Electronic device cooling system and cooling method

Abstract

[Problem] To provide a cooling system and a cooling method capable of efficiently cooling an electronic device with extremely high heat generation through immersion in a conductive cooling liquid such as water. [Solution] A waterproofed electronic device that includes a substrate and at least one heating element mounted on the substrate and is covered with waterproof coating or a waterproof bag is immersed in a cooling tank filled with cooling liquid. A cold plate having a body, a fluid inlet, and a fluid outlet is disposed inside or outside the waterproof coating or bag. The cold plate is thermally connected to the heating element. A fluid machine causes pressure energy directed from the fluid inlet to the fluid outlet to act on a fluid passing through a flow path formed in the body of the cold plate.

Description

Cooling system and cooling method for electronic device

[0001] The present invention relates to a cooling system and a cooling method for electronic devices, and in particular to a cooling system and a cooling method for electronic devices that require high performance, stable operation, or low power consumption operation and generate a large amount of heat themselves, such as supercomputers, data centers, artificial intelligence processing systems, quantum computing systems, cryptographic processing systems, and blockchain processing systems.

[0002] In recent years, one of the biggest challenges determining the performance limits of computer-related equipment is power consumption. The importance of research into power efficiency, particularly in supercomputers, has already been widely recognized. Specifically, speed performance per watt (Flops / W) has become one of the metrics for evaluating supercomputers. Furthermore, it is estimated that more than 30% of the total power consumed by data centers is spent on cooling, creating a growing demand for reducing power consumption through improved cooling efficiency. Furthermore, recent global warming and extreme heat caused by extreme weather have rendered conventional cooling methods insufficient to cool data centers during the summer, creating an urgent need to improve the cooling capacity of existing systems. Furthermore, the rapid growth of artificial intelligence processing, the increasing need for encryption processing, the rapid increase in cryptocurrency mining processing—a key example of blockchain processing—and the development of the metaverse, which is expected to see rapid growth, all of these factors require an exponential increase in the processing power of data centers and computer systems, creating a significant demand for increased cooling capacity.

[0003] Air and liquid cooling systems have traditionally been used to cool supercomputers and data centers. Liquid cooling systems use liquids, which have significantly better heat transfer properties than air, and are generally considered to have good cooling efficiency. For example, the "TSUBAME-KFC" system developed by the Tokyo Institute of Technology achieved 4.50 GFlops / W using a liquid immersion cooling system using synthetic oil, earning it first place in the "Supercomputer Green500 List" announced in November 2013 and June 2014. However, because the cooling liquid uses synthetic oil, which has high viscosity and forms an oil film, it is difficult to completely remove the oil adhering to electronic devices when they are removed from the oil-immersion rack, making electronic device maintenance (specifically, adjustment, inspection, repair, replacement, and expansion; the same applies below) extremely difficult. Furthermore, there have been reports of problems with the synthetic oils used, such as corroding electronic boards and gaskets that make up the cooling system in a short period of time, causing them to break down, and leaking refrigerant, hindering operation.

[0004] On the other hand, immersion cooling systems using fluorocarbon-based coolants instead of synthetic or mineral oils, which cause the above-mentioned problems, have been proposed. Specifically, examples of immersion cooling systems using fluorocarbon-based coolants (hydrofluoroether (HFE) compounds known under the trade names "Novec 7100" (a trademark of 3M; the same applies hereinafter)," "Novec 7200," and "Novec 7300") are disclosed in, for example, Patent Documents 1 and 2.

[0005] In addition to these, since 2014, the present inventor has been developing a new liquid immersion cooling system and a series of related technologies that directly cools electronic devices by circulating a cooling liquid that is difficult to evaporate and contains a fully fluorinated substance as its main component within the open space of a cooling tank (for example, Patent Document 3).

[0006] However, PFAS (Perfluoroalkyl Substances and Polyfluoroalkyl Substances), which include all of these fluorocarbon-based coolants, have long been known to have adverse effects on the human body, agricultural crops, and the natural environment, and in December 2022, the world's largest manufacturer announced that it would completely cease production by the end of 2025, and in Europe, both production and use are expected to be banned by law within a few years. Therefore, there is a need for a new immersion cooling method that does not use any harmful compounds such as PFAS as a refrigerant, has superior cooling capacity compared to immersion cooling methods that use PFAS or other refrigerants, and is more affordable and can be used widely worldwide.

[0007] A typical example of a cooling method that does not use any harmful compounds such as PFAS as a refrigerant is one that can use ordinary water (tap water or industrial water) that is not pure water. Specifically, instead of a heat sink that is attached in direct contact with the upper surface of the semiconductor of the CPU (central processing unit), which is the main heat source in computer equipment, this method attaches a "water-cooled block" that contains a flow path for water to pass through inside a copper or aluminum block (see, for example, Patent Document 4).

[0008] Furthermore, another cooling method that can utilize water has been proposed, in which a semiconductor chip mounted on a circuit board is stored in a flexible bag, and the bag is immersed in a container filled with water as a cooling liquid. When the bag is filled with water or when the pressure inside the bag is reduced, the bag shrinks and deforms due to the pressure difference between the inside and outside of the bag, and the bag is tightly attached to the semiconductor device (for example, Patent Document 5).

[0009] Another cooling method that can utilize water has been proposed: natural water-cooled computers, which use river, lake, ocean, or tap water as a cooling source to directly cool the computer. Specifically, this cooling method involves immersing a computer whose board surface is coated with parylene resin in water (see, for example, Non-Patent Document 1).

[0010] Furthermore, a cooling method has been proposed in which the entire substrate is completely covered with an ultra-nano hydrophobic coating thin film made of silicon compound nanoparticles to create an electronic device with excellent waterproof and moisture-resistant properties, and the device is then immersed in water (e.g., Patent Document 6).

