WO2025064431A1 - Systems and methods for distributed heat transfer - Google Patents

Abstract

A remote boiler is disposed within a reservoir of immersion cooling fluid. The remote boiler is mechanically and thermally coupled with one or more hollow heat pipes containing a heat transfer fluid. The one or more hollow heat pipes provide a conduit for the heat transfer fluid to move from a heat source such as a component of a computing system to the remote boiler. The heat transfer fluid may boil inside the one or more hollow heat pipes and carry waste heat from the component to the remote boiler, which then transmits the waste heat to the immersion cooling reservoir.

Description

SYSTEMS AND METHODS FOR DISTRIBUTED HEAT TRANSFER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Application No., 63/583,557, filed September 18, 2023, and U.S. Provisional Application No. 63/612,059, filed December 19, 2023, which are hereby incorporated by reference in their entireties.

BACKGROUND

[0002] As feature sizes and transistor sizes have decreased for computing hardware such as integrated circuits (ICs) including chips and semiconductor dies, the amount of heat generated by a single chip, such as a microprocessor, has increased. Computing hardware that has traditionally been air cooled has evolved to levels of power consumption requiring more heat dissipation than can be provided by air alone. In some cases, immersion cooling of ICs in a tank containing a coolant fluid is employed to maintain ICs at appropriate operating temperatures.

[0003] One type of immersion cooling is two-phase immersion cooling, in which heat from a semiconductor die is high enough to boil the coolant fluid. The boiling creates a coolant fluid vapor in the tank, which is condensed by cooling coils back to liquid form. Heat from the semiconductor dies can then be sunk into the liquid-to-gas and gas-to-liquid phase transitions of the coolant fluid with the result that the semiconductor dies are kept at an acceptable temperature.

[0004] In many immersion cooling systems, space within an immersion cooling tank is limited. Total submersion in immersion cooling fluid is typically reserved for computing hardware such as GPUs in order to maximize computational density. However, other components may still generate significant amounts of heat that must be dissipated to ensure proper operation. No present solution exists to utilize the greatly improved heat transfer capability of two-phase immersion cooling liquid for components that are not totally submerged in the immersion cooling liquid.

SUMMARY

[0005] Two-phase immersion cooling has emerged as a highly promising technology for improving computational density by improving waste heat removal as compared to traditional server cooling technologies such as air cooling. Two-phase immersion cooling works by immersing computational hardware such as logic integrated circuits (ICs) in a dielectric fluid that has a boiling point below a maximum operating temperature of one or more immersed logic ICs. The phase transition between the liquid and vapor phases can provide orders of magnitude more efficient heat transfer between a logic IC and a heat dissipation medium than air cooling.

[0006] Space within an immersion cooling container, and particularly within a reservoir of immersion cooling liquid, is limited. To maximize space and cost efficiency, most of the available volume within the reservoir of immersion cooling liquid may be occupied by computing hardware. This may leave little room in the reservoir for immersion of peripheral components such as network interface cards, memory, networking switches, and the like. However, these peripheral components may benefit from the enhanced cooling provided by two- phase immersion cooling liquid.

[0007] Additionally, smaller components (such as quad small form factor pluggable (QSFP) transceivers) may have a limited surface area to contact a heat transfer medium such as a heat sink. The present technology is directed toward a form factor that can provide effective heat transfer for small surface areas or component form factors that cannot benefit from traditional heat sinks.

[0008] To enable these peripheral components to utilize the beneficial cooling of two-phase immersion cooling despite the limited space within the immersion cooling liquid reservoir, the inventors have developed apparatuses for transferring heat from components disposed outside of an immersion cooling reservoir into the immersion cooling reservoir itself. Because of the superior heat transfer performance of immersion cooling fluid compared to air, heat transfer apparatuses in accordance with the present technology may be three to four orders of magnitude more efficient at transferring heat from a heat source such as an integrated circuit, network interface card, network switch, or other components disposed within a headspace or vapor space of an immersion cooling system.

[0009] In some aspects, the techniques described herein relate to an apparatus for distributed heat transfer, the apparatus including a remote boiler disposed within a reservoir of an immersion cooling fluid; one or more heat pipes physically coupled to the remote boiler, each heat pipe of the one or more heat pipes including a channel configured to convey a heat transfer fluid; and wherein each heat pipe is thermally coupled with at least one component disposed externally to the reservoir of the immersion cooling fluid.

