Apparatus and system for cooling an electronic device - Patent application

Abstract

An apparatus and system are provided for cooling a plurality of electronic devices (25, 26) disposed on a circuit board (1). The apparatus comprises a plurality of cold plates (7, 8), each cold plate (7, 8) having a thermally conductive surface for cooling an electronic device (25, 26) thermally coupled thereto. The apparatus comprises a support frame to which each of the plurality of cold plates (7, 8) is attached, the support frame being configured for attachment to the circuit board to hold the thermally conductive surfaces of the plurality of cold plates (7, 8) in thermal contact with the plurality of electronic devices (25, 26). The support frame is arranged and configured to hold the thermally conductive surfaces of each of the plurality of cold plates (7, 8) in different positions relative to the support frame.

Description

[Technical field]

[0001] Technical Field The present disclosure relates to an apparatus and system for cooling an electronic device. [Background technology]

[0002] background Computers, servers, and other devices used for data processing (referred to as Information Technology or IT) typically include printed circuit boards (PCBs). On these PCBs are small devices called Integrated Circuits (ICs) that may include a central processing unit (CPU), an Application Specific Integrated Circuit (ASIC), a Graphical Processing Unit (GPU), a Random Access Memory (RAM), and others. All of these electronic components or devices generate heat when in use. To maximize the performance of the IT, the heat must be dissipated to keep the contents at an optimal temperature. These considerations also apply to other types of electronic devices or systems.

[0003] IT is usually contained within a case, enclosure, or housing. For example, for a server, this enclosure may be referred to as a server chassis. Server chassis typically adhere to several industry standards that specify the height of each chassis, referred to as 1RU (one rack unit) or 1OU (one open unit), which are also abbreviated as 1U or 1OU. The smaller of the two main standards is 1RU / 1U, which is 44.45mm or 1.75 inches in height. Such units are sometimes referred to as "blade" servers in terms of shape and style, although, for example, such server chassis may not need to be plugged or plugged into a backplane.

[0004] Different server products can utilize more than one RU / OU at a time for a chassis, for example a 2U chassis uses two rack units. The size of each server chassis is typically kept to a minimum to maximize the amount of computing power per server rack (the server rack is the main housing to which the server chassis are added). Nevertheless, 3U, 4U and 5U systems are commonly used, although reduced space requirements are generally desired.

[0005] Typically, electronic components or devices used on or in IT are cooled using air. This usually involves some sort of heat sink, with fins or similar placed either directly on the chip surface or in contact with a thermal interface material (TIM) between the two components. In addition to the heat sink, each enclosure uses a series of fans to draw air through the enclosure, removing heat from the heat sink and expelling it out of the chassis. This type of heat sink is used in conjunction with server equipment side cooling, such as air conditioning. This cooling method is not particularly efficient, has high running costs, and uses a large amount of space to manage the air used for cooling.

[0006] This method of cooling IT has been used almost exclusively for high-volume IT and server equipment. However, in recent years, the limitations of cooling equipment with air have reduced the peak performance of heat-generating chips. As technology halves in size for the same performance every few years (as exemplified by Moore's Law), the heat generated by chips increases as component footprints decrease. This increases the size and complexity of heat sinks designed for air cooling. This often results in an increase in the required server chassis size, and therefore a decrease in computing power within a single rack.

[0007] As an alternative to air cooling, liquid cooling can be used. Liquid cooling can, in some cases, provide more efficient heat transfer from electronic components or devices and therefore greater cooling power. These liquids include dielectric fluids, mineral oil and water, to name a few. Several existing approaches using liquid cooling are known. For example, WO 2018 / 096362, by the same applicant as this disclosure and incorporated herein by reference, describes a liquid immersion cooling approach in which a primary liquid coolant, typically a dielectric liquid, is pumped into a sealed chassis so that the primary liquid coolant remains inside. A heat exchanger is also located within the chassis, transferring heat from the primary liquid coolant to a secondary liquid coolant (which may be shared between multiple chassis) that flows outside the chassis, typically water or water-based (which is advantageous because it has a high specific heat capacity).

[0008] In light of this, WO 2019 / 048864, also by the same applicant as the present disclosure and incorporated herein by reference, describes several types of heat sinks that may be mounted on, around, or adjacent to an electronic device, or that the electronic device may be mounted on or around the heat sink. The heat sink defines an internal volume for storing and maintaining a primary liquid coolant adjacent to the electronic device. As the primary liquid coolant flows (by pumping and / or convection) within the chassis, it is directed into the internal volume of the heat sink to improve cooling of the electronic device (e.g., an IC that becomes particularly hot during operation, or a power supply unit). The primary liquid coolant then flows out of the heat sink internal volume (e.g., by overflowing and / or flowing through holes in the volume) and is collected together with the remaining primary liquid coolant within the chassis to cool other electronic devices (e.g., other components or ICs mounted on PCBs or otherwise within the chassis). The primary liquid coolant is cooled again by a heat exchanger within the chassis, and heat is transferred to a secondary liquid coolant. In this approach, the level of the primary liquid coolant within the chassis can be kept low and certainly lower than the level of the primary liquid coolant within the heat sink internal volume. This creates liquid cooling at multiple levels (heights), reducing the amount of liquid coolant required and allowing efficient single-phase (i.e., liquid-phase only) cooling of the electronic device. Because primary liquid coolant can be expensive, difficult to contain, and prone to contamination, this approach can provide significant advantages in terms of reduced cost and complexity.

[0009] WO 2021 / 099768, also by the same applicant as the present disclosure and incorporated herein by reference, describes a cold plate having an external receptacle. The external receptacle defines a volume that can receive (e.g., through a nozzle), store and / or maintain a primary liquid coolant to provide heat transfer (e.g., in a conventional manner) between a primary liquid coolant outside the cold plate and a secondary liquid coolant flowing through the cold plate. The primary and secondary liquid coolants are distinct, separate and physically isolated from one another (although thermally coupled). Systems employing a hybrid of immersion cooling and cold plates are known. Summary of the Invention [Problem to be solved by the invention]

[0010] While these known liquid cooling systems provide good performance, it would be desirable to provide an improved liquid coolant-based system having high performance and efficiency. Moreover, as circuit boards become more densely packed, it becomes difficult to position the various different heat sinks and / or cold plates in the correct locations. [Means for solving the problem]

[0011] overview Against this background, there is provided an apparatus for cooling a plurality of electronic devices arranged on a circuit board according to claim 1. There is also provided a system for cooling a plurality of electronic devices arranged on a circuit board according to claim 24.

[0012] The present disclosure relates to an apparatus for cooling a plurality of electronic devices disposed on a circuit board. The electronic devices may be chips or individual electrical components, and the various chips or components may be densely packed on the circuit board. The apparatus includes a plurality of cold plates (such as, for example, any of the cold plates described in International Publication No. 2021 / 099768, which is incorporated herein by reference). Each cold plate has a thermally conductive surface for cooling an electronic device thermally coupled thereto, for example, when in contact with the cold plate. A support frame is provided to which each of the plurality of cold plates is attached. The support frame is configured to be attached (e.g., by being screwed or rigidly physically coupled) to the circuit board to hold the thermally conductive surfaces of the plurality of cold plates in thermal contact (e.g., to enable heat transfer) with the plurality of electronic devices. The support frame is arranged and configured to hold the thermally conductive surfaces of each of the plurality of cold plates in different positions relative to the support frame. The position of each of the cold plates relative to the support frame may be, for example, one or more of an angle relative to the support frame, a distance from the support frame (e.g., measured directly between the cold plate and its point of attachment to the support frame), and / or a lateral position along the support frame (e.g., all cold plates are substantially the same distance from the support frame, but may be spaced apart).

[0013] By attaching multiple cold plates to a single support frame, multiple cold plates can be held in different positions to provide cooling to multiple electronic devices in a space-efficient manner. By providing a single support frame used to hold multiple cold plates in place, a high density arrangement of electronic devices can be efficiently cooled since the shared support frame can take up less space on the circuit board than each cold plate's individual attachment mechanism (e.g., one socket per cold plate). Existing solutions typically utilize one relatively large mounting structure per cold plate. Thus, conventional configurations require a relatively large gap around each electronic device to provide space for the associated mounting structure. In contrast, the present disclosure provides a single support frame such that multiple cold plates can be secured to a circuit board without each cold plate needing a dedicated mounting structure.

