Systems for improving heat transfer and methods for assembling a computing system

Abstract

This application describes a system and related method for applying indium to a heat transfer surface. The system includes a chassis disposed within a housing, having at least one slot for receiving blades. The blades disposed in the slots of the chassis include a first circuit board having a plurality of components mounted on a substrate. The blades further include a first heat sink comprising metal. The first heat sink comprising metal is arranged to transfer heat from the first circuit board to a cooling system via a first interface between a first surface of the first heat sink and a second surface of the chassis, wherein indium is permanently bonded to the first surface of the first heat sink or the second surface of the chassis, or both the first surface of the first heat sink and the second surface of the chassis.

Description

Technical Field

[0001] This disclosure relates to a system for applying indium to heat transfer surfaces. Prior Technology

[0002] Semiconductor-based integrated circuits used in electronic components (such as digital processors) include digital circuits based on complementary metal-oxide-semiconductor (CMOS) technology. However, CMOS technology has reached its limits in terms of device size. Furthermore, the power consumption of CMOS-based digital circuits at high clock speeds has increasingly become a limiting factor for high-performance digital circuits and systems. For example, servers in data centers increasingly consume significant amounts of power. Even when CMOS circuits are not in use, power consumption is still partly a result of power loss due to energy dissipation. This is because even when these circuits are not in use and do not consume any dynamic power, they still consume power to maintain the state of the CMOS transistors.

[0003] An alternative to using CMOS-based processors and related components is to use superconducting logic-based components and elements. Superconducting logic-based components and elements can also be used to process quantum information, such as qubits. However, these elements need to operate at low temperatures and therefore require additional cooling. In some cases, CMOS-based components and superconducting logic-based components can be integrated into a single system. Summary of the Invention

[0004] In one embodiment, this disclosure relates to a system including a housing configured to maintain a pressure inside the housing that is lower than the pressure outside the housing. The system may further include a chassis disposed within the housing. The chassis may include at least one slot for receiving blades. The blades may include a circuit board having a plurality of components mounted on a substrate. The chassis may be coupled to a cooling system to maintain at least a subset of the plurality of components operating in an environment having a temperature of 200 g / L or less. The blades disposed in the slots of the chassis may include a first heat sink comprising metal. The first heat sink comprising metal may be arranged to transfer heat from a first circuit board to the cooling system via a first interface between a first surface of the first heat sink and a second surface of the chassis, wherein indium is permanently bonded to the first surface of the first heat sink or the second surface of the chassis, or both the first surface of the first heat sink and the second surface of the chassis.

[0005] In another embodiment, this disclosure relates to a method for assembling a computing system comprising at least one blade including a first circuit board and a second circuit board, wherein at least one of the first or second circuit boards includes a superconducting component configured to operate in an environment having a temperature of 200 gEV or less. The method may include forming a first heat sink configured to transfer heat from the first circuit board to a cooling system associated with the computing system. The method may further include forming a second heat sink configured to transfer heat from the second circuit board to the cooling system associated with the computing system. The method may further include permanently bonding indium to a first selected surface of the first heat sink, wherein the first selected surface is part of a first heat transfer path from the first circuit board to the cooling system. The method may further include permanently bonding indium to a second selected surface of the second heat sink, wherein the second selected surface is part of a second heat transfer path from the second circuit board to the cooling system. The method may further include mounting the first and second circuit boards in a chassis associated with the computing system.

[0006] In another embodiment, this disclosure relates to a system including a housing configured to maintain a lower internal pressure than an external pressure. The system may further include a chassis disposed within the housing, wherein the chassis includes at least one slot for receiving blades, wherein the blades include a first circuit board having a plurality of superconducting components mounted on a first substrate and a second circuit board having a plurality of non-superconducting components mounted on a second substrate. The chassis may be coupled to a cooling system to maintain the plurality of superconducting components in an environment having a temperature of 200 gErvin or less. The chassis may be coupled to a cooling system to maintain the plurality of non-superconducting components in an environment having a temperature of 300 gErvin or less. The blade disposed in a slot in the chassis may include a first heat sink comprising metal, wherein the first heat sink is arranged to transfer heat from the first circuit board to the cooling system via a first interface between a first surface of the first heat sink and a second surface of the chassis, and wherein indium is permanently bonded to the first surface of the first heat sink or the second surface of the chassis or both the first surface of the first heat sink and the second surface of the chassis. The blade may further include a second heat sink comprising metal, wherein the second heat sink is arranged to transfer heat from the second circuit board to the cooling system via a second interface between a third surface of the second heat sink and a fourth surface of the chassis, and wherein indium is permanently bonded to the third surface of the second heat sink or the fourth surface of the chassis or both the third surface of the second heat sink and the fourth surface of the chassis.

[0007] This invention is provided to introduce a series of concepts in a simplified form, which are described in more detail below in the embodiments. This invention is not intended to identify key or essential features of the claimed object, nor is it intended to limit the scope of the claimed object. Simple Explanation of the Diagram

[0008] This disclosure is illustrated by example and is not limited to the accompanying drawings, in which the same element symbols indicate similar elements. The elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale.

[0009] Figure 1 illustrates a cryogenic system including a housing according to one example, the housing including a chassis for receiving a circuit board.

[0010] Figure 2 shows a diagram of a blade used in conjunction with the chassis in Figure 1, based on an example.

[0011] Figure 3 shows a diagram of another blade used in conjunction with the chassis in Figure 1, according to another example.

[0012] Figure 4 shows a diagram of the blades in Figure 2, which are partially inserted into a part of the chassis according to an example.

[0013] Figure 5 shows a view of the blades of Figure 3 inserted into the chassis of Figure 1 according to an example.

[0014] Figure 6 is a view with additional details of the blades based on an example.

