CN110006282B

CN110006282B - Thermal ground plane

Info

Publication number: CN110006282B
Application number: CN201810011928.8A
Authority: CN
Inventors: 瑞恩·约翰·路易斯; 杨荣贵; 李云城
Original assignee: Kaiwen Thermal Engineering Technology Co
Current assignee: University of Colorado
Priority date: 2018-01-05
Filing date: 2018-01-05
Publication date: 2020-12-15
Anticipated expiration: 2038-01-05
Also published as: CN110006282A

Abstract

The application relates to the field of heat exchange and discloses a thermal ground plane. For example, thermal ground planes have vapor cores of variable thickness. The thermal ground plane includes a first enclosure and a second enclosure, wherein the second enclosure and the first enclosure are configured to enclose a working fluid. The thermal ground plane further includes an evaporator region disposed at least partially on at least one of the first enclosure and the second enclosure, a condenser region disposed at least partially on at least one of the first enclosure and the second enclosure, and a wicking structure disposed between the first enclosure and the second enclosure. The vapor core is at least partially defined by a gap between the first shell and the second shell, the gap having a thickness that is variable between the first shell and the second shell.

Description

Thermal ground plane

Technical Field

The present application relates to the field of heat exchange, and more particularly to a thermal ground plane.

Background

Thermal ground planes are commonly used in devices that require tight spaces where the thermal ground plane thickness is very thin, such as mobile electronic devices. In addition, for many thermal ground planes, thermal conductivity may be related to the thickness of the vapor core. For example, in the case of 45 ℃ steam, the effective thermal conductivity of the thermal interface layer may be reduced from 30,000W/mK to 7,000W/mK as the gap decreases from 200 μm to 100 μm. When the gap is reduced from 100 μm to 50 μm, the effective thermal conductivity of the thermal interface layer may be further reduced, for example from 7000 to 2000W/mK. For example, gap variations of 50 μm or 100 μm may result in significant changes in the thermal performance of vapor transport. The thickness of the hot floor may create other thermal problems. There is a challenge in the art to produce a thermal ground plane that can be used in confined spaces that are thin but still provide effective thermal performance.

Disclosure of Invention

Some embodiments of the present application provide a thermal ground plane such that a vapor core within the thermal ground plane has a variable thickness, such that vapor transport of the thermal ground plane may be optimized.

In order to solve the above technical problem, some embodiments of the present application provide a thermal ground plane, including a first casing and a second casing, where the second casing and the first casing are configured to enclose a working fluid. The thermal ground plane may further include an evaporator region disposed at least partially on at least one of the first enclosure and the second enclosure, a condenser region disposed at least partially on at least one of the first enclosure and the second enclosure, and a wicking structure disposed between the first enclosure and the second enclosure. The vapor core is at least partially defined by a gap between the first shell and the second shell, the gap having a thickness that is variable between the first shell and the second shell, the vapor core for vapor transport between the evaporator region and the condenser region.

In some embodiments, the gap may be designed to provide space for expanding the vapor core gap.

In some embodiments, the thickness of the gap adjacent the evaporator region is less than the average gap thickness.

In some embodiments, the thickness of the gap not adjacent to the evaporator region is greater than the average gap thickness.

In some embodiments, either or both of the first and second shells comprise a material that stretches and/or contracts to enlarge the gap.

In some embodiments, the thermal ground plane may include a plurality of spacers disposed within the gap.

In some embodiments, the wicking structure may be in contact with either or both of the first shell layer and/or the second shell.

In some embodiments, the thermal ground plane may include additional wicking structures in contact with the wicking structures and the evaporator region.

In some embodiments, the plurality of spacers may comprise copper or a polymer encapsulated by a hermetic seal.

In some embodiments, the plurality of spacers may comprise springs.

In some embodiments, the plurality of spacers may comprise an elastomeric material.

In some embodiments, the thickness of the gap may be less than 50 μm.

In some embodiments, the gap may be defined by an internal pressure greater than ambient pressure.

