially in a single plane and the heat pipes are all similarly oriented. Thus, the flat heat pipe array includes two substantially flat opposite sides, herein referred to as faces or surfaces of the heat pipe array. The faces or surfaces are connected to one another at their perimeters by edges or ends of the heat pipe array. (The faces of the array may include externally visible grooves along each edge of separation between adjacent heat pipes of the array.)
As used herein, an axis of an array of parallel heat pipes refers to the direction of primary heat transfer along the length of each of the heat pipes. Primary heat transfer, as used herein, refers to heat transfer by the mechanism that is characteristic of heat pipes, and includes evaporation of an internally sealed working fluid in one region, internal migration of the vapor to a region of condensation, and internal migration of the condensed fluid back to the region of evaporation. Any heat transfer in a heat pipe array in a direction other than that of the axis may be assumed to be due to secondary or parasitic heat transfer modes (e.g., heat conduction along the casing or shell of the heat pipe array, radiative or convective transfer across grooves in the array, or other secondary effects). The length of the array refers to the size of a face of the array in direction that is parallel to the array axis. The width of the array refers to the size of the face of the array in the direction that is perpendicular to that of the axis. The thickness of the array refers to the perpendicular distance between the faces of the array.
When the layered heat pipe structure is installed, a region of one face of a flat heat pipe array of a first layer of the structure is thermally coupled to the heat producing element.
As used herein, thermal contact or a thermal connection between surfaces of two bodies refers to a direct connection or bond between adjacent bodies that enables conductive heat transfer from one of the bodies to the other. The thermal contact may include an intermediary medium in the form of a thermal interface material (TIM) that fills an interface between the surfaces of the bodies. A used herein, thermal coupling between two bodies or surfaces refers may include one or more additional thermally conductive bodies (such as a copper plate) that intervene between the surfaces of the thermally coupled bodies.
Typically, the area of the heat pipe array is larger than the area of the heat producing element. In such a case, the heat producing element may be thermally connected to one face of a heat conducting plate. The opposite face of the heat conducting plate may be thermally connected to a region of a face of a heat pipe array of the first layer. For example, the heat conducting plate may be made of a heat conducting metal or other material, e.g., copper or another heat conductive material. The width of the face of the heat conduction plate may be similar to the width of the heat pipe array. Thus, the heat that is produced by the heat producing element may be laterally distributed across the width of the heat pipe array. Such lateral distribution of the produced heat may increase the effectiveness of the first layer in longitudinally conducting the produced heat away from the heat producing element. For example, the effectiveness may be increased by increasing the number of heat pipes of the array over which the produced heat is distributed. The heat conducting plate may be incorporated into, e.g., may be permanently bonded to and may be provided together with, the layered heat pipe structure.
A face of each flat heat pipe array of the second layer of the layered heat pipe structure is thermally connected to a face of at least one flat heat pipe array of the first layer. The thermal connection between the first and second layer is such that the face of the second layer partially overlaps the face of the first layer. For example, the second layer may be thermally connected to a region of a face of the first layer that is opposite the region of the face of the first layer that is thermally coupled to the heat producing element. Alternatively or in addition, the second layer may be thermally connected to a longitudinal end region of a face of the first layer that extends laterally beyond the region of thermal contact with the heat producing element (e.g., with a conducting plate that is thermally connected to the heat producing element).
The axes of the heat pipe arrays of each layer (subsequent to the first layer) are arranged at a nonzero angle (e.g., right angle or oblique angle) to the axes of the heat pipe arrays of the previous layer. The nonzero angle is sufficient to enable at least an end region of some or all of the heat pipes of the subsequent (e.g., second) layer to extend laterally beyond the width of the previous (e.g., first) layer. Thus, the subsequent layer may act to increase the area over which the heat is dissipated. For example, the nonzero angle may be greater than 45°. The area of the region of dissipation of the heat may be further increased or maximized if the axis of the heat pipe arrays of the subsequent layer is substantially perpendicular to the axes of the heat pipe arrays of the previous layer (the nonzero angle being approximately 90°).