[0015] Figure 7 shows a flowchart of a method for assembling a computing system including at least one blade. Implementation

[0016] The examples described in this disclosure relate to cryogenic systems in which indium is applied to heat sinks and heat loads. Some examples of cryogenic systems include computing systems with superconducting components and elements. Some examples of this disclosure relate to computing systems that include components operating at cryogenic temperatures (e.g., 200 gEwen or less). In one example, the computing system is housed in a vacuum assembly. In this example, the superconducting system may include one or more superconducting components formed on a substrate. The superconducting components may include integrated circuit chips mounted on the substrate. Packaging these superconducting components is challenging because these components may need to withstand large variations in ambient temperature (e.g., from about 300 gEwen to about 4 gEwen or less).

[0017] Superconducting components and elements can use Josephson junctions to implement circuit-related functions. An illustrative Josephson junction may comprise two superconductors coupled via a region that impedes current. This impeding region may be a physical narrowing of the superconductor itself, a metallic region, or a thin insulating barrier layer. As an example, a superconductor-insulator-superconductor (SIS) type Josephson junction can be implemented as part of a superconducting circuit. As an example, a superconductor is a material capable of carrying direct electrical current (DC) in the absence of an electric field. Superconductors have a critical temperature (Tc) below which they exhibit zero resistance. Niobium is one such superconductor, having a critical temperature (Tc) of 9.3 kelvin. Below Tc, niobium is a superconductor; however, above Tc, niobium behaves as a resistive ordinary metal. Therefore, in a SIS type Josephson junction, the superconductor may be a niobium superconductor and the insulator may be an Al₂O₃ barrier layer. In a SIS junction, superconducting electrons are described by quantum mechanical wave functions. The phase difference between the phases of the superconducting electron wave functions of two superconductors over time corresponds to the potential difference between the two superconductors.

[0018] As needed, various superconducting circuits, including transmission lines, can be formed by coupling multiple Josephson junctions with inductors or other components. Microwave pulses can travel through these transmission lines under the control of at least one clock cycle. Microwave pulses can be positive, negative, or a combination thereof. Microwave pulses can have frequencies up to 10 GHz or higher. Any circuit board or other type of structure (such as interpolators within such superconducting circuits) may be required to support not only high-frequency microwave signals but also DC signals. Although superconductivity offers several benefits (including lower resistance and better bandwidth characteristics), superconducting materials need to operate at temperatures below their critical temperature and therefore require additional cooling.

[0019] Figure 1 illustrates a cryogenic system 100 according to one embodiment, including a housing 110 comprising a chassis for receiving blades. In this embodiment, the housing 110 may be configured to maintain a pressure inside the housing lower than the pressure outside the housing. In one embodiment, the housing 110 may be configured to maintain a vacuum inside the housing. The lower pressure inside the housing may be a vacuum, corresponding to a pressure in the range of 10⁻³ Torr to 10⁻¹⁰ Torr. Therefore, certain components of the cryogenic system 100 (e.g., processors and memory) may be located inside the vacuum-maintaining housing 110. Using a vacuum ensures the absence of convection and thereby advantageously allows components operating at vastly different temperatures to be housed in the same chassis or another such structure. The housing 110 may also maintain thermal insulation relative to ambient temperature.

[0020] Referring again to Figure 1, housing 110 may include one or more chassis for receiving blades (e.g., computing blades). As used herein, the term "chassis" includes, but is not limited to, any structure for interface connection with a blade having at least one circuit board. The term "chassis" also includes any part that can be individually machined and mounted as part of a structure for receiving blades. In this example, housing 110 may include chassis 120. In one example, chassis 120 may have only blades mounted with superconducting components capable of operating in environments with temperatures of 200 K or below. Alternatively, the circuit board may include superconducting components and semiconductor components (e.g., CMOS-based integrated circuits). The circuit board may include components other than superconducting and non-superconducting components. As examples, the circuit board may include components such as passive resistors, discrete capacitors, discrete inductors, micro-electromechanical systems (MEMS), optical components, or other types of components for computing, storage, and networking applications. Depending on the type of components mounted on the circuit boards inserted into the slots (e.g., slots 122 and 124) corresponding to chassis 120, different temperature zones can be maintained within the housing. This can be achieved through a combination of thermal insulation and cooling (via liquid helium or other such coolants). Regarding components mounted on the circuit boards, as used herein, the phrase "operating in an environment having a temperature or below" means that the corresponding circuit board is thermally linked to a portion of the chassis maintained at or below a specified temperature (e.g., 200 K, 300 K, or 77 K).

[0021] The housing 110 may further include a plurality of heat shields, which can be configured to thermally insulate portions of each of the circuit boards inserted into slots corresponding to those in the chassis 120. In one example, the heat shields may be formed of copper or aluminum and may be further encased in multiple layers of insulation. Figure 1 shows an example heat shield 130, which may be cooled via liquid nitrogen or liquid helium flowing through each of the conduits 142 and 144 shown in Figure 1. The conduits 142 and 144 carrying liquid nitrogen or liquid helium may be brazed or otherwise attached to a cold plate associated with a suitable thermal environment. As an example, aluminum or copper sidewalls may be mounted adjacent to the superconducting component. The aluminum or copper sidewalls may also be cooled via liquid nitrogen or liquid helium flowing through the conduits (e.g., conduits 142 and 144 in Figure 1).

