Deformed Mesh Thermal Ground Plane
Some embodiments include a thermal ground plane comprising a first casing layer and a second casing layer where the outer periphery of the first casing layer and the outer periphery of the second casing layer are bonded to each other. The thermal ground plane including a working fluid disposed within the first casing layer and the second casing layer. The thermal ground plane may also include a permeable wick disposed between the first casing layer and the second casing layer; and a deformed mesh disposed between the first casing layer and the permeable wick, the deformed mesh comprising a mesh with deformed mesh portions that form vapor channels and nondeformed mesh portions that form liquid channels.
Recent developments of higher integration and higher performance electronic devices have led to increased heat dissipation requirements. Similarly, electronic device miniaturization has led to increased heat generation density. This is becoming increasingly important with the miniaturization and advancements in smart phones and other similar devices as well as with electronic vehicles.
SUMMARYSome embodiments include a thermal ground plane comprising a first casing layer and a second casing layer where the outer periphery of the first casing layer and the outer periphery of the second casing layer are bonded to each other. The thermal ground plane including a working fluid disposed within the first casing layer and the second casing layer. The thermal ground plane may also include a permeable wick disposed between the first casing layer and the second casing layer; and a deformed mesh disposed between the first casing layer and the permeable wick, the deformed mesh comprising a mesh with deformed mesh portions that form vapor channels and nondeformed mesh portions that form liquid channels.
In some embodiments, deformed mesh comprises a plurality of fibers woven together. In some embodiments, the deformed mesh comprises a plurality of mesh layers. In some embodiments, the deformed mesh portions are mesh portions that have been compressed. In some embodiments, the deformed mesh comprises an array nondeformed mesh portions. In some embodiments, the deformed mesh comprises a mesh with a first surface that is substantially flat and a second surface that has been deformed to include a plurality of ridges or pillars.
In some embodiments, the deformed mesh is disposed between the first casing and the second casing with the second surface positioned toward the first casing. In some embodiments, the deformed mesh is disposed between the first casing and the second casing with the second surface positioned toward the permeable wick.
In some embodiments, the thermal ground plane may include a planar mesh disposed between the deformed mesh and the permeable wick.
In some embodiments, the permeable wick includes a plurality of pillars.
In some embodiments, the deformed mesh includes an internal artery.
In some embodiments, the deformed mesh includes a first mesh layer with a first pore size and a second mesh layer with a second pore size that is different than the first pore size.
In some embodiments, the deformed mesh comprises a metallic polymer, metal coated polymer, ceramic coated polymer, ALD coated polymer, copper coated steel, copper coated stainless steel.
In some embodiments, the permeable wick comprises permeable structures selected from the list consisting of a woven mesh, a nonwoven mesh, a plurality of pillars, a plurality of particles, one or meshes, a plurality of channels, a plurality of micropillars, and a plurality of microchannels.
Some embodiments include a thermal ground plane that includes a first casing layer and a second casing layer. In some embodiments, the outer periphery of the first casing layer and the outer periphery of the second casing layer are bonded to each other. A working fluid may be disposed within the first casing layer and the second casing layer. The thermal ground plane may include a plurality of structures disposed within the first casing layer and the second casing layer. In some embodiments, each of the plurality of structures include a mesh structure and an internal artery disposed within the mesh structure.
In some embodiments, each mesh structure comprises a plurality of mesh layers.
In some embodiments, the internal artery extends from the first casing to the second casing. In some embodiments, the internal artery is surrounded by the mesh structure. In some embodiments, each internal artery extends along an entire length of each respective mesh structure. In some embodiments, the internal artery comprises a plurality of internal arteries disposed within each mesh structure.
In some embodiments, the thermal ground plane may include a second mesh disposed between at least two of the mesh structures, the second mesh comprising a mesh having a higher permeability than the mesh structures.
A thermal ground plane is disclosed, that includes a first casing layer (e.g., first casing layer), a second casing layer (e.g., bottom casing), liquid structures, and vapor structures. Either or both the liquid structures, and vapor structures may include a deformed structure.