[0011] Japanese Patent No. 10,717,881 specification Kazuki Fujiwara et al., Information Processing Society of Japan Research Report High Performance Computing (HPC) "The First Step Towards a Direct Natural Water-Cooled Computer" 2017-HPC-158(5), pp.1-5 (March 1, 2017) URL: http: / / research.nii.ac.jp / ~koibuchi / pdf / ikki-sighpc158.pdf

[0012] The cooling system disclosed in Patent Document 4 uses water as a refrigerant, rather than the harmful substances such as PFAS used in Patent Documents 1 to 3. A water-cooled block mounted on the surface of a semiconductor element mounted in an electronic device is provided with a flowing water path to first cool the water-cooled block, and then only cool the semiconductor element that is in direct contact with the water-cooled block. Therefore, other electronic components and electronic boards that are not in direct contact with the water-cooled block and that generate a significant amount of heat but still require cooling cannot benefit from the cooling, and must be cooled separately using a method such as air cooling. Furthermore, in electronic devices used in recent supercomputers and data centers, in addition to the CPU (Central Processing Unit), there are many other components that need to be cooled, including the GPU (Graphics Processing Unit), high-speed memory, chipsets, power-related components such as FETs (Field Effect Transistors), electrolytic capacitors, network units, bus switch units, and SSDs (Solid State Drives). It is difficult to adequately cool all of these components, which have significantly different heat dissipation amounts, using air-cooling, which has inferior cooling capacity compared to liquid-cooling. Furthermore, a large amount of cooling water is typically required to supply water to the water-cooled block, and the water-cooled block itself is large and does not have a fin-like shape like a heat sink, which can obstruct the airflow path for air cooling. Furthermore, at least two piping paths are required to supply water to and recover it from the water-cooled block, and the piping paths installed to cool the water-cooled block also obstruct the airflow path for cooling to a certain extent, resulting in extremely low cooling efficiency for objects that the water-cooled block does not directly cool. For this reason, it is easy to predict that the cooling performance will be significantly insufficient for the latest CPUs, which consume significantly more than 100W of power, or high-performance GPUs for generative AI, which consume more than 500W.

[0013] Furthermore, the cooling system disclosed in Non-Patent Document 1 completely covers the entire electronic components and electronic board with a thin film of parylene, which does not conduct electricity and is impermeable to water, and then the entire electronic components and electronic board coated with the parylene thin film are immersed in water or seawater, and the low temperature of the water or seawater that comes into contact with the entire parylene thin film is used to cool the equipment.

[0014] Similarly, the cooling system disclosed in Patent Document 6 also completely covers the entire electronic components and electronic board with an ultra-nano hydrophobic coating film made of silicon compound nanoparticles that are non-conductive and impermeable to water, and then the entire electronic components and electronic board coated with the hydrophobic coating film are immersed in water, and the low temperature of the water that comes into contact with the entire hydrophobic coating film is used to cool the equipment.

[0015] In both the cooling systems of Non-Patent Document 1 and Patent Document 6, all of the electronic components and electronic boards to be cooled are in contact with the refrigerant, water or seawater, via a parylene thin film or a hydrophobic coating thin film. For this reason, when highly efficiently cooling a CPU or other major heat source, the cooling capacity and efficiency are inevitably inferior compared to cooling systems in which a heat sink is in direct contact with the surface of a semiconductor, such as a water-cooled block, and the heat sink is directly cooled by a refrigerant such as water.

[0016] The water-cooling method disclosed in Patent Document 5 involves storing a semiconductor device in a flexible bag and immersing it in a coolant such as water to achieve cooling. However, like a thin film coating, the bag prevents the surface of the semiconductor device from coming into direct contact with the coolant, which results in a problem of reduced cooling performance, particularly when efficiently cooling a CPU or other major heat source.

[0017] Therefore, an object of the present invention is to solve the problems of the conventional technology described above and to provide a cooling system and a cooling method that can efficiently cool electronic devices that generate a large amount of heat by immersing them in a conductive coolant such as water.

[0018] To solve the above problems, one aspect of the present invention provides a cooling system that cools an electronic device by immersing it in ordinary water (tap water, industrial water, seawater, etc.), a typical example of a coolant that is electrically conductive and highly thermally conductive. In a preferred embodiment of the cooling system according to the present invention, the cooling system includes: a cooling tank containing a coolant; a waterproof electronic device in which the electronic device, including a substrate and at least one heat generating element mounted on the substrate, is covered with a waterproof coating or waterproof bag; a cold plate including a body, a fluid inlet, and a fluid outlet; and at least one fluid machine. At least one surface of the body of the cold plate is thermally connected to the at least one heat generating element. A part or all of the cold plate is disposed inside or outside the waterproof coating or waterproof bag. The at least one fluid machine applies pressure energy to a fluid passing through a flow path formed in the body of the cold plate, from the fluid inlet to the fluid outlet.

[0019] In a preferred embodiment of the above cooling system, the cooling liquid may be water, the fluid machine may be a pump or a submersible pump placed in a circulation path from the fluid outlet of the cold plate back to the fluid inlet, and the fluid passing through the flow path formed in the body of the cold plate may be a refrigerant that is cooled by a heat exchanger in the circulation path.

[0020] In addition, in a preferred embodiment of the above cooling system, the cooling liquid may be water, the fluid machine may be an underwater pump connected to the fluid inlet of the cold plate, the fluid passing through the flow path formed within the body of the cold plate may be a portion of the cooling liquid, and the underwater pump may apply pressure energy to the portion of the cooling liquid.

[0021] Furthermore, in a preferred embodiment of the above cooling system, the cooling system may further include an inlet-side manifold disposed inside the waterproof coating or waterproof bag or outside the waterproof coating or waterproof bag, and the electronic device may include a plurality of heating elements and a plurality of cold plates, and each outlet of the inlet-side manifold may be fluidly connected to each fluid inlet of the plurality of cold plates.