[0022] Referring again to Figure 1, a thermosiphon (or similar system) can be used as part of a cooling system. As part of a thermosiphon, gravity-driven natural convection (where a cooler fluid (e.g., liquid helium or liquid nitrogen) flows downwards and a warmer fluid flows upwards) can be used to cool the cold plate and other components associated with the cooling system. A thermosiphon may include downward-flowing liquid and returning vapor. It should be understood that the temperature ranges mentioned herein relate to the temperature of the heat transfer elements (e.g., radiators or chassis) to which these components are coupled, and not to the temperature of the components themselves. Therefore, phrases such as "operating at..." or "maintaining at..." represent the temperature of the heat transfer elements to which these components are coupled for heat transfer purposes. Although Figure 1 shows a specific arrangement of components, substrates, and other components, these can be arranged differently. Additionally, fewer or additional components, substrates, and other components may be present.

[0023] Figure 2 illustrates a blade 200 used in the chassis 120 of Figure 1 according to one example. The blade 200 may include one or more circuit boards. As used herein, the term "blade" includes, but is not limited to, computing blades, storage blades, communication blades, or any combination of computing, storage, or communication functions. Additionally, the term "blade" includes any shape or size structure for mounting at least one circuit board to the chassis. Each of the circuit boards may have several integrated circuits mounted thereon. Furthermore, each of the circuit boards may be coupled to a corresponding heat sink. In this example, the blade 200 may include a heat sink 210 coupled to a circuit board 230 having a substrate 231 having superconducting components 232, 234, 236, and 238 mounted thereon. In this example, the superconducting components 232, 234, 236, and 238 may be configured to operate in an environment having a temperature of 4.2 K or below 4.2 K. Superconducting components 232, 234, 236, and 238 can be packaged and formed in many different configurations. As examples, the superconducting components can be configured as a multi-chip module, a ball-grid array (BGA) package, a system-in-package (SIP), or a package-on-package (POP). Blade 200 may further include another heat sink 220 bonded to another circuit board 240. Although not shown in Figure 2, circuit board 240 may also have a substrate with superconducting components mounted thereon. In one instance, superconducting components may include a central-processing unit (CPU), a graphics-processing unit (GPU), an artificial intelligence processor, a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), an application-specific standard product (ASSP), a system-on-a-chip system (SOC), or a complex programmable logic device (CPLD).

[0024] Referring again to Figure 2, the heat sink 210 may have at least two surfaces 262 and 264 that interface with corresponding portions of a chassis configured to receive the blades 200 (e.g., chassis 120 in Figure 1). In this example, the heat sink 210 may be made of aluminum or another type of metal. In one example, the aluminum may be high-purity aluminum having at least 99.999% by weight. In another example, the aluminum may be high-purity aluminum having at least 99.99% by weight. Indium may be pressed onto surfaces 262 and 264 by applying high pressure. In one example, the pressure may be in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI. Surfaces 262 and 264 may be cleaned with water or alcohol before pressing the indium. Surfaces 262 and 264 may also be treated with acid to remove oxides. By using a die to limit the displacement of the press, the thickness of indium can be set to a predetermined thickness during the pressing process. In this example, the pressure used to press the indium against these surfaces results in a permanent bond between the indium and the metal used to form the heat sink 210. Several objectives are achieved in this way: (1) a good mechanical bond between the indium and the heat sink; (2) a good thermal bond between the indium and the heat sink; and (3) a flat indium surface. Advantageously, this process does not include any of the parts that are thermally bonded together. In one example, pure aluminum can be used to form the heat sink 210, and indium can be permanently bonded to a suitable surface of the heat sink 210. In one example, the aluminum can be high-purity aluminum having at least 99.999% by weight. In another example, the aluminum can be high-purity aluminum having at least 99.99% by weight. Indium can also be used to refurbish the surface of the heat sink with pre-existing indium by pressing additional indium onto these surfaces.

[0025] Referring again to Figure 2, indium can also be permanently bonded to certain surfaces of the heat sink 220 in a similar manner. The blade 200 may further include two wedge locks 252 and 254. Once the blade 200 is inserted into its slot, the wedge locks 252 and 254 can be used to press the heat sink in a manner that ensures a tight coupling between each heat sink and the opposing surface of the chassis. This process increases the gap 222 between the heat sink 210 and the heat sink 220. Once permanently bonded to the appropriate surfaces of the heat sink, indium may adhere to these surfaces, such that even when the blade 200 is removed and reinserted into its associated slot with the chassis, the indium may not detach or be otherwise removed. Although the example in Figure 2 mentions the use of aluminum, other metals can also be used. For example, copper with a high residual-resistance ratio (RRR) can also be used. Alternatively, other types of clamping elements can be used instead of wedge locks. Furthermore, surfaces permanently bonded to indium are shown only as examples. Indium or similar metals can be bonded to heat sinks and other surfaces of the substrate associated with the circuit board.

[0026] Figure 3 illustrates a circuit board 300 according to one example. The blade 300 may include one or more circuit boards. Each of the circuit boards incorporated as part of the blade 300 may have several integrated circuits mounted thereon. Additionally, each of the circuit boards may be coupled to a corresponding heat sink. In this example, the blade 300 may include two circuit boards 330 and 340. Circuit boards 330 and 340 may be interconnected via a combination of rigid and flexible interconnects. Flexible interconnects 352 and 354 may be used to connect components mounted on circuit board 330 to connectors 362 and 364 coupled to another circuit board 360. Similarly, flexible interconnects 356 and 358 may be used to connect components mounted on circuit board 340 to connectors coupled to circuit board 360. Other interconnect arrangements may also be used to allow signals to propagate from one circuit board to another and vice versa.