Typically, heat pipe arrays of a single layer of the layered heat pipe structure are arranged substantially parallel to one another. Thus, each layer may be characterized by a single axis. In some cases, different heat pipe arrays of a layer may be oriented nonparallel to one another.
The layered heat pipe structure may be thermally coupled to a heat sink. For example, a last (e.g., second) layer of the layered heat pipe structure may be thermally coupled to the heat sink. The heat sink may be actively cooled by forced convection or otherwise, or may be passively cooled. For example, the heat sink may include an array of fins, vertical chimneys, or other structure that promotes heat dissipation by radiation or natural (e.g., guided natural) convection.
An interface of thermal contact between surfaces of layers of heat pipe arrays (or of other components) of the layered heat pipe structure, or between the layered heat pipe structure and the heat producing element, the conducting plate, or the heat sink, may include a thermally conductive thermal interface material to reduce thermal resistance at the interface. The thermal interface material is heat conductive, thus facilitating conduction of heat from one surface at the interface to the other.
The thermal interface material is configured to adhere to the surfaces at the thermal connection and to enable contiguous thermal connection (e.g., without holes or spaces) between the two surfaces. For example, the thermal interface material may include a thermal grease, paste, adhesive, epoxy, pad, sheet, or other type or form of thermal material. Where the thermal bond is intended to be permanent, e.g., between layers of the layered heat pipe structure, the thermal bond may include a curable thermal interface material adhesive that permanently bonds to the two surfaces. In other places, the thermal connection may be anticipated to be broken at times. Under some circumstances, thermally connected surfaces may be expected to be separated from one another at some point after the thermal connection is made. Typically, surfaces may be separated from one another to enable access to a component for servicing. For example, the layered heat pipe structure may be removed from the heat producing element (e.g., a CPU, GPU, or other integrated circuit device) in order to enable access to the heat producing element for servicing. In this case, the thermal connection is expected to be non-permanent. The thermal connection may include a thermal interface material in the form of non-curable thermal grease or a similar material that remains in the form of a gel and enables future separation of the bonded surfaces.
By using a layered heat pipe structure for heat dissipation, the heat that is generated by the heat producing element may be dissipated two-dimensionally. Heat from the heat producing element that is dissipated by the heat pipe array of the first layer at the (longitudinal) end regions of the first layer may be dissipated laterally by the heat pipe array of the second layer.
The layered heat pipe structure may thus convey heat two-dimensionally, similarly to performance of a two-dimensional vapor chamber. However, production of a typical vapor chamber may be expensive, requiring custom design and production in accordance with a required size for a particular use or purpose. For example, production of such a vapor chamber may require manufacture of a top and bottom plate to size, enclosure of an area of wick material and a quantity of working fluid between the top and bottom plates, and closing the plates onto one another while sealing the edges (e.g., by soldering or welding).
On the other hand, a layered heat pipe structure in accordance with an embodiment of the present invention may be made relatively inexpensively. Since the structure of a heat pipe array has one-dimensional longitudinal symmetry, the heat pipe array may be manufactured by extrusion. The extruded piece includes a contiguous outer shell that forms the top and bottom and lateral sides of the array. The contiguous outer shell is impermeable to the working fluid of the heat pipe array.
The interior structure of the extruded piece may include longitudinal barriers at the edges that separate adjacent heat pipes of the heat pipe array. For example, the edges may be in the form of longitudinal crimps (e.g., externally visible as longitudinal grooves). The edges may prevent or inhibit migration of the working fluid of the heat pipe in a direction that excessively deviates from the axis of the heat pipe array.
The interior structure may include a longitudinal microstructure of ridges, wall, and channels of such size as to longitudinally conduct the working fluid within the heat pipe array by capillary action. (As used herein, a microstructure is to be understood as referring to a structure that is much smaller than the overall dimensions of the heat pipe array, and not as implying a particular length scale of the structure.)
