Immersion cooling capacitor, method for manufacturing the same, and electronic equipment equipped therewith

Abstract

The present invention provides a liquid immersion cooling capacitor equipped with a highly reliable, long-life sleeve, a method for manufacturing the same, and an electronic device equipped with the liquid immersion cooling capacitor. [Solution] The capacitor 5000, which is immersed and cooled by a refrigerant, comprises a capacitor element 500, an electrolyte and a case 400, a sealing body 200 that seals its opening, and a sleeve 300 that covers a part of the outer surface of the case. The sleeve has information such as the capacitor's characteristics, model number, and polarity identification printed on it, and is made of polyvinyl chloride or polyethylene terephthalate. Preferably, the refrigerant is a hydrocarbon-based immersion cooling refrigerant.

Description

Technical Field

[0001] The present invention relates to a capacitor for immersion cooling, a method for manufacturing the same, and an electronic device including the same.

Background Art

[0002] In recent years, in order to cope with the increase in heat generation accompanying the high density and total power consumption of electronic devices and components such as data centers and supercomputers, it is known that the number of electronic devices using immersion cooling with a refrigerant has been increasing. In immersion cooling, as the name implies, the entire or part of an electronic device such as a circuit board including the capacitor itself is immersed in a refrigerant, and high-efficiency cooling is promoted.

[0003] In addition, in various capacitors typified by aluminum electrolytic capacitors, it is not uncommon for a sleeve, which is a resinous coating material, to be attached to an exterior case (for example, an aluminum case) that houses capacitor elements and electrolytes. It is common for various symbol numbers, product types, electrical characteristics of capacitors, lot numbers, etc. to be printed on the sleeve.

[0004] In Patent Document 1 below, for the purpose of providing a method for manufacturing an electrolytic capacitor that can release the air accumulated between the exterior case and the sleeve of the electrolytic capacitor to the outside and suppress the rise of the sleeve end and the swelling wrinkles on the sleeve surface, in a method for manufacturing an electrolytic capacitor produced by covering a bottomed cylindrical exterior case 2 in which a constriction groove 5 is formed with an insulating sleeve 11 by heat shrinkage, 1) at least one air hole 10 having a circle with a diameter of 0.01 to 1.0 mm or a shape corresponding to this area is formed in the sleeve 11, 2) the sleeve 11 in which the air hole 10 is formed is placed on the exterior case 2, and 3) the sleeve 11 placed on the exterior case 2 is heat-shrunk to cover the sleeve 11 on the exterior case 2.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-205411 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] If the resin sleeve, which is the outer casing material of a liquid immersion cooling condenser, is continuously immersed in the refrigerant used in liquid immersion cooling for an extended period, the sleeve may deform, causing a portion of the sleeve to lift up, potentially allowing refrigerant to enter between the outer casing and the sleeve, or even causing the sleeve to detach.

[0007] Generally, important information such as the capacitor's characteristics, product model number, and terminal polarity is printed on the sleeve. If the sleeve detaches from the capacitor, it becomes impossible to determine the capacitor's characteristics, product model number, and polarity, which raises concerns about significant problems in maintenance, repair, and regular replacement of parts.

[0008] Furthermore, even if the sleeve does not detach from the outer case, there is a concern that deformation of the sleeve could cause the ink printed on it to peel off or fade, potentially leading to the same problems described above.

[0009] The present invention has been made in view of the above-mentioned problems, and aims to provide a liquid immersion cooling capacitor equipped with a highly reliable and long-life sleeve, a method for manufacturing the same, and an electronic device equipped with the same. [Means for solving the problem]

[0010] The present invention relates to an immersion cooling capacitor which is cooled by immersion with a refrigerant, and comprises a capacitor element, an electrolyte, a case housing the capacitor element and the electrolyte, a sealing body that seals the opening of the case, and a sleeve that covers at least a part of the outer surface of the case, wherein the sleeve is made of polyvinyl chloride or polyethylene terephthalate.

[0011] Furthermore, the immersion cooling condenser of the present invention is preferably characterized in that the refrigerant is a hydrocarbon-based immersion cooling refrigerant.