[0010] In some aspects, the heat transfer fluid includes deionized water.

[0011] In some aspects, the remote boiler and each of the one or more heat pipes includes copper. [0012] In some aspects, each heat pipe is thermally coupled with the at least one component through a respective thermal transfer pad.

[0013] In some aspects, the remote boiler further includes one or more chambers, each chamber fluidically coupled to a respective heat pipe of the one or more heat pipes.

[0014] In some aspects, each heat pipe includes a wick disposed within the channel of the heat pipe.

[0015] In some aspects, a surface of the remote boiler or a surface of each of the one or more heat pipes includes a surface treatment.

[0016] In some aspects, the surface treatment includes a pattern, a coating, a roughening, one or more trenches, one or more scratches, or one or more gouges.

[0017] All combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are part of the inventive subject matter disclosed herein. The terminology used herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).

[0019] FIG. 1A-B illustrate an exploded view of a distributed heat transfer apparatus in accordance with the present technology.

[0020] FIG. 2 illustrates a top and side view of a heat transfer apparatus in accordance with the present technology.

[0021] FIG. 3 illustrates a bottom view of a heat transfer apparatus including remote boiler, heat pipes, plurality of thermal transfer pads, and aluminum base.

[0022] FIG. 4 illustrates an aluminum base and copper plate for use with a heat transfer apparatus. [0023] FIG. 5 illustrates several views of an aluminum base.

[0024] FIG. 6 illustrates a copper plate in accordance with the present technology.

[0025] FIG. 7 illustrates a bottom plate for a remote boiler.

[0026] FIG. 8 illustrates a top plate for a remote boiler.

[0027] FIGS. 9A-9E illustrate individual heat pipes in accordance with the present technology.

[0028] FIG. 10 depicts aspects of an immersion cooling system for dissipating heat from one or more semiconductor die packages via immersion cooling.

DETAILED DESCRIPTION

[0029] FIGS. 1A-B illustrate an exploded view of a distributed heat transfer apparatus 100 in accordance with the present technology. Apparatus 100 may include a remote boiler 110 (boiler top and bottom plate components indexed as 2 and 8 respectively in FIG. 1A) including one or more cavities configured to interface with the channels in a respective heat pipes. The remote boiler may be disposed within an immersion cooling fluid, such as in a reservoir of immersion cooling liquid.

[0030] The remote boiler may be mechanically and thermally coupled to one or more heat pipes, which may allow for the transfer and/or phase transition of a heat transfer fluid from the remote boiler to a distal end of a heat pipe disposed on or adjacent to a heat source such as a component 150 to be cooled (e.g., a network interface card (NIC), optical switch, high-bandwidth memory, or the like). Component 150 may be disposed partially or entirely above or externally to the reservoir of immersion cooling liquid. The one or more heat pipes 120a-e (indexed as 3-7 in FIG. 1A) may include channels for conveying fluid and may be disposed above the reservoir of immersion cooling fluid. Each of the one or more heat pipes 120a-e may be disposed on or in thermal and/or physical contact with the component 150 as well as remote boiler 110. In an embodiment, each of the one or more heat pipes 120a-e may define a substantially adiabatic section.

[0031] Apparatus 100 may additionally include one or more thermal transfer pads (indexed as 19-27 in FIG. 1A). The one or more thermal transfer pads may conform to one or more surfaces of a plurality of components with which they are in contact, improving thermal transfer between the plurality of components.

[0032] A remote boiler 110 may be hollow or solid. A remote boiler 110 may include a solid copper heat spreader and a boiling enhancement coating disposed on the solid copper heat spreader. A remote boiler 110 may be made of copper, graphite, tungsten, a combination of the foregoing (such as graphite-impregnated copper), or the like. A remote boiler 110 may be configured to receive one or more heat pipes 120a-e that conform to channels within the remote boiler 110. In an embodiment, a remote boiler 110 may include a vapor chamber configured to circulate a heat transfer fluid from liquid form in an area adjacent to a heat load. The heat transfer fluid vaporizes, and the increased pressure forces the heat transfer fluid vapor into a distal area of lower temperature. The vapor recondenses and transfers carried heat to a physical structure such as a heat fin, and the recondensed cooling liquid flows back to the area adjacent to the heat load.