The extruded piece may be cut to length, and its ends sealed (e.g., by crimping, or by a combination of crimping, soldering, welding, application of a sealant material, by another method, or by a combination of methods). Prior to sealing the ends, an appropriate quantity of the working fluid may be injected or otherwise introduced into each heat pipe of the heat pipe array.
FIG. 1 schematically illustrates components of an assembly in which an electronic component is passively cooled by a layered heat pipe structure, in accordance with an embodiment of the present invention.
FIG. 2A schematically illustrates the assembly whose components are shown in FIG. 1. FIG. 2B shows a schematic rotated view of the assembly shown in FIG. 2A. FIG. 2C shows a schematic lateral cross section of the assembly shown in FIG. 2A.
In passively cooled electronic component assembly 10, heat producing element 12 is passively cooled by layered heat pipe structure 20. For example, passively cooled electronic component assembly 10 may represent part of a portable or miniaturized computer or similar electronic device. Passively cooled electronic component assembly 10 may be configured to dissipate heat that is produced by heat producing element 12 in order to ensure proper operation of heat producing element 12 or another element of the electronic device.
The vertical and horizontal orientation of components of passively cooled electronic component assembly 10 as shown in FIG. 1 approximately corresponds to the orientation of the components when the electronic device of which passively cooled electronic component assembly 10 is part is in operation. Thus, a component that is depicted with a vertical or horizontal orientation is typically so oriented when the electronic device is in use.
Heat producing element 12 may represent a CPU, GPU, or another electronic component that produces heat that is to be dissipated by layered heat pipe structure 20. Heat producing element 12 may be mounted in an element socket 14 on a circuit board 16. Circuit board 16 may be mounted in a case or housing of a computer or other device. Typically, circuit board 16 may include additional electronic components and connectors. For example, circuit board 16 may represent a motherboard of a computing device or processor.
Layered heat pipe structure 20 includes at least two layers of heat pipe arrays. As shown, layered heat pipe structure 20 includes two layers, first layer 20 a and second layer 20 b. First layer 20 a includes a single first flat heat pipe array 22, and second layer 20 b includes two second flat heat pipe arrays 26. First array axis 24 is approximately perpendicular to second array axes 28.
A layered heat pipe structure may include more than two layers. Each layer may include one, two, or more heat pipe arrays. The axes of all heat pipe arrays in a single layer may be parallel to one another (as are second array axes 28), or may be somewhat nonparallel (e.g., with a nonzero angle that may be limited by space constraints). The axes of the heat pipe arrays in adjacent layers may be perpendicular to one another, or may be oriented at an oblique angle relative to one another.
Heat conducting plate 18 may be reversibly thermally connected to heat producing element 12. For example, front projecting face 18 a of heat conducting plate 18 may be configured to thermally connect to heat producing element 12. A size and shape of front projecting face 18 a may approximately match a size and shape of heat producing element 12 (or of a family of similarly shaped and size heat producing elements 12). An interface between front projecting face 18 a and heat producing element 12 may be filled by an appropriate thermal interface material. Typically, the thermal connection between heat producing element 12 and front projecting face 18 a may be non-permanent in order to enable future access to heat producing element 12. For example, a thermal interface material that is used to provide a conductive thermal connection between heat producing element 12 and front projecting face 18 a may include a non-curable thermal grease, paste, pad, or similar material.
Heat conducting plate 18 may be constructed of copper or of another thermally conductive metal or material. The area of rear face 18 b of heat conducting plate 18 is larger than the area of front projecting face 18 a and of heat producing element 12. Thus, heat conducting plate 18 may function to spread heat that is produced by heat producing element 12 over an area that is larger than that of heat producing element 12.
Rear face 18 b of heat conducting plate 18 is thermally connected to front face 23 a of at central region 22 b of first flat heat pipe array 22 of first layer 20 a. The thermal connection between heat conducting plate 18 and front face 23 a of first flat heat pipe array 22 may be permanent, e.g., with a thermal interface material that is curable or in the form of a thermal adhesive, or non-permanent.