[0012] Furthermore, the present invention relates to a method for manufacturing an immersion cooling capacitor, which is subjected to immersion cooling using a refrigerant and comprises a capacitor element, an electrolyte, a case for housing the capacitor element and the electrolyte, and a sealing body for sealing the opening of the case, characterized in that the method comprises the steps of housing the capacitor element and the electrolyte in the case and sealing the opening with the sealing body, and covering at least a part of the outer surface of the sealed case with a sleeve made of polyvinyl chloride or polyethylene terephthalate.

[0013] Furthermore, the present invention's method for manufacturing an immersion cooling condenser is preferably characterized in that the refrigerant is a hydrocarbon-based immersion cooling refrigerant.

[0014] Furthermore, the electronic device of the present invention comprises a housing, a circuit board equipped with at least an immersion cooling capacitor disposed inside the housing, and an electronic device in which a hydrocarbon-based immersion cooling refrigerant is filled inside the housing, wherein the immersion cooling capacitor is disposed in a state of being immersed in the hydrocarbon-based immersion cooling refrigerant, and the immersion cooling capacitor comprises an immersion cooling capacitor as described above. The sealing body may be a sealing rubber or a sealing plate made of phenolic resin, or any other material and shape suitable for sealing and enclosing the capacitor may be used. [Effects of the Invention]

[0015] We can provide a liquid immersion cooling capacitor with a highly reliable, long-life sleeve, a method for manufacturing the same, and electronic equipment equipped with the same. [Brief explanation of the drawing]

[0016] [Figure 1](a) is a schematic diagram illustrating the experimental setup of this embodiment, and (b) is a diagram illustrating the type of sleeve used in the experiment and the temperature conditions of the hydrocarbon-based immersion cooling refrigerant. [Figure 2] (a) is a diagram illustrating the outline of the observation method used to check the external condition after 2000 hours, (b) is a diagram showing the results of measuring and calculating the height difference h between the maximum and minimum heights within the space between A and B at both ends of the captured image, (c) is a graph plotting all the data from Figure 2(b), and (d) is a graph plotting the average values ​​of A, B, and C for each capacitor in Figure 2(b). [Figure 3] This table shows the observation results of the printing condition on the sleeve surface after immersion in a hydrocarbon-based immersion cooling refrigerant for 2000 hours. [Figure 4] This is a schematic diagram illustrating the sleeve of the present invention and its surrounding configuration in a liquid immersion cooling capacitor. [Modes for carrying out the invention]

[0017] Generally, a capacitor sleeve is an insulating material that covers the outside of the capacitor case and is known to have all or part of the functions of indicating polarity and other characteristics and electrical characteristics.

[0018] Furthermore, the polarity (+ or -) of capacitors is often printed on the sleeve, serving as an indicator to confirm correct connections during assembly or maintenance / replacement.

[0019] On the other hand, while fluorine-based refrigerants have been the mainstream choice for immersion cooling, their high cost and environmental pollution concerns are expected to lead to a further increase in demand for silicon-based and hydrocarbon-based immersion cooling refrigerants in the future.

[0020] Examples of hydrocarbon-based refrigerants for liquid immersion cooling include petroleum-based hydrocarbons such as paraffinic mineral oils and naphthenic mineral oils; synthetic oils such as poly-α-olefins (PAOs) and synthetic petroleum obtained by Fischer-Tropsch synthesis; and bio-oils; and the like. Among these, the hydrocarbon-based refrigerant for liquid immersion cooling is preferably one or more selected from synthetic oils, more preferably one or more selected from synthetic petroleum, and even more preferably poly-α-olefins (PAOs) or synthetic petroleum obtained by Fischer-Tropsch synthesis. In the present disclosure, "poly-α-olefins (PAOs)" are those obtained by hydrogenating the terminal double bonds of α-olefin polymers. The poly-α-olefin is preferably a homopolymer or copolymer of α-olefins having 2 or more and 32 or less carbon atoms, more preferably a homopolymer or copolymer of α-olefins having 6 or more and 16 or less carbon atoms, and even more preferably a homopolymer or copolymer of one or more α-olefins selected from the group consisting of α-octene, 1-decene, 1-dodecene, and 1-tetradecene, and particularly preferably a homopolymer of 1-decene. The degree of polymerization of the poly-α-olefin is preferably 2 or more, more preferably 3 or more, and also preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less. That is, examples of the preferred range of the degree of polymerization of the poly-α-olefin include ranges such as 2 or more and 10 or less, 2 or more and 8 or less, and 3 or more and 5 or less. The number of carbon atoms of the poly-α-olefin is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more, and also preferably 80 or less, more preferably 70 or less, and even more preferably 60 or less. That is, examples of the preferred range of the number of carbon atoms of the poly-α-olefin include ranges such as 10 or more and 80 or less, 20 or more and 70 or less, and 30 or more and 60 or less.