[0033] Apparatus 100 may further include one or more bases and/or plates to interface with a component 150 and maximize a surface area for heat transfer to occur. For example, apparatus 100 may include one or more bases or plates, such as aluminum base 130-9, copper plate 140-10, aluminum plate 130-14, and copper cage plate 130-16. These bases and/or plates may contact one or more thermal transfer pads to improve the transfer of heat from a component 150.

[0034] FIG. 2 illustrates a top and side view of heat transfer apparatus 100 in accordance with the present technology including dimensions in mm. In an embodiment, apparatus 100 may include a plurality of heat pipes 120a-e, such as five heat pipes 120a-e. Each heat pipe may be hollow and include a wick to help channel or convey a heat transfer fluid up and down the heat pipe during operation via capillary action. In an embodiment, the heat transfer fluid may be deionized water, though other fluids may be suitable. In an embodiment, the heat pipes 120a-e may be made of copper, graphite, tungsten, or other suitable material having advantageous thermal transfer properties. The heat pipes 120a-e may alternatively be solid copper and transmit heat entirely through conduction.

[0035] In an embodiment, a heat pipe in accordance with the present technology may be a thermosiphon, an oscillating heat pipe, or a looped heat pipe. A looped heat pipe may be a hollow or solid continuous loop. A looped heat pipe may utilize geometry and gravity to transport a heat transfer fluid from a heat load to a heat exchange portion and back to the heat load. The liquid heat transfer fluid may boil and change phase to vapor. The vapor then rises and recondenses on an inner surface of the looped heat pipe such that the condensed liquid heat transfer fluid flows back down a different portion of the loop than the vapor rose through. This may have an added benefit that vapor rising from the heat load does not raise the temperature of (and reduce the heat capacity of) the liquid heat transfer fluid, which may then reduce the amount of heat that can be absorbed by the liquid heat transfer fluid before becoming vapor. [0036] FIG. 3 illustrates a bottom view of apparatus 100 including the remote boiler 110 and heat pipes 120a-e, as well as a plurality of thermal transfer pads (labeled thermal pads in FIG. 3) and aluminum base 130, including dimensions in mm. Each of the plurality of thermal transfer pads may be 1 mm thick Tflex™ SF10 Silicone Free Thermal Gap Filler produced by Laird™. Each thermal transfer pad may reduce a thermal resistance between two components and may deflect when compressed between the two components to maximize the contact area (and heat transfer) between the two components through the thermal transfer pad. A thermal transfer pad may have a thermal conductivity of approximately 10 W/mK. An aluminum base 130 may have any suitable shape to provide a thermal transfer path and structural support for a heat source and heat pipes 120a-e. The aluminum base 130 may additionally provide a mechanical and thermal attachment for one or more copper plates, the one or more copper plates being in direct or indirect (through one or more thermal transfer pads) contact with the heat source.

[0037] FIG. 4 illustrates an aluminum base 130 and copper plate 140 for use with apparatus 100. As described with reference to FIG. 3, the aluminum base 130 and copper plate 140 may provide both structural support and a thermal path between a heat source and one or more heat pipes 120a-e. One or more copper plates may have any suitable shape, for example to provide a suitably large contact area between the copper plate 140 and the heat source. An aluminum base 130 may include a cutout, depression, or recessed area that corresponds to the shape of and receives a portion of the copper plate.

[0038] A pressure and/or force exerted on one or more thermal transfer pads by one or more of an aluminum base 130 and/or copper plate 140 may be specified. For example, a total thermal pad force may be about 190 N, for example between about 180 N and about 200 N, between about 150 N and about 250 N, between about 100 N and about 300 N, between about 50 N and 1000 N, or any suitable force. A total thermal pad force may correspond to a thermal pad pressure. One or more screws, nuts, bolts, or other suitable attachment means for attaching one or more components of apparatus 100 may be tightened to apply a predetermined amount of pressure. For example, one or more screws attaching one or more components of apparatus 100 to one another may be tightened to apply about 20 psi of pressure, between about 18 psi and about 22 psi, between about 15 psi and about 25 psi, between about 10 psi and about 40 psi, between about 5 psi and about 100 psi, or any suitable pressure. This pressure may enable suitable thermal contact between components such as an aluminum base 130 and a copper plate, or a copper plate 140 and a heat source such as a network interface card.