A thermal ground plane is a type of vapor chamber, in which the first casing layer and the second casing layer form a hermetic seal, and within that sealed region is a wick which is permeated with a liquid. The liquid may be in thermodynamic equilibrium with a saturated vapor phase. The vapor phase may permeate a cavity which is supported by some vapor structure. When heat is applied at any location, the liquid evaporates and increases the temperature of the vapor by a small amount. That increase in temperature results in a local area of increased pressure, which then generates a flow of the vapor away from the high pressure region, and thereby carries heat away by convection. The heat is rejected away from the vapor core in the colder regions when the vapor condenses, and the condensate is pulled back to the hot region by capillary forces within the wick. The utilization of convection allows the thermal ground plane system to achieve high amounts of heat transfer with low temperature gradients, and thereby a high effective thermal conductivity. The capillary forces in the wick may be high enough to overcome any drag forces in the wick, drag forces in the vapor phase, pressure drops associated with phase change, and hydrostatic effects of gravity. The drag forces are influenced by thermosphysical properties of the fluids and the effective permeability of the wick and vapor core structures.
In some embodiments, a thermal ground plane my enclose a working fluid. The working fluid may generate a gas-liquid phase change under an atmosphere in between the first casing and the second casing. The working fluid may, for example, comprise water, alcohol, alternative fluorocarbon or the like. The alternative fluorocarbon, for example, may follows the list established by the US Environmental Protection Agency (EPA). In some embodiments, the working liquid be an aqueous compound. In some embodiments, the working liquid be water.
The evaporation region 130 and the condensation region 135 may be disposed on the same layer: the first casing layer 110 or the second casing layer 115. Alternatively, the evaporation region 130 and the condensation region 135 may be disposed on different layers of the first casing layer 110 and the second casing layer 115
In some embodiments, the vapor structure 125 and/or liquid structure 120 may be formed from an initial structure (e.g., a mesh) that has been deformed into various geometric shapes that may improve thermal transport, the flow permeability, the capillary radius, the effective thermal conductivity, the effective heat transfer coefficient of evaporation, and/or the effective heat transfer coefficient of condensation. In some embodiments, the initial structure may include multiple layers of mesh.
In some embodiments, the outer periphery of the first casing layer 110 and the outer periphery of the second casing layer 115 may be sealed such as, for example, hermetically sealed.
The planar mesh 210, for example, may comprise a woven mesh or a nonwoven mesh. The planar mesh 210, for example, may comprise a metallic polymer, metal coated polymer, ceramic coated polymer, ALD coated polymer, copper coated steel, copper coated stainless steel, etc. A nonwoven mesh may comprise a mesh where the fibers are randomly distributed. A nonwoven mesh may comprise a sheet with ordered or nonordered array of holes etched in the sheet. The sheet may be metallic or polymer. A woven mesh may comprise a ordered distribution of fibers.
In some embodiments, the liquid structure 120 may comprise a porous structure. In some embodiments, the liquid structure 120 may produce capillary pressure that allows liquid to flow through the liquid structure 120.
The planar mesh 210, for example, may separate the vapor structure 125 and the planar mesh 210. The planar mesh 210, may enhance the capillary effect, permeability effect, or the heat transfer associated with phase change between liquid and vapor.
A mesh, for example, may comprise a woven mesh or a nonwoven mesh. A mesh, for example, may comprise a metallic polymer, metal coated polymer, ceramic coated polymer, ALD coated polymer, copper coated steel, copper coated stainless steel, etc. A nonwoven mesh may comprise a mesh where the fibers are randomly distributed. A nonwoven mesh may comprise a sheet with ordered or nonordered array of holes etched in the sheet. The sheet may be metallic or polymer. A woven mesh may comprise a ordered distribution of fibers.
In some embodiments, the deformed mesh 305 may be solid. In some embodiments, the deformed mesh 305 may be porous, which may, for example, allow vapor to flow between cavities defined by the first casing layer 110 and the deformed mesh 305.