[0022] In addition, in a preferred embodiment of the above cooling system, the cooling system may further include an outlet manifold disposed inside the waterproof coating or waterproof bag or outside the waterproof coating or waterproof bag, and each inlet of the outlet manifold may be fluidly connected to each fluid outlet of the multiple cold plates.

[0023] Furthermore, in a preferred embodiment of the above cooling system, an opening having an area larger than the area of ​​the at least one heating element may be formed in the waterproof coating or the waterproof bag, and when a part or all of the cold plate is disposed outside the waterproof coating or the waterproof bag, a peripheral area of ​​the opening in the waterproof coating or the waterproof bag may be watertightly connected to at least one surface of the main body of the cold plate, and the surface of the at least one heating element may be thermally connected to at least one surface of the cold plate through the opening in the waterproof coating or the waterproof bag.

[0024] In addition, in a preferred embodiment of the cooling system, the system may include a bonding layer that provides a watertight connection between the area surrounding the opening of the waterproof coating or waterproof bag and at least one surface of the cold plate, and the bonding layer may be formed from a bonding film made of different materials, a double-sided adhesive tape, or a watertight packing.

[0025] Furthermore, in a preferred embodiment of the cooling system, the inlet manifold, the bodies of the cold plates, and the fluid inlets may be disposed inside a waterproof coating or a waterproof bag, and the openings of the fluid outlets of the cold plates may be disposed outside the waterproof coating or the waterproof bag.

[0026] In addition, in a preferred embodiment of the cooling system, the inlet manifold and the fluid inlet openings of each of the multiple cold plates may be arranged inside a waterproof coating or a waterproof bag, and the main bodies and fluid outlet openings of each of the multiple cold plates may be arranged outside the waterproof coating or the waterproof bag.

[0027] Furthermore, in a preferred embodiment of the cooling system, the inlet manifold may be disposed inside a waterproof coating or a waterproof bag, and the fluid inlet openings, the bodies, and the fluid outlet openings of the multiple cold plates may be disposed outside the waterproof coating or the waterproof bag.

[0028] In addition, in a preferred embodiment of the cooling system, the inlet manifold, the fluid inlet openings of the multiple cold plates, the bodies, and the fluid outlet openings may be arranged outside a waterproof coating or a waterproof bag.

[0029] Furthermore, in a preferred embodiment of the cooling system, the main body of each of the plurality of cold plates may be disposed inside a waterproof coating or a waterproof bag, and the inlet manifold and the fluid inlet openings and fluid outlet openings of each of the plurality of cold plates may be disposed outside the waterproof coating or the waterproof bag.

[0030] In a preferred embodiment of the cooling system, the cooling system may include a plurality of submersible pumps as fluid machinery, the electronic device may include a plurality of heat generating elements and a plurality of cold plates, the coolant may be water, and each of the plurality of submersible pumps may be connected to a respective fluid inlet of the plurality of cold plates. The fluid passing through the flow passages formed in each body of the plurality of cold plates may be a portion of the coolant, and each of the submersible pumps may apply a respective pressure energy to a portion of the coolant.

[0031] Furthermore, in a preferred embodiment of the cooling system, the bodies of the cold plates may be disposed inside a waterproof coating or a waterproof bag, and the submersible pumps and the fluid inlet openings and fluid outlet openings of the cold plates may be disposed outside the waterproof coating or the waterproof bag.

[0032] In addition, in a preferred embodiment of the above cooling system, the multiple submersible pumps, the bodies of the multiple cold plates, the fluid inlet openings, and the fluid outlet openings may be arranged outside a waterproof coating or a waterproof bag.

[0033] Furthermore, in a preferred embodiment of the cooling system, the cooling system may further include an inlet manifold and a submersible pump as the fluid machine, the electronic device may include a plurality of heat generating elements and a plurality of cold plates, the coolant may be water, the submersible pump may be connected to an inlet of the inlet manifold, and each outlet of the inlet manifold may be fluidly connected to each fluid inlet of the plurality of cold plates. The fluid passing through the flow passages formed in each body of the plurality of cold plates may be a portion of the coolant, and the submersible pump may apply pressure energy to the portion of the coolant.

[0034] In addition, in a preferred embodiment of the above cooling system, the main bodies of the multiple cold plates may be arranged inside a waterproof coating or a waterproof bag, and the submersible pump, the inlet manifold, and the fluid inlet openings and fluid outlet openings of the multiple cold plates may be arranged outside the waterproof coating or the waterproof bag.

[0035] Furthermore, in a preferred embodiment of the above cooling system, the submersible pump, the inlet manifold, the bodies of the multiple cold plates, the fluid inlet openings and the fluid outlet openings may be arranged outside a waterproof coating or a waterproof bag.

[0036] In a preferred embodiment of the cooling system, the electronic device may include a plurality of heating elements and a plurality of cold plates, and a fluid outlet of one of the plurality of adjacent cold plates may be fluidly connected to a fluid inlet of the other cold plate via the connecting pipe.

[0037] Furthermore, in a preferred embodiment of the cooling system, the electronic device may include a plurality of heat generating elements, and at least one surface of the body of the cold plate may be thermally connected to the plurality of heat generating elements.

[0038] Additionally, according to another aspect of the present invention, there is provided a method for cooling an electronic device, the method including the steps of: immersing a waterproofed electronic device, the waterproofed electronic device including a substrate and at least one heat generating element mounted on the substrate, covered with a waterproof coating or a waterproof bag, in a cooling bath containing a cooling liquid to cool the waterproofed electronic device; and forcing the fluid to flow through a body of a cold plate to cool the at least one heat generating element thermally connected to the cold plate.