The exemplary embodiments in this application are not intended to define or define the application, but rather to provide an aid in understanding the application. Other embodiments are discussed in the detailed description that follows. The benefits of one or more embodiments may be further understood by examining this specification or by practicing one or more embodiments.

Drawings

The features, details and effects of the present application can be better understood with reference to the detailed description of the embodiments and the accompanying drawings. One or more embodiments of the present application are illustrated by way of example in the accompanying drawings and not by way of limitation, in which elements having the same reference numeral designations in the drawings are shown as similar elements and the drawings are not to be construed as limited, unless otherwise specified.

Fig. 1 is a schematic illustration of a thermal ground plane according to some embodiments provided by way of example herein;

FIG. 2 is a graphical representation of the effective thermal conductivity of vapor transport at a 0.25mm thin thermal ground plane according to some embodiments provided by way of example herein;

fig. 3 is a side view thermal ground plane including a thermal ground plane of a vapor core of variable thickness according to some embodiments provided by way of example herein;

FIGS. 4A, 4B, 5A, and 5B are schematic illustrations of steps of fabricating a thermal ground plane having a variable thickness vapor core according to some embodiments provided by way of example herein;

fig. 6A and 6B are schematic thermal ground planes with extended thickness and/or lower height for a first portion of a plurality of spacers in some embodiments provided by way of example according to the present application;

fig. 7A and 7B are schematic thermal ground plane diagrams with extended thickness and/or lower height and a corrugated or crushed profile for a first portion of a plurality of spacers in some embodiments provided by way of example according to the present application;

FIG. 8 is a schematic thermal ground plane according to some embodiments provided by way of example herein;

FIGS. 9A, 9B, 10A, and 10B are schematic illustrations of steps of fabricating a thermal ground plane having a variable thickness vapor core according to some embodiments provided by way of example herein;

FIG. 11 is a schematic thermal ground plane that may include an additional wicking structure disposed within the vapor core in some embodiments provided by way of example in accordance with the present application, wherein the thermal ground plane may be positioned within the wicking structure in an area proximate to a circuit component (e.g., a circuit component that may produce more heat than other circuit components);

fig. 12 is a schematic thermal ground plane with a first enclosure having a variable height that can accommodate the contour of the device enclosure in some embodiments provided by way of example according to the present application. In some embodiments, voids associated with the device housing may be utilized to enhance vapor transport;

FIG. 13 is a schematic thermal ground plane with a variable height first enclosure and a variable height second enclosure according to some embodiments provided by way of example herein; and

fig. 14 is a schematic thermal ground plane with a variable height first enclosure and a variable height second enclosure according to some embodiments provided by way of example herein.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that numerous technical details are set forth in order to provide a better understanding of the present application in various embodiments of the present invention. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments.

The application discloses a thermal ground plane including a variable thickness vapor core. In some embodiments, the vapor core thickness may correspond to the three-dimensional shape of the circuit element and/or the device housing in which the thermal ground plane may be placed. The present application also discloses a method for manufacturing a thermal ground plane having a variable thickness vapor core.

Fig. 1 is a schematic diagram of an exemplary thermal ground plane 100, according to some embodiments. Thermal ground plane 100 includes a first housing 105 and a second housing 110, where first housing 105 and second housing 110 are sealed together to enclose a vapor core 115 and/or a wicking structure 120. The first housing 105 and the second housing 110 may also enclose the working fluid in a vapor and/or wicking structure. Thermal ground plane 100 may be disposed proximate heat source 130 and/or heat sink 140. The area of thermal ground plane 100 near heat source 130 may be evaporator region 135 and/or the area of thermal ground plane 100 near heat sink 140 may be condenser region 145. For example, the working fluid may evaporate from heat generated by the heat source 130 at or near the evaporator region 135 and/or the vapor may condense near the heat sink 140 or condenser region 145 where heat is absent. The steam may flow from the evaporator region 135 to the condenser region 145 via the steam core 115. The working fluid may flow from the condenser region 145 to the evaporator region 135 through the wicking structure 120.