In some embodiments, the plurality of pillars may be supported by particles of material 315 under, below, above, or on both sides of the plurality of pillars 310, as shown in the side view of TGP 350 shown in
In some embodiments, the plurality of pillars 310 may be formed with the deformed mesh 305 by depressing pillar shapes into the deformed mesh 305. The deformed mesh 305 may undergo either inelastic or plastic deformation, as shown in
In some embodiments, the permeable wick may include a plurality of pillars 505 disposed on the second casing layer 115. The plurality of pillars 505 may, for example, be uniformly or nonuniformly distributed. The plurality of pillars 505 may, for example, be a plurality of micropillars. The plurality of pillars 505 may be formed, for example, by mechanical scribing, milling, chemical etching, photolithography, etching, and/or electroplating.
The TGP 500 may include a vapor structure 125 that comprises a plurality of particle structures 515 that each include a plurality of particles. The plurality of particles may include sintered particles.
When liquid evaporates within a TGP, heat may flow through the vapor-liquid interface. By extending the area of the vapor-liquid interface, the thermal resistance of evaporation may be reduced. In some embodiments, the mesh 510 may be textured with a textured surface 610 on the vapor-side such that liquid may be pulled away from the pores into the textured area by capillary forces associated with texturing, which may increase the area associated with heat evaporation. In some embodiments, the textured surface 610 may be formed by chemically etching the mesh 510 with a non-uniform etch process. In some embodiments, the textured surface 610 may be formed by laser or mechanical scribing, sintering particles to the surface of the planar mesh, patterning the planar mesh with out-of-plane features by photolithography, and/or etching or deposition, non-lithography based deposition through a template such as inverse opal structures or plating through randomly distributed defects in a film, non-templated anisotropic deposition techniques such as rapid plating, and/or non-templated anisotropic etching techniques such as de-alloying, etc.
In some embodiments, the ribs can be formed into pillars 820 by compressing the folded mesh at intervals in the y-direction, as shown in
The deformed mesh portions 905 may form vapor channels 915 between the nondeformed mesh portions 910. The deformed mesh 902 may be disposed within the TGP 900 on a permeable wick 920. The deformed mesh 902, for example, may include either woven or nonwoven mesh. The vapor channels 915 may occur within gaps between nondeformed mesh portions 910 and the first casing layer 110. The deformed mesh portions 905 (and/or the vapor channels) may be created by any deformation process such as, for example, the deformation process shown in
In some embodiments, the deformed mesh 902 may include multiple layers of the same type of mesh (e.g., the same thread count or same pore sizes) stacked on upon another or multiple layers of different types of mesh (e.g., different thread counts or different pore sizes) stacked one upon another. In some embodiments, the deformed mesh 902 may include spacing layers between different mesh layers.
In some embodiments, the nondeformed mesh portions 910 (e.g., the liquid channels) may comprise any of a variety of different configurations such as, for example, pillars (as shown in
In some embodiments, the deformed mesh portions 905 may be formed by compressing multiple layers of mesh through a compressive mask such as, for example, as shown in
In some embodiments, the deformed mesh portions 905 may be bonded to the permeable wick 920. In some embodiments, the permeable wick 920 may be a woven or nonwoven mesh layer as shown in
The deformed mesh portions 905 may be created, formed, compressed, etc. such as, for example, by the deformation process shown in
In some embodiments, the deformed mesh portions 905 may or may not be bonded with the first casing layer 110. In some embodiments, the deformed mesh portions 905 may or may not be bonded with the second casing layer 115. In some embodiments, bonding may include thermocompression bonding, thermosonic bonding, electroplating, etc.
In some embodiments the layers of the deformed mesh 1205 may include meshes with different mesh weave types, thread count, wire diameter, or mesh material. In some embodiments, the lower deformations may be selectively compressed in the same or a different manner as the selective compression of the upper deformations.
The deformed mesh 1205 may be created by the deformation process shown in
In some embodiments, the pitch between deformations of the first deformed mesh 1405 may be larger than the pitch between deformations of the second deformed mesh 1410. In some embodiments, the height of the deformations of the first deformed mesh 1405 may be larger than the height of the deformations of the second deformed mesh 1410. In some embodiments, the number of deformations of the first deformed mesh 1405 may be fewer than the number of deformations of the second deformed mesh 1410.