[0021] In addition, the petroleum-based hydrocarbon and the synthetic petroleum are preferably a mixture of hydrocarbons having 15 or more and 50 or less carbon atoms, and more preferably a mixture of hydrocarbons having 18 or more and 50 or less carbon atoms. Each hydrocarbon may be any of a linear hydrocarbon, a branched hydrocarbon, and a cyclic hydrocarbon, but is preferably a linear hydrocarbon or a branched hydrocarbon.

[0022] In addition, the hydrocarbon-based liquid immersion cooling refrigerant is preferably a fluorine-free hydrocarbon, and more preferably a petroleum-based hydrocarbon. In the present disclosure, the "fluorine-free hydrocarbon" may be a hydrocarbon that does not contain any fluorine, or a hydrocarbon that unavoidably contains fluorine as an impurity.

[0023] Examples of the silicone oil include polysiloxanes such as polydimethylsiloxane and polymethylphenylsiloxane.

[0024] In addition, the coolant may be used alone, or two or more kinds may be used in combination at an arbitrary combination and ratio.

[0025] In addition, the coolant is preferably insulating. Further, in terms of not inhibiting the gigahertz band wireless communication, the relative permittivity of the coolant is preferably 3.0 or less, and more preferably 2.5 or less.

[0026] However, when the substrate is immersed in the hydrocarbon-based liquid immersion cooling refrigerant, the sleeve attached to the capacitor is likely to be affected by the hydrocarbon-based refrigerant, and it has been found that the sleeve expands.

[0027] The expanded sleeve may detach from the outer case of the capacitor. In server applications, maintenance is performed regularly. At this time, since the sleeve detaches from the capacitor, the electrical characteristics of the capacitor are unknown, which causes complexity.

[0028] Therefore, in capacitors with immersion cooling, it is necessary to use a sleeve that has suitable resistance for hydrocarbon-based immersion cooling refrigerants as the sleeve that comes into contact with the immersion cooling refrigerant. Furthermore, there is a risk that a detached sleeve may affect other electronic components. The present invention aims to provide a capacitor that can be applied to immersion cooling systems that typically use hydrocarbon-based immersion cooling refrigerants.

[0029] Figure 4 illustrates the capacitor sleeve 300 of the present invention in a liquid immersion cooling capacitor 5000. The materials, material structure, and composition ratios of the capacitor described below are typical examples and are not limited to those described here, except for the technical features of the sleeve.

[0030] Capacitor 5000 is an example of an electronic component, such as an immersion cooling capacitor. Capacitor 5000 includes a capacitor element 500, terminals, an outer casing 400, a sealing body 200, and a sleeve 300. The terminals are connected to the capacitor element 500 and protrude from one end face of the capacitor element 500. Part of the capacitor element 500 and the terminals are inserted into the outer casing 400. The sealing body 200 is placed in the opening of the outer casing 400, sealing the inside of the outer casing 400. In other words, part of the capacitor element 500 and the terminals are sealed inside the outer casing 400. The terminals penetrate the sealing body 200 and protrude from the sealing body 200 as lead wires 600, including a lead wire 700.

