This disclosure relates generally to heat management for electronic devices and, more particularly, to cold plates and liquid cooling systems for electronic devices.
Liquid cooling systems are commonly used in computing devices to manage heat generated by the electronic components. For instance, computers often include cooling liquid systems to manage the heat generated by the central processing unit (CPU).
In general, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. The figures are not to scale. Instead, the thickness of the layers or regions may be enlarged in the drawings. Although the figures show layers and regions with clean lines and boundaries, some or all of these lines and/or boundaries may be idealized. In reality, the boundaries and/or lines may be unobservable, blended, and/or irregular.
As used in this patent, stating that any part (e.g., a layer, film, area, region, or plate) is in any way on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, indicates that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween.
As used herein, connection references (e.g., attached, coupled, connected, and joined) may include intermediate members between the elements referenced by the connection reference and/or relative movement between those elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and/or in fixed relation to each other. As used herein, stating that any part is in “contact” with another part is defined to mean that there is no intermediate part between the two parts.
Unless specifically stated otherwise, descriptors such as “first,” “second,” “third,” etc., are used herein without imputing or otherwise indicating any meaning of priority, physical order, arrangement in a list, and/or ordering in any way, but are merely used as labels and/or arbitrary names to distinguish elements for ease of understanding the disclosed examples. In some examples, the descriptor “first” may be used to refer to an element in the detailed description, while the same element may be referred to in a claim with a different descriptor such as “second” or “third.” In such instances, it should be understood that such descriptors are used merely for identifying those elements distinctly that might, for example, otherwise share a same name.
As used herein, “approximately” and “about” modify their subjects/values to recognize the potential presence of variations that occur in real world applications. For example, “approximately” and “about” may modify dimensions that may not be exact due to manufacturing tolerances and/or other real world imperfections as will be understood by persons of ordinary skill in the art. For example, “approximately” and “about” may indicate such dimensions may be within a tolerance range of +/−10% unless otherwise specified in the below description.
As used herein, the phrase “in communication,” including variations thereof, encompasses direct communication and/or indirect communication through one or more intermediary components, and does not require direct physical (e.g., wired) communication and/or constant communication, but rather additionally includes selective communication at periodic intervals, scheduled intervals, aperiodic intervals, and/or one-time events.
As used herein, “processor circuitry” is defined to include (i) one or more special purpose electrical circuits structured to perform specific operation(s) and including one or more semiconductor-based logic devices (e.g., electrical hardware implemented by one or more transistors), and/or (ii) one or more general purpose semiconductor-based electrical circuits programmable with instructions to perform specific operations and including one or more semiconductor-based logic devices (e.g., electrical hardware implemented by one or more transistors). Examples of processor circuitry include programmable microprocessors, Field Programmable Gate Arrays (FPGAs) that may instantiate instructions, Central Processor Units (CPUs), Graphics Processor Units (GPUs), Digital Signal Processors (DSPs), XPUs, or microcontrollers and integrated circuits such as Application Specific Integrated Circuits (ASICs). For example, an XPU may be implemented by a heterogeneous computing system including multiple types of processor circuitry (e.g., one or more FPGAs, one or more CPUs, one or more GPUs, one or more DSPs, etc., and/or a combination thereof) and application programming interface(s) (API(s)) that may assign computing task(s) to whichever one(s) of the multiple types of processor circuitry is/are best suited to execute the computing task(s).
Electronic devices, such as computers, laptops, servers, etc. often include electrical components that generate heat. For example, processor circuitry, hard drives, batteries, and/or other electrical components typically generate heat during operation. The amount of heat generated is often greater in high-power computing areas, such as with artificial intelligence, machine learning, high-speed graphical processing units (GPUs), and accelerators. Heat can negatively affect the performance of an electrical component as well as other nearby components and, thus, negatively impact the performance of the electronic device and/or systems including the device. Therefore, it is important to cool the electronic device and/or its components to reduce (e.g., prevent or limit) negative effects of heat on the performance of the electronic device and/or surrounding components.
Some electronic devices utilize a liquid cooling system. A liquid cooling system includes a cold plate (which may also be referred to as a cooler, cooling device, cooling element, cooling appliance, or cooling block) that is disposed (e.g., located, positioned) on or near the electronic device and/or otherwise in thermal contact with the electronic device. The liquid cooling system includes a pump that pumps cooling liquid, such as a dielectric fluid, through the cold plate. The cooling liquid absorbs heat from the cold plate and thus the electronic device, thereby allowing the temperature of the electronic device to be controlled either at a set temperature or within a range of safe temperatures over which the device can operate properly. The liquid cooling system pumps the heated cooling liquid through a radiator or condenser. In some examples, one or more fans are mounted near the radiator or condenser that force air across the radiator or condenser to reduce the temperature of the cooling liquid. The cooling liquid is then pumped back to the cooler and the cycle is repeated. The amount of heat that can be removed from the electronic device is at least partially dependent on the cooling capability of the cold plate.