In some embodiments, the wicking structure 120 may be deposited on either or both of the first housing 105 and the second housing 110. In some embodiments, the thermal ground plane (e.g., of which the wicking structure 120 is a part) may include a plurality of microstructures. The microstructures may include, for example, a plurality of nanowires, an array of nanowires, or a plurality of capped micropillars deposited on a plurality of micropillars. In some embodiments, the wicking structure 120 may be understood as a wicking layer or a wicking structure layer.

In some embodiments, the working fluid may comprise water or any other coolant that may transfer heat from the evaporator region 135 to the condenser region 145, for example, by one or more of the following mechanisms: a) the evaporation of the working fluid forms a vapor by absorbing heat emitted from the heat source 130; b) the evaporative transport of the working fluid from the evaporator region 135 to the condenser region 145; c) cooling provided by the heat sink 145, condensing the vapor to a liquid; and/or d) returning liquid from condenser region 145 to evaporator region 135 by capillary pumping pressure created by wicking structure 120.

In some embodiments, the thermal performance of the thermal ground plane may depend on the configuration, but may be about 3-50 times that of copper.

In some embodiments, the first housing 105 and/or the second housing 110 and/or the wicking structure 120 may comprise copper, stainless steel, silicon, a polymer, copper-clad polyimide (Kapton) and/or a flexible material, and/or the like.

In some embodiments, the operation of the thermal ground plane is associated with a plurality of thermal resistances. For example, the thermal resistance may include: a) the evaporator region passes through the thermal resistance (Re, shell) of the thermal ground plane shell; b) thermal resistance (Re, wire mesh) through an aqueous wicking structure (e.g., copper wire mesh) in the evaporator zone; c) a thermal resistance (Ra, steam) to transport steam from the evaporator to the condenser through the steam core; d) thermal resistance through an aqueous wicking structure within the condenser (Rc, wire mesh); e) thermal resistance through the thermal ground plane housing (Rc, housing) within the condenser region; f) thermal conduction resistance (Ra, wire mesh) from condenser to evaporator along the moisture wicking structure; and/or g) thermal conduction resistance (Ra, shell) along the shell from the condenser to the evaporator.

For thick thermal ground planes (e.g., thicknesses of about 1mm or greater), the gap (or height) of the vapor core is large/high. Thus, steam may be transported through the vapor core with little flow resistance and/or negligible vapor phase conduction resistance (Ra, steam). However, for thin thermal ground planes (e.g., less than about 1mm thick or between 0.25mm and 0.35mm thick), the clearance (or height) of the vapor core is significantly reduced. In some cases, vapor phase conductive resistance (Ra, steam) may play a major role. The overall thermal performance of such a thin thermal ground plane may depend on the gas phase conduction performance.

For example, the thermal performance of gas phase conduction can be represented by the effective thermal conductivity of gas phase conduction. The effective thermal conductivity K of this gas phase conduction is shown in FIG. 2_vaporPossibly influenced by the clearance v of the steam core and/or the steam temperature T. For example, when the gap v is reduced from 200um to 100um, the effective thermal conductivity K of the steam with a temperature T of 45 ℃_vaporCan be reduced from 30000W/mK to 7000W/mK. For example, when the gap v is reduced from 100um to 50um, the effective thermal conductivity can be further reduced from 7000W/mK to 2000W/mK. For example, a gap varying between 50um and 100um can result in significant changes in the thermal properties of the gas phase conduction.

The thickness of mobile systems such as smartphones, tablets, watches, wearable devices, laptops, and/or wearable electronic devices is very important. In the design phase, it must be carefully considered to reserve 50um or 100um space for each device. Some embodiments of the invention may incorporate a thermal ground plane with a variable vapor core thickness. In some embodiments, the variable thickness of the thermal ground plane may match the void of the mobile system.

There are gaps in almost all smart phones, tablets, laptops, or wearable electronic devices. In some embodiments, such voids may be used to provide a thicker vapor core for the thermal ground plane, which may be used to improve vapor phase conduction.