[0031] The capacitor element 500 includes an anode foil 510, a cathode foil 520, a separator 530, and an electrolyte (not shown). The anode foil 510 and the cathode foil 520 are connected to different terminals (lead wires 600 and 100 in Figure 4). The anode foil 510, cathode foil 520, and separator 530 are stacked and wound together so that the separator 530 is positioned between the anode foil 510 and the cathode foil 520, forming a wound element. This wound element forms the capacitor element 500. The capacitor may also be of the multilayer type. In a multilayer capacitor, flat anode foils and cathode foils are stacked alternately with a separator in between. Then, an electrolyte is impregnated into this multilayer to form a capacitor element comprising an anode, a cathode, a separator, and an electrolyte.

[0032] Furthermore, the voids within the capacitor element 500 and the separator 530 are filled with or impregnated with an electrolyte. The electrolyte may be a liquid electrolyte or a gel electrolyte, or it may contain both a liquid electrolyte and a gel electrolyte, or it may contain both a liquid electrolyte or a gel electrolyte and a solid electrolyte. The solid electrolyte may include, for example, a conductive polymer. If the liquid electrolyte is gelled, and the gel electrolyte layer electrically isolates the anode foil and the cathode foil, and the gel electrolyte can maintain its shape on its own, the separator 530 may be excluded from the configuration of the capacitor 5000.

[0033] Furthermore, the anode foil 510 constitutes the anode electrode of the capacitor 5000. The anode foil 510 is, for example, a valve-acting metal foil such as tantalum foil or aluminum foil, and is, for example, a strip-shaped foil. The anode foil 510 is formed by etching, depositing valve-acting metal powder onto the surface of a rolled metal foil, or forming valve-acting metal powder onto the surface of a rolled metal foil and sintering it, and an expanding layer is formed on its surface. That is, the anode foil 510 may be a powder laminated foil with an expanding layer of a powder layer formed by aggregating valve-acting metal powder, or an etched foil with an etched surface on a stretched foil. That is, the expanding layer consists of tunnel-shaped pits, sponge-like pits, or voids between densely packed powder particles. A dielectric film is formed on the surface of the expanding layer.

[0034] Furthermore, tunnel-shaped etching pits are holes carved in the direction of the foil thickness. These tunnel-shaped etching pits are typically formed by passing a direct current through an acidic aqueous solution containing halogen ions, such as hydrochloric acid. The tunnel-shaped etching pits can be further expanded by passing a direct current through an acidic aqueous solution containing halogen ions, such as nitric acid. Sponge-like etching pits form a sponge-like layer consisting of a series of fine voids. These sponge-like etching pits are formed by passing an alternating current through an acidic aqueous solution containing halogen ions, such as hydrochloric acid.

[0035] Furthermore, the powder is a valve metal powder of the same or different type as the foil. This powder is obtained by methods such as grinding, atomization, melt spinning, rotating disk method, and rotating electrode method. The atomization method can be water atomization, gas atomization, or water-gas atomization. When the powder layer is formed by sintering, it is made by pasteuring with a binder and solvent, applying it to the foil and drying it, and then heating and sintering it in a vacuum or reducing atmosphere. When the powder layer is formed by vapor deposition, this powder layer is made by methods such as resistance heating vapor deposition or electron beam heating vapor deposition. That is, the powder layer formed by vapor deposition is created by heating a valve metal of the same or different type as the foil using resistance heat or electron beam energy to evaporate it, and depositing the vapor of valve metal particles onto the surface of the foil.

[0036] Furthermore, the dielectric film is formed on the uneven surface of the expanded layer. Typically, the dielectric film is an oxide film formed on the uneven surface of the expanded layer, and if the anode foil is made of aluminum, it is an aluminum oxide layer obtained by oxidizing the uneven surface of the expanded layer. In the chemical conversion treatment to form the dielectric film, a voltage is applied to the anode foil in the chemical conversion solution to achieve a desired withstand voltage. The chemical conversion solution is a halogen ion-free solution, such as a phosphoric acid-based chemical conversion solution such as ammonium dihydrogen phosphate, a boric acid-based chemical conversion solution such as ammonium borate, or an adipic acid-based chemical conversion solution such as ammonium adipate. In the chemical conversion treatment to form the dielectric film, it is preferable to form a dielectric film with a thickness of 0.9 to 1.5 nm in order to obtain a withstand voltage of 1 V.