Some known cold plates include a set of fins located in a cavity in the cold plate. The fins effectively increase the surface area of the cold plate and help to transfer heat from the electronic device to the cooling liquid. Some cooling systems utilize a two-phase cooling liquid. In particular, as the cooling liquid is heated in the cold plate, the cooling liquid vaporizes into a gaseous form. This transformation from liquid to vapor bubbles increases the heat absorption and improves the cooling capability of the cold plate. Superior performance of two-phase liquid cooling is seen when vapor bubbles start quickly generating and detaching from the surface at a higher frequency with reduced (e.g., minimal) wall superheat. Wall superheat refers to the difference between the wall temperature and the cooling liquid temperature. However, with higher heat loads, the wall superheat tends to increase in known cold plates. For instance, in some known cold plates, the temperature difference between wall temperature and cooling liquid temperature is almost 55° C. The maximum reliability temperature of silicon is around 100 to 110° C. Therefore, these known cold plates have difficulty effectively handling higher total heat loads and higher heat fluxes (e.g., heat flow intensity or density) generated by high-powered electronic devices.
Disclosed herein are example cold plates with improved cooling capabilities and that can handle higher heat loads and/or higher heat fluxes from high performance electronic devices. An example cold plate disclosed herein includes a plurality of fins, referred to as a fin bank, constructed of metal foam. The metal foam may be, for example, copper foam or aluminum foam. The metal foam has an open-cell foam structure, which has a network of voids or cells that are interconnected. Therefore, the surface of the fins has small voids or cells. This surface structure promotes (e.g., increases) bubble formation that results in smaller bubbles and quicker detachment of the bubbles from the surface. In other words, these small voids or cells form nucleation sites for bubble formation and detachment. As such, this surface structure enables the cooling liquid to vaporize more quickly. Therefore, the metal foam acts as a boiling enhancement coating to increase liquid-to-vapor transformation. This boiling enhancement reduces the wall superheat and thereby increases the cooling capability of the cold plate. Increasing the cooling capacity in this manner enables the liquid cooling system to more efficiently absorb heat from the electronic device, thereby reducing the temperature of the electronic device and/or its components and enabling the electronic device to operate more efficiently.
As noted above, the use of liquids to cool electronic components is being explored for its benefits over more traditional air cooling systems, as there are increasing needs to address thermal management risks resulting from increased thermal design power in high performance systems (e.g., CPU and/or GPU servers in data centers, accelerators, artificial intelligence computing, machine learning computing, cloud computing, edge computing, and the like). More particularly, relative to air, liquid has inherent advantages of higher specific heat (when no boiling is involved) and higher latent heat of vaporization (when boiling is involved). In some instances, liquid can be used to indirectly cool electronic components by cooling a cold plate that is thermally coupled to the electronic component(s). An alternative approach is to directly immerse electronic components in the cooling liquid. In direct immersion cooling, the liquid can be in direct contact with the electronic components to directly draw away heat from the electronic components. To enable the cooling liquid to be in direct contact with electronic components, the cooling liquid is electrically insulative (e.g., a dielectric liquid).
A liquid cooling system can involve at least one of single-phase cooling or two-phase cooling. As used herein, single-phase cooling means the cooling fluid (sometimes also referred to herein as cooling liquid or coolant) used to cool electronic components draws heat away from heat sources (e.g., electronic components) without changing phase (e.g., without boiling and becoming vapor). Such cooling fluids are referred to herein as single-phase cooling fluids, liquids, or coolants. By contrast, as used herein, two-phase cooling means the cooling fluid (in this case, a cooling liquid) vaporizes or boils from the heat generated by the electronic components to be cooled, thereby changing from the liquid phase to the vapor phase. The gaseous vapor may subsequently be condensed back into a liquid (e.g., via a condenser) to again be used in the cooling process. Such cooling fluids are referred to herein as two-phase cooling fluids, liquids, or coolants. Notably, gases (e.g., air) can also be used to cool components and, therefore, may also be referred to as a cooling fluid and/or a coolant. However, indirect cooling and immersion cooling typically involve at least one cooling liquid (which may or may not change to the vapor phase when in use). Example systems, apparatus, and associated methods to improve cooling systems and/or associated cooling processes are disclosed herein.