The mesh 1505 may be deformed to include a pattern having a plurality of pillars using a press fixture with male and female sides as shown in
The deformed mesh 1605 may include small deformations 1635 compressed into the compressed portions of the deformed mesh 1605. The small deformations 1635, for example, may extend out of plane relative to the compressed portions of the deformed mesh 1605 as shown in
The deformed mesh 1605 can be formed using a press as shown in
The physics of vapor transport through the vapor channel 2010 show that the pressure drop of the vapor may be proportional to the cube of the channel height. This non-linear behavior, for example, may mean that if the height of the vapor channels 2010 is increased in some regions and reduced in regions parallel to the flow, then there may be a net benefit. Such a condition may be met by arteries within the vapor channel 2010. The mesh structure 2005 may comprise a plurality of mesh layers stacked one upon another forming the mesh structure 2005.
In some embodiments, the vapor channel 2010 may be defined by the first casing layer 110, a mesh layer, and the sides of one or more mesh structure 2005. Some vapor channels 2010 may also be defined by the edge of the TGP 2000.
In some embodiments, an evaporation region (e.g., evaporation region 130) may be disposed at or near portions of the TGP 2500 shown in
In some embodiments, the capillary pressure may be low and/or the spacing between features (e.g., pore spacing in mesh structure 2005) may be large such as 75, 100, 150, 200 micron, etc. The capping mesh 2840 my have small feature sizes, such as 1, 5, 10, 25, 50 um etc., which may create higher capillary pressure. For example, the mesh structure 2005 may have a pore size of about 250 microns and the capping mesh 2840 may have a pore size of about 50 microns. As another example, the mesh structure 2005 may have a pore size of about 50 microns and the capping mesh 2840 may have a pore size of about 5-10 microns.
In some embodiments, internal arteries 2905 may enhance the thermal resistance of a TGP by a factor of 2.
In some embodiments, the deformed mesh 2910 and the internal arteries 2905 may be disposed upon or beneath a permeable wick. In some embodiments, a planar mesh may be disposed between the deformed mesh 2910 and a permeable wick.
The deformed mesh 2910 may form vapor channels 2915 in between deformed mesh 2910.
The deformed mesh structure 2910B, for example, may include internal arteries 2905B that may not extend along the entire length of the deformed mesh structure 2910B. The internal arteries 2905B may comprise a plurality of internal arteries 2905B with mesh portions 3005 in between. This may, for example, prevent the spreading of vapor along the whole artery if there is ingress of vapor into one of the liquid flow open areas.
In some embodiments, the deformed mesh 3210 may extend across a diagonal between the first casing layer 110 and the planar mesh 210 dividing the flow into 2 regions, which may result in an increase in flow resistance. In some embodiments, a diagonal deformed mesh 3210 can be deformed to allow the majority of the flow through a vapor core 3205 with large pores. In some embodiments, wires comprising the mesh of the deformed mesh 3210 can be further deformed to increase the flow area. In some embodiments, the deformation can promote flow in a single direction, while maintaining higher flow resistance in a perpendicular direction. In some embodiments, the TGP vapor core can include multiple different regions with different deformed meshes 3210 to promote the vapor flow in different directions within each region.
In some embodiments, a plurality of particles 3215 may be disposed between the deformed mesh 3210 and the first casing layer
In some embodiments, the microparticles and/or nanoparticles may be sintered together to form pillars. In some embodiments, the microparticles and/or nanoparticles may comprise copper, glass, other metals, or other ceramics. In some embodiments, the pillars may include microparticles and/or nanoparticles having different radii. In some embodiments, a fraction of the particles may sinter to bond to the remaining microparticles and/or nanoparticles and form a solid pillar, such as, for example, with copper nanoparticles sintering to seal copper microparticles.
In some embodiments the microparticles and/or nanoparticles may be cleaned of oxides prior to placing the microparticles and/or nanoparticles on the second casing layer 115 using acid vapor, liquid acid, hydrogen bearing gas, or hydrogen-bearing plasma.
In some embodiments, the microparticles and/or nanoparticles may be sintered at elevated temperatures. In some embodiments, microparticles and/or nanoparticles sinter to a mesh layer to form the wick or vapor structure. In some embodiments, the microparticles and/or nanoparticles may be sintered in a vacuum environment, in an inert gas atmosphere, or in a reducing atmosphere. In some embodiments, the pillars formed by sintering may be bonded to a mesh layer at an elevated temperature and/or subsequently bonded to a cladding layer at lower temperature.