[0014] The cold plate positions may be different positions, and each cold plate position may be a distance from and / or an angle relative to the support frame. Similarly, in the case of a perfectly flat circuit board, the distance and angle may be measured relative to the circuit board instead. Nevertheless, due to manufacturing tolerances, the circuit board may not be perfectly flat, and so the angles and distances are typically defined relative to the support frame in this disclosure. A first subset (i.e., one or more) of the plurality of cold plates may be at a first distance from the support and a second subset (i.e., one or more) of the plurality of cold plates may be at a second distance from the support frame to enable cooling of electronic devices having different heights (or at slightly different heights due to defects in the circuit board). In the context of this disclosure, a subset of the plurality of cold plates may include only a single cold plate, or a subset may include multiple cold plates.

[0015] Different electronic devices have different thicknesses, and thus the apparatus disclosed herein may be able to accommodate chips of different heights. Similarly, chips whose top surfaces are not perfectly parallel to the circuit board (i.e., at different angles relative to the circuit board) may also be accommodated. For example, an electronic device may not sit perfectly flat on the circuit board (e.g., due to the manner in which it is mounted), and thus a support frame that allows the cold plate to be held in slightly different positions (e.g., heights and / or angles) may advantageously allow such devices to be cooled. Moreover, while it may seem possible to cool two adjacent electronic devices by a single cold plate spanning the two electronic devices, in reality, the two adjacent electronic devices are unlikely to be mounted with their top surfaces perfectly parallel. This means that slight differences in the angles of the electronic devices may prevent a single cold plate from effectively cooling two electronic devices simultaneously. Thus, a single support structure that allows multiple cold plates to simultaneously cool adjacent electronic devices using the cold plates and allows the cold plates to be freely positioned in different positions (e.g., heights and / or angles) can provide a space-efficient solution that provides good cooling for multiple devices. In generalized terms, at least one cold plate, and optionally multiple cold plates (or even all cold plates) can be rotatably attached to the support frame, which can improve engagement with the respective electronic devices.

[0016] Moreover, various electronic devices may have different finishes and may not be equally flat (e.g., due to manufacturing limitations). Often, a TIM (e.g., indium metal, thermal paste, thermal grease, gap filler, thermal pad, thermal tape, etc.) is placed between the electronic device and the heat sink or cold plate. Manufacturing and / or installation imperfections (e.g., deviations in height, angle, flatness, surface finish, etc.) can prevent proper TIM compression, which can have serious effects on cooling. The TIM is often compressed to a thickness of 0.02 mm, which means that micrometer-level differences in height / angle / flatness can have a large effect on heat transfer. Thus, the imperfections of these effects also mean that it is extremely difficult to reliably cool an electronic device with a single cold plate. Thus, the support frame described herein can enable cooling of a variety of different electronic devices by allowing multiple different cold plates to be at slightly different angles on a single support frame. A TIM can be provided between the electronic device described herein and the cold plate described herein. The TIM can be provided on the electronic device and / or the cold plate.

[0017] Throughout this disclosure, a first subset and a second subset of the plurality of cold plates are described. Nevertheless, one or more further subsets (e.g., a third, a fourth, a fifth, a sixth, etc.) of the plurality of cold plates may be provided at respective distances from the support frame. By providing a support frame configured to hold different subsets of the plurality of cold plates at different positions relative to the support frame, it is possible to hold the cold plates against electronic devices having different sizes and / or different positions (e.g., different heights and / or angles). By allowing multiple cold plates to be held in contact with multiple different electronic devices simultaneously, efficient cooling of a potentially large number of electronic devices in a variety of configurations can be achieved.

[0018] In particular, the apparatus of the present invention does not include a circuit board or any electronic device. The apparatus of the present invention is a stand-alone component that can be adapted to an existing circuit board to cool an electronic device with its top surface in a different position (e.g., vertical position, angle, etc.). The present invention is a device suitable for attachment to a circuit board and for holding a cold plate near an electronic device requiring cooling. For example, the apparatus may be retrofitted.

[0019] In this disclosure, distances between cold plates and / or electronic devices or circuit boards may be described. These distances may be described with reference to circuit boards and / or electronic devices to aid in visualization, as circuit boards (especially planar circuit boards) provide a natural reference point for describing electronic devices having different heights. It will be appreciated that in a preferred embodiment, the total distance from the top of the support frame to the bottom of the support frame will be approximately equal to the sum of the distance from the top surface of the support frame to the thermally conductive surface, the distance from that thermally conductive surface to the respective electronic device, the thickness of that electronic device, and the thickness of the circuit board. Thus, for any given device, the distance between the cold plate and the circuit board can be converted to the distance between the cold plate and the top of the support frame. As previously mentioned, the present invention can be considered at its most general level as an apparatus comprising a plurality of cold plates and a support frame configured to hold the thermally conductive surfaces of the cold plates at different distances from the support frame (i.e., the support frame, rather than the circuit board, can be used as the reference point for any distance measurements).

[0020] Thus, in generalized terms, an embodiment of the present disclosure can be described as an apparatus for cooling a plurality of electronic devices disposed on a circuit board. The apparatus comprises a plurality of cold plates, each cold plate having a thermally conductive surface, and a support frame to which each of the plurality of cold plates is attached. The support frame is configured to hold a thermally conductive surface of at least a first cold plate in a first position relative to the circuit board and to hold a thermally conductive surface of at least a second cold plate in a second position relative to the circuit board. The first distance and the second distance may be different. In the context of the present disclosure, the term circuit board is intended to encompass any substrate or surface on which electronic devices, such as electronic components and chips, may be disposed. The circuit board may be a PCB, a breadboard, a stripboard, or any other type of surface on which electronic devices may be attached.

[0021] Where multiple subsets of cold plates are described herein, a first subset may be at a first location (e.g., distance from and / or angle relative to the support frame), a second subset may be at a second location, a third subset may be at a third location, and so on. Thus, each of the multiple subsets of cold plates may include one or more cold plates at different locations relative to the support frame. Nevertheless, there may be several subsets at the same height (or angle). For example, a first subset may be at a first distance, a second subset may be at a second distance, and a third subset may be at the first distance. The precise distance between the cold plates and the support frame depends on (and may be adjustable to accommodate) the particular arrangement of the electronic device.

[0022] Liquid cooling may be employed in the present disclosure, with multiple cold plates advantageously combined into an assembly, with each cold plate providing liquid cooling to one or more heat sources (e.g., electronic devices). Coolant may be supplied to any particular subset of the cold plates in either parallel or series, depending on the piping routing. Thus, the cold plates described in the present disclosure may define an interior volume configured to receive liquid coolant therein to transfer heat from the electronic devices to the interior volume. The interior volume may have a closed top, for example, to prevent the coolant from leaking out of the cold plate. One or more cold plates may have an open top, for example, to allow the coolant to overflow from the cold plate (as described in WO 2019 / 048864), so that the coolant contacts and cools other components located at a lower level on the circuit board. Some of the cold plates in this disclosure can be considered as a composite of a heat sink (which provides a thermally conductive surface for cooling an electronic device) and an upper portion that retains liquid coolant and holds it over the lower heat sink portion of the cold plate. The upper portion can be a closed structure or an open structure with a retaining vertical wall but no top surface. At least one cold plate can include a base and a retaining wall that together define a volume for holding liquid coolant, which can be arranged and configured to allow the liquid coolant to overflow beyond the retaining wall.

[0023] The path of the liquid coolant can be determined by the arrangement of connecting tubes or hoses to the individual cold plates. For example, the coolant can be used to first cool components whose temperatures are closest to the maximum operating temperature, and then the used coolant can be fed to other cold plates to cool components that are not as close to their maximum operating temperature. Thus, the flow path can be optimized based on the temperature limits of the individual heat sources. For example, electronic devices (e.g., chips) with relatively low temperature limits can be cooled first, followed by the remaining chips. In some embodiments of the present disclosure, multiple outer chips (e.g., optical modules) are arranged around one or more inner chips. In such embodiments, the outer chips are cooled in parallel first (i.e., cold plates in thermal contact with the outer chips receive liquid coolant in parallel with each other), and then the outlet flow of those outer cold plates is passed to a central cold plate above the inner chip (which may be, for example, an ASIC chip), after which the coolant exits the cold plate.