[0039] FIG. 5 illustrates several views of an aluminum base 130 including dimensions in mm. Aluminum base 130 may be plated or finished with a suitable finish such as nickel. In an embodiment, aluminum base 130 may be AL 6063 aluminum. Aluminum base 130 may include one or more thermal transfer pads and may have a total height of about 5.6 mm. An important aspect of apparatus 100 is that it is volumetrically efficient for heat transfer due to the limited amount of space within an immersion cooling system. In an embodiment, an immersion cooling system in accordance with the present technology may contain ten or more servers, each server having a plurality of heat removal apparatuses 100. All of the volume used by an apparatus 100 is not available for computing hardware such as Al accelerators, GPUs, memory modules, and the like. Therefore, it is particularly advantageous for a heat transfer apparatus 100 to have a high heat flux per unit volume capability.

[0040] FIG. 6 illustrates a copper plate 140 in accordance with the present technology. Copper plate 140 may be configured to interface with a portion of aluminum base 130, such that the entirety of at least one surface of copper plate 140 is mechanically and thermally coupled to aluminum base 130. Copper plate 140 may have any suitable shape and/or dimensions, which may be specified in accordance with a heat source from which heat is to be removed. Copper plate 140 may include a passivation finish.

[0041] FIG. 7 illustrates a bottom plate 112 for remote boiler 110. Bottom plate 112 may be made of copper and may provide a portion of a fluid chamber included in remote boiler 110. Bottom plate 112 may include a passivation finish, or may include one or more boiling enhancement coatings, which are referenced in greater detail with respect to FIG. 10. For example, bottom plate 112 may include surface treatments, coatings, gouges, scratches, trenches, may be roughened, may include one or more additional materials disposed on a surface of bottom plate 112 via sintering, or any suitable surface treatment or coating designed to enhance boiling and/or encourage nucleation site formation on a surface of bottom plate 112 exposed to immersion cooling fluid.

[0042] FIG. 8 illustrates a top plate 114 for remote boiler 110. Top plate 114 may be made of copper and may provide a portion of a fluid chamber included in remote boiler 110. Top plate 114 may include a passivation finish, or may include one or more boiling enhancement coatings, which are referenced in greater detail with respect to FIG. 10. For example, top plate 114 may include surface treatments, coatings, patterns, gouges, scratches, trenches, may be roughened, may include one or more additional materials disposed on a surface of top plate 114 via sintering, or any suitable surface treatment or coating designed to enhance boiling and/or encourage nucleation site formation on a surface of top plate 114 exposed to immersion cooling fluid. [0043] FIGS. 9A-9E illustrate individual heat pipes 120a-e in accordance with the present technology. Heat pipes 120a-e may be hollow or solid and may be made of any suitable material including copper, aluminum, tungsten, graphite, or the like. In an embodiment, heat pipes 120a-e may be a combination of materials, such as a graphite-impregnated copper. In an embodiment, an inner and/or surface of any or all of heat pipes 120a-e may be textured, patterned, or roughened to promote heat transfer, fluid wicking, condensation, boiling, nucleation, or a suitable effect. Any or all of heat pipes 120a-e may include a wick structure, for example a cylindrical wire that follows a central axis of the heat pipe and allows for heat transfer fluid inside of heat pipes 120a-e to migrate from a remote boiler to a heat source. A heat source may be located above a remote boiler relative to the gravity vector, and a wick structure may provide liquid heat transfer fluid a means to travel up the heat pipe to the heat source. A wick structure used in accordance with the present technology may be similar to or the same as wick structures described in U.S. Patent Application No. 18/327,615, filed June 1, 2023 and entitled "Boiler Enhancement Coatings with Active Boiling Management,” which is incorporated herein by reference in its entirety.

[0044] Further examples of arrangements of heat transfer apparatuses and components that may be cooled by heat transfer apparatuses may be found in U.S. Provisional Patent Application 63/583,557, filed September 18, 2023 and entitled “Remote Boiler,” the entirety of which is incorporated herein by reference.