First flat heat pipe array 22 includes an array of parallel oriented, adjacent flat heat pipes. For example, first flat heat pipe array 22 may be produced by extrusion. The longitudinal direction of heat transfer within the heat pipes of first flat heat pipe array 22 is indicated by first array axis 24. For example, first array axis 24 may be horizontal. Thus, first flat heat pipe array 22 may convey heat from heat conducting plate 18 laterally toward array end regions 22 a.
One or both of array end regions 22 a of first flat heat pipe array 22 extend laterally beyond rear face 18 b of heat conducting plate 18. For example, if front face 23 a of central region 22 b of first flat heat pipe array 22 overlaps and is thermally connected to heat conducting plate 18, the heat may be laterally conveyed toward array end regions 22 a. Thus, heat that is produced by heat producing element 12 may be transferred by first flat heat pipe array 22 away from heat producing element 12 toward array end regions 22 a.
Rear face 23 b of first flat heat pipe array 22 is thermally connected to a front face 27 a one or more second flat heat pipe arrays 26 of second layer 20 b. For example, a second flat heat pipe array 26 may partially overlap and be thermally connected to rear face 23 b at each array end region 22 a of first flat heat pipe array 22. As another example, a layer that includes a single second flat heat pipe array may partially overlap and be thermally connected across the lateral width of first flat heat pipe array 22.
Front face 27 a of a region of second flat heat pipe array 26 that is thermally connected to first flat heat pipe array 22 is substantially parallel to the surface of first flat heat pipe array 22.
The thermal connection between rear face 23 b of first flat heat pipe array 22 and front face 27 a of each second flat heat pipe array 26 may be permanent, e.g., with a thermal interface material that is curable or in the form of a thermal adhesive, or non-permanent.
The longitudinal direction of heat transfer within the heat pipes of second flat heat pipe array 26 is indicated by second array axis 28. For example, second array axis 28 may be vertical. Thus, first flat heat pipe array 22 may convey heat from first flat heat pipe array 22 vertically along second array axis 28 of second flat heat pipe array 26.
In the example shown, first flat heat pipe array 22 is thermally connected to the lower part of second flat heat pipe array 26. Thus, most of second flat heat pipe array 26 extends above first flat heat pipe array 22. In some cases, first flat heat pipe array 22 may be thermally connected to the central part of second flat heat pipe array 26 such that second flat heat pipe array 26 extends symmetrically above and below first flat heat pipe array 22. In some cases, first flat heat pipe array 22 may be thermally connected to the upper part of second flat heat pipe array 26 such that most of second flat heat pipe array 26 extends below first flat heat pipe array 22.
Although, in the example shown, first array axis 24 is horizontal and second array axis 28 is vertical, other arrangements are possible. For example, first array axis 24 may be vertical while second array axis 28 is horizontal, or one or both may be slanted at an oblique angle to the vertical and horizontal.
Rear face 27 b of second flat heat pipe array 26 may be thermally coupled to heat sink 30. For example, rear face 27 b of second flat heat pipe array 26 may be thermally connected to heat sink 30. The thermal connection between rear face 27 b of second flat heat pipe array 26 and heat sink 30 may be permanent, e.g., with a thermal interface material that is curable or in the form of a thermal adhesive, or may be non-permanent.
As another example, the thermal coupling may include one or more intervening structures that are placed between rear face 27 b of second flat heat pipe array 26 and heat sink 30. For example, one or more conducting plates or additional layers of flat heat pipe arrays may be placed between second flat heat pipe array 26 and heat sink 30.
The length of second flat heat pipe array 26 may be selected to be substantially equal or matched to the length of heat sink 30. Thus, heat that is conducted along the length of second flat heat pipe array 26 may be distributed along the length of heat sink 30. The distribution of heat along the length of heat sink 30 may facilitate efficient heat dispersion to the ambient atmosphere. The width of second flat heat pipe array 26 may be selected so as to approximately match the width of array end region 22 a. For example, in some cases, a layer of second flat heat pipe arrays 26 may cover a large fraction (e.g., over 50%, in some cases about 70%, or another fraction) of the surface area of heat sink 30.
Heat sink 30 may include one or more structures or features to facilitate convective or radiative dispersion of heat. As shown, heat sink 30 is passively cooled.