The different height components on the circuit board of the mobile device form a plurality of voids. Such voids may be used to enhance vapor phase conduction of the thermal ground plane, spreading chip heat to the phone case. Similar gaps exist in other areas within the mobile system.

In addition, the mobile device has a variable pitch on the housing. In some embodiments, voids on the shell may also be used to optimize vapor phase conduction of the thermal ground plane.

A typical thermal ground plane is shown in fig. 1, which is flat. In such a flat plate configuration, the vapor core may be designed for optimal performance. In some embodiments, the vapor core and other material layers of the thermal ground plane may vary, and available voids may be used. In most cases, the temperature difference from one side of the thickness to the other is small for thin thermal ground planes. Therefore, the wicking structure may not be as effective as attaching the wicking structure directly to the heat-generating chip. The elimination of the wicking structure attached to the chip facilitates the manufacture of different vapor cores and their associated housings.

Vapor cores with different gaps may be formed using stamping or other forming processes. And such different gaps may also be formed by pressurizing the vapor core and deforming the housing against the circuit board. In this embodiment, the housing may be a flexible material and/or plastic. After the molding process, the shell of the thermal ground plane may be strengthened.

As shown in fig. 2, increasing the steam core portion by 50um or 100um is effective to enhance gas phase conduction in the thermal ground plane. The figure also shows that the gas phase conduction is strongly affected by the steam temperature. Therefore, the reinforcing effect significantly affects a portion far from the heat generating chip. In these sections, the steam temperature is low, thus resulting in poor gas phase conduction. These parts refer to parts that may benefit from any enhancement.

Fig. 3 is a side view of a thermal ground plane 500 including a variable thickness vapor core 520 according to some embodiments. In some embodiments, thermal ground plane 500 includes a first enclosure 510 (e.g., a first enclosure) and a second enclosure 535 (e.g., a second enclosure). First enclosure 510 and second enclosure 535 may be sealed together to encapsulate the other elements of thermal ground plane 500. Thermal ground plane 500 may further include a wicking structure 515 and a vapor core 520. The wicking structure 515 may be coupled, attached, in contact with, and disposed on the first housing 510. In some embodiments, the wicking structure 515 may be made of copper, stainless steel, titanium, ceramic, or polymer. In some embodiments, the wicking structure may include or be coated with additional layers to prevent its reaction with the fluid, if desired.

In some embodiments, thermal ground plane 500 may be disposed between circuit board 530 having

circuit elements

525 and 540 and device housing 505. In this example, the height of the circuit board 530 with the

circuit elements

525 and 540 may vary. The second housing 535 has a variable shape to accommodate the variable shape circuit board 530 and circuit components 525 and 540 (e.g., processor, memory, integrated circuit, etc.). The variable shape of the second shell 535 may form a vapor core 530 having a variable thickness. As shown, vapor core 530 may vary in thickness whether vapor core 520 is in circuit element 525 or in proximity to circuit element 540.

In some embodiments, a variable width vapor core may enhance vapor phase conduction within thermal ground plane 500.

In some embodiments, the evaporator region can be formed near

circuit element

525 or 540. In some embodiments, the evaporator region may not be formed near

circuit elements

525 or 540.

As shown in fig. 3, vapor core 520 is thicker at the portion of the thermal ground plane corresponding to the circuit board void. In some embodiments, different portions of the vapor core may differ in thickness. In some embodiments, the second shell 535 of the thermal ground plane 500 may have a contoured shape, a three-dimensional shape, a varying shape, a non-planar shape, and the like. In some embodiments, wicking structure 515 and/or first shell 510 of thermal ground plane 500 may be substantially flat. In some embodiments, both first shell 510 and second shell 535 of thermal ground plane 500 may have a contoured shape, a three-dimensional shape, a varying shape, a non-planar shape, and the like.

In some embodiments, the evaporator region can be at least partially disposed on the first shell 510 and/or the second shell 535. For example, the evaporator region can be designed within the first housing 510 and/or the second housing 535 such that it is located, in use, near a heat source, e.g., near one or

more circuit elements

525 and 540.