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In the illustrated example, the example liquid cooling system 1700 includes an example cold plate 1704, an example pump 1706, an example condenser 1708, an example fan 1710, and an example reservoir 1712. The example cold plate 1704 may also be referred to as a cooler or cooling block. The example liquid cooling system 1700 also includes a fluid circuit 1714 that fluidically couples the cold plate 1704, the pump 1706, and the condenser 1708. The condenser 1708 may be referred to as a heat exchanger. The fluid circuit 1714 can include any type and/or number of fluid lines (e.g., hoses, tubes), fluid channels, connectors, valves, and/or a system of the foregoing that fluidically couples two or more of the components. The fluid circuit 1714 has cooling liquid, such as liquid dielectric (e.g., mineral oil, silicon oil, etc.). In other examples, the cooling liquid can be another type of liquid, such as water, deionized water, refrigerant, and/or a glycol/water solution.
In some examples, the cold plate 1704 is coupled directly or indirectly (e.g., via one or more layers) to the electronic device 1702. For example, the cold plate 1704 can be coupled to the electronic device 1702 via one or more threaded fasteners (e.g., bolts, screws, etc.), welding, soldering, adhesives, etc. In the illustrated example, the cold plate 1704 is on (e.g., disposed on) the electronic device 1702. In some examples, the cold plate 1704 is in direct contact with the electronic device 1702. For example, the cold plate 1704 can be in direct contact with a top surface of a casing or integrated heat spreader of the electronic device 1702. In other examples, one or more intermediary components or layers are disposed between the cold plate 1704 and the electronic device 1702. In other examples, the cold plate 1704 is disposed close to, but spaced apart from, the electronic device 1702. The cold plate 1704 can be constructed of any thermally conductive material, such as a metal. In some examples, the cold plate 1704 is at least partially constructed of copper. In other examples, the cold plate 1704 can be constructed of other materials, such as aluminum, brass, steel, etc.
During operation, the pump 1706 pumps the cooling liquid through the fluid circuit 1714. The cooling liquid flows through one or more fluid passageways in the cold plate 1704. The cold plate 1704 absorbs heat from the electronic device 1702, which is transferred to the cooling liquid passing through the cold plate 1704, thereby reducing the temperature of the electronic device 1702. In some examples, the cooling liquid transforms from a liquid phase into a gaseous or vapor phase in the cold plate 1704. The cooling liquid/vapor is then transferred via the fluid circuit 1714 to the condenser 1708. The condenser 1708 dissipates the heat to the surrounding ambient air and the vapor condenses back into liquid form. In some examples, the fan 1710 is activated to direct ambient air across the condenser 1708 to help further reduce the temperature of the cooling liquid. The cooling liquid, after being cooled in the condenser 1708, is pumped back to the cold plate 1704 and the cycle is repeated. The fluid circuit 1714 of this example includes a continuous flow of cooling liquid/vapor. In some examples, the reservoir 1712 contains additional cooling liquid to ensure a sufficient amount of cooling liquid is maintained in the fluid circuit 1714. As such, the cooling liquid flowing through the cold plate 1704 absorbs the heat from the electronic device 1702 to reduce the temperature of the circuitry in the electronic device 1702. This enables for example, processor circuitry and/or other components to operate at higher frequencies to meet higher processing demands. This also enables processor circuitry and/or other components to operate at high powers before hitting a temperature limit in the electronic device 1702.