Alternatively or in addition, a heat sink may be actively cooled. For example, a fan or blower may be provided to force air flow through the heat sink, around the heat sink, or both. A liquid may be circulated through the heat sink and through an external heat exchanger to remove heat from the heat sink. Heat may be removed from the heat sink by a circulating refrigerant that cools the heat sink by evaporative cooling. The heat sink may include thermoelectric devices that operate to remove heat from the heat sink. Other active heat removal mechanisms may be used.
For example, heat sink 30 may include channels 34. Channels 34 may serve to increase the effective area of interface between heat sink 30 and the ambient atmosphere. In addition, channels 34 may be shaped to promote internal air flow when oriented vertically as shown. The internal air flow through channels 34 may be induced and maintained by a chimney effect. For example, air that is heated within channel 34 may rise to the top of channel 34. The rising may draw cool air into the bottom of channel 34, which also rises when heated, thus sustaining the chimney effect air flow. The induced air flow may further facilitate convective heat transfer to the surrounding ambient atmosphere.
Heat sink 30 may include fin structure 32. Fin structure 32 may increase the effective surface area of heat sink 30, thus facilitating convective heat transfer to the ambient atmosphere. Surfaces of fin structure 32 may be configured to facilitate radiative heat transfer to the surroundings. For example, surfaces of fin structure 32 may be prepared (e.g., painted or coated) to have a high emissivity. The combination of high emissivity and increased surface area may promote radiative heat dissipation.
In some cases, layered heat pipe structure 20 may be produced as a single unit of permanently connected layers (e.g., first layer 20 a including first flat heat pipe array 22, and second layer 20 b including second flat heat pipe arrays 22). The single unit may be thermally connected at a later time (e.g., during assembly of passively cooled electronic component assembly 10) directly to a heat producing element 12 or may be thermally coupled to heat producing element 12 via heat conducting plate 18. Similarly, the single unit may be thermally coupled at a later time (e.g., during assembly of passively cooled electronic component assembly 10) to heat sink 30. In some cases, layered heat pipe structure 20 may be produced in a unit that includes a permanently attached heat conducting plate 18, a permanently attached heat sink 30, or both (e.g., passively cooled electronic component assembly 10 produced as a unit).
Passively cooled electronic component assembly 10 may be incorporated into a computer or similar device. Typically, passively cooled electronic component assembly 10 may be incorporated into a portable or miniaturized device where active (e.g., forced air) cooling is precluded or undesirable, or represents a less attractive option.
For example, where noiselessness is advantageous, passive cooling may be preferred over possibly noisy operation of a motorized fan, blower, or pump for active cooling. In a device that is designed for portability, passive cooling may enable weight reduction by reducing electrical power requirements (e.g., enabling reduction of the size of a power supply or storage battery). Where miniaturization is advantageous, elimination of fans may enable reducing the size of a case or housing if the device.
When passively cooled electronic component assembly 10 is in operation, heat producing element 12 produces heat as a byproduct of its operation. For example, heat producing element 12 may include a CPU, GPU, or other electronic or other heat producing component of a computing device. Heat producing element 12 is typically held in an element socket 14 on a circuit board 16.
Heat that is generated by heat producing element 12 is conducted to front projecting face 18 a of heat conducting plate 18. For example, a thermal interface material may fill an interface at a thermal connection between heat producing element 12 and front projecting face 18 a. Typically, the thermal interface material forms a nonpermanent connection between heat producing element 12 and front projecting face 18 a. For example, the thermal interface material may include an uncured thermal grease or paste. The nonpermanent connection may enable access to heat producing element 12. For example, accessing heat producing element 12 may enable removal of heat producing element 12 from element socket 14 on circuit board 16, e.g., for testing or for replacement with a different heat producing element 12.
Heat conduction within heat conducting plate 18 (e.g., made of copper) may conduct the generated heat to rear face 18 b of heat conducting plate 18. Rear face 18 b is overlapped by and thermally connected to front face 23 a at a central region 22 b of first flat heat pipe array 22 of first layer 20 a of layered heat pipe structure 20. For example, a thermal interface material may fill an interface between heat conducting plate 18 and front face 23 a at a central region 22 b of first flat heat pipe array 22. The thermal interface material may be an uncured material to form a nonpermanent connection, or the thermal interface material may be a cured thermal adhesive that permanently attaches heat conducting plate 18 to first flat heat pipe array 22.