In some embodiments, the condenser zone may be at least partially disposed on the first shell 510 and/or the second shell 535. For example, the condenser zone may be designed within the first housing 510 and/or the second housing 535 such that it is located near a region that is cooler than the heat source in use.

Steam core 520 includes 2 thinner

steam core sections

520A and 520B, and 3 thicker

steam core sections

520C, 520D, and 520E. In some embodiments, the thickness of

vapor core regions

520A and 520B is less than the average thickness of the vapor cores. In some embodiments, the thickness of

vapor core regions

520C, 520D, and 520E is greater than the average thickness of the vapor cores. In some embodiments, one or more of

vapor core regions

520A and 520B have a thickness of less than about 50 μm to about 100 μm. In some embodiments, one or more of

vapor core regions

520C, 520D, and 520E have a thickness of greater than about 50 μm to about 100 μm.

Fig. 4A, 4B, 5A, and 5B illustrate steps of fabricating a thermal ground plane with a variable thickness vapor core according to some embodiments. For example, in fig. 4A, a plurality of spacers 615 may be disposed or fabricated on the second housing 535. The plurality of spacers 615 may be disposed on the second housing 535 by electroplating, metal etching, polymer deposition, photolithography, vapor deposition, and the like. In some embodiments, the plurality of spacers may be hermetically sealed or coated with a corrosion resistant coating.

For example, in fig. 4B and 5A, the second housing 535 and the plurality of spacers 615 may be pressed against the forming substrate 605, for example, using the forming top plate 610. For example, the molding substrate 605 may have a three-dimensional form, shape or model of the circuit board 530 of the

circuit elements

525 and 540. In some embodiments, the shape of the molding substrate 605 may be defined by a circuit board void.

Fig. 5B shows thermal ground plane 600 with permanently deformed second shell 535 and a plurality of spacers 615 integrated with other layers. In this example, wicking structure 515 is in contact with, coupled to, disposed on, grown on first housing 510. In this example, the first housing 510 may be flat. In this example, thermal ground plane 600 includes a vapor core having a variable thickness. In some embodiments, the gas within thermal ground plane 600 may be vented before water or other cooling fluid is filled into thermal ground plane 600. Various other steps may include: sealing the first housing 510 and the second housing 535 together; filling the thermal ground plane 600; and one or more coatings for thermal ground plane 600, etc. In some embodiments, during normal operation, the water vapor pressure within thermal ground plane 600 may be lower than atmospheric pressure. For example, a lower pressure may cause one or both of the shell and/or other layers of the thermal ground plane to be pulled in a direction opposite the barrier used to define the vapor core. In some embodiments, each molding step of thermal ground plane 600 may be accomplished by a molding step using a set of fixtures. In some embodiments, each forming step of the thermal ground plane 600 may be accomplished by a roll-to-roll forming process.

Various other techniques may be used to form the height of the plurality of spacers 615. For example, some of the plurality of spacers 615 may be etched away using photolithographic techniques. In some embodiments, the height of the spacers may be unevenly distributed, thereby eliminating the need to deform the spacers. In some embodiments, the second housing 535 may be molded according to a desired shape, and then a spacer may be formed on the second housing 535. In some embodiments, the separator layer may be a continuous mesh layer or a porous layer. A single layer may be composed of two or more sublayers.

In some embodiments, the plurality of spacers 615 may comprise copper or a polymer material. In some embodiments, the plurality of spacers may comprise any type of metal.

Fig. 6A and 6B illustrate a thermal ground plane 800 having an extended thickness and/or a lower height for a first portion of a plurality of spacers 815B. Thermal ground plane 800 may further have a second portion of plurality of spacers 815A, wherein the second portion of plurality of spacers 815A has an extended thickness and/or a higher height. A first portion of plurality of spacers 815B may be disposed in a portion of vapor core 520 at a first thickness, and a second portion of plurality of spacers 815A may be disposed in a portion of vapor core 520 at a second thickness. The first thickness may be less than the second thickness. In some embodiments, a first portion of the plurality of spacers 815B having an extended thickness and/or a lower height may compress the extension. Fig. 7A and 7B illustrate a thermal ground plane 800 having a first portion of a plurality of spacers 915B with an expanded thickness and/or a lower height and a wrinkled or crushed profile that may be formed by compression of the thermal ground plane 900.