[0037] Furthermore, the cathode foil 520 constitutes the cathode electrode of the capacitor 5000. The cathode foil 520, like the anode foil 510, is formed by expanding a base foil made of the valve metal described above. It is formed on a base foil selected from the valve metals described above. The etching process of the base foil is the same as in the case of the anode foil 510, so the explanation is omitted. An oxide film is formed on the expanded layer of the cathode foil 520. This oxide film may be intentionally formed or may occur naturally (spontaneous oxide film). The oxide film is formed by a chemical conversion treatment in which a voltage is applied in a halogen ion-free solution such as an aqueous solution of adipic acid or boric acid, and is a thin oxide film of about 1 to 10 V. The spontaneous oxide film is a thin oxide film formed by the reaction of the cathode foil with oxygen in the air.

[0038] Furthermore, the cathode foil 520 may also be a carbon foil in which a carbon layer is laminated onto a base foil. The carbon layer is laminated onto one side or both sides of the surface-expanded base foil. In other words, the carbon layer penetrates the etching layer and engages with the base foil, reinforcing the base foil in addition to its function as a cathode. This carbon layer is composed, for example, of a carbon material as the main material and a binder and dispersant as additives. The carbon material can be activated carbon, carbon black, carbon nanohorns, amorphous carbon, natural graphite, artificial carbon, graphitized Ketjenblack, mesoporous carbon, fibrous carbon, etc. Activated carbon can be produced, for example, from natural plant tissue such as coconut shells, synthetic resins such as phenol, or fossil fuels such as coal, coke, or pitch.

[0039] Carbon black includes Ketjenblack, acetylene black, channel black, or thermal black. Fibrous carbon includes carbon nanotubes and carbon nanofibers. Carbon nanotubes may be single-walled carbon nanotubes, which consist of a single layer of graphene sheet, or multi-walled carbon nanotubes (MWCNTs), which consist of two or more layers of graphene sheet rolled coaxially to form a multi-layered tube wall. The binder may be a resin-based binder such as styrene-butadiene rubber, polyvinylidene fluoride, or polytetrafluoroethylene, which is bonded to the carbon material. For the dispersant, sodium carboxymethylcellulose may be used, for example.

[0040] The separator 530 is an insulating material and may include kraft, as well as any other separator material such as Manila hemp, esparto, hemp, rayon, cellulose, or mixtures thereof.

[0041] The terminals are made of a conductive metal, such as aluminum. The terminals are, for example, lead wires 600, 100 and tab terminals. The lead terminals 600, 100 include a lead wire 700 made of metal wire and a terminal portion. The lead wire 700 is connected to the terminal portion by, for example, arc welding. The terminal portion comprises a roughly cylindrical round bar portion 900 and a flattened portion 950 formed by, for example, press working. The round bar portion 900 has an inclined portion on the side of the flattened portion 950, where the thickness decreases linearly to the thickness of the flattened portion 950. The tab terminal also includes a flat portion made of, for example, a thin strip of metal foil. One end of the tab terminal is connected to an external terminal attached to the sealing body. The lead terminals 600, 100 and tab terminals are electrically connected to the anode foil 510 and cathode foil 520 by, for example, cold pressure welding or stitch connection.

[0042] The sealing body 200 is made of, for example, insulating rubber. The sealing body 200 has through holes at positions corresponding to the lead terminals 600 and 100. The lead terminals 600 and 100 of the capacitor element 500 pass through the through holes in the sealing body 200 and are exposed to the outside of the capacitor 5000. When tab terminals are used as terminals, the sealing body may be, for example, a phenolic laminate with external terminals attached. The external terminals attached to the phenolic laminate are connected to one end of the tab terminals protruding from the capacitor element.

[0043] The electrolyte can be a liquid electrolyte, a gel electrolyte, or a solid electrolyte containing a conductive polymer. The electrolyte may also consist of a liquid electrolyte or a gel electrolyte and a solid electrolyte, forming a so-called hybrid electrolytic capacitor.