[0024] It can be difficult to use a single cold plate to cool a circuit board (e.g., a printed circuit board or PCB) with multiple electronic devices (e.g., chips) at different positions (e.g., heights or angles). The same is true for various other arrangements of electronic devices on a surface (e.g., a breadboard or stripboard) where multiple electronic devices are at different positions. Manufacturing tolerances and error stacks of the cold plate at the chip-heat sink interface can make it difficult to position the cold plate accurately enough to contact various components at different positions. Thus, some embodiments of the present disclosure are directed to addressing these challenges and providing an apparatus incorporating multiple cold plates that can move independently of each other. Being able to independently control the position of the cold plates helps overcome these issues and allows for improved contact between the heat source and the heat sink (e.g., the cold plate). This independence can be used to achieve improved thermal interface material (TIM) compression, resulting in better cooling performance.

[0025] In some embodiments, to achieve improved TIM compression, the circuit board with electronic devices thereon and the cold plates may be pressed together using two separate plates (which may be formed from steel), referred to in this disclosure as lower and upper compression plates. The compression plates press the electronic devices against the thermally conductive surface of the cold plate. A typical heat sink requires a base plate and a socket for alignment before compression, which may be difficult to implement on a particular chip layout. Thus, the cold plate may be attached to the upper compression plate to form the cold plate assembly. Thus, the purpose of the upper compression plate is to first position the cold plate in the correct position and then apply a compressive force to the electronic device. Compression limiting may be achieved by providing standoffs (or other spacers / protrusions) between the two compression plates. The upper and lower compression plates may be considered to be the first and second parts of a support frame, and the plates need not be flat (although in some embodiments the plates are flat). The standoffs may also be considered to be part of the support frame of the apparatus described in this disclosure.

[0026] As previously mentioned, some embodiments of the present disclosure allow for addressing manufacturing and / or mounting imperfections. One feature advantageous for providing such flexibility is the provision of a resilient member, such as a spring, between the cold plate and the upper compression plate. The resilient member can be compressed by a specified displacement to achieve a desired TIM actuation pressure. The pressure can be selected to achieve good thermal coupling by abutting the cold plate with the electronic device. Different cooling requirements for different electronic devices may mean that a higher compression may be desired for one component than another, but traditional mounting methods (e.g., springs at each corner of a single cold plate) do not easily allow multiple cold plates in a dense area to be efficiently cooled by the cold plate. In embodiments of the present disclosure, the resilient member (e.g., springs) can allow the cold plate to have the freedom to rotate to perfectly align with a poorly mounted or poorly finished electronic device. Additionally, in some embodiments, the pressure provided can be fine-tuned using a threaded disk insert that seats within the upper compression plate. For example, by screwing the insert downwards (i.e., toward the electronic device below the cold plate), the amount that the elastic member is compressed increases, and therefore a greater compressive force is achieved. This adjustability may be used to account for manufacturing errors that result in the chip being placed in a different position (e.g., height and angle) and / or to ensure that the chip is not subjected to excessive force.

[0027] As previously mentioned, some embodiments of the present disclosure employ liquid cooling (although the cold plates described herein need not necessarily be liquid cooled). Liquid cooling can be provided by a closed-loop cooling configuration in which coolant is constrained to pass through each cold plate. In some embodiments, a hybrid configuration can be provided. In a hybrid configuration, some electronic components are submerged or at least partially submerged in coolant within the chassis (e.g., coolant allowed to overflow or leak from some cold plates), while other components are held in contact with a cold plate through which liquid coolant flows (although the cold plate need not be flushed with liquid). In either case, each cold plate using liquid cooling can have separate inlet and outlet ports for receiving coolant and allowing the coolant to exit the cold plate.

[0028] To improve heat transfer from the electronic device to the coolant, one or more protrusions, such as fins or skiving, may be provided in the cold plate. In a preferred embodiment, a gasket is positioned in each cold plate between a lower copper skived heat sink and an upper portion of the cold plate, which is typically made from steel (although other materials may be used). Although skiving is employed, other protrusions (e.g., pins, rods, fins, baffles, channels, etc.) may be used. The gasket prevents the coolant from bypassing the protrusions in the interior volume defined by the cold plate. Thus, the gasket maximizes the wetted area of ​​the heat sink and enhances cooling performance. A boss may be provided on the surface of the gasket to allow the gasket to be precisely positioned and to prevent the gasket from being disturbed (e.g., washed away) by the coolant.

[0029] The cold plate described in the present disclosure can be provided as a stand-alone component. In particular, the present disclosure provides a cold plate for cooling an electronic device, the cold plate defining an interior volume configured to receive a liquid coolant therein for transferring heat from the electronic device to the interior volume, the cold plate comprising a thermally conductive surface for cooling the electronic device thermally coupled to the electronic device, one or more protrusions on an interior surface of the interior volume, and a gasket configured to restrain the liquid coolant from flowing around the one or more protrusions. The interior surface of the cold plate and / or a surface of the gasket can include one or more bosses configured to engage complementary surfaces of the gasket or the interior surface of the cold plate to align the gasket within the cold plate. Such a cold plate can be used to efficiently cool the electronic device.

[0030] In some embodiments, the present disclosure provides an apparatus for cooling a plurality of electronic devices disposed on a circuit board, the apparatus comprising: a plurality of cold plates, each cold plate having a thermally conductive surface for cooling an electronic device thermally coupled thereto; and a support frame to which each of the plurality of cold plates is attached, the support frame being configured to be attached to the circuit board so as to hold the thermally conductive surfaces of the plurality of cold plates in thermal contact with the plurality of electronic devices, the support frame comprising a first plate and an opposing second plate, the second plate being displaced relative to the first plate, the first plate being movable such that the displacement between the first plate and the second plate can be changed, and at least one of the plurality of cold plates being rotatably attached to the first plate.

[0031] For each embodiment disclosed in this disclosure, where structural features of the device are described, methods for manufacturing and / or operating those features may additionally be provided. Combinations of embodiments are also possible. Furthermore, combinations of specific features of the device are also disclosed, and such combinations are compatible. Specific examples of such combinations are provided purely by way of example.

[0032] List of drawings The present disclosure can be practiced in several ways and preferred embodiments will now be described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0033] [Figure 1A] FIG. 1 is an isometric view of an apparatus for cooling an electronic device in a first embodiment. [Figure 1B] FIG. 1 is an isometric view of an apparatus for cooling an electronic device in a first embodiment. [Figure 2A] FIG. 1 is an isometric view of a portion of the device of the first embodiment. [Figure 2B] FIG. 2 is a side view of a portion of the device of the first embodiment. [Figure 2C] FIG. 1 is an isometric view of a portion of the device of the first embodiment. [Figure 3A] FIG. 2 is a plan view of a cold plate of the apparatus of the first embodiment. [Figure 3B] FIG. 2 is a side view of the cold plate of the apparatus of the first embodiment. [Figure 3C] FIG. 2 is an isometric view of the cold plate of the apparatus of the first embodiment. [Figure 3D] FIG. 2 is an isometric view of the cold plate of the apparatus of the first embodiment. [Figure 3E] FIG. 2 is an isometric view of the cold plate of the apparatus of the first embodiment. [Figure 3F] FIG. 2 is an isometric view of the cold plate of the apparatus of the first embodiment. [Figure 4A] FIG. 1 is an isometric view of a portion of the device of the first embodiment. [Figure 4B] FIG. 1 is an isometric view of a portion of the device of the first embodiment. [Figure 5A] FIG. 2 is a plan view of a portion of the device of the first embodiment. [Figure 5B] FIG. 2 is a side view of a portion of the device of the first embodiment. [Figure 5C] FIG. 1 is an isometric view of a portion of the device of the first embodiment. [Figure 6A] FIG. 2 is an isometric view of the cold plate of the apparatus of the first embodiment. [Figure 6B] FIG. 2 is an isometric view of the cold plate of the apparatus of the first embodiment. [Figure 7] FIG. 2 illustrates a heat sink that can serve as either of the cold plates of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Detailed Description 1A-6B show a first embodiment of an apparatus for cooling a plurality of electronic devices 25, 26 disposed on a circuit board. In generalized terms, the apparatus comprises a plurality of cold plates 7, 8. Each cold plate 7, 8 has a thermally conductive surface for cooling an electronic device 25, 26 thermally coupled thereto. The apparatus comprises a support frame to which each of the plurality of cold plates is attached. The support frame is configured to be attached to the circuit board so as to hold the thermally conductive surfaces of the plurality of cold plates 7, 8 in thermal contact with the plurality of electronic devices 25, 26. Moreover, the support frame is arranged and configured to hold the thermally conductive surfaces of a first subset of the plurality of cold plates 7, 8 in a first position relative to the support frame (and thus also relative to the circuit board, since the support frame is attached to the circuit board) and to hold the thermally conductive surfaces of a second subset of the plurality of cold plates 7, 8 in a second position relative to the circuit board (and thus also relative to the circuit board, since the support frame is attached to the circuit board). A first subset of the plurality of cold plates may be considered to be cold plates 7 and a second subset of the plurality of cold plates may be considered to be cold plates 8.