[0039] According to the present invention, a waterproof electronic device, including a substrate and at least one heat-generating element mounted on the substrate, is covered with a waterproof film or waterproof bag and immersed in a cooling bath containing a coolant. A cold plate having a body, a fluid inlet, and a fluid outlet is disposed inside or outside the waterproof film or bag. The cold plate is thermally connected to the heat-generating element, and a fluid machine applies pressure energy from the fluid inlet to the fluid outlet to the fluid passing through a flow path formed in the body of the cold plate. In addition to the coolant in the cooling bath cooling the entire waterproof electronic device (primary cooling), the fluid forced through the flow path formed in the body of the cold plate locally and powerfully removes heat from the heat-generating element, which is the main heat source (secondary cooling). Technology for locally cooling a heat source using a cold plate, also known as direct liquid cooling, has been known for some time. The present invention makes it possible, for the first time, to apply this technology to a system that cools electronic devices by immersing them in a conductive coolant such as water. Electronic devices, which generate a very large amount of heat and whose heat output increases daily, can be cooled highly efficiently by immersing them in a conductive coolant such as water.

[0040] The above and other objects and advantages of the present invention will be more clearly understood through the following description of the embodiments, although the embodiments described below are merely examples and the present invention is not limited thereto.

[0041] 1 is a diagram showing the configuration of essential parts in an example of a cooling system; FIG. 2 is a diagram showing the overall configuration of an example of a cooling system; FIG. 3 is a partial cross-sectional view of an electronic device that has been waterproofed in an example of a cooling system; FIG. 4 is a partial cross-sectional view of an electronic device that has been waterproofed in another example of a cooling system; FIG. 5 is a partial cross-sectional view of an electronic device that has been waterproofed in yet another example of a cooling system; FIG. 6 is a partial cross-sectional view of an electronic device that has been waterproofed in yet another example of a cooling system; FIG. 7 is a partial cross-sectional view of an electronic device that has been waterproofed in yet another example of a cooling system; FIG. 8 is a diagram showing the configuration of essential parts in yet another example of a cooling system; FIG. 9 is a partial cross-sectional view of an electronic device that has been waterproofed in yet another example of a cooling system; FIG. 10 is a partial cross-sectional view of an electronic device that has been waterproofed in yet another example of a cooling system;

[0042] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the cooling system according to the present invention will now be described in detail with reference to the drawings.

[0043] 1 to 3 , a cooling system 1 shown as an example includes a cooling tank 3 containing a coolant 4, a waterproof electronic device 100 formed by covering an electronic device 10 including a substrate 31 and a plurality of heating elements 33 mounted on the substrate 31 with a waterproof bag 11, a plurality of cold plates 20, and a pump 8. The cold plate 20 includes a main body 21, a fluid inlet 23, and a fluid outlet 25. A flow path through which the fluid passes is formed within the main body 21 of the cold plate 20. The flow path may be formed to increase the area in contact with the fluid, and may be, for example, a mesh-like hole, a zigzag hole, or a space with a number of fins or pins arranged at predetermined intervals within the main body 21.

[0044] In the illustrated example, all of the multiple cold plates 20 may be disposed inside the waterproof bag 11, and at least one surface (e.g., the back surface) of the main body 21 of each of the multiple cold plates 20 may be thermally connected to each of the multiple heating elements 33. Also, an inlet-side manifold 27 and an outlet-side manifold 29 may be disposed inside the waterproof bag 11. Each outlet of the inlet-side manifold 27 may be fluidly connected to each fluid inlet 23 of the multiple cold plates 20, and each inlet of the outlet-side manifold 29 may be fluidly connected to each fluid outlet 25 of the multiple cold plates 20. The cold plates 20, the inlet-side manifold 27, and the outlet-side manifold 29 may be mechanically fixed to the substrate 31 by a fixing mechanism such as a screw.

[0045] In the circulation path that runs from the fluid outlet 25 of the cold plate 20 through the outlet manifold 29, the fluid return pipe 7b, the heat exchanger 9, the pump 8, the fluid feed pipe 7a, the inlet manifold 27, and back to the fluid inlet 23 of the cold plate 20, the pump 8 applies pressure energy from the fluid inlet 23 to the fluid outlet 25 to the fluid passing through the flow path formed in the body 21 of the cold plate 20. The fluid heated in the cold plate 20 by the action of the pump 8 passes through the heat exchanger 9, where it is cooled and sent to the cold plate 20. This circulating fluid may be water, but may also be another refrigerant.

[0046] The waterproof bag 11 may be made of a water-resistant, heat-resistant, and watertight synthetic resin film (e.g., polyethylene, polypropylene, polyester, etc.). In the illustrated example, the upper portion of the waterproof bag 11 does not need to be airtight or watertight; it is sufficient that at least the portion immersed in the coolant is airtight. In this case, during operation of the cooling system 1, the relatively flexible waterproof bag 11 is pressed by the hydraulic pressure of the surrounding coolant 4, thereby bringing the inner surface of the waterproof bag 11 into relatively close contact with both sides of the circuit board 31, the various electronic components 35 mounted on the circuit board, the network communication cable 36, the power cable 37 and the connectors connecting them, the cold plate 20, the inlet manifold 27, and the outlet manifold 29.

[0047] The cooling tank 3 contains a sufficient amount of coolant 4 to immerse the waterproof electronic device 100. The coolant 4 may be ordinary water (tap water, industrial water, seawater, etc.). A coolant supply pipe 5a and a coolant return pipe 5b connected to the cooling tank 3 provide paths for discharging the coolant heated in the cooling tank 3 from the cooling tank 3 and returning the coolant cooled by a heat exchanger (not shown) to the cooling tank 3. In the waterproof electronic device 100 immersed in the coolant 4, the coolant 4 cools the entire waterproof electronic device 100, and the fluid forced to pass through the flow path formed in the body 21 of the cold plate 20 locally and powerfully removes heat from the heat-generating element 33.