In the illustrated example, the body 1802 defines a cavity 1818. In this example, the cavity 1818 is formed or defined in the base 1804 (e.g., in the first side 1808 of the base 1804). In some examples, the cavity 1818 is formed via stamping. The body 1802 also has an inlet opening and an outlet opening fluidically coupled to the cavity 1818 such that a fluid passageway is defined between the inlet opening and the outlet opening. For example, in the illustrated example, the lid 1806 has an inlet opening 1820 and an outlet opening 1822, extending between the first and second sides 1812, 1814. When the cold plate 1800 is assembled, the inlet opening 1820 and the outlet opening 1822 are aligned with a portion of the cavity 1818. As such, the inlet opening 1820, the cavity 1818, and the outlet opening 1822 define a fluid flow passageway through the body 1802. When cooling liquid is supplied to the inlet opening 1820, the cooling liquid flows through the inlet opening 1820, through the cavity 1818, and out of the outlet opening 1822. In some examples, the cold plate 1800 includes connectors 1824, 1826 in the inlet and outlet openings 1820, 1822, respectively. The connectors 1824, 1826 are used for connecting a fluid line (e.g., a hose, a tube, a pipe, etc.) of the fluid circuit 1714 (
To increase heat absorption while the cooling liquid is flowing through the cavity 1818, the cold plate 1800 can include a plurality of fins. In this example, the cold plate 1800 includes an example fin bank 1828. In the illustrated example, the fin bank 1828 includes a base plate 1830 and a plurality of fins 1832 (one of which is referenced in
In some examples, the fin bank 1828 is coupled to the base 1804 in the cavity 1818. For example, as shown in
In this example, the fin bank 1828 is constructed of metal foam. For example, the fin bank 1828 may be a substantially solid block or piece of metal foam. The shape of the fin bank 1828 can be formed by cutting or stamping a block of metal foam, examples of which are disclosed in further detail herein. In some examples, the fin bank 1828 is constructed of copper foam. In other examples, the fin bank 1828 can be constructed of another type of metal foam material, such as a nickel foam, an aluminum foam, a steel foam, or a combination of metal foams. In some examples, the metal foam has a coating, such as a bronze coating. In other examples, the metal foam is not coated, sintered, or plated. In some examples, the metal foam of the fin bank 1828 is an open-cell-structure foam material. In an open-cell-structure foam material, the cells (sometimes referred to as pores, voids or cavities) in the foam material are interconnected and a form a network of channels. For example,
Therefore, because the fin bank 1828 is constructed of a metal foam, the surfaces of the fins 1832 are not smooth. Instead, the surfaces of the fins 1832 have small openings or voids formed by the mesh strands or ligaments of the metal material. These voids on the surface form nucleation sites for bubbles to form and depart from the surface of the fins 1832 and the base plate 1830. Further, the reduced material on the surface results in lower surface tension needed to detach from the surface. This surface structure promotes smaller bubbles that generate and depart at a higher frequency than known fin banks. As such, the cooling liquid can more easily convert from the liquid form to the gaseous or vapor form, which improves the cooling capability of the cold plate 1800. The example cold plate 1800 increases the amount of energy per unit area that can be removed and, thus, can remove more energy for the same area.
While in this example the fin bank 1828 includes the base plate 1830 and the fins 1832, in other examples the fins 1832 may not be connected by a base plate. Instead, individual fins of metal foam material can be separately coupled to the base 1804.
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An example method of manufacturing disclosed herein includes compressing a block of metal foam with a tool to form a fin bank. The example method can further include disposing the fin bank in a cavity of a body of a cold plate. For example, as shown in
In the illustrated example, the cold plate 2100 includes metal foam 2122, such as copper foam or aluminum foam. The example metal foam 2122 may have any of the example properties discussed above in connection with the fin bank 1828. However, in this example, the metal foam 2122 is substantially rectangular and does not include fins. When the cold plate 2100 is assembled, the metal foam 2122 can be coupled (e.g., via the braze film 2120) to an inner surface of the base 2104 in the cavity 2110.
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An example method of manufacturing disclosed herein includes compressing a block of metal foam with a tool. The example method can further include disposing the metal foam in a cavity of a body of a cold plate. For example, as shown in
“Including” and “comprising” (and all forms and tenses thereof) are used herein to be open ended terms. Thus, whenever a claim employs any form of “include” or “comprise” (e.g., comprises, includes, comprising, including, having, etc.) as a preamble or within a claim recitation of any kind, it is to be understood that additional elements, terms, etc., may be present without falling outside the scope of the corresponding claim or recitation. As used herein, when the phrase “at least” is used as the transition term in, for example, a preamble of a claim, it is open-ended in the same manner as the term “comprising” and “including” are open ended. The term “and/or” when used, for example, in a form such as A, B, and/or C refers to any combination or subset of A, B, C such as (1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) B with C, or (7) A with B and with C. As used herein in the context of describing structures, components, items, objects and/or things, the phrase “at least one of A and B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B. Similarly, as used herein in the context of describing structures, components, items, objects and/or things, the phrase “at least one of A or B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B. As used herein in the context of describing the performance or execution of processes, instructions, actions, activities and/or steps, the phrase “at least one of A and B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B. Similarly, as used herein in the context of describing the performance or execution of processes, instructions, actions, activities and/or steps, the phrase “at least one of A or B” is intended to refer to implementations including any of (1) at least one A, (2) at least one B, or (3) at least one A and at least one B.