[0035] An isometric view of such an apparatus is shown in FIG. 1A. In FIG. 1A, a multi-heat source cold plate assembly (herein referred to as MHSC (Multi Heat Source Cold Plate)) according to a first embodiment is attached to a circuit board 1. Below the circuit board 1, a plate 5 (made of steel, but other materials may be used, such as other metals, such as aluminum, or plastics, such as nylon, glass reinforced plastic, composites, etc.) is provided. The plate 5 is also referred to as the lower compression plate throughout this disclosure. The plate 5 supports the PCB and is separated from the circuit board 1 by a thin insulating layer. This insulating layer ensures that there is no metallic (i.e., thermal and / or electrical) contact between the plate and the circuit board 1.

[0036] Unlike most heat sink assemblies, this design does not use a socket to place the heat sink in place. Instead, the first and second subsets 7, 8 of the multiple cold plates 7, 8 in this embodiment are all attached to an upper compression plate 6 that is bolted to a lower compression plate 5 through a circuit board 1 using bolts 4. This ensures accurate alignment of the cold plates 7, 8 with respect to the chips 25, 26 on the PCB. Thus, this embodiment comprises a support frame that comprises two distinct parts, a first part being the upper plate 6 to which the cold plates 7, 8 are attached, and a second part being the lower plate 5. The support frame acts to hold the thermally conductive surface of the cold plates 7, 8 (i.e., the underside of the cold plates opposite their attachment points to the support frame) in thermal contact with the electronic devices 25, 26. In this embodiment, the thermally conductive surface is the bottom surface of the lower portion 18, 23 of the cold plates that contacts the electronic devices 25, 26.

[0037] In a general sense, the support frame of the present disclosure may comprise a first portion (e.g., a first plate, such as the compression plate described above) to which each of the multiple cold plates is attached, and a second portion (e.g., a second plate, such as the compression plate described above) opposite the first portion. The first portion may be for attachment to a circuit board, and the second portion may be for holding the cold plates in place. Preferably, the first and second portions of the support frame are configured to be drawn together (e.g., they are both configured to attach to the circuit board) to hold the thermally conductive surfaces of the multiple cold plates in thermal contact with the multiple electronic devices. Thus, the support frame may be configured to compress the multiple electronic devices between the multiple cold plates and the circuit board, which can ensure that good thermal contact between the electronic devices and the cold plates is maintained. For example, the first and second portions may effectively clamp the circuit board to hold the cold plates in contact with the electronic devices. Insulation may be provided on the support frame to insulate (electrically and / or thermally) the support frame from the circuit board.

[0038] Returning to the specific description of the first embodiment, FIG. 1B shows an exploded view of the MHSC assembly. There are a total of five cold plates 7, 8 in this assembly. The first subset of the plurality of cold plates is four cold plates 7, and the second subset of the plurality of cold plates is a single cold plate 8. The second subset is a central cold plate 8 that sits above the ASIC chip 26 on the circuit board 1, and the first subset is four outer cold plates 7 that sit above the eight optical modules 25. Between the cold plates 7, 8 and the upper compression plate 6, there are provided a plurality of elastic members 9 (i.e., at least one elastic member per cold plate), which are springs 9 in this embodiment. When the outer four bolts 4 are tightened, the cold plates 7, 8 contact the ASIC chip 26 and the optical module 25, which causes the springs 9 to be compressed by the upper compression plate 6. The springs 9 allow the cold plates 7, 8 to rotate when in contact with the electronic devices 25, 26, thereby allowing the cold plates to seat flush against the electronic devices 25, 26. When the resilient members 9 are compressed by abutting against the electronic devices 25, 26 on the circuit board, each resilient member 9 pulls the attached cold plates 7, 8 away from the support frame. The cold plates 7, 8 are attached via the springs 9 in this embodiment, but may be attached via other means (e.g., screwed or rigidly attached) in other embodiments. In some cases, leaf springs may be used.

[0039] Using the spring constant and Hooke's law (which relates the force on a spring to its spring constant and its extension or compression), it is possible to determine the displacement required to obtain a particular force (e.g., the maximum compressive force that the chip 26 of the optical module 25 can withstand) between the cold plates 7, 8 and the circuit board chips 25, 26. For example, the cold plates 7, 8 and / or the electronic devices 25, 26 can be provided with TIMs, and the elastic members 9 can be adjusted (by changing their position or by replacing them with springs having different spring constants) to achieve the desired level of TIM compression.

[0040] In the generalized terms used above, the apparatus of the present disclosure preferably further comprises one or more elastic members (helical springs or constant force springs, but rubber parts can also be used) attached to at least one cold plate, preferably each cold plate, the one or more elastic members being configured to pull each at least one cold plate away from the support frame. The elastic members may be provided between the support frame and the cold plate. The elastic members can act as biasing means configured to bias the cold plate outwardly from the support frame. In case the support frame includes two parts, the elastic members may be configured to pull the associated cold plate away from one of the parts. For example, in a preferred embodiment, the elastic members push the cold plate outwardly from the upper compression plate of the support frame and towards the lower compression plate of the support frame. In case the support frame of the present disclosure includes two distinct parts, the one or more elastic members can be attached to the first part of the support frame (i.e. the part to which the cold plate is attached). Preferably, at least one cold plate, and preferably each cold plate, is rotatably attached to the support frame (e.g., via a resilient member), thereby allowing the cold plate to rotate when held against the electronic device, thereby tolerating manufacturing and / or attachment imperfections. A resilient member (such as a spring) may be a particularly advantageous way to allow the cold plate to rotate, provide flexibility to accommodate variations, and optimize the compression force achieved. Alternative means for achieving rotation may also be used, such as, for example, a ball and socket joint.

[0041] Standoffs 10 are positioned between the upper compression plate 5 and the lower compression plate 6 to prevent over-compression (i.e., limit how close the two parts of the support frame 5, 6 can be), thereby reducing the possibility of damaging the chips 25, 26. Together with the compression plates 5, 6, the standoffs 10 form part of the support frame; that is, the support frame is a composite structure comprising multiple elements (plates 5, 6 and standoffs 10). Nevertheless, the support frame may be a unitary structure that can be attached (e.g., bolted or screwed) directly to a circuit board to hold the cold plates 7, 8 in thermal contact with the electronic devices 25, 26.

[0042] Thus, in a general sense, embodiments of the present disclosure may include one or more protrusions between the first and second portions of the support frame, the one or more protrusions being configured to limit the distance between the first and second portions of the support frame. The protrusions may be spacers or standoffs. The protrusions may be considered to be part of the support frame, such that the support frame includes first and second opposing portions, with the third portion being a protrusion between the first and second portions. Advantageously, such protrusions may prevent excessive compressive forces from being applied to the electronic device. When the first and second portions of the support frame are retracted together, they each abut against the protrusion. If any further compressive forces are applied, these compressive forces act on the protrusions and not on the electronic device.