[0045] FIG. 10 depicts aspects of an immersion cooling system 1000 for dissipating heat from one or more semiconductor die packages 1005 via immersion cooling. Each package 1005 can include one or more semiconductor dies that produce heat when the system is in operation. The immersion cooling system 1000 in the illustrated example of FIG. 10 is a two-phase immersion cooling system, though the invention may also be implemented in a single-phase immersion cooling system. One or more semiconductor die packages 1005 may be 3DIC stacks in accordance with the present technology. For example, one or more semiconductor die packages 1005 may include a logic IC and at least one memory module bonded to the logic IC using a hybrid bond or micro-bump bond.

[0046] Immersion cooling systems may provide particular advantage to 3DIC stacks due to the lower surface area to volume ratio of a 3DIC stack compared to the individual components of the 3DIC stack (e.g., a bonded logic IC and memory module will have a lower surface area to volume ratio than the combined logic IC and memory module when physically separated) as well as the additional heat generated by state of the art logic ICs. This lower surface area to volume ratio means waste heat generated by the 3DIC stack may not be as efficiently dissipated and may require better cooling performance than air cooling can provide. Two-phase immersion cooling in particular can provide this additional heat removal required by 3DIC stacks.

[0047] Immersion cooling system 1000 includes a container such as tank 1020 filled, at least in part, with immersion cooling liquid 1064. The immersion cooling system 1000 can further include at least one chiller 1080 that flows a heat-transfer fluid through at least one condenser coil 1070 that is disposed in the tank 1020 and headspace 1008. Condenser coil 1070 and chiller 1080 may be part of a heat exchanger. The packages 1005 can be mounted on one or more printed circuit boards (PCBs) 1057 that are immersed, at least in part, in the immersion cooling liquid 1064. Immersion-cooling system 1000 may further include a filter 1075 disposed adjacent to the tank 1020.

[0048] Filter 1075 may include a filtration media, a housing, and a pump configured to force immersion cooling liquid 1064 through filter 1075 to remove contaminants, particulates, or other impurities that may be added to immersion cooling liquid 1064 during use. Filter 1075 may be housed outside of tank 1020 while being in fluidic communication with immersion cooling liquid 1064 in tank 1020. Alternatively, filter 1075 may be submerged within immersion cooling liquid 1064 inside of tank 1020.

[0049] Immersion cooling liquid 1064 may be a hydrocarbon, a fluoroketone, an oil, or a similar dielectric liquid that will act as an insulator while simultaneously transferring heat from package 1005 more efficiently than air. An example of immersion cooling liquid 1064 is Novec™ 649 produced by 3M™. An exemplary immersion cooling liquid 1064 used in accordance with embodiments of the present invention may have a dielectric constant baseline value of about 1.8- 2 at a frequency of about 1 kHz.

[0050] In an embodiment of the invention, immersion cooling liquid 1064 may be considered unacceptably contaminated if the dielectric constant and/or dielectric loss tangent of immersion cooling fluid being used in an immersion cooling system 1000 differs by a threshold amount as compared to unused or pure immersion cooling liquid 1064. For example, immersion cooling liquid 1064 may be considered unacceptably contaminated or degraded if the dielectric constant and/or dielectric loss tangent differs by a threshold of 10% or more as compared to unused or pure immersion cooling liquid 1064. In an embodiment, a dielectric constant and/or dielectric loss tangent variation threshold may be 20%, 15%, 5%, 3%, 1%, or any suitable threshold.

[0051] Contamination of the immersion cooling liquid 1064 and resulting changes to dielectric constant and/or dielectric loss tangent may alter or negatively impact operation of components within immersion cooling liquid 1064 including semiconductor die(s) 1050. An altered dielectric constant and/or dielectric loss tangent may result in undesirable cross-talk between components on a PCB, additional noise or reduction in signal strength transmitted along exposed wires of a PCB or semiconductor die(s) 1050 submerged in immersion fluid, and/or signal dissipation through the immersion cooling liquid 1064. Signal loss may be severe enough that two elements may be effectively represented as being separated by an open circuit despite being physically connected. In an embodiment, a dielectric constant and/or dielectric loss tangent variation threshold may be selected based on an observed or inferred effect on one or more submerged semiconductor die(s) 1050. For example, an increase in PCIe bit error rate above an error rate baseline may be correlated with an increase in dielectric constant and/or dielectric loss tangent above a dielectric constant and/or dielectric loss tangent baseline. Accordingly, operation of semiconductor die(s) 1050 may be throttled or suspended when a dielectric constant and/or dielectric loss tangent of immersion cooling liquid 1064 exceeds a predetermined threshold.