[0027] Referring again to Figure 3, circuit board 330 may include non-superconducting components (e.g., CMOS, BiCMOS, or other types of components suitable for operation where cryogenic temperatures are not required). As an example, the non-superconducting components may include components 332 and 334 mounted on substrate 331. In this example, non-superconducting components 332 and 334 may be configured to operate in an environment with temperatures above 77 K and up to 400 K. In one example, a preferred temperature may be 233 K. The temperature environment may be maintained by a combination of thermal insulation and cooling using water or another coolant. As an example, copper sidewalls (included as part of or otherwise coupled to chassis 120) may be mounted adjacent to the non-superconducting components. The copper sidewalls may also be cooled by water (or another coolant) flowing through conduits or other components. Non-superconducting components 332 and 334 may be packaged and formed in many different configurations. As an example, non-superconducting components can be configured as multi-chip modules, ball grid array (BGA) packages, system-in-package (SIP) packages, or stacked packages (POP). In this example, non-superconducting components may include memory components, including any of non-volatile or volatile memory components. Volatile memory components may include any of various types of random access memory components, including dynamic random-access memory (DRAM) components. Non-volatile memory components may include any of various types of memory components that can store information even when no power is applied, including flash memory components. Non-superconducting components may further include field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip (SOC) systems, or complex programmable logic elements (CPLDs). Therefore, non-superconducting components may also include components such as ASICs, ASSPs, SOCs, CPLDs, or other types of controllers that can coordinate communication between superconducting and non-superconducting components. Non-superconducting components can be formed using various semiconductor manufacturing processes, including optical imaging, patterning, annealing, contact formation, and packaging.

[0028] Referring again to Figure 3, circuit board 340 may include superconducting components 342, 344, 346, and 348 mounted on substrate 341. In this example, superconducting components 342, 344, 346, and 348 may be configured to operate in an environment having a temperature of 4.2 K or below 4.2 K. The temperature environment may be maintained as described in Figure 1. Superconducting components 342, 344, 346, and 348 may be packaged and formed in many different configurations. As examples, superconducting components may be configured as multi-chip modules, ball grid array (BGA) packages, system-in-package (SIP), or stacked package (POP). In one example, superconducting components may include a central processing unit (CPU), graphics processing unit (GPU), artificial intelligence processor, field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), application-specific standard product (ASSP), system-on-a-chip (SOC), or complex programmable logic element (CPLD).

[0029] Each of the superconducting components may comprise a stack of superconducting and dielectric layers formed on a substrate. In one example, the superconducting component may be formed to support signals ranging from DC to frequencies greater than 10 GHz. In this example, the superconducting component may be fabricated on a large silicon substrate, such as a 200 mm wafer, a 300 mm wafer, or even larger wafer, which may be divided into multiple grains. In one example, the substrate may be made of silicon or any other thermally insulating or conductive material. Furthermore, in this example, signal traces and ground planes may be formed by sputtering niobium or similar superconducting materials. As an example, niobium compounds, such as niobium nitride (NbN) or niobium titanium nitride (NbTiN), may also be used. Other physical vapor deposition (PVD) methods, such as molecular beam epitaxy (MBE), may also be used. Depending on the type of material used for the trace, sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), evaporation, or atomic layer deposition (ALD) processes can also be used. Therefore, for example, CVD processes can be used to form niobium compounds such as NbN and NbTiN.

[0030] Superconducting components may include a dielectric layer formed on a substrate. The dielectric layer can be formed by depositing a dielectric material (e.g., a liquid crystal polymer (LCP)) onto a wafer substrate. A superconducting layer can be formed on top of the dielectric layer. The superconducting layer can be formed using any of the deposition processes such as CVD or PECVD, followed by photolithography to pattern the deposited material. Placement and wiring design tools used to create layouts of superconducting wires or other components can be used to create the layout of the superconducting structure. As an example, photoresist can be patterned to protect only those superconducting layer regions, which will be formed as superconducting wires or other structures (e.g., metal layers) as defined by the layout of a particular layer. Other superconducting metals or metal alloys may also be used as part of this step. In one example, a mesoscopic window and trace can be formed by conformally depositing niobium in the same deposition step used to form the trace. The mesoscopic window trap can be patterned directly in an image-enhancing polyimide or etched in a separate step. Metal traces and interlayer windows can be defined in the same subtractive etching step. Pad connections can be configured to support Ti / Au or Ti / Al pads for various wire bonding or flip chip bump and wire bonding technologies, such as indium solder bumps, tin-silver (SnAg) solder bumps, gold stud bumps, copper pillar bumps, or other electrical interconnect bump types.

[0031] Referring again to Figure 3, heat sink 312 may be coupled to substrate 331 of circuit board 330. Heat sink 312 may have at least two surfaces (e.g., surfaces 262 and 264 similar to those of heat sink 210 in Figure 2) that interface with corresponding portions of a chassis (e.g., chassis 120 in Figure 1) configured to receive blades 300. In this way, heat sink 312 may allow heat to be transferred from non-superconducting components (e.g., non-superconducting components 332 and 334) to a cooling system associated with the system including blades 300. Another heat sink 322 may be coupled to substrate of a circuit board mounted on the opposite side of circuit board 330. Similarly, heat sink 316 may be coupled to substrate 341 of circuit board 340. Heat sink 316 may have at least two surfaces (e.g., surfaces 262 and 264 similar to those of heat sink 210 in Figure 2) that interface with a corresponding portion of a chassis (e.g., chassis 120 in Figure 1) configured to receive blades 300. In this way, heat sink 316 may allow heat transfer from superconducting components (e.g., superconducting components 342, 344, 346, and 348) to a cooling system associated with the system including blades 300. Another heat sink 326 may be coupled to a substrate of a circuit board mounted on the opposite side of circuit board 340. As previously explained, components mounted on circuit boards 330 and 340 may be interconnected via flexible interconnects, which may then be coupled to circuit board 360. Heat sink 314 may be coupled to circuit board 360. Heat sink 314 may have at least two surfaces (e.g., surfaces 262 and 264 similar to those of heat sink 210 in Figure 2) that interface with a corresponding portion of a chassis (e.g., chassis 120 in Figure 1) configured to receive blades 300. In this way, heat sink 314 may allow heat to be transferred from the flexible interconnect and circuit board 360 to a cooling system associated with the system including blades 300. Another heat sink 324 may be attached to the other side of circuit board 360.