[0043] The support frame of the device described herein can be configured for attachment to the circuit board by various means. In the embodiment shown in Figure 1B, the support frame comprises two plates 5, 6 screwed together, with the screws passing through holes in the circuit board to draw the two parts 5, 6 together and clamp onto the circuit board, although in other implementations the support frame can be screwed directly onto the circuit board. In any case, it is preferred that when installed the support frame is not movable relative to the circuit board, and the support frame can be attached directly or indirectly to the circuit board to achieve such a rigid connection.

[0044] In FIG. 2A, an exploded view of the cold plates 7, 8 and the upper compression plate 6 is shown. FIG. 2A demonstrates how the components are attached to one another. Locating bolts 11 pass through the upper compression plate 6, through the springs 9 and into the top surface of the cold plate assembly 7, 8. The purpose of the locating bolts 11 is to restrain the springs 9 between the upper compression plate 6 and the cold plates 7, 8 to keep them vertical. The bolts 11 effectively act as shafts that limit the movement of the cold plates 7, 8. With all the cold plates 7, 8 attached to the upper compression plate 6, this forms a single assembly. Returning to the generalized terminology used above, the locating bolts 11 can be described as alignment pins configured to hold the resilient members in alignment.

[0045] Thus, generally speaking, the apparatus described herein may include at least one (preferably a plurality of) alignment pins configured to constrain the alignment of the respective resilient members. For example, each alignment pin may pass through the resilient member. The alignment pins may be part of the support frame. For example, the alignment pins may hold the respective resilient members substantially perpendicular to a surface of the support frame (e.g., upper compression plate 6) and / or substantially perpendicular to a surface (e.g., thermally conductive surface and / or top surface) of the respective cold plate. The alignment pins may extend into the body of the cold plate. That is, the outer surface of the cold plate may have a recess through which the alignment pin may pass. For example, the body of the cold plate may have a channel arranged to accommodate the alignment pin.

[0046] The piping configuration that supplies liquid coolant to the cold plates 7, 8 is shown in Figures 2A, 2B, and 2C. Figure 2A is an exploded view with the piping omitted to aid in visualization of how the piping fits into the assembly. Figure 2B is a side view of the assembly, also with the piping omitted, and Figure 2C is an isometric view with the piping in place, with the piping and connectors simplified for clarity.

[0047] In this embodiment, the coolant enters the system through one pipe 13 and is divided into four outer cold plates 7 that sit above the optical modules 25. Each outer cold plate 7 receives coolant through an inlet, where it passes through the chambers of each cold plate 7 and exits the cold plate 7 through an outlet. Pipes 15 transport the coolant into the central cold plate 8 in parallel with the coolant from the other outer cold plates 7. The coolant then exits through one central port 12 of the central cold plate 8 and is transported outwardly from the cold plate to be recirculated. The pipes 12, 15 are connected to the cold plates 7, 8 using push-fit connectors 14. Nevertheless, various other types of connections such as olive compression fittings could be used.

[0048] Coolant can be supplied to the individual cold plates 7, 8 in parallel or series depending on the piping configuration, which can be useful for chips with different cooling requirements. Like many cooling systems, the system in this embodiment is a closed loop where coolant flows in through one pipe and flows out through another. Nevertheless, this configuration of piping can be modified for use with cold plates having an open top to allow the coolant to overflow therefrom, as described in WO 2019 / 048864.

[0049] In a general sense, in the apparatus of the present disclosure, at least one cold plate of a first subset of the plurality of cold plates, preferably each cold plate, comprises an inlet configured to receive liquid coolant to transfer heat from the electronic device to the liquid coolant, and an outlet configured to supply liquid coolant to a second subset of the plurality of cold plates. In a preferred embodiment, the first subset is cold plate 7 and the second subset is cold plate 8. The first and second subsets may be connected via various types of pipes, conduits, and / or tubes.

[0050] At least one cold plate, preferably each cold plate, of the second subset of the plurality of cold plates may comprise an inlet configured to receive liquid coolant from the first subset of the plurality of cold plates to transfer heat from the electronic device to the liquid coolant. At least one cold plate, preferably each cold plate, of the second subset of the plurality of cold plates may comprise an outlet configured to supply liquid coolant to one or more further subsets of cold plates of the plurality of cold plates (e.g., to cool further devices) or to a heat exchanger (e.g., to remove heat from the liquid coolant and recirculate the coolant for further use). The first subset of the plurality of cold plates may include a plurality of cold plates configured to receive liquid coolant in series with each other (i.e., each cold plate of the first subset is in series with each other cold plate of the first subset) or in parallel with each other (i.e., each cold plate of the first subset is in parallel with each other cold plate of the first subset). Similarly, a second subset of the plurality of cold plates may include a plurality of cold plates arranged to receive liquid coolant in series with one another (i.e., each cold plate of the second subset is in series with each other cold plate of the first subset) or in parallel with one another (i.e., each cold plate of the second subset is in parallel with each other cold plate of the first subset). In this manner, the flow of coolant may be such that the electronic devices most in need of cooling receive the coldest (i.e., freshest) coolant.

[0051] 3A and 3B, bottom and side views, respectively, of the individual cold plates 7, 8 in an assembled state are shown. FIG. 3A shows the cold plate heat transfer surface plate at the bottom of the cold plates 7, 8. The heat transfer surface is a copper surface 18, 23 with a raised square surface that mates with a chip on the circuit board 1. A number of screws 19 are provided around the outside of the copper plates 18, 23 to fasten the copper plates 18, 23 to the steel upper portion 15, 20 of the cold plates 7, 8. FIG. 3B shows a side view of the configuration of FIG. 3A, showing the bottom (i.e., heat transfer surface) of the copper plates 18, 23 of the central cold plate assembly 8 seated lower (i.e., closer to the electronic chip or further away from the upper portion 6 of the device) than the corresponding heat transfer surface of the outer cold plate 7. This is due to the variable height of the chips 25, 26 on the circuit board 1. Additionally, there may be slight variations in the angle of the top surface of the chips 25, 26 that are not visually perceptible during use (i.e., when the cold plates 7, 8 are in contact with the chips 25, 26), and the cold plates 7, 8 may rotate slightly to a corresponding angle when a compressive force is applied (i.e., when the support frame is attached to the circuit board). In order to maximize contact between the cold plates 7, 8 and the chips 25, 26 on the circuit board 1, independence between these cold plates 7, 8 is advantageous due to the difficulty of machining a single heat sink that can accommodate different chip heights, which is exacerbated by manufacturing tolerances.

[0052] 3C and 3D show two different cold plate 7, 8 subassemblies in isometric views. As mentioned above, the outer cold plate 8 in FIG. 3C has four holes. In FIG. 3C, the two outermost holes 28 are through holes that allow coolant to enter and exit the cold plate 7. The two inner holes 29 are for the positioning bolts 11 that align the cold plate 7 to the upper compression plate 6 and keep the springs 9 vertical. In FIG. 3D, the four outer holes 28 and the central hole 28 allow coolant to enter and exit the cold plate 8. The four smaller holes 29 are located around the edge of the cold plate 8 and are configured to receive the positioning bolts 11 to align the cold plate 8 and keep the springs 9 vertical.

[0053] 3E and 3F show isometric exploded views of the outer cold plate 7 and the center cold plate 8, respectively. Each cold plate 7,8 comprises a lower portion 18,23 including a heat transfer surface and an upper portion 15,20 for attachment to the support frame of the apparatus. Both cold plates 7,8 are sealed using O-rings 17,21 that extend around the outer edge of the respective cold plate 7,8. The O-rings 17,21 and corresponding grooves in the cold plates 7,8 are specified according to British Standards to ensure a high quality seal to prevent coolant from leaking from the cold plates 7,8. Screws 19 are used to fit the copper skived heat sink plates 18,23 to the steel upper portions 15,20 of the cold plates 7,8.