[0052] Changes to dielectric constant and/or dielectric loss tangent may be caused by contaminants within immersion cooling liquid 1064. In some cases, changes to dielectric constant and/or dielectric loss tangent may be reversed by filtering the contaminants from immersion cooling liquid 1064. In some embodiments, upon detecting an increase in dielectric constant and/or dielectric loss tangent of immersion cooling liquid 1064, controller 1002 may instruct filter 1075 to increase filtration throughput or notify a user that an immersion cooling liquid 1064 filtration media may need to be replaced. If a dielectric constant and/or dielectric loss tangent exceeds a predetermined threshold, controller 1002 may throttle or shut down one or more semiconductor die(s) 1050, generate a notification that immersion cooling liquid 1064 should be replaced, trigger an alarm, etc.

[0053] The illustrated example of FIG. 10 is not intended to be to scale. The immersion cooling system 1000 may house and provide immersion cooling liquid 1064 to tens, hundreds, or even thousands of packages 1005. In some cases, the immersion cooling system 1000 can be small (e.g., the size of a floor unit air conditioner, approximately 1 meter high, 0.5 meter width, 0.5 meter depth or length). In some implementations, the immersion cooling system can be large (e.g., the size of a van or larger, approximately 2.5 meters high, 2.5 meters width, 4 meters depth or length).

[0054] The immersion cooling system 1000 can also include a controller 1002 (e.g., a microcontroller, programmable logic controller (PLC), microprocessor, field-programmable gate array, logic circuitry, memory, or some combination thereof) to manage system operation. Controller 1002 can perform various system functions such as monitoring temperatures of system components, cooling fluid level, tank access, chiller operation etc. The controller 1002 can further issue commands to control system operation such as executing a start-up sequence, executing a shut-down sequence, assigning workloads among the packages, changing cooling fluid level, changing the temperature of the heat-transfer fluid circulated by the chiller 1080, etc. In some implementations, controller 1002 can include (or itself be) a baseboard management controller (BMC) 1004. That is, the BMC 1004 may monitor and control all aspects of system operation for the immersion cooling system 1000 in addition to monitoring and controlling workloads of the semiconductor dies 1050 in the packages 1005 cooled by the system. The immersion cooling system 1000 can also include a network interface controller (NIC 1003) to allow the system to communicate over a network, such as a local area network or wide area network. The immersion cooling system 1000 can further include a fluid sensor array 1090 having a plurality of fluid sensors 1010. Fluid sensors 1010 may include one or more leak detection sensors at least partially submerged in immersion cooling liquid 1064.

[0055] The semiconductor die(s) 1050 and can be mounted on and attached to a printed circuit board (PCB) 1055 (sometimes referred to as a substrate) in device package 1005. The package 1005 can be made commercially available as an off-the-shelf (OTS) product. The package 1005 can be used for single-phase or two-phase immersion cooling of at least one semiconductor die 1050, such as a microprocessor (e.g., a central processing unit (CPU) and/or graphics processing unit (GPU)), voltage regulator (VR), high bandwidth memory (HBM), a digital signal processing (DSP) die, an artificial intelligence (Al) accelerator, an application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), and/or other densely patterned semiconductor die.

[0056] In the two-phase immersion cooling system 1000 of FIG. 10, heat flows from the semiconductor die 1050 where it is generated into the heat spreader 1052. The heat spreader 1052 is in thermal contact with an immersion cooling liquid 1064 that can flow over and extract heat from the heat spreader 1052. The amount of heat delivered by the heat spreader 1052 to the immersion cooling liquid 1064 is enough to boil the immersion cooling liquid 1064 that contacts the heat spreader 1052 (creating bubbles 1065 and potentially creating froth 1067 when bubbles 1065 reach the surface of immersion cooling liquid 1064). The vapor 1066 from the boiled immersion cooling liquid 1064 can be cooled and condensed back to liquid droplets 1068, for example, by the condenser coil 1070. The heat-transfer fluid, such as chilled water, from the chiller 1080 can be circulated through the condenser coil 1070 to lower the temperature of the condenser coil 1070 below the condensation point in the headspace 1008 of the tank 1020. As a result, vapor 1066 condenses on exterior surfaces of the condenser coil 1070 and liquid droplets 1068 from the condensed vapor can drip and/or flow back to the immersion cooling liquid 1064. Although a single condenser coil 1070 is depicted in FIG. 10, there can be a plurality of condenser coils 1070 in tank 1020 to condense the vapor 1066 into droplets. Some or all of the condenser coils 1070 may or may not be located directly over the PCBs 1057. Instead, the condenser coil(s) 1070 can be located near one or more walls of the tank 1020, such that the condenser coil(s) 1070 are not directly over the PCBs 1057 on which the packages 1005 are mounted.