In the event that a region of high permeability dries out through this mechanism, the vapor can be contained such that the entire wick does not dry out, by having multiple regions of high permeability connected by regions of low capillary radius. Then if one region of high permeability dries out, the vapor/liquid interface will be arrested at the region of low capillary radius, and therefore not spread into the adjacent region of high permeability. Because the regions of low capillary radius are porous, liquid will flow between adjacent regions of high permeability. This structure follows a similar mechanism to the method used to transport fluid up the woody structure of plants through the so-called xylem, while preventing cavitation-so this design of wick can be referred to “artificial xylem”. In some embodiments, the regions of high permeability can be formed by cutting or deforming a mesh, while the regions of low capillary radius can be formed by the un-deformed mesh; in such a manner, liquid flows between adjacent high permeability regions in-plane, as in
Some TGPs can include other wick structures (e.g. permeable wicks) that can allow in-plane low capillary radius regions and high permeability regions.
In some embodiments, the regions of high permeability may have an aspect ratio and/or angle which allows a region in one layer to connect to three or more regions in the upper or lower layer, as shown in
In some embodiments, the mesh 3710 may include nano-porous scale features, with a maximum pore size of 10 nm, 50 nm 100 nm, 200 nm, etc; in some embodiments the nano-porous mesh is formed for example by track etching, by dealloying glass or metallic alloys, by nano-porous anodizing, by selective etching of self-assembled micelles, by sintering nanoparticles, etc.
The term “permeable wick” may include one or more of a woven mesh, a nonwoven mesh, a plurality of pillars, a plurality of particles, one or meshes, a plurality of channels, a plurality of micropillars, a plurality of microchannels, etc. A permeable wick may also include foam and/or an inverse opal structure.
A term “mesh” may include a plurality of woven fibers (e.g., woven mesh) or a plurality of nonwoven fibers (a nonwoven mesh). A mesh may comprise metallic polymer fibers, metal coated polymer fibers, ceramic coated polymer fibers, ALD coated polymer fibers, copper coated steel fibers, copper coated stainless steel fibers, metal fibers, polymer fibers, copper fibers, stainless steel fibers, copper coated stainless steel, etc. A nonwoven mesh may comprise a mesh with a random distribution of fibers. A nonwoven mesh may comprise a sheet with ordered or nonordered array of holes etched in a sheet, which may be metallic or polymer. A woven mesh may comprise an ordered distribution of fibers. A nonwoven mesh may also include planar sheet formed additively such as: sintering microparticles and/or nanoparticles, electroplating through a template, rapid plating with bubble generation, deposition of metal/polymer/ceramic over a template, anodizing, etc.
Unless otherwise specified, the term “substantially” means within 5% or 10% of the value referred to or within manufacturing tolerances. Unless otherwise specified, the term “about” means within 5% or 10% of the value referred to or within manufacturing tolerances.
The conjunction “or” is inclusive.
The terms “first”, “second”, “third”, etc. are used to distinguish respective elements or blocks or steps. and are not used to denote a particular order of those elements unless otherwise specified or order is explicitly described or required.
Numerous specific details are set forth to provide a thorough understanding of the claimed subject matter. However, those skilled in the art will understand that the claimed subject matter may be practiced without these specific details. In other instances, methods, apparatuses or systems that would be known by one of ordinary skill have not been described in detail so as not to obscure claimed subject matter.
Embodiments of the methods disclosed may be performed in the operation of such computing devices. The order of the blocks presented in the examples above can be varied—for example, blocks can be re-ordered, combined, and/or broken into sub-blocks. Certain blocks or processes can be performed in parallel.
The use of “adapted to” or “configured to” is meant as open and inclusive language that does not foreclose devices adapted to or configured to perform additional tasks or steps. Additionally, the use of “based on” is meant to be open and inclusive, in that a process, step, calculation, or other action “based on” one or more recited conditions or values may, in practice, be based on additional conditions or values beyond those recited. Headings, lists, and numbering included are for ease of explanation only and are not meant to be limiting.