[0054] Both heat sinks 18, 23 have protrusions 30 in the form of skived fins on their undersides which increase the surface area for the coolant and thus improve thermal cooling of this particular system (although other materials, manufacturing methods and / or other types of protrusions, e.g., pins, baffles, etc., may be used). To prevent the coolant from bypassing the fins of the heat sinks, gaskets 16, 22 are placed between the fins and the upper steel heat sink components 15, 20. The gaskets 16, 22 restrain the flow of coolant in the cold plates 7, 8 to ensure that the coolant passes over the protrusions 30, thereby improving thermal efficiency.

[0055] Although FIGS. 3E and 3F show a cold plate having a two-piece construction, the cold plate may include more or fewer components (e.g., including three or more parts, or a unitary structure formed, for example, by 3D printing).

[0056] In a general sense, in the apparatus described herein, at least one cold plate, and preferably each cold plate, defines an interior volume that is configured to receive liquid coolant therein so as to transfer heat from an electronic device to the interior volume of the respective cold plate. As mentioned above, the interior volume may be open or closed, and in some embodiments, some cold plates may have a closed configuration while other cold plates may have an open configuration. The precise arrangement may depend on the nature of the electronic device requiring cooling. In any case, at least one cold plate, and preferably each cold plate, includes one or more protrusions on the interior surface of the interior volume. Such protrusions may aid in cooling by dispersing and / or agitating the fluid flow within the interior volume (ensuring that the coolant is distributed evenly across the heat transfer surface). Moreover, such protrusions increase the surface area of ​​the interior volume to improve heat transfer. The one or more protrusions may include any one or more of skiving, fins, pins, ridges, channels, and baffles. Other types of protrusions are contemplated.

[0057] Referring now to Figure 4A, an isometric view of the upper compression plate 6 assembly is shown. The upper compression plate 6 assembly is thick enough to prevent deformation under load. As best seen in Figures 1A, 1B, and 2C, larger through holes in the upper compression plate allow piping 12, 13, 15 to be routed to the cold plates 7, 8.

[0058] FIG. 4B shows an exploded view of the upper compression plate 6 and its insert 24. The upper compression plate includes inserts 24 that seat within the compression plate, which can be used to adjust the compression displacement of the elastic members 9 that attach to the cold plates 7, 8. The threaded inserts 24 have notches so that they can be rotated (e.g., to screw the inserts 24 in and out of the compression plate) using a tool to adjust their position (and thus adjust the compression of the springs 9 if rotated when the device is installed). The inserts 24 have through holes drilled to allow the alignment bolts 11 to pass through as shown in FIG. 2A.

[0059] Returning to the generalized terms used above, at least one cold plate, and preferably each cold plate, is adjustably attached to the support frame to allow adjustment of the distance (e.g., as measured in the z-direction perpendicular to the circuit board) between the support frame and the heat transfer surface of the at least one cold plate, and preferably each cold plate. Adjustability can be provided by a threaded portion (as in the case of insert 24), but other repositioning means can be used. Similarly, the distance between the heat transfer surface and the circuit board may be adjustable. Each subset of the multiple cold plates may be moved simultaneously to adjust the distance of the entire subset (i.e., a single adjustment mechanism may be capable of moving multiple cold plates). Alternatively, each cold plate may be independently adjustable (i.e., each cold plate may have an independent adjustment mechanism that allows independent movement independent of all other cold plates). It is preferred that the distance between the support frame and the heat transfer surface of the at least one cold plate, and preferably each cold plate, is independently adjustable.

[0060] In a preferred embodiment, at least one elastic member, and preferably each elastic member, is attached to the support frame by an adjustable attachment portion configured to allow adjustment of the position of the base of the respective elastic member. The base can be considered to be the end of the elastic member distal to the cold plate. The elastic member or members can be attached (e.g., rigidly attached) to the support frame, for example, by an adjustable attachment portion. The adjustable attachment portion can be, for example, a threaded insert, such as the insert 24 described above. Preferably, the adjustable attachment portion is screwed into the support frame and can thus be rotated (e.g., screwed) by the user. Nevertheless, the present disclosure is not limited to threaded inserts, and any portion of the support frame whose position is adjustable by the user can serve as an adjustable attachment portion for the elastic member. Advantageously, the force exerted by the multiple cold plates on the electronic device can be adjusted, for example, by adjusting the position of the base of the respective elastic member. By bringing the cold plate closer to the circuit board, the elastic member is compressed less when the cold plate is in contact with the electronic device, and therefore less force is exerted on the cold plate. This allows the magnitude of the force to be precisely controlled, reducing the possibility of the electronic components being crushed.

[0061] 5A, 5B, and 5C, the circuit board 1 and the lower compression plate 5 are shown in top, side, and isometric views, respectively. The circuit board 1 is simplified, but includes one central chip, which in this example is an ASIC chip 26. Surrounding the ASIC chip 26 are eight optical chips 25. All of these chips 25, 26 are directly cooled by the MHSC of the present disclosure. The path of the liquid coolant is determined by the arrangement of the tubes 12, 13, 15 to the individual cold plates 7, 8. The coolant is used to first cool the components whose temperature is closest to the maximum operating temperature using the outer cold plate 7, and then the used coolant is fed to the other cold plates 8 to cool the components that are not as close to their maximum operating temperature. In this case, the outer cold plates 7 first receive the coolant in parallel with each other. The coolant then flows from the outer cold plates 7 to the central cold plate 8. This flow path arrangement configuration is used because the temperature limits of the optical module 25 and the ASIC chip 26 are 75°C and 90°C, respectively. Therefore, there is a higher need to supply fresh coolant to the optical module 25. The temperature limits are determined by the power of the chips, and the number and layout of the cold plates are determined by the location of the heat source (i.e., the chip that generates the heat). Therefore, the device of the present disclosure is not limited to this five-plate configuration, and various different layouts may be provided to cool different chip configurations. Furthermore, different electrical components have different cooling requirements, and therefore these temperature requirements (i.e., 75°C and 90°C for the optical module 25 and the ASIC chip 26, respectively) are not intended to be limiting, and electronic devices having any other temperature requirements can be used with the embodiments of the present disclosure.

[0062] FIG. 5A further illustrates smaller chips 27 around the edge of the circuit board 1, representing other heat sources that may be cooled. For example, these smaller chips 27 may be cooled by expanding the MSHC assembly to allow for cooling the smaller chips using additional sets of cold plates. Additionally or alternatively, at least one (and optionally all) of the cold plates 7, 8 may have an open top so that coolant may leak from the heat sinks 7, 8 onto nearby chips 27 to cool those chips. In other words, the cold plates 7, 8 may define an interior volume for receiving liquid coolant and an open top through which the coolant may overflow, for example as described in XYZ, which is incorporated herein by reference.

[0063] In the generalized terms used above, in a preferred embodiment, the first subset of the plurality of cold plates includes a plurality, preferably four, cold plates arranged to receive liquid coolant in parallel, and the second subset of the plurality of cold plates is a single cold plate arranged to receive liquid coolant from the first subset of the plurality of cold plates. The first subset of the plurality of cold plates may include a plurality of cold plates arranged around (e.g., substantially at the same height, but radially around) the second subset of the plurality of cold plates. Such an arrangement may provide efficient coolant to, for example, the circuit board 1 shown in Figures 5A, 5B, and 5C.

[0064] 6A and 6B, a bottom exploded view of the center cold plate 8 and outer cold plate 7 is shown. Both assemblies have flat gaskets 16, 22 that seat between the copper skived heat sinks 18, 23 and the steel upper components 15, 20. These gaskets 16, 22 are provided to prevent coolant from bypassing the protrusions 30 (which in this embodiment are skived fins). There are notches in the gaskets 16, 22 that are aligned using bosses present on the upper steel pieces 15, 20 to keep the gaskets 16, 22 precisely positioned. The chamber is sealed using O-rings 21, 17 that seat in grooves around the outer edges of the upper steel pieces 15, 20.