In some embodiments, the lattice structure 515 may be disposed on the plurality of

partitions

815A, 815B, and/or 915B, and/or between the plurality of

partitions

815A, 815B, and/or 915B and the first housing 510.

Fig. 8 illustrates a thermal ground plane 1000 according to some embodiments. Grid structure 515 within thermal ground plane 1000 may be disposed between

multiple partitions

815A, 815B, and/or 915B. In some embodiments, a plurality of

spacers

815A, 815B, and/or 915B may be disposed on the second housing.

Fig. 9A, 9B, 10A, and 10B illustrate steps of fabricating a thermal ground plane with a variable thickness vapor core according to some embodiments. In some embodiments, the plurality of spacers 715 may include spacers having spring-like mechanical properties. For example, the plurality of spacers 715 may include micro springs, micro suspensions, micro flexures made of copper, other metallic materials, or elastomeric polymers encapsulated by hermetic seals. In some embodiments, the mechanical stiffness of plurality of spacers 715 may be sufficient to keep the vapor core at a low vacuum. In some embodiments, the plurality of spacers 715 and/or the first shell 510 and/or the second shell 535 are not sufficiently rigid to allow the vapor core 520 shape to follow the configuration of the circuit board 530 (and/or the circuit components 525 and/or 540) under the pressure of the mobile system enclosure (e.g., shell 505). In the area having the void, the steam core 520 may naturally expand. In some embodiments, the height or size of the plurality of spacers 715 may not be evenly distributed, and thus, the amount of deformation of the plurality of spacers 715 may be designed to accommodate different voids. In some embodiments, the plurality of spacers 715 may be formed on the housing after the first housing 510 and/or the second housing 535 are formed into the desired shape. For example, the plurality of spacers 715 may be a continuous mesh layer or a porous layer. A monolayer may consist of 2 or more sublayers.

In some embodiments, the plurality of spacers may be resilient (e.g., spring-like mass), allowing the thermal ground plane to self-adjust and/or deform into the circuit board gap. In some embodiments, vapor core 520 may include a plurality of elastomeric isolators that are variable in height. In some embodiments, the resilient or spring-like separator and the first housing 510 and/or the second housing 535 may deform according to the clearance for enhanced gas phase conduction. In some embodiments, the coolant may optionally be operated under positive pressure to push the first housing 510 and/or the second housing 535 outward, such that the coolant itself is used as a spring-like material.

Fig. 11 illustrates a thermal ground plane 1300 that may include an additional wicking structure 1320 disposed within the vapor core, and the thermal ground plane may be placed in an area near a circuit element (e.g., a circuit element that may produce more heat than other circuit elements). For example, additional wicking structures 1320 may be used to reduce the high heat flux generated by some circuit elements. In some embodiments, additional wicking structure 1320 may be connected, in contact with, and/or coupled to one or more additional wicking structures 515 and/or first shell 510. In some embodiments, the additional wicking structure 1320 may be made of copper, stainless steel, titanium, ceramic, or polymer. In some embodiments, additional wicking structure 1320 may include or be coated with additional layers to prevent its reaction with the fluid, if desired.

In some embodiments, additional wicking structure 1320 may be coupled to wicking structure 515, for example, in order to provide for liquid water to remain continuously evaporated. The vapor temperature in the region near the heat generating chip (e.g., circuit element) is high and the corresponding vapor phase conducts well. This allows the vapor core thickness to be reduced in this hot zone without degrading performance.