[0032] In this example, each of the heat sinks associated with blade 300 may be made of aluminum or another type of metal. In one example, the aluminum may be high-purity aluminum having a weight percentage of at least 99.999%. In another example, the aluminum may be high-purity aluminum having a weight percentage of at least 99.99%. Indium can be pressed onto the relevant surfaces of the heat sink by applying high pressure. In one example, the pressure may be in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI. Before pressing the indium, suitable surfaces may be cleaned with water or alcohol. These surfaces may also be treated with acid to remove surface oxides. By using a die to limit the displacement of the press, the thickness of the indium can be set to a predetermined thickness during the pressing process. In this example, the pressure used to press the indium against these surfaces results in a permanent bond between the indium and the metal used to form the heat sink. In one example, pure aluminum can be used to form the heat sink (e.g., heat sinks 312, 322, 314, 324, 316, and 326), and indium can be permanently bonded to a suitable surface of the respective heat sink. In one example, the aluminum can be high-purity aluminum having at least 99.999% by weight. In another example, the aluminum can be high-purity aluminum having at least 99.99% by weight. The blade 300 may further include a number of wedge locks (e.g., wedge locks 372, 374, 382, ​​384, 392, and 394), which can function in a similar manner to the wedge locks previously described with respect to Figure 2. Once permanently bonded to a suitable surface of the heat sink, indium may adhere to these surfaces such that even when the blade 300 is removed and reinserted into the slot associated with the chassis, the indium may not detach or be otherwise removed. Although the example in Figure 3 mentions the use of aluminum, other metals may also be used. As an example, copper with a high residual resistivity (RRR) may also be used. Alternatively, other types of clamping elements can be used instead of wedge locks. Furthermore, surfaces permanently bonded to indium are shown only as examples. Indium or similar metals can be bonded to heat sinks and other surfaces of the substrate associated with the circuit board.

[0033] With respect to each of the circuit boards described with respect to blade 200 of Figure 2 and blade 300 of Figure 3, superconducting or non-superconducting components may communicate with each other using circuit traces formed on the top or bottom surface of each of the substrates (e.g., substrates 331 and 341). The circuit traces may be formed using suitable manufacturing processes, including but not limited to selective laser sintering, fused deposition modeling, direct metal laser sintering, stereolithography, cladding, electron beam melting, direct electron beam fabrication, aerosol jetting, inkjet printing, semi-solid freeform fabrication, digital light processing, two-photon polymerization, laminated object fabrication, 3D printing, or other similar manufacturing processes. In one example, the circuit traces may be made of niobium (or another suitable superconducting material) in the region of the substrate including the superconducting component. This region may exclude any common metal, such as copper. In another region, the circuit traces may be made of niobium and copper (or another suitable metal or a metal alloy including a superconducting metal and a common metal) including the non-superconducting component.

[0034] Figure 4 shows a view 400 of the blade 200 of Figure 2, partially inserted into a portion of the chassis 120 of Figure 1 according to one example. In this example, the chassis portion 410 may include several surfaces that interface with a heat sink having indium pressed therein. In this example, the surface 414 of the top heat sink is shown interfaced with surface 412 of the chassis portion 410. Additionally, the surface 424 of the top heat sink is shown interfaced with surface 422 of the chassis. Another portion of the bottom heat sink is shown interfaced with surface 416 of the chassis portion 410. As explained earlier, wedges 452 and 454 can be used to increase the pressure between the surfaces having indium pressed therein to improve heat transfer. Although Figure 4 shows a specific arrangement of components, these components may be arranged in different ways. Furthermore, fewer or additional components, heat sinks, and other circuit boards may be present.

[0035] Figure 5 shows a view 500 of the blade 300 of Figure 3, partially inserted into a portion of the chassis 120 of Figure 1 according to one example. In this example, portions 510, 540, and 570 of the chassis may include several surfaces that interface with a heat sink having indium pressed therein. In this example, surface 514 of the top heat sink is shown interfaced with surface 512 of portion 510 of the chassis. Additionally, surface 524 of the top heat sink is shown interfaced with surface 522 of the chassis. As previously explained, wedge locks 552 and 554 can be used to secure the coupling between surfaces having indium pressed therein to improve heat transfer. Other heat sinks may also have indium pressed into similar surfaces to allow for better thermal coupling between the heat sink and the corresponding portion of the chassis. In this example, portion 510 of the chassis may be associated with a circuit board having semiconductor components 532 and 534 mounted thereon. Chassis portion 540 can be associated with circuit boards having connectors 542 and 544. Chassis portion 570 can be associated with circuit boards having superconducting components 572, 574, 576, and 578. Each portion of the chassis can be maintained at a different temperature by means of heat transfer to cool it. Although Figure 5 shows a specific arrangement of the components, these components can be arranged in different ways. Additionally, there may be fewer or additional components, heat sinks, and other circuit boards.

[0036] Figure 6 is a view 600 with additional details of the blades according to one example. As shown in view 600, wedge locks 650 can be used to separate heat sinks 610 and 620 from each other to improve thermal contact between heat sinks 610 and 620 and the chassis (or another heat transfer element). In this example, two circuit boards 630 and 640 are shown. The surface of circuit board 630 is bonded to the surface of heat sink 610, and the surface of circuit board 640 is bonded to the surface of heat sink 620. The thermal interface between the circuit boards and the heat sinks can be flat. Efficient heat transfer via the interface between the surface of the heat sink and the chassis (at the edge of the blades) (as shown in Figure 6 and earlier in Figures 4 and 5) can reduce stress introduced by poor matching of the coefficient of thermal expansion (CTE) between the material used to form the substrate and the metal used to form the heat sink.