[0065] Thus, in the general terms used above, at least one cold plate, and preferably each cold plate, may advantageously comprise a gasket therein, the gasket being arranged and configured to restrain the liquid coolant to flow around one or more protrusions. Such a gasket may further improve cooling efficiency. An inner surface of the cold plate (e.g., a bottom surface of the upper portion of the cold plate) and / or a surface of the gasket may include one or more bosses arranged and configured to engage a complementary surface of the gasket or an inner surface of the cold plate to align the gasket within the cold plate. Such bosses may ensure that the gasket is held in alignment with the cold plate, thereby reducing the possibility of the gasket becoming dislodged by the flow of coolant (interfering with the function of the gasket).

[0066] Referring now to FIG. 7, a heat sink is shown that can serve as a cold plate in the apparatus described herein. The heat sink is shown in FIG. 8C of WO 2019 / 048864 and described in further detail therein. The heat sink can be held in contact with the electronic device. The heat sink defines an interior volume for storing and maintaining liquid coolant adjacent to the electronic device. As the liquid coolant flows (by pumping and / or convection), it is directed into the interior volume of the heat sink, improving cooling of the electronic device. The liquid coolant then flows out of the heat sink interior volume (e.g., by overflowing and / or flowing through holes in the volume) and is collected within the bottom of the chassis (e.g., on the surface of the circuit board) for cooling other electronic devices (e.g., other components or ICs mounted on PCBs or otherwise within the chassis). The primary liquid coolant can be cooled by a heat exchanger within the chassis. A heat sink may be provided downstream of any of the cold plates of the above described embodiments (eg, cold plates 7, 8) to provide additional cooling for the electronic devices.

[0067] The heat sink of Figure 7 comprises a pipe 35 and a nozzle 33 positioned such that the nozzle 33 is centrally located relative to a volume defined by a retaining wall 31. A partial lid 32 is provided to cover a portion of the internal volume. One or more openings in the partial lid 32 may allow liquid coolant from the nozzle 33 to reach the internal volume. The partial lid 32 may be attached to a portion of the nozzle 33, although this may not be required.

[0068] The exact operation of the heat sink and other variations on this heat sink are described in more detail in WO 2019 / 048864, which is incorporated by reference. In any case, the partial lid 32 can be connected to any of the support frames described herein so that the heat sink can be in contact with the electronic device. Alternatively, the partial lid 32 may be omitted and the heat sink may be attached to the support frame by other means. For example, a rigid structure may be provided that spans the heat sink, which structure can be used to attach to the support frame (including via a resilient member). Moreover, other types of heat sinks (e.g., any of the heat sinks described in WO 2019 / 048864) can be adapted to attach to the support frame described herein. For example, any of the heat sinks in Figures 3, 8, 8A-8F, 9-12, 20-26, 29, 30 of WO 2019 / 048864 can be configured to attach to the support frame of the present disclosure. In any event, in generalized terms, in the apparatus described herein, at least one of the multiple cold plates includes a base and a retaining wall that together define a volume for holding liquid coolant, preferably configured such that the liquid coolant overflows the retaining wall.

[0069] Although the present invention is not limited to comprising a circuit board or an electronic device, some embodiments of the present disclosure encompass the apparatus described herein with a circuit board and / or a plurality of electronic devices. Accordingly, the present disclosure also provides a system for cooling a plurality of electronic devices disposed on a circuit board, the system comprising a plurality of electronic devices disposed on the circuit board and any embodiment of the apparatus described herein configured to cool the plurality of electronic devices. A top surface of each electronic device may be in thermal contact with at least one of the thermally conductive surfaces of the plurality of cold plates, and the top surface of each of the plurality of electronic devices may be in a different position.

[0070] Upon reading the above embodiments, one skilled in the art will understand that it is preferred that the liquid coolant be kept in liquid form, or in other words, that there is no phase change of the liquid coolant, since evaporation of the liquid coolant may reduce the heat transfer capability of the gas coolant.

[0071] In a preferred embodiment, a first plate of the support frame (e.g., upper compression plate 6) may be movable relative to a second plate (e.g., lower compression plate 5) so that the displacement between the two plates 5, 6 can be varied. This can be achieved by screwing and / or loosening (tightening and / or untightening) the bolts 4 that hold the two plates together. Additionally or alternatively, adjustment of the distance between the plates 5, 6 can be achieved by adjusting the height of the standoffs 10. Various other methods of adjusting the distance between the plates 5, 6 can be provided.

[0072] In some embodiments, the first plate can be moved to be in an inclined arrangement relative to the second plate. That is, the amount of displacement between the first plate 5 and the second plate 6 may be variable across the orientation of the plates. There may be a non-zero angle between the first plate 5 and the second plate 6. This may be achieved by screwing and / or loosening some of the bolts 4 more than others. Alternatively or additionally, other methods may be used to change the angle between the first plate and the second plate. These include, but are not limited to, adjusting the angle of the standoffs 10, adjusting the height of some of the standoffs 10, changing the angle of the bolts 4. By adjusting the angle such that the first plate is inclined relative to the second plate, the amount of displacement between the first plate and the second plate is independently adjustable between different cold plates or different sets of cold plates (e.g., the displacement between the first plate and the second plate may be independently adjustable for a first set of cold plates and a second set of cold plates). The cold plate may be rotatably attached to the first plate so that good thermal contact between the electronic devices 25, 26 and the cold plate may still be maintained even though the first plate is tilted relative to the second plate.

[0073] It will be appreciated that many variations can be made to the above-described devices, systems, and methods while maintaining the aforementioned advantages. For example, where a particular type of flexible material is described, alternative materials can be provided that provide the same or similar functionality. In particular, while copper and steel are described, various other metals (e.g., aluminum) or any other material with high thermal conductivity can be used to provide a thermal interface. Additionally, where a support frame is described that includes steel (e.g., a steel compression plate), other rigid materials can be used. Although a tube for transporting a liquid coolant is described, any conduit, tube, hose, etc. can be used.

[0074] Although an apparatus comprising a cold plate is described, the present disclosure also provides an apparatus employing any type of heat sink to cool a plurality of electronic devices disposed on a circuit board. Such an apparatus comprises a plurality of heat sinks, each heat sink having a thermally conductive surface for cooling an electronic device thermally coupled thereto, and a support frame to which each of the plurality of heat sinks is attached, the support frame being configured for attachment to the circuit board to hold the thermally conductive surfaces of the plurality of heat sinks in thermal contact with the plurality of electronic devices, the support frame being arranged to hold the thermally conductive surfaces of a first subset of the plurality of heat sinks in a first position relative to the support frame and the thermally conductive surfaces of a second subset of the plurality of heat sinks in a second position relative to the support frame. The heat sinks may be a cold plate or any other suitable cooling element. The heat sinks may be configured similarly to the cold plate described above. For example, the positions of the heat sinks may be independently adjustable (e.g., by adjusting an elastic member). The heat sinks may be held by the support frame (e.g., including first and second opposing portions such as plates) as described above. The heat sink may be in contact with the electronic device. The heat sink may be liquid cooled (e.g., using series and / or parallel connections) or may not employ liquid cooling at all. The heat sink may have various protrusions thereon to aid in heat transfer.

[0075] The particular device described herein is a 3U configuration, however the device can be readily adapted to 1U, 2U, 3U, 4U and 5U (and even higher) systems.

[0076] Some embodiments described herein use liquid cooling, and in those embodiments, a variety of fluids (e.g., dielectric fluids) can be used, as well as mineral oil and water. The type of coolant can be selected depending on the particular needs of the electronic device.

[0077] Throughout this disclosure, the terms "chip," "component," and "device" are sometimes used interchangeably. All of these are examples of electronic devices that can be cooled using the present invention.

[0078] The embodiments of the present disclosure show an electronic device disposed on a circuit board beneath the cold plate, however, it will be understood that the support frame described herein can be used to hold the cold plate against a vertically mounted circuit board, i.e., the support frame can press the cold plate horizontally against an electronic device mounted on a vertical surface.

[0079] Moreover, the above embodiments focus on the case where there is only one circuit board. Nevertheless, additional circuit boards (e.g., PCBs) can be provided. For example, an optical device may be mounted on an additional PCB that is mounted on top of the main PCB. Thus, the support frame described herein that holds the thermally conductive surfaces at different positions can be advantageously used with multiple circuit board arrangements. That is, in the aspects and embodiments described herein, the support frame may be an apparatus for cooling multiple electronic devices arranged on one or more circuit boards.