[0048] Next, other examples of the cooling system will be described with reference to Figures 4 to 14. Note that the same reference numerals are used for the same parts as in Figures 1 to 3.

[0049] FIG. 4 shows a partial cross-section of a waterproofed electronic device in another example of a cooling system. This cooling system differs from the cooling systems shown in FIGS. 1 to 3 in that the opening of the fluid outlet 25 of the cold plate 20 in the waterproofed electronic device 110 is located outside the waterproof bag 11 and that the outlet manifold 29 and the fluid return pipe 7b are not required. Another difference is that a fluid feed pipe 7c branches off from the coolant return pipe 5b and connects to the heat exchanger 9, thereby forming a separate circulation path from the fluid outlet 25 of the cold plate 20 through the cooling tank 3, the coolant return pipe 5b, the fluid return pipe 7c, the heat exchanger 9, the pump 8, the fluid feed pipe 7a, the inlet manifold 27, and back to the fluid inlet 23 of the cold plate 20 (see FIG. 2). Note that, in order to locate the opening of the fluid outlet 25 of the cold plate 20 outside the waterproof bag 11, the fluid outlet 25, which is made up of, for example, a pipe, must pass through a penetration formed in the waterproof bag 11. In this case, it is advisable to take appropriate measures such as providing a sealant at the penetration portion to ensure watertightness.

[0050] FIG. 5 shows a partial cross section of a waterproofed electronic device in yet another example of a cooling system. This cooling system differs from the cooling systems shown in FIGS. 1 to 3 in that, in the waterproofed electronic device 200, the opening of the fluid outlet 25 of the cold plate 20 and substantially the entire body 21 of the cold plate 20 are disposed outside the waterproof bag 11; the waterproof bag 11 has an opening 15 with an area larger than the area of ​​the heating element 33, and the area surrounding the opening 15 is watertightly connected to the back surface of the body 21 of the cold plate 20 (and, as shown, between the slit in the waterproof bag 11 and the front surface of the body 21 of the cold plate 20) via a bonding layer 41. Similar to the example shown in FIG. 4, the outlet manifold 29 and fluid return pipe 7b are not required, and a fluid feed pipe 7c branches off from the coolant return pipe 5b and connects to the heat exchanger 9, forming a separate circulation path.

[0051] The bonding layer 41 is formed by using a dissimilar material bonding film, double-sided adhesive tape, or watertight packing to connect the back surface (or front surface) of the main body of the cold plate 20 to the outer surface (inner surface) of the waterproof bag. The dissimilar material bonding film, double-sided adhesive tape, or watertight packing that forms the bonding layer 41 may have an opening of the same shape as the opening 15.

[0052] An example of a dissimilar material bonding film for forming the bonding layer 41 is the "Metaseal" (product name of Fujimori Kogyou Co., Ltd.) series. Because this dissimilar material bonding film is formed into a film of uniform thickness, it can be sandwiched between the back surface (rear surface) of the cold plate 20 and the outer surface (inner surface) of the waterproof bag 11 and heat-pressed to form a bonding layer bonding the cold plate 20 and the waterproof bag 11. A heat press or an iron-type heater can be used for heat-pressing, allowing the bonding process between the base block 21B and the non-conductive bag 11 to be completed easily and in a short time (several seconds or less). The method for forming the bonding layer 41 is not limited to heat-pressing, and various methods, such as pressure, ultrasonic waves, electromagnetic waves, and light irradiation, can also be used.

[0053] By forming the bonding layer 41 from a dissimilar material bonding film, it is possible to achieve a surface bond between the back surface (rear surface) of the cold plate 20 and the outer surface (inner surface) of the waterproof bag 11 with a uniform film thickness and no variation in adhesive strength.

[0054] Another example of a dissimilar material bonding film that forms a bonding layer is "WelQuick" (a Resonac product name) manufactured by Resonac Corporation. This dissimilar material bonding film utilizes the solid-liquid phase change of the film material to complete the bonding process in a short time (a few seconds). It also allows for reheating after bonding to allow for peeling and re-adhesion. This allows for easy collection of waterproofed electronic devices from cooling systems after a certain period of use, and for the cold plate 20 to be easily peeled from the waterproof bag 11, resulting in high resource reusability.

[0055] Here, the dissimilar material bonding film can be preferably formed into a sheet or film shape and then cut. However, this is not limiting. For example, if a certain environment is established in which various conditions, including the film thickness and shape, can be appropriately controlled, a bonding layer 41 formed from the dissimilar material bonding film can be obtained starting with a liquid or gel adhesive material. Specifically, as an example, a mold is first placed on the surface of the cold plate and filled with the liquid or gel adhesive material, thereby forming a coating of the adhesive material of the desired shape and volume on the surface of the cold plate. Next, with the coating of the adhesive material in contact with the back surface (surface) of the cold plate and the outer surface (inner surface) of the waterproof bag, the coating of the adhesive material can be solidified by methods such as thermocompression, pressure, ultrasonic waves, electromagnetic waves, or light irradiation. In this way, a bonding layer formed from the dissimilar material bonding film can be obtained starting from a liquid or gel adhesive material.

[0056] Alternatively, the bonding layer may be formed using double-sided adhesive tape. For example, a high-strength acrylic foam tape (e.g., 3M VHB Tape) can be cut to the desired size and shape to prepare the double-sided adhesive tape for the bonding layer. One side of the double-sided adhesive tape is pressed onto the back surface (surface) of the cold plate or the outer surface (inner surface) of the waterproof bag, and then the outer surface (inner surface) of the waterproof bag 11 or the back surface (surface) of the cold plate is pressed onto the other side of the double-sided adhesive tape to form a bonding layer bonding the cold plate and the waterproof bag. The use of double-sided adhesive tape has the advantage that it does not require a heat treatment, making it easy to form the bonding layer. When using double-sided adhesive tape, it is preferable to arrange the cut tape so that the bonding layer forms a continuous, closed band surrounding the opening of the bag 11.