First flat heat pipe array 22 is configured to transfer heat laterally in a direction parallel to first array axis 24. In passively cooled electronic component assembly 10, first flat heat pipe array 22 conveys heat horizontally from heat conducting plate 18. Thus, generated heat may be transferred from central region 22 b of first flat heat pipe array 22 to array end regions 22 a that laterally extend beyond rear face 18 b of heat conducting plate 18.
Rear face 23 b of each array end region 22 a of first flat heat pipe array 22 is overlapped by and thermally connected to front face 27 a of a second flat heat pipe array 26 of second layer 20 b of layered heat pipe structure 20. In some cases, the second layer of layered heat pipe structure 20 may include a single second flat heat pipe array that is wide enough to overlap both array end regions 22 a of first flat heat pipe array 22. For example, a thermal interface material may fill an interface between rear face 23 b of first flat heat pipe array 22 and front face 27 a of each second flat heat pipe array 26. The thermal interface material may be a cured thermal adhesive that permanently attaches rear face 23 b of first flat heat pipe array 22 to front face 27 a of second flat heat pipe array 26.
Thus, first flat heat pipe array 22 may distribute heat along the width of each second flat heat pipe array 26. Each second flat heat pipe array 26 conveys heat in a direction that is parallel to second array axis 28, and, as shown, perpendicularly to the direction of heat distribution (first array axis 24) in first flat heat pipe array 22. As shown, in passively cooled electronic component assembly 10 second array axis 28 is configured to convey heat vertically above and below first flat heat pipe array 22.
In some cases (e.g., if constrained by other design considerations), the direction of conveyance of heat by the second flat heat pipe array may be at an oblique (non-perpendicular) angle to the direction of conveyance of heat by the first flat heat pipe array.
Rear face 27 b of each second flat heat pipe array 26 of second layer 20 b of layered heat pipe structure 20 is thermally connected to heat sink 30. For example, a thermal interface material may fill an interface between rear face 27 b of second flat heat pipe array 26 and heat sink 30. The thermal interface material may be an uncured material to form a nonpermanent connection, or the thermal interface material may be a cured thermal adhesive that permanently attaches second flat heat pipe array 26 to heat sink 30.
Heat sink 30 is configured to passively or actively transfer heat to the ambient atmosphere or to another cooler body. The area of second flat heat pipe arrays 26 may be matched to the area of heat sink 30 such that the area of second flat heat pipe arrays 26 is approximately equal to, or covers most of, the area of heat sink 30. Thus, the second layer of layered heat pipe structure 20 may distribute heat from heat producing element 12 over all or most of heat sink 30. The distribution of heat over heat sink 30 may enable efficient transfer of heat from heat producing element 12 to the ambient atmosphere.
In some cases, each second flat heat pipe array 26 may be separately thermally connected or coupled to a separate heat sink.
In passively cooled electronic component assembly 10, heat sink 30 is a passively cooled structure. Heat sink 30 includes an array of channels 34 that are vertically oriented. Each channel 34, when a wall of that channel 34 is heated, is designed to generate a chimney-effect flow of air through that channel 34. Each second flat heat pipe array 26 may distribute heat vertically along heat sink 30. Thus, each second flat heat pipe array 26 may distribute heat along a wall of each channel 34. In this manner, heat may be distributed along the length of each channel 34. This distribution of heat along a channel 34 may enable effective cooling by that channel 34.
Heat sink 30 may include a fin structure 32 or other structure to facilitate radiative or convective heat transfer to the surroundings. Alternatively or in addition, a heat may include other structures to facilitate passive heat transfer to the surroundings.
Different embodiments are disclosed herein. Features of certain embodiments may be combined with features of other embodiments; thus certain embodiments may be combinations of features of multiple embodiments. The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be appreciated by persons skilled in the art that many modifications, variations, substitutions, changes, and equivalents are possible in light of the above teaching. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