[0057] To improve thermal performance in two-phase immersion cooling system 1000, the heat spreader 1052 can include a boiling enhancement coating (BEC) on at least one surface. The BEC can be formed from copper or a copper alloy and can be porous, for example, though BECs can take various forms. In some cases, the BEC is a micro porous copper coating having a thickness from approximately or exactly 50 microns to 500 microns thick (which may be produced by electroplating and/or etching). In some implementations, the BEC comprises a mesh copper layer bonded (e.g., via resistance heating) to at least an outer surface of the heat spreader 1052. In some cases, the BEC is applied as particulates to at least one smooth surface of the heat spreader 1052 and then subsequently sintered to adhere to one another and to the heat spreader 1052. The BEC provides an improved surface area to contact the immersion cooling liquid 1064 and can increase the heat transfer coefficient from the heat spreader 1052 to the immersion cooling liquid 1064 by up to a factor of 15 versus a smooth surface on the heat spreader 1052. Accordingly, BECs can increase thermal conductivity to, and accelerate the boiling of, the immersion cooling liquid 1064.

[0058] Additional arrangements, applications, and methods of use of boiling enhancement coatings and enclosures, including with semiconductor dies and 3DIC stacks, are described in the below U.S. Patent Applications.

[0059] U.S. Patent Application No. 18/327,615, filed June 1, 2023 and entitled "Boiler Enhancement Coatings with Active Boiling Management,” discloses heat spreader and boiling enhancement enclosure architectures thermally and/or mechanically coupled to one or more semiconductor dies or logic ICs that may be used for passive and/or active management of immersion cooling fluid boiling, including through the use of valves to control pressure of boiling immersion cooling fluid within a boiling enhancement chamber, particularly in paragraph [0018]-[0039] and FIGS. 3-5B. The entirety of U.S. Patent Application No. 18/327,615 is incorporated herein by reference.

[0060] U.S. Provisional Patent Application No. 63/500,167, filed May 4, 2023 and entitled “Direct to Chip Heat Spreader and Boiler Enhancement Coatings for Microelectronics,” discloses heat spreader and BECs thermally and/or mechanically coupled to one or more semiconductor dies, logic ICs, and/or 3DIC stacks, particularly in paragraphs [0015]-[0033] and FIGS. 2A-4. BEC form factors may include graphite heat spreader architectures, vapor chambers, heat pipes 120a-e, copper plates, fins, and the like. BEC form factors may be thermally and/or mechanically coupled to the one or more semiconductor dies, logic ICs, and/or 3DIC stacks through a thermally conductive epoxy, and may have varying dimensions relative to a surface to which the semiconductor dies and/or logic ICs are mounted. The entirety of U.S. Provisional Patent Application No. 63/500,167 is incorporated herein by reference.

[0061] U.S. Patent Application No. 18/460,091, filed September 1, 2023 and entitled “Direct to Chip Application of Boiling Enhancement Coating,” discloses BECs and methods for applying BECs to semiconductor dies, logic ICs, and/or 3DIC stacks in accordance with the present technology. In particular, paragraphs [0024] -[0046] and FIGS. 2A-5 disclose embodiments of BEC layers, adhesives, solders, sintering, laser ablation, meshes, and other BECs and BEC application methods. The entirety of U.S. Patent Application No. 18/460,091 is incorporated herein by reference.

[0062] U.S. Provisional Patent Application No. 63/506,945, filed June 8, 2023 and entitled “Vapor-Shedding Structures for Boiler Plates in Two-Phase Immersion Cooling Systems,” discloses structures that may be thermally and/or mechanically coupled to computing hardware such as one or more semiconductor dies, logic ICs, and/or 3DIC stacks to enable the shedding of immersion cooling vapors generated from the boiling of immersion cooling fluid during operation of the computing hardware. In particular, paragraphs [0021] -[0039] and FIGS. 3A-5 disclose vapor-shedding structures including varying porosities, constituent materials, and geometries relative to the computing hardware on which they are mounted. The entirety of U.S. Provisional Patent Application No. 63/506,945 is incorporated herein by reference.