[0037] Figure 7 illustrates a flowchart 700 of a method for assembling a computing system including at least one blade. Step 710 may include forming a first heat sink configured to transfer heat from a first circuit board to a cooling system associated with the computing system. The first heat sink may be any of the heat sinks described earlier. Step 720 may include forming a second heat sink configured to transfer heat from a second circuit board to a cooling system associated with the computing system. Each of the first and second heat sinks may be any of the heat sinks described earlier with respect to blade 200 of Figure 2 and blade 300 of Figure 3. Similarly, each of the first and second circuit boards may be any of the circuit boards described earlier with respect to blade 200 of Figure 2 and blade 300 of Figure 3. In this example, forming the first heat sink may include machining a first aluminum block, and forming the second heat sink may include machining a second aluminum block. Each of the first and second aluminum blocks may be high-purity aluminum having at least 99.999% by weight of aluminum. In another instance, the aluminum may be high-purity aluminum having at least 99.99% by weight of aluminum.

[0038] Step 730 may include permanently bonding indium to a first selected surface of a first heat sink, wherein the first selected surface is part of a first heat transfer path from the first circuit board to the cooling system. Step 740 may include permanently bonding indium to a second selected surface of a second heat sink, wherein the second selected surface is part of a second heat transfer path from the second circuit board to the cooling system. The respective surfaces may be cleaned with water or alcohol before permanently bonding the indium. In one example, permanently bonding indium to the first selected surface of the first heat sink may include pressing indium onto the first selected surface of the first heat sink and pressing indium onto the first selected surface using a pressure in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI. Similarly, permanently bonding indium to the second selected surface of the second heat sink may include pressing indium onto the second selected surface of the second heat sink and pressing indium onto the second selected surface using a pressure in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI. Advantageously, no heat is applied to any part of the heat sink during the permanent bonding of indium to the respective surfaces. By using a die to limit the displacement of the press, the thickness of the indium can be set to a predetermined thickness during the pressing process. In this example, the pressure used to press the indium against these surfaces results in a permanent bond between the indium and the metal used to form the heat sink. Several objectives are achieved in this way: (1) a good mechanical bond between indium and the heat sink; (2) a good thermal bond between indium and the heat sink; and (3) a flat indium surface.

[0039] Step 750 may include mounting the first and second circuit boards in a chassis associated with the computing system. As an example, the circuit boards may be mounted as part of blades entering the chassis (e.g., chassis 120 of Figure 1) as described earlier. Although flowchart 700 describes these steps as being performed in a specific order, these steps do not necessarily need to be performed in that order. Additionally, as part of the method described in flowchart 700 of Figure 7, fewer or more steps may be performed.

[0040] In summary, in one embodiment of this disclosure, a system including a housing configured to maintain a lower internal pressure than an external pressure is provided. The system may further include a chassis disposed within the housing. The chassis may include at least one slot for receiving a blade. The blade may include a circuit board having a plurality of components mounted on a substrate. The chassis may be coupled to a cooling system to maintain at least a subset of the plurality of components operating in an environment having a temperature of 200 g / L or less. The blade disposed in the slot of the chassis may include a first heat sink comprising metal. The first heat sink comprising metal may be arranged to transfer heat from a first circuit board to the cooling system via a first interface between a first surface of the first heat sink and a second surface of the chassis, wherein indium is permanently bonded to the first surface of the first heat sink or the second surface of the chassis, or both the first surface of the first heat sink and the second surface of the chassis.

[0041] Indium can be permanently bonded to the first surface of the first heat sink or the second surface of the chassis, or both, by pressing indium onto the corresponding surface using a pressure ranging from 4,000 pounds per square inch (PSI) to 16,000 PSI.

[0042] The blade may further include a second circuit board mounted on the opposite side of the first circuit board, having a second plurality of components mounted on a second substrate, and a second heat sink comprising metal, wherein the second heat sink is arranged to transfer heat from the second circuit board to the cooling system via a second interface between a third surface of the second heat sink and a fourth surface of the chassis, and wherein indium is permanently bonded to the third surface of the second heat sink or the fourth surface of the chassis or both the third surface of the second heat sink and the fourth surface of the chassis. Indium can be permanently bonded to the third surface of the second heat sink or the fourth surface of the chassis or both the third surface of the second heat sink and the fourth surface of the chassis by pressing indium onto the respective surface using a pressure in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI.

[0043] The blade may include a first wedge lock and a second wedge lock, configured to further separate the first radiator from the second radiator to improve thermal contact between the first radiator and the chassis and to improve thermal contact between the second radiator and the chassis. The metal may be high-purity aluminum having at least 99.99% by weight aluminum. Lower pressures within the housing may correspond to pressures in the range of 10⁻³ Torr to 10⁻¹⁰ Torr.

[0044] In another embodiment, this disclosure relates to a method for assembling a computing system comprising at least one blade including a first circuit board and a second circuit board, wherein at least one of the first or second circuit boards includes a superconducting component configured to operate in an environment having a temperature of 200 gEV or less. The method may include forming a first heat sink configured to transfer heat from the first circuit board to a cooling system associated with the computing system. The method may further include forming a second heat sink configured to transfer heat from the second circuit board to the cooling system associated with the computing system. The method may further include permanently bonding indium to a first selected surface of the first heat sink, wherein the first selected surface is part of a first heat transfer path from the first circuit board to the cooling system. The method may further include permanently bonding indium to a second selected surface of the second heat sink, wherein the second selected surface is part of a second heat transfer path from the second circuit board to the cooling system. The method may further include mounting the first and second circuit boards in a chassis associated with the computing system.