While the present subject matter has been described in detail with respect to specific embodiments thereof, 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 should be understood that the present disclosure has been presented for purposes of example rather than limitation, and does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.
Claims
1. A thermal ground plane, including:
- a first casing layer;
- a second casing layer where outer peripheries of the second casing layer are hermetically sealed with outer peripheries of the first casing layer to form a TGP housing case;
- a vapor transport layer disposed nearby the first casing layer in the TGP housing case;
- a vapor transport layer disposed nearby the second casing layer in the TGP housing case; and
- a working fluid filled in the TGP housing case.
2. The thermal ground plane according to claim 1, wherein the vapor transport layer comprises a first deformed mesh including:
- a plurality of vapor channels;
- a plurality of first deformed mesh parts; and
- a plurality of first mesh parts that are cross-connected to each other.
3. The thermal ground plane according to claim 2, wherein the liquid transport layer comprises a second deformed mesh including:
- a plurality of liquid channels;
- a plurality of second deformed mesh parts; and
- a plurality of second mesh parts which are cross-connected to each other.
4. The thermal ground plane according to claim 3, wherein a plurality of ridges in the first mesh parts are correspondingly stacked between each two of the ridges in the second mesh parts.
5. The thermal ground plane according to claim 1, wherein the vapor transport layer and the liquid transport layer are formed into an integrated part structure by a compression step.
6. The thermal ground plane according to claim 3, wherein the working fluid flows through the first mesh parts and the second mesh parts, and the first and second mesh parts are connected, respectively by the first deformed mesh parts and the second deformed mesh parts, wherein the first mesh parts are bonded to the first casing layer, and the second mesh parts are bonded to the second casing layer.
7. The thermal ground plane according to claim 3, further including a planar mesh structure, which is disposed between the vapor transport layer and the liquid transport layer, to separate the vapor transport layer and the liquid transport layer, wherein the working fluid flows between the planar mesh structure, the vapor transport layer and the liquid transport layer.
8. The thermal ground plane according to claim 7, wherein the first mesh part contacts an inner surface of the first casing layer, and the first deformed mesh parts include a plurality of first ridge to be a plurality of support pillars for keeping a space between the planar mesh structure and the first casing layer, to form a vapor transmission passage.
9. The thermal ground plane according to claim 8, wherein the second mesh parts are stacked on the planar mesh structure, and the second deformed mesh parts include a plurality of second ridges to be a plurality of support pillars for keeping a space between the second casing layer and the planar mesh structure.
10. The thermal ground plane according to claim 3, wherein the first mesh parts are correspondingly stacked on the second mesh parts to form a curved mesh structure.
11. The thermal ground plane according to claim 1, wherein the liquid transport layer includes at least two mesh structures, each of the mesh structures includes at least one capillary channel which uses capillary phenomena to transport the working fluid.
12. The thermal ground plane according to claim 3, wherein the first deformed mesh includes a plurality of first fiber parts which are interwoven with each other, and the second deformed mesh includes a plurality of second fiber parts which are interwoven with each other.
13. The thermal ground plane according to claim 3, wherein the first deformed mesh includes a plurality of first mesh layers stacked on each other, and the second deformed mesh includes a plurality of second mesh layers stacked on each other.
14. The thermal ground plane according to claim 2, wherein the vapor channels form an internal arterial network.
15. The thermal ground plane according to claim 7, wherein the planar mesh structure includes a plurality of pores, and the pores include smaller sizes than the vapor channels to prevent the vapor in the vapor channels from flowing into the liquid transport layer.
16. The thermal ground plane according to claim 1, wherein material of the first and second casing layers, includes a combination of copper, polymer, and composite material of copper and polymer.
17. The thermal ground plane according to claim 1, wherein the hermetic seal between the first and second casing layers are shaped by thermocompression bonding or laser welding, to form the TGP housing case.
Type: Application
Filed: Aug 22, 2023
Publication Date: Dec 7, 2023
Inventors: Ryan Lewis (Boulder, CO), Jason West (Boulder, CO), Kyle Wagner (Boulder, CO), Dylan McNally (Boulder, CO), Keller Lofgren (Boulder, CO)
Application Number: 18/454,061