[0057] Alternatively, the bonding layer may be formed by a watertight packing. For example, various rubber packings (typically O-rings) in a continuous, closed strip or line shape can be used. The watertight packing is placed between the back surface of the cold plate and the outer surface of the waterproof bag so as to surround the opening of the bag 11. The cold plate is then fixed to the substrate by screwing or the like. In this fixed state, the watertight packing elastically deforms, applying an appropriate surface pressure in a strip or line shape to the area surrounding the opening 15 of the bag 11, thereby maintaining a watertight seal on both sides of the surrounding area.

[0058] FIG. 6 shows a partial cross section of a waterproofed electronic device in yet another example of a cooling system. This cooling system differs from the cooling system including the waterproofed electronic device 200 shown in FIG. 5 in that in the waterproofed electronic device 210, the opening of the fluid outlet 25 of the cold plate 20 and the entire body 21 of the cold plate 20 are disposed outside the waterproof bag 11, and the area surrounding the opening 15 of the waterproof bag 11 is watertightly connected to the back surface and the surface of the body 21 of the cold plate 20 facing the fluid inlet 23 via a bonding layer 41. Similar to the example shown in FIG. 5, the outlet manifold 29 and fluid return pipe 7b are not required, and a fluid feed pipe 7c branches off from the coolant return pipe 5b and connects to the heat exchanger 9, forming a separate circulation path. Furthermore, the fluid inlet 23 of the cold plate 20 must pass through a penetration formed in the waterproof bag 11, but the penetration may be appropriately treated, such as by providing a sealant, to maintain watertightness.

[0059] Figure 7 shows a partial cross section of a waterproof electronic device in yet another example of a cooling system. This cooling system differs from the cooling system including the waterproof electronic device 210 shown in Figure 6 in that the openings of the fluid inlet 23 and fluid outlet 25 of the cold plate 20, as well as the entire main body 21, are disposed outside the waterproof bag 11 in the waterproof electronic device 220. The rest of the cooling system is the same as the example shown in Figure 6. Note that each outlet of the inlet manifold 27 must pass through a through-hole formed in the waterproof bag 11, and it is recommended to provide a sealant or other appropriate treatment at the through-hole to maintain watertightness.

[0060] Figure 8 shows a partial cross section of a waterproofed electronic device in yet another example of a cooling system. This cooling system differs from the cooling system including the waterproofed electronic device 220 shown in Figure 7 in that in the waterproofed electronic device 230, the inlet manifold 27, the opening of the fluid inlet 23 of the cold plate 20, the opening of the fluid outlet 25, and the entire main body 21 are disposed outside the waterproof bag 11. The rest is the same as the example shown in Figure 7. Unlike the example shown in Figure 7, except for the formation of the opening 15 in the waterproof bag 11, there is no need to form a penetration in the waterproof bag 11, resulting in excellent watertightness.

[0061] 9 and 10 are front and partial cross-sectional views of a waterproofed electronic device in yet another example of a cooling system. This cooling system differs from the cooling system including the waterproofed electronic device 110 shown in FIG. 4 in that the inlet manifold 27 and the openings of the fluid inlet 23 and fluid outlet 25 of the cold plate 20 are disposed outside the waterproof bag 11, and the openings of the fluid inlet 23 and fluid outlet 25 of the cold plate 20 are disposed on the front side of the cold plate 20. The rest of the cooling system is the same as the example shown in FIG. 4. The fluid inlet 23 and fluid outlet 25 of the cold plate 20 must pass through penetrations formed in the waterproof bag 11, and it is recommended to provide appropriate treatment, such as providing a sealant at the penetrations, to maintain watertightness.

[0062] FIG. 11 shows a partial cross-section of a waterproofed electronic device in yet another example of a cooling system. This cooling system differs from the cooling system including the waterproofed electronic device 300 shown in FIG. 10 in that, in the waterproofed electronic device 400, multiple submersible pumps 28 are connected to the fluid inlets 23 of multiple cold plates 20, respectively. In this example, there is no need to configure a fluid circulation path from the cooling tank 3 through the coolant return pipe 5b, the fluid return pipe 7c, the heat exchanger 9, the pump 8, the fluid feed pipe 7a, the inlet manifold 27, and back to the fluid inlets 23 of the cold plates 20. Instead, a portion of the coolant may pass through a flow path formed within the body 21 of the cold plate 20, and the submersible pump 29 may apply pressure energy to this portion of the coolant. When the submersible pump 29 is connected to each of the multiple cold plates 20, the flow rate or volume of the fluid passing through the cold plates can be individually controlled. This enables appropriate temperature management in large-scale electronic devices equipped with multiple CPUs or GPUs, depending on the heat generation of the CPUs or GPUs. The fluid inlet 23 and fluid outlet 25 of the cold plate 20 must pass through a penetration formed in the waterproof bag 11, but it is advisable to take appropriate measures such as providing a sealing material at the penetration to ensure watertightness.

[0063] FIG. 12 shows a partial cross section of a waterproofed electronic device in yet another example of a cooling system. This cooling system differs from the cooling system including the waterproofed electronic device 230 shown in FIG. 8 in that a submersible pump 28 is connected to the fluid inlet 23 of each of the multiple cold plates 20 in the waterproofed electronic device 500 and may be disposed on the surface side of the cold plate 20. Like the example shown in FIG. 8, this example does not require the formation of a penetration in the waterproof bag 11, except for the formation of the opening 15 in the waterproof bag 11, and thus has excellent watertightness. Also, like the example shown in FIG. 11, this example does not require the formation of a fluid circulation path from the cooling tank 3 through the coolant return pipe 5b, the fluid return pipe 7c, the heat exchanger 9, the pump 8, the fluid feed pipe 7a, the inlet manifold 27, and back to the fluid inlet 23 of the cold plate 20. Additionally, this example has many advantages over the example in which a submersible pump 29 is connected to each of the multiple cold plates 20.