[0045] As part of this method, forming the first heat sink may include machining a first aluminum block, and forming the second heat sink may include machining a second aluminum block, wherein each of the first and second aluminum blocks may be high-purity aluminum having at least 99.99% by weight of aluminum.

[0046] Alternatively, permanently bonding indium to a first selected surface of the first heat sink may include pressing indium onto the first selected surface of the first heat sink and pressing the indium onto the first selected surface using a pressure in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI. No heat may be applied to the first heat sink during the permanent bonding of indium to the first selected surface of the first heat sink.

[0047] Furthermore, permanently bonding indium to a second selected surface of the second heat sink may include pressing indium onto the second selected surface of the second heat sink and pressing the indium onto the second selected surface using a pressure ranging from 4,000 pounds per square inch (PSI) to 16,000 PSI. No heat may be applied to the second heat sink during the permanent bonding of indium to the second selected surface of the second heat sink. Finally, the method may include assembling the first circuit board, the second circuit board, the first heat sink, and the second heat sink into the computing blades before mounting the first and second circuit boards in a chassis associated with the computing system.

[0048] In another embodiment, this disclosure relates to a system including a housing configured to maintain a lower internal pressure than an external pressure. The system may further include a chassis disposed within the housing, wherein the chassis includes at least one slot for receiving blades, wherein the blades include a first circuit board having a plurality of superconducting components mounted on a first substrate and a second circuit board having a plurality of non-superconducting components mounted on a second substrate. The chassis may be coupled to a cooling system to maintain the plurality of superconducting components in an environment having a temperature of 200 gErvin or less. The chassis may be coupled to a cooling system to maintain the plurality of non-superconducting components in an environment having a temperature of 300 gErvin or less. The blade disposed in a slot in the chassis may include a first heat sink comprising metal, wherein the first heat sink is arranged to transfer heat from the first circuit board to the cooling system via a first interface between a first surface of the first heat sink and a second surface of the chassis, and wherein indium is permanently bonded to the first surface of the first heat sink or the second surface of the chassis or both the first surface of the first heat sink and the second surface of the chassis. The blade may further include a second heat sink comprising metal, wherein the second heat sink is arranged to transfer heat from the second circuit board to the cooling system via a second interface between a third surface of the second heat sink and a fourth surface of the chassis, and wherein indium is permanently bonded to the third surface of the second heat sink or the fourth surface of the chassis or both the third surface of the second heat sink and the fourth surface of the chassis.

[0049] A first circuit board may be coupled to a third circuit board via a first set of flexible interconnects, and a second circuit board may be coupled to the third circuit board via a second set of flexible interconnects, wherein the third circuit board may be maintained at a temperature equal to or below 77 gelvin. The first set of flexible interconnects may be coupled to the second set of flexible interconnects to allow signal exchange between a plurality of superconducting components and a plurality of non-superconducting components.

[0050] Indium can be permanently bonded to a first surface of a first heat sink or a second surface of a chassis, or both, by pressing indium onto a corresponding surface using a pressure ranging from 4,000 pounds per square inch (PSI) to 16,000 PSI. Alternatively, indium can be permanently bonded to a third surface of a second heat sink or a fourth surface of a chassis, or both, by pressing indium onto a corresponding surface using a pressure ranging from 4,000 pounds per square inch (PSI) to 16,000 PSI.

[0051] The blade may include a first wedge lock and a second wedge lock, which are configured to further separate the first radiator from the second radiator to improve the thermal contact between the first radiator and the chassis and improve the thermal contact between the second radiator and the chassis.

[0052] It should be understood that the methods, modules, and components described herein are merely illustrative. For example, and not limitingly, illustrative types of superconducting devices may include field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip (SoCs), complex programmable logic devices (CPLDs), etc.

[0053] Furthermore, in an abstract yet explicit sense, effectively "associating" any arrangement of components used to achieve the same function in order to achieve the desired functionality. Thus, any two components combined in this paper to achieve a specific function can be considered as "associated" with each other to achieve the desired functionality, regardless of the architecture or intermediate components. Similarly, any two such associated components can be considered as "operably connected" or "coupled" to each other to achieve the desired functionality.

[0054] Furthermore, those skilled in the art will recognize that the boundaries between the functions of the above operations are merely illustrative. The functions of multiple operations may be combined into a single operation, and / or the functions of a single operation may be distributed across additional operations. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be varied in various other embodiments.

[0055] While this disclosure provides specific examples, various modifications and changes may be made without departing from the scope of this disclosure as set forth in the following claims. Therefore, this specification and figures should be viewed in an illustrative rather than restrictive sense, and all such modifications are intended to be included within the scope of this disclosure. Any benefits, advantages, or problem-solving solutions described herein with respect to specific examples are not intended to be construed as key, essential, or fundamental features or elements of any or all claims.

[0056] Furthermore, as used herein, the terms "a(a)" or "an(an)" are defined as one or more. Also, the use of introductory phrases such as "at least one" and "one or more" in the claims should not be construed as implying that the introduction of another claim element by the indefinite article "a(a)" or "an(an)" limits any particular claim containing such introduced claim element to an invention containing only one such element, even if the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles (such as "a(a)" or "an(an)"). The same applies to the use of definite articles.

[0057] Unless otherwise stated, terms such as "first" and "second" are used to arbitrarily distinguish between the elements described by these terms. Therefore, these terms are not necessarily intended to indicate the time or other priority of these elements.