Fig. 12 illustrates a thermal ground plane 1400 having a first shell 1410, wherein the first shell 1410 has a variable height that can accommodate the contour of the device housing 505. In some embodiments, voids associated with the device housing 505 may be utilized to enhance gas phase conduction. The device housing 505 of each system is an important element of thermal management. For example, heat may be carried from

circuit elements

525 and 540 into the ambient air. In some embodiments, the purpose of thermal management may be to spread heat from the heat generating

circuit elements

525 and 540 to the device housing 505 for cooling by the ambient environment. Many device housings (e.g., device housing 505) may not be flat. For example, the device housing may have a three-dimensional shape to accommodate different design requirements. This results in various voids in the device housing. According to some embodiments, the vapor core 820 of the thermal ground plane 1400 may have a variable thickness, forming a three-dimensional shape for accommodating the device enclosure 505. In some embodiments, wicking structure 815 may be disposed adjacent to circuit board 530 and/or circuit elements 525 and/or 540.

Fig. 13 illustrates a thermal ground plane 1500 having a variable height first housing 1410 and a variable height second housing 1535 according to some embodiments. For example, the first housing 1410 may have a variable height that accommodates the device housing 805. For example, second housing 1535 may have a variable height that accommodates circuit board 530 and/or

circuit elements

525 and 540. In this example, the wicking structure 1515 may contact, attach, couple, grow, be disposed on the second housing 1535.

Fig. 14 illustrates a thermal ground plane 1600 having a first housing 1410 of variable height and a second housing 1535 of variable height according to some embodiments. For example, the first housing 1410 may have a variable height that accommodates the device housing 805. For example, second housing 1535 may have a variable height that accommodates circuit board 530 and/or

circuit elements

525 and 540. In this example, wicking structure 1615 may contact, attach, couple, grow, and be disposed on first housing 1410.

In some embodiments, thermal ground plane 1500 and/or thermal ground plane 1600 voids in device housing 805 and/or circuit board 530 (and/or circuit elements 525 and/or 540) may be used to enhance vapor phase conduction. In some embodiments, one or more wicking structures may be disposed adjacent the first shell 805 and/or the second shell 835, wherein the first shell 805 and/or the second shell 835 are disposed adjacent the circuit element.

Some embodiments include a circuit board having one or more voids formed by creation, construction, and design, among other things, for optimized gas phase conduction within an associated thermal interface plane. The design of a typical circuit board may be optimized by incorporating considerations of electrical, mechanical, thermal, and/or other performance metrics. The gap may also be optimized. For example, the circuit board may be designed to enhance gas phase conduction within the core associated with the thermal ground plane. While voids are always present, their arrangement may be optimized, for example, to enhance gas phase conduction. The primary considerations also relate to size, including the gap of the gap and/or the steam temperature within the gap. At low steam temperatures, the gas phase conduction effect may be poor. In some cases, it may be desirable to enlarge the size of the vapor core in areas away from the heat source (e.g., circuit components). In these areas, the steam temperature is low and gaps are added to achieve efficient conduction.

Some embodiments may further include a device housing having voids created by creation, arrangement, design, and construction to optimize gas phase conduction. The design of a typical device housing may incorporate considerations of electrical, mechanical, thermal, and other performance metrics. The gap may also be optimized. In some embodiments, the voids may be used to enhance the associated thermal performance of the gas phase conduction and thermal ground plane. For example, the circuit board and/or the housing (or casing) may represent critical components in a mobile system. Voids are always present and, therefore, the void arrangement can be optimized to enhance the associated thermal performance of the gas phase conduction and thermal ground plane. For example, primary considerations may include size, including the clearance of the voids and the steam temperature within the voids.

The term "substantially" refers to 5% or 10% of the value referred to or within manufacturing tolerances.

Various embodiments are disclosed. The various embodiments may be combined, partially or wholly, to form further embodiments.

Numerous specific details are set forth herein in order to provide a thorough understanding of the claimed subject matter. However, it will be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, methods, devices, or systems that are well known to those of ordinary skill have not been described in detail so as not to obscure claimed subject matter.

Method embodiments disclosed herein may be performed in the operation of a computing device. The order of the blocks of cells in the above examples may vary, e.g., the blocks of cells may be reordered, combined, and/or broken into sub-blocks. Some blocks or processes of cells may be executed in parallel.