[0044] The electrolyte comprises a solvent and a solute dissolved in the solvent, and may further contain additives. The solvent may be either a protic polar solvent or an aprotic polar solvent. Examples of protic polar solvents include monohydric alcohols, polyhydric alcohols, oxyalcohol compounds, and water. Examples of aprotic polar solvents include sulfones, amides, lactones, cyclic amides, nitriles, and oxides. The solute comprises anionic and cationic components and is typically an organic acid or its salt, an inorganic acid or its salt, or a complex compound of an organic acid and an inorganic acid or an ionically dissociable salt thereof, and is used alone or in combination of two or more. The anionic acid and the cationic base may be added separately to the electrolyte as solute components.

[0045] The solid electrolyte has, for example, an electrolyte layer containing a conductive polymer. The conductive polymer is a conjugated polymer or a doped conjugated polymer. The conjugated polymer is a known conjugated polymer such as polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene, with poly(3,4-ethylenedioxythiophene) being preferred. The conjugated polymer may be a single conjugated polymer, a composite conjugated polymer, or a copolymer of two or more monomers.

[0046] The outer casing 400 is, for example, a bottomed cylindrical aluminum case. A sleeve 300 made of, for example, polyvinyl chloride or polyethylene terephthalate is fitted to the outside of the outer casing 400.

[0047] [Capacitor manufacturing process] When manufacturing a capacitor element 500 as shown in Figure 4(a), first, lead wires 600 and 100 to be attached to the anode foil 510 and cathode foil 520 are formed, as shown in Figure 4(b). Specifically, a terminal portion consisting of a round bar portion 900 and a flat portion 950 is welded to a lead wire 700 made of, for example, a CP wire with copper formed around an iron wire to form the lead terminals 600 and 100.

[0048] Then, the surface of the lead wire 700 is plated with tin, for example. In the following, the welded portion between the terminal portion and the lead wire 700 is referred to as the lead weld portion 800. As for the welding method for the lead weld portion 800, for example, a method can be used in which the round bar portion 900 and the lead wire 700 are butted together, a high temperature is created by spark discharge or the like, and both ends of the round bar portion 900 and the lead wire 700 are melted and joined.

[0049] Next, as shown in Figure 4(b), the flattened portions 950 of the lead terminals 600 and 100 formed as described above are joined to the anode foil 510 and the cathode foil 520, respectively. Then, a separator 530 is interposed between the anode foil 510 and the cathode foil 520 and the wire is wound to fabricate the capacitor element 500.

[0050] Furthermore, the capacitor element 500 is impregnated with an electrolyte solution in which ethylene glycol is the main solvent.

[0051] Subsequently, as shown in Figure 4(a), the round rod portions 900 of the lead wires 600 and 100 of the capacitor element 500 are inserted into through holes formed in a sealing body 200 made of, for example, EPT rubber. Then, the capacitor element 500 is housed in a bottomed cylindrical outer case 400 made of, for example, aluminum. The open end of the outer case 400 is then sealed by drawing, and a sleeve 300 made of, for example, polyvinyl chloride or polyethylene terephthalate is attached to the outside of the outer case 400 to complete the capacitor.

[0052] Furthermore, the sleeve 300 is typically attached to the outside of the outer casing 400 as follows: The tubular sleeve 300 is cut to a predetermined length and placed over the surface of the capacitor's outer casing 400. In this case, the diameter of the sleeve 300 is made larger than the diameter of the outer casing 400. Then, the capacitor with the sleeve 300 attached is heated. As a result, the sleeve 300 shrinks due to the heat and adheres tightly to the outer surface of the outer casing 400.

[0053] [Electronic equipment] A circuit board containing capacitors 5000, each fitted with a polyvinyl chloride or polyethylene terephthalate sleeve 300, along with other electronic components, is placed inside an electronic device enclosure filled with a hydrocarbon-based immersion cooling refrigerant.

[0054] As described above, the present invention is characterized by the use of a sleeve 300 made of polyvinyl chloride or polyethylene terephthalate. Using a sleeve 300 made of polyvinyl chloride or polyethylene terephthalate improves resistance to refrigerants used for immersion cooling, and in particular significantly improves durability against hydrocarbon-based refrigerants. The experimental results are described below.