As used herein, singular references (e.g., “a”, “an”, “first”, “second”, etc.) do not exclude a plurality. The term “a” or “an” object, as used herein, refers to one or more of that object. The terms “a” (or “an”), “one or more”, and “at least one” are used interchangeably herein. Furthermore, although individually listed, a plurality of means, elements or method actions may be implemented by, e.g., the same entity or object. Additionally, although individual features may be included in different examples or claims, these may possibly be combined, and the inclusion in different examples or claims does not imply that a combination of features is not feasible and/or advantageous.
From the foregoing, it will be appreciated that example systems, methods, apparatus, and articles of manufacture have been disclosed that improve the cooling capability of a cold plate in a liquid cooling system. Examples disclosed herein advantageously utilize metal foam material, which promotes (e.g., increases) formation of smaller bubbles that form on the foam and detach from the foam more quickly, compared to known structures in known cold plates. This fast formation/detachment reduces wall superheat (i.e., the difference between the wall temperature and the cooling liquid temperature) and improves the cooling capability of the cold plate. Further, metal foam is relatively inexpensive. Therefore, examples disclosed herein result in a less expensive, two-phase cooling cold plate. Also, metal foam is light weight, which reduces weight of the overall cold plate.
Examples and combinations of examples disclosed herein include the following:
Example 1 is a cold plate for an electronic device. The cold plate comprises a body defining a cavity. The body has an inlet opening and an outlet opening fluidically coupled to the cavity such that a fluid passageway is defined between the inlet opening and the outlet opening. The cold plate also comprises metal foam in the cavity.
Example 2 includes the cold plate of Example 1, wherein the metal foam is an open-cell-structure foam material.
Example 3 includes the cold plate of Examples 1 or 2, wherein the metal foam is copper foam or aluminum foam.
Example 4 includes the cold plate of any of Examples 1-3, wherein the metal foam has a relative density of 3-12%.
Example 5 includes the cold plate of any of Examples 1-4, wherein the metal foam is a compressible metal foam.
Example 6 includes the cold plate of any of Examples 1-5, wherein the metal foam is included in a fin bank. The fin bank includes a base plate and a plurality of fins extending from the base plate.
Example 7 includes the cold plate of Example 6, wherein the metal foam in the base plate has a lower porosity than the metal foam in the fins.
Example 8 includes the cold plate of Examples 6 or 7, wherein the fins are parallel to and spaced apart from each other.
Example 9 includes the cold plate of any of Examples 6-8, wherein the body includes a base and a lid, the cavity defined in the base.
Example 10 includes the cold plate of Example 9, wherein the fins are engaged with the lid.
Example 11 includes the cold plate of any of Examples 6-10, wherein the base plate of the fin bank is coupled to the base via brazing.
Example 12 includes the cold plate of Example 11, further including braze film between the base plate and a surface of the base in the cavity.
Example 13 includes the cold plate of any of Examples 1-12, wherein the metal foam increases bubble formation and detachment.
Example 14 includes the cold plate of any of Examples 1-13, wherein the metal foam reduces wall superheat of the cold plate.
Example 15 is a method comprising compressing a block of metal foam with a tool to form a fin bank, the fin bank including a base plate and a plurality of fins extending from the base, and disposing the fin bank in a cavity of a body of a cold plate.
Example 16 includes the method of Example 15, further including heating the cold plate in a brazing oven to couple the fin bank to the body.
Example 17 includes the method of Examples 15 or 16, wherein the metal foam in the base plate has a lower porosity than the metal foam in the fins.
Example 18 is a cold plate for an electronic device. The cold plate comprises a base defining a cavity, metal foam in the cavity, and a lid having a plurality of fins. The fins extend into the cavity and engage with the metal foam.
Example 19 includes the cold plate of Example 18, wherein the metal foam is coupled to the base via brazing.
Example 20 includes the cold plate of Examples 18 or 19, wherein the metal foam is an open-cell-structure foam material.
Example 21 is a method comprising disposing a block of metal foam in a cavity of a base of a cold plate and coupling a lid to the base, the lid having a plurality of fins, such that when the lid is coupled to the base the fins extend into the cavity and engage the block of metal foam.
Example 22 includes the method of Example 21, further including heating the cold plate in a brazing oven to couple the block of metal foam to the base.
The following claims are hereby incorporated into this Detailed Description by this reference. Although certain example systems, methods, apparatus, and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all systems, methods, apparatus, and articles of manufacture fairly falling within the scope of the claims of this patent.