[0058] 100: Cryogenic System 110: Outer shell 120: Chassis 122: Slot 124: Slot 130: Heat shield 142: Pipeline 144: Pipeline 200: Blade 210: Radiator 220: Radiator 222: Gap 230: Circuit board 231:Substrate 232: Superconducting components 234: Superconducting components 236: Superconducting components 238: Superconducting components 240: Circuit board 252: Wedge Lock 254: Wedge Lock 262: Surface 264: Surface 300: Circuit Board 312: Radiator 314: Radiator 316: Radiator 322: Radiator 324: Radiator 326: Radiator 330: Circuit board 331:Substrate 332: Non-superconducting components 334: Non-superconducting components 340: Circuit board 341:Substrate 342: Superconducting components 344: Superconducting components 346: Superconducting components 348: Superconducting components 352: Flexible interconnect 354: Flexible interconnect 356: Interconnectors 358: Interconnector 360: Circuit Board 362: Connector 364: Connector 372: Wedge Lock 374: Wedge Lock 382: Wedge Lock 384: Wedge Lock 392: Wedge Lock 394: Wedge Lock 400: View 410: Part 412: Surface 414: Surface 416: Surface 422: Surface 424: Surface 452: Wedge Lock 454: Wedge Lock 500: View 510: Part 512: Surface 514: Surface 522: Surface 524: Surface 532: Semiconductor Components 534: Semiconductor Components 540: Part 542: Connector 544: Connector 552: Wedge Lock 554: Wedge Lock 570: Part 572: Superconducting components 574: Superconducting components 576: Superconducting components 578: Superconducting components 600: View 610: Radiator 620: Radiator 630: Circuit Board 640: Circuit Board 650: Wedge Lock 700: Flowchart 710: Steps 720: Steps 730: Steps 740: Steps 750: Steps

[0059] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A system for improving heat transfer, the system comprising: A housing configured to maintain a pressure inside the housing lower than a pressure outside the housing; and a chassis disposed inside the housing, wherein the chassis includes at least one slot for receiving a blade, wherein the blade includes a first circuit board having a plurality of components mounted on a substrate, wherein the chassis is coupled to a cooling system to maintain at least a subset of the plurality of components operating in an environment having a temperature of 200 g / L or less, wherein the blade is disposed in at least one slot in the chassis, and the blade includes a first heat sink comprising a metal. The first heat sink is arranged to transfer heat from the first circuit board to the cooling system via an interface between a first surface of the first heat sink and a second surface of the chassis, and indium is permanently bonded to the first surface of the first heat sink or the second surface of the chassis or both the first surface of the first heat sink and the second surface of the chassis. The blade also includes a second circuit board having a second plurality of components mounted on a second substrate and mounted on an opposite side of the first circuit board, and a second heat sink comprising a metal, wherein the second heat sink is arranged to transfer heat from the second circuit board to the cooling system via a second interface between a third surface of the second heat sink and a fourth surface of the chassis, and indium is permanently bonded to the third surface of the second heat sink or the fourth surface of the chassis or both the third surface of the second heat sink and the fourth surface of the chassis.

2. The system as claimed in claim 1, wherein indium is permanently bonded to a corresponding surface by pressing it against a pressure in the range of 4,000 pounds per square inch (PSI) to a second surface of the chassis or both the first surface of the first heat sink and the second surface of the chassis by using a pressure in the range of 4,000 pounds per square inch (PSI) to a corresponding surface.

3. The system as claimed in claim 1, wherein indium is permanently bonded to the third surface of the second heat sink or the fourth surface of the chassis, or both the third surface of the second heat sink and the fourth surface of the chassis, by pressing indium onto a corresponding surface using a pressure in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI.

4. The system as claimed in claim 3, wherein the blade includes a first wedge lock and a second wedge lock configured to further separate the first radiator from the second radiator to improve thermal contact between the first radiator and the chassis and to improve thermal contact between the second radiator and the chassis.

5. A method for assembling a computing system, the computing system including at least one blade comprising a first circuit board and a second circuit board, wherein at least one of the first circuit board or the second circuit board includes a superconducting component configured to operate in a cryogenic environment having a temperature of 200 gEV or below, the method comprising the steps of: forming a first heat sink configured to transfer heat from the first circuit board to a cooling system associated with the computing system; forming a second heat sink configured to transfer heat from the second circuit board to a cooling system associated with the computing system; permanently bonding indium to a first selected surface of the first heat sink, wherein the first selected surface is part of a first heat transfer path from the first circuit board to a first heat transfer path from the first circuit board to a first heat transfer path from the first circuit board to a first selected surface of the cooling system; permanently bonding indium to a second selected surface of the second heat sink, wherein the second selected surface is part of a second heat transfer path from the second circuit board to a second heat transfer path from the second circuit board to a second heat transfer path from the second circuit board to a first ... the second heat transfer path from 6. The method as described in claim 5, wherein the step of forming the first heat sink includes the step of machining a first aluminum block, and wherein the step of forming the second heat sink includes the step of machining a second aluminum block, wherein each of the first aluminum block and the second aluminum block comprises high-purity aluminum having at least 99.99% by weight of aluminum.

7. The method as described in claim 5, wherein the step of permanently bonding indium to the first selected surface of the first heat sink includes the steps of: pressing indium onto the first selected surface of the first heat sink and pressing indium onto the first selected surface using a pressure in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI.

8. The method as described in claim 7, wherein no heat is applied to the first heat sink during the permanent bonding of indium to the first selected surface of the first heat sink.

9. The method as described in claim 5, wherein the step of permanently bonding indium to the second selected surface of the second heat sink includes the steps of: pressing indium onto the second selected surface of the second heat sink and pressing indium onto the second selected surface using a pressure in the range of 4,000 pounds per square inch (PSI) to 16,000 PSI.

10. The method as described in claim 9, wherein no heat is applied to the second heat sink during the permanent bonding of indium to the second selected surface of the second heat sink.

11. The method as described in claim 5 further includes the step of assembling the first circuit board, the second circuit board, the first heat sink, and the second heat sink into a computing blade before installing the first circuit board and the second circuit board in the chassis associated with the computing system.

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