[0080] Each feature disclosed in this specification, unless expressly stated otherwise, may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features.

[0081] As used throughout this disclosure (including the claims), unless the context dictates otherwise, singular forms of terms used in this disclosure should be construed to include the plural, and vice versa, where the context permits. For example, unless the context dictates otherwise, singular references in this disclosure (including the claims), such as "a" or "an" (such as an electronic device or a cold plate) mean "one or more" (e.g., one or more electronic devices, or one or more cold plates). Throughout the description and claims of this disclosure, the words "comprise," "include," "have," and "containing," as well as variations of these words, such as "comprising" and "comprising" (or the like), mean "including, but not limited to," and are not intended to (and do not) exclude other components.

[0082] Any examples provided in this disclosure, or the use of exemplary language (such as words like "example," "etc," "for example," etc.) are intended merely to better describe the disclosure and do not pose limitations on the scope of the disclosure unless specifically claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.

[0083] Any steps described herein may be performed in any order or simultaneously unless otherwise stated or the context requires otherwise. Furthermore, if a step is described as being performed after another step, this does not exclude the intervening step from being performed.

[0084] All aspects and / or features disclosed herein may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. In particular, the preferred features of the present disclosure are applicable to all aspects and embodiments of the present disclosure and may be used in any combination. Similarly, features described in non-essential combinations may be used separately (not in combination).

[0085] Methods of manufacturing and / or operating any of the disclosed devices (or arrangements of devices) are also provided, which may include providing each of the disclosed features and / or configuring each feature for the described function.

Claims

1. 1. An apparatus for cooling a plurality of electronic devices disposed on a circuit board, comprising: a plurality of cold plates, each cold plate having a thermally conductive surface for cooling an electronic device thermally coupled thereto; a support frame to which each of the plurality of cold plates is attached, the support frame being configured for attachment to the circuit board to hold the thermally conductive surfaces of the plurality of cold plates in thermal contact with the plurality of electronic devices; wherein the support frame is configured to hold the thermal transfer surface of each of the plurality of cold plates at a different position relative to the support frame.

2. 2. The apparatus of claim 1, wherein the position relative to the support frame includes an angle relative to the support frame, the support frame being configured to hold a thermally conductive surface of at least one cold plate, and preferably each cold plate, at a different angle relative to the support frame.

3. 3. The apparatus of claim 1 or claim 2, wherein the position relative to the support frame includes a distance from the support frame, the support frame being configured to maintain the thermal conduction surfaces of a first subset of the plurality of cold plates at a first distance from the support frame and to maintain the thermal conduction surfaces of a second subset of the plurality of cold plates at a second distance from the support frame.

4. 10. Apparatus according to any preceding claim, wherein at least one cold plate, and preferably each cold plate, is rotatably attached to the support frame.

5. 13. An apparatus according to any preceding claim, wherein at least one cold plate, and preferably each cold plate, is attached to the support frame by one or more resilient members, the one or more resilient members being configured to pull each said at least one cold plate away from the support frame.

6. 6. The apparatus of claim 5, further comprising at least one alignment pin configured to constrain the orientation of at least one resilient member, preferably each resilient member.

7. 10. An apparatus as described in any preceding claim, wherein the support frame comprises a first portion to which each of the plurality of cold plates is attached and a second portion opposite the first portion, preferably wherein one or more resilient members are attached to the first portion of the support frame.

8. 8. The apparatus of claim 7, wherein the first and second portions of the support frame are configured to be drawn together to hold the thermally conductive surfaces of the plurality of cold plates in thermal contact with the plurality of electronic devices.

9. 9. The apparatus of claim 7 or claim 8, further comprising one or more protrusions between the first and second portions of the support frame, the one or more protrusions configured to limit a distance between the first and second portions of the support frame.

10. the first portion of the support frame is a plate, and / or the second portion of the support frame is a plate, and / or The apparatus of any one of claims 7 to 9, wherein the support frame is configured to compress the plurality of electronic devices between the plurality of cold plates and the circuit board.

11. at least one, and preferably each, cold plate is adjustably attached to said support frame to allow adjustment of the distance between said support frame and said heat transfer surface of at least one, and preferably each, cold plate; and / or 10. A method according to any preceding claim, wherein the distance between the support frame and the heat transfer surface of at least one cold plate, preferably each cold plate, is independently adjustable.

12. 10. An apparatus according to any preceding claim, wherein the force exerted by at least one of the plurality of cold plates on the electronic device is adjustable, preferably by adjusting the position of a base of a respective resilient member.

13. Apparatus according to any of the preceding claims when dependent on claim 5 or claim 6, wherein at least one elastic member, preferably each elastic member, is attached to the support frame by an adjustable attachment portion configured to allow adjustment of the position of a base of the respective elastic member.

14. The device of claim 13 , wherein the adjustable attachment portion is screwed into the support frame.

15. The plurality of cold plates includes a first subset and a second subset, and at least one cold plate, preferably each cold plate, of the first subset of the plurality of cold plates comprises: an inlet configured to receive liquid coolant so as to transfer heat from the electronic device to the liquid coolant; an outlet configured to supply the liquid coolant to the second subset of the plurality of cold plates; 13. An apparatus according to any preceding claim, comprising:

16. The plurality of cold plates includes a first subset and a second subset, and at least one cold plate, preferably each cold plate, of the second subset of the plurality of cold plates comprises: an inlet configured to receive the liquid coolant from the first subset of the plurality of cold plates to transfer heat from the electronic device to the liquid coolant; and preferably The liquid coolant is one or more further subsets of cold plates of the plurality of cold plates; or heat exchanger an outlet configured to supply 13. An apparatus according to any preceding claim, comprising:

17. the plurality of cold plates includes a first subset and a second subset; the first subset of the plurality of cold plates includes a plurality of cold plates configured to receive liquid coolant in series or in parallel; and / or 2. The apparatus of any preceding claim, wherein the second subset of the plurality of cold plates comprises a plurality of cold plates configured to receive liquid coolant in series or in parallel.

18. the plurality of cold plates includes a first subset and a second subset; the first subset of the plurality of cold plates includes a plurality, preferably four, cold plates arranged to receive liquid coolant in parallel, and the second subset of the plurality of cold plates is a single cold plate arranged to receive liquid coolant from the first subset of the plurality of cold plates; and / or 2. The apparatus of any preceding claim, wherein the first subset of the plurality of cold plates comprises a plurality of cold plates disposed about the second subset of the plurality of cold plates.

19. 13. An apparatus as described in any preceding claim, wherein at least one cold plate, and preferably each cold plate, defines an internal volume, said internal volume configured to receive liquid coolant therein so as to transfer heat from the electronic device to the internal volume of the respective cold plate.

20. 20. The apparatus of claim 19, wherein at least one cold plate, and preferably each cold plate, comprises one or more protrusions on an inner surface of the internal volume, preferably the one or more protrusions comprising any one or more of skives, fins, pins, ridges, channels, and baffles.

21. 21. The apparatus of claim 20, wherein at least one, and preferably each, cold plate includes a gasket therein, the gasket being configured to restrain the liquid coolant from flowing around the one or more protrusions.

22. 22. The apparatus of claim 21 , wherein an inner surface of the cold plate and / or a surface of the gasket includes one or more bosses configured to engage a complementary surface of the gasket or an inner surface of the cold plate to align the gasket within the cold plate.

23. 13. An apparatus as described in any preceding claim, wherein at least one of the plurality of cold plates comprises a base and a retaining wall that together define a volume for holding liquid coolant, preferably arranged such that liquid coolant overflows over the retaining wall.

24. 1. A system for cooling a plurality of electronic devices disposed on a circuit board, comprising: a plurality of electronic devices disposed on a circuit board; An apparatus according to any preceding claim, configured for cooling said plurality of electronic devices; A system comprising:

25. 25. The system of claim 24, wherein a top surface of each electronic device is in thermal contact with at least one of the thermally conductive surfaces of the plurality of cold plates, and the top surface of each of the plurality of electronic devices is in a different position relative to the support frame.

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