1. A structure for transferring heat from a heat producing element to a heat sink, the structure comprising:

a first layer comprising a first flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a first array axis and configured to be thermally coupled to the heat producing element; and

a second layer comprising a second flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a second array axis,

wherein the first flat heat pipe array and the second flat heat pipe array partially overlap and are in thermal contact, the first array axis and the second array axis forming a nonzero angle, so that the second flat heat pipe array extends beyond the first flat heat pipe array, the second flat heat pipe array configured to be thermally coupled to the heat sink.

2. The structure of claim 1, wherein the second array axis is substantially perpendicular to the first array axis.

3. The structure of claim 1, wherein thermal coupling between the first flat heat pipe array and the heat producing element comprises a heat conducting plate.

4. The structure of claim 1, wherein the first array axis is configured to be substantially horizontal when the heat producing element is in operation.

5. The structure of claim 1, configured such that the second array axis is substantially vertical when the heat producing element is in operation.

6. The structure of claim 1, wherein the first flat heat pipe array comprises a central region that is configured to be thermally coupled to the heat producing element, and wherein the second flat heat pipe array overlaps an end region of the first flat heat pipe array.

7. The structure of claim 6, wherein the second layer comprises two flat heat pipe arrays, each of the two flat heat pipe arrays overlapping and in thermal contact with a different end regions of the first flat heat pipe array.

8. The structure of claim 1, wherein an interface at the thermal contact between the second flat heat pipe array and the first flat heat pipe array includes a thermal interface material.

9. The structure of claim 9, wherein the thermal interface material comprises a thermal adhesive.

10. An assembly comprising:

a heat producing element;

a heat sink; and

a structure for transferring heat from the heat producing element to the heat sink, the structure comprising:

a first layer comprising a first flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a first array axis from a first region of said at least one first flat heat pipe array that is thermally coupled to the heat producing element, to a second region of the first flat heat pipe array; and

a second layer comprising at least one second flat heat pipe array of a plurality of substantially parallel and adjacent heat pipes for conveying heat substantially along a second array axis that forms a nonzero angle with the first array axis, the second flat heat array overlapping and in thermal contact with the second region of the first flat heat pipe array and thermally coupled to the heat sink.

11. The assembly of claim 10, wherein the second array axis is substantially perpendicular to the first array axis.

12. The assembly of claim 10, further comprising a heat conducting plate, one face of which is in thermal contact with the heat producing element, and another face of which is in thermal contact with the first region the first flat heat pipe array.

13. The assembly of claim 12, wherein an interface of thermal contact between the heat conducting plate and the heat producing element comprises an uncured thermal interface material.

14. The assembly of claim 10, wherein the heat producing element is held in a socket of a circuit board.

15. The assembly of claim 10, configured such that the first array axis is substantially horizontal and the second array axis is substantially vertical when the assembly is operating.

16. The assembly of claim 10, wherein the heat sink is configured to be passively cooled.

17. The assembly of claim 16, wherein the heat sink comprises a plurality of channels configured to produce an internal flow of air when heat is conveyed from the heat producing element to the heat sink and when the channels are substantially vertical.

18. The assembly of claim 10, wherein a length of said at least one second flat heat pipe array is substantially equal to a length of the heat sink.

19. The assembly of claim 10, wherein the first region of the first flat heat pipe array comprises a central region of the first flat heat pipe array, the second region of the first flat heat pipe array comprises an end region of the first flat heat pipe array.

20. The assembly of claim 19, wherein said at least one second flat heat pipe array comprises two flat heat pipe arrays, each of the two flat heat pipe arrays overlapping and in thermal contact with a different end region of the first flat heat pipe array.