The terms "adapted to" or "configured to" as used herein have an open and inclusive meaning and do not exclude an apparatus being adapted to or configured to perform other tasks or steps. Furthermore, the term "based on" is also to be taken in an open and inclusive sense, as well as a process, step, calculation, or other action that is "based on" one or more recited conditions or values may in fact be based on other conditions or values in addition to the recited conditions or values. The headings, lists, and numbers included herein are for convenience of explanation only and are not intended to be limiting.

While specific embodiments of the subject matter have been described in detail, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, it will be understood that the present disclosure has been described by way of example only, and not by way of limitation, and does not preclude inclusion of modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.

Some embodiments of the present application also provide the following examples.

Example 1. a thermal ground plane, comprising:

a first housing;

a second housing, the second housing and the first housing configured to enclose a working fluid;

an evaporator zone disposed at least partially on at least one of the first housing and the second housing;

a condenser zone at least partially disposed on at least one of the first shell and the second shell;

a wicking structure disposed between the first housing and the second housing;

a vapor core at least partially defined by a gap between the first shell and the second shell, wherein a thickness of the gap varies between the first shell and the second shell.

Example 2. the thermal ground plane according to example 1, wherein the gap is designed to provide space for expanding the vapor core gap.

Example 3. the thermal ground plane according to example 1 or 2, wherein a thickness of the gap adjacent to the evaporator region is less than the average gap thickness.

Example 4. the thermal ground plane according to examples 1, 2 or 3, wherein the thickness of the gap not adjacent to the evaporator region is greater than the average gap thickness.

Example 5. the thermal ground plane according to any one of examples 1 to 4, wherein either or both of the first shell and the second shell comprise a material that stretches and/or contracts to enlarge the gap.

Example 6. the thermal ground plane according to any one of examples 1 to 5, wherein the wicking structure layer is in contact with either or both of the first shell layer and/or the second shell.

Example 7. the thermal ground plane according to any one of examples 1-6, further comprising an additional wicking structure in contact with the wicking structure and the evaporator region.

Example 8. the thermal ground plane according to any one of examples 1 to 7, wherein the gap is defined by an internal pressure higher than ambient pressure.

Example 9 the thermal ground plane according to any one of examples 1 to 8, further comprising a plurality of spacers disposed within the gap.

Example 10 the thermal ground plane according to example 9, wherein the plurality of spacers comprise copper or a polymer encapsulated by a hermetic seal.

Example 11 the thermal ground plane according to example 9, wherein the plurality of spacers may include springs.

Example 12 the thermal ground plane according to example 9, wherein the plurality of spacers may include an elastomeric material.

Example 13. the thermal ground plane according to example 9, wherein the thickness of the gap may be less than 50 μm.

It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.

Claims

1. A thermal ground plane, comprising:

a first housing;

a wicking structure disposed between the first housing and the second housing;

a vapor core at least partially defined by a gap between the first and second housings, wherein a thickness of the gap varies between the first and second housings, the vapor core for vapor transport between the evaporator region and the condenser region.

2. The thermal ground plane according to claim 1, wherein the gap is designed to provide space for expanding the vapor core gap.

3. The thermal ground plane according to claim 1, wherein a thickness of a gap adjacent to the evaporator region is less than an average gap thickness.

4. The thermal ground plane according to claim 1, wherein a thickness of the gap not adjacent to the evaporator region is greater than an average gap thickness.

5. The thermal ground plane according to claim 1, wherein either or both of the first shell and the second shell comprise a material that stretches and/or contracts to expand a gap.

6. The thermal ground plane of claim 1, wherein the wicking structure layer is in contact with either or both of the first shell layer and/or the second shell.

7. The thermal ground plane according to claim 1, further comprising an additional wicking structure in contact with the wicking structure and the evaporator region.

8. The thermal ground plane according to claim 1, wherein the gap is defined by an internal pressure higher than an ambient pressure.

9. The thermal ground plane according to any one of claims 1 to 8, further comprising a plurality of spacers disposed within the gap.

10. The thermal ground plane according to claim 9, wherein the plurality of spacers comprise copper or a polymer encapsulated by a hermetic seal.