[0064] FIG. 13 shows the configuration of essential parts of yet another example of a cooling system. This cooling system differs from the cooling system including the waterproofed electronic device 100 shown in FIG. 2 in that, in the waterproofed electronic device 600, the fluid outlet 25 of one of the adjacent cold plates 20 (four cold plates in the illustrated example) is fluidly connected to the fluid inlet 23 of the other cold plate via connecting piping 8. In other words, the multiple cold plates 20 are connected via connecting piping 8. Unlike the example shown in FIG. 2, this example does not require an inlet manifold or an outlet manifold. The fluid feed piping 7b may be fluidly connected to the fluid inlet 23 of the first cold plate of the multiple connected cold plates, and the fluid return piping 7b may be fluidly connected to the fluid outlet 25 of the last cold plate.

[0065] Fig. 14 shows the configuration of the main components of yet another example of a cooling system. This cooling system differs from the cooling system including the waterproof electronic device 600 shown in Fig. 13 in that, in the waterproof electronic device 610, at least one surface of the main body 21 of one cold plate 20 is thermally connected to multiple heat generating elements (four heat generating elements in the illustrated example). In other words, the multiple cold plates in the example of Fig. 13 may be integrated to form a single cold plate.

[0066] Although one example and several other examples of the cooling system have been described above with reference to the drawings, further modifications may be made to the details of the components. For example, with respect to the fluid circulation path, in the example of the cooling system shown in Figure 2, the pump 8 and the heat exchanger 9 are arranged outside the cooling tank 3, but one or both of them may be arranged inside the cooling tank 3 or immersed in the cooling liquid 4. When the pump 8 is immersed in the cooling liquid 4, a submersible pump may be used.

[0067] 11 and 12, multiple submersible pumps 28 are connected to the fluid inlets 23 of the multiple cold plates 20, but this configuration may be modified as follows. That is, as in the example shown in FIG. 9, an inlet manifold 27 may be used, and each outlet of the inlet manifold 27 may be connected to each fluid inlet of the multiple cold plates 20. The submersible pump 28 may then be connected to the inlet of the inlet manifold 27. In this configuration, the submersible pump connected to the inlet of the inlet manifold 27 applies pressure energy to a portion of the coolant, causing the portion of the coolant to pass through the outlets of the inlet manifold 27 and through flow paths formed in the bodies of the multiple cold plates.

[0068] Furthermore, for example, although an example of covering an electronic device with a waterproof bag has been shown as a specific example of waterproofing treatment for an electronic device, other specific examples of waterproofing treatment for an electronic device include covering the electronic device with a parylene thin film (e.g., Non-Patent Document 1), and covering the electronic device with an ultra-nano hydrophobic coating thin film using silicon compound nanoparticles (e.g., Patent Document 5). When an electronic device has a relatively flat structure, including a cold plate, it can be said that such waterproofing treatment is easy to perform.

[0069] 2 , an exemplary configuration of the cooling system 1 will be described in further detail. Two or more waterproofed electronic devices 100 may be immersed in the coolant 4 contained in the cooling tank 3. A top plate 3A may be installed in the cooling tank 3 to reduce evaporation of the coolant 4. Furthermore, the waterproofed electronic device 100 may include, in the waterproof bag 11, a wireless power supply unit (not shown) for supplying power to the electronic device 10, instead of a power cable, and may also include, in the waterproof bag 11, a wireless communication unit (not shown) for enabling wireless communication between the waterproofed electronic device 100 and the outside, instead of a network communication cable.

[0070] The present invention can be widely applied to cooling systems and cooling methods that efficiently cool electronic devices by immersing them in a conductive coolant such as ordinary water, tap water, or seawater.

[0071] 1 Cooling system 3 Cooling tank 3A Top plate 4 Coolant (water) 5a Coolant feed pipe 5b Coolant return pipe 7a Fluid feed pipe 7b, 7c Fluid return pipe 8 Connecting pipe 9 Heat exchanger 10 Electronic device 100, 110, 200, 210, 220, 230, 300, 400, 500 Waterproofed electronic device 11 Waterproof bag 15 Opening 20 Cold plate 21 Cold plate body 23 Fluid inlet (pipe) 25 Fluid outlet (pipe) 27 Inlet manifold 28 Submersible pump 29 Outlet manifold 31 Substrate (PCB) 35 Electronic component 36 Network communication cable 37 Power cable 41 Bonding layer

Claims

1. A cooling system for cooling an electronic device by immersing the electronic device in a coolant, the cooling system comprising: a cooling tank filled with the coolant; a waterproofed electronic device including a substrate and at least one heat-generating body mounted on the substrate, the waterproofed electronic device being covered with a waterproof coating or a waterproof bag; a cold plate including a main body, a fluid inlet, and a fluid outlet, at least one surface of the main body being thermally connected to the at least one heat-generating body, and a part or all of the cold plate being disposed inside or outside the waterproof coating or the waterproof bag; the cold plate; and at least one fluid machine that applies pressure energy from the fluid inlet to the fluid outlet to a fluid passing through a flow path formed in the main body of the cold plate.

2. The cooling system according to claim 1, wherein the coolant is water, the fluid machine is a pump or a submersible pump disposed in a circulation path returning from the fluid outlet of the cold plate to the fluid inlet, and the fluid passing through the flow path formed in the main body of the cold plate is a refrigerant cooled by a heat exchanger in the circulation path.