[0063] U.S. Provisional Application No. 63/513,828, filed July 14, 2023 and entitled “Grinding Apparatuses and Methods for Mechanically Modifying Surfaces of Processors to Promote Boiling of a Coolant Liquid,” discloses methods for creating boiling enhancement modifications to surfaces such as the surfaces of computing hardware such as one or more semiconductor dies, logic ICs, and/or 3DIC stacks, particularly in paragraphs [0036]-[0095] and FIGS. 2A-8. For example, grooves, patterns, gouges, trenches, or other structures may be added to a surface or lid of a processor, semiconductor die, logic IC, 3DIC stack component, and/or BEC to encourage nucleation sites for bubbles of immersion cooling vapor to form during a cooling process, thus decreasing the thermal resistance between the processor, semiconductor die, logic IC, and/or 3DIC stack component and the surrounding immersion cooling fluid. The entirety of U.S. Provisional Patent Application No. 63/513,828 is incorporated herein by reference. [0064] U.S. Provisional Patent Application No. 63/513,829, filed July 14, 2023 and entitled “Electrical Connector Having a Heater to Facilitate Boiling of a Coolant Liquid to Improve Signal Integrity in Immersion Cooling Environment,” discloses heaters for promoting boiling of immersion cooling fluid near electrical connectors such as connections between components of a 3DIC stack and enable improved impedances at those connectors, particularly in paragraphs [0019]- [0052] and FIGS. 1 A-3B. The entirety of U.S. Provisional Patent Application No. 63/513,829 is incorporated herein by reference.

[0065] U.S. Provisional Patent Application No. 63/603,242, filed November 28, 2023 and entitled “Woven Boiler Enhancement Coatings,” provides additional examples of BECs including woven BECs with variable weave patterns, densities, attachment mechanisms, and materials (including copper and tungsten) that may be attached to computing hardware such as one or more semiconductor dies, logic ICs, and/or 3DIC stacks in order to promote more efficient heat transfer and immersion cooling vapor nucleation, particularly in paragraphs [0031]- [0055] and FIGS. 3-7. The entirety of U.S. Provisional Patent Application No. 63/603,242 is incorporated herein by reference.

[0066] Immersion cooling system 1000 may additionally include a remote boiler 1095. The remote boiler 1095 is shown as being disposed in thermal and mechanical contact with NIC 1003. The remote boiler 1095 may be any suitable remote boiler in accordance with the present technology. Remote boiler 1095 may include a heat sink disposed within immersion cooling liquid 1064 as well as one or more heat pipes 120a-e configured to provide a closed path for a single phase or two-phase heat spreader fluid from the heat sink to the area adjacent to NIC 1003.

CONCLUSION

[0067] While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0068] Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0069] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

[0070] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0071] The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0072] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0073] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0074] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

1. An apparatus for distributed heat transfer, the apparatus comprising: a remote boiler disposed within a reservoir of an immersion cooling fluid; and one or more heat pipes physically coupled to the remote boiler, each heat pipe of the one or more heat pipes comprising a channel configured to convey a heat transfer fluid; wherein each heat pipe is thermally coupled with at least one component disposed externally to the reservoir of the immersion cooling fluid.

2. The apparatus of claim 1, wherein the heat transfer fluid comprises deionized water.

3. The apparatus of claim 1, wherein the remote boiler and each of the one or more heat pipes comprises copper.

4. The apparatus of claim 1, wherein each heat pipe is thermally coupled with the at least one component through a respective thermal transfer pad.

5. The apparatus of claim 1, wherein the remote boiler further comprises one or more chambers, each chamber fluidically coupled to a respective heat pipe of the one or more heat pipes.

6. The apparatus of claim 1, wherein each heat pipe comprises a wick disposed within the channel of the heat pipe.

7. The apparatus of claim 1, wherein a surface of the remote boiler or a surface of each of the one or more heat pipes comprises a surface treatment.

8. The apparatus of claim 7, wherein the surface treatment comprises a pattern, a coating, a roughening, one or more trenches, one or more scratches, or one or more gouges.