3. The cooling system according to claim 1, wherein the coolant is water, the fluid machine is a submersible pump connected to the fluid inlet of the cold plate, the fluid passing through the flow path formed in the main body of the cold plate is a part of the coolant, and the submersible pump applies the pressure energy to the part of the coolant.

4. The cooling system according to claim 1, further comprising an inlet-side manifold disposed inside or outside the waterproof coating or the waterproof bag, the electronic device including a plurality of heat-generating bodies and a plurality of cold plates, and each outlet of the inlet-side manifold being fluid-connected to each fluid inlet of the plurality of cold plates.

5. The cooling system further includes an outlet-side manifold disposed inside or outside the waterproof film or the waterproof bag, and each inlet of the outlet-side manifold is fluidly connected to each fluid outlet of the plurality of cold plates. The cooling system according to claim 4.

6. An opening having an area larger than the area of the at least one heating element is formed in the waterproof film or the waterproof bag. When a part or all of the cold plates are disposed outside the waterproof film or the waterproof bag, a region around the opening of the waterproof film or the waterproof bag and at least one surface of the body of the cold plate are watertightly connected, and the surface of the at least one heating element and the at least one surface of the cold plate are thermally connected through the opening of the waterproof film or the waterproof bag. The cooling system according to claim 1.

7. The cooling system according to claim 6, further including a bonding layer that watertightly connects a region around the opening of the waterproof film or the waterproof bag and at least one surface of the cold plate, and the bonding layer is formed of a dissimilar material bonding film, a double-sided adhesive tape, or a waterproof packing.

8. The inlet-side manifold, each body and each fluid inlet of the plurality of cold plates are disposed inside the waterproof film or the waterproof bag, and the openings of each fluid outlet of the plurality of cold plates are disposed outside the waterproof film or the waterproof bag. The cooling system according to claim 4.

9. The inlet-side manifold and the openings of each fluid inlet of the plurality of cold plates are disposed inside the waterproof film or the waterproof bag, and each body and the openings of each fluid outlet of the plurality of cold plates are disposed outside the waterproof film or the waterproof bag. The cooling system according to claim 4.

10. The inlet-side manifold is disposed inside the waterproof film or the waterproof bag, and the openings of the fluid inlets of the plurality of cold plates, each body, and the openings of the fluid outlets are disposed outside the waterproof film or the waterproof bag. The cooling system according to claim 4.

11. The inlet-side manifold and the openings of the fluid inlets of the plurality of cold plates, each body, and the openings of the fluid outlets are disposed outside the waterproof film or the waterproof bag. The cooling system according to claim 4.

12. Each body of the plurality of cold plates is disposed inside the waterproof film or the waterproof bag, and the inlet-side manifold and the openings of the fluid inlets and the openings of the fluid outlets of the plurality of cold plates are disposed outside the waterproof film or the waterproof bag. The cooling system according to claim 4.

13. The cooling system includes a plurality of submersible pumps as the fluid machinery, the electronic device includes a plurality of heat-generating bodies and a plurality of cold plates, the coolant is water, each of the plurality of submersible pumps is connected to the fluid inlet of each of the plurality of cold plates, and the fluid passing through the flow path formed in each body of the plurality of cold plates is a part of the coolant, and each submersible pump applies each pressure energy to a part of the coolant. The cooling system according to claim 1.

14. Each body of the plurality of cold plates is disposed inside the waterproof film or the waterproof bag, and the plurality of submersible pumps and the openings of the fluid inlets and the openings of the fluid outlets of the plurality of cold plates are disposed outside the waterproof film or the waterproof bag. The cooling system according to claim 13.

15. The plurality of submersible pumps and each body, the openings of the fluid inlets, and the openings of the fluid outlets of the plurality of cold plates are disposed outside the waterproof film or the waterproof bag. The cooling system according to claim 13.

16. The cooling system further includes an inlet-side manifold and includes a submersible pump as the fluid machine. The electronic device includes a plurality of heat-generating elements and a plurality of cold plates. The coolant is water. The submersible pump is connected to the inlet of the inlet-side manifold. Each outlet of the inlet-side manifold is in fluid connection with each fluid inlet of the plurality of cold plates. The fluid passing through the flow path formed in each body of the plurality of cold plates is a part of the coolant, and the submersible pump acts on a part of the coolant with pressure energy. The cooling system according to claim 1.

17. Each body of the plurality of cold plates is disposed inside the waterproof coating or the waterproof bag. The submersible pump, the inlet-side manifold, the openings of each fluid inlet and each fluid outlet of the plurality of cold plates are disposed outside the waterproof coating or the waterproof bag. The cooling system according to claim 16.

18. The submersible pump, the inlet-side manifold, each body of the plurality of cold plates, the openings of each fluid inlet and each fluid outlet are disposed outside the waterproof coating or the waterproof bag. The cooling system according to claim 16.

19. The cooling system further includes one or more connecting pipes disposed inside or outside the waterproof coating or the waterproof bag. The electronic device includes a plurality of heat-generating elements and a plurality of cold plates. The fluid outlet of one of the adjacent cold plates of the plurality of cold plates is in fluid connection with the fluid inlet of the other cold plate through the connecting pipe. The cooling system according to claim 1.

20. The electronic device includes a plurality of heat-generating elements. At least one surface of the body of the cold plate is in thermal connection with the plurality of heat-generating elements. The cooling system according to claim 1.

21. A method for cooling an electronic device, comprising: immersing a waterproofed electronic device, which is formed by covering an electronic device including a substrate and at least one heat-generating body mounted on the substrate with a waterproof coating or a waterproof bag, in a cooling tank filled with a coolant to cool the device; and forcibly circulating a fluid through the inside of a cold plate to cool the at least one heat-generating body thermally connected to the cold plate.