[0055] (Examples) In this embodiment, durability tests were conducted against hydrocarbon-based immersion cooling refrigerants for capacitors according to Examples 1 to 4 and Comparative Examples 1 and 2, which are substrate-free capacitors equipped with three types of sleeves made of polyethylene terephthalate, polyvinyl chloride, and polyolefin.

[0056] The capacitors in Examples 1 to 4 and the capacitors in Comparative Examples 1 and 2 all used the same type of self-supporting, circuit board-mounted capacitor with dimensions of φ30 mm × height 60 mm, differing only in the material of the outer sleeve.

[0057] The capacitor element of the same type of capacitor is a wound element including a wound anode foil, cathode foil, and separator. The anode foil is an aluminum foil with tunnel pits and a dielectric film on its surface. The cathode foil is, for example, an etched aluminum foil. The separator is kraft paper. In the capacitor element, an insulator separator is placed between the anode foil and the cathode foil, insulating the anode foil and cathode foil from each other. The capacitor element has two tab terminals protruding from one end face of the wound element, and these two tab terminals are each connected to two external terminals of a sealing body, which is connected to the capacitor element. The two tab terminals extend from the anode foil and cathode foil of the wound element, respectively. An electrolyte mainly composed of ethylene glycol was used as the electrolyte. A plate with a paper phenol layer and a rubber layer was used as the sealing plate. Other details of the internal structure, configuration, and manufacturing method of the capacitor itself are known, so they are omitted from this explanation.

[0058] Examples 1 and 3 consisted of capacitors with polyethylene terephthalate (PET) sleeves attached to the capacitor's outer casing, while Examples 2 and 4 consisted of capacitors with polyvinyl chloride (PVC) sleeves attached to the capacitor's outer casing. Comparative Examples 1 and 2 consisted of capacitors with polyolefin (PO) sleeves attached to the capacitor's outer casing.

[0059] As shown in Figure 1(a), the capacitors 1000 according to Examples 1 to 4 and Comparative Examples 1 and 2 were immersed in a liquid immersion cooling refrigerant 2000 filled in a sealed container 3000. As shown in Figure 1(b), the presence or absence of sleeve lifting or peeling over time was observed for Examples 1 to 4 and Comparative Examples 1 and 2 under two temperature conditions: when the liquid immersion cooling refrigerant 2000 was set to 70°C and when it was set to 80°C.

[0060] Furthermore, the sealed container 3000 shown in Figure 1(a) was made of heat-resistant glass, and a hydrocarbon-based immersion cooling refrigerant 2000 was used as the immersion cooling refrigerant. The appearance and printing condition were checked after 2000 hours when the hydrocarbon-based immersion cooling refrigerant 2000 was maintained at 70°C and when it was maintained at 80°C.

[0061] Figure 2(a) is a diagram illustrating the outline of the observation method used to confirm the external appearance after 2000 hours. First, three randomly selected locations on the side (outer surface of the sleeve) of the capacitors in Examples 1 to 4 and Comparative Examples 1 and 2, after being immersed in a hydrocarbon-based immersion cooling refrigerant 2000 for 2000 hours, were photographed.

[0062] Next, shape correction was applied to each captured image to flatten it. In other words, since the side surface of the capacitor captured in the photograph is part of the curved surface that forms the side of the cylindrical shape, the shape processing was then performed electronically to flatten it in order to understand the height differences caused by lifting or peeling of the sleeve, etc.

[0063] Subsequently, height measurements were performed on the flattened image, and the height difference h (the maximum difference in the distance the sleeve floats from the case) was measured, as shown in Figure 2(a). A and B in Figure 2(a) indicate the range of the capacitor height. Here, the height difference h is calculated as the difference between the maximum height and the minimum height within the space between A and B at both ends of the captured image.

[0064] Furthermore, to measure this height difference h, a one-shot 3D shape measuring machine VR6200 (manufactured by Keyence Corporation) was used. The measurement conditions were set to measure the entire area (18 cm vertically x 24 cm horizontally), with a magnification of 12x, and correction was performed using autofocus (AF). Shape correction was set to perform cylindrical correction using surface shape correction.

[0065] The measurement results of the height difference h obtained in this manner are shown in Figure 2(b). The measurement locations A, B, and C for the height difference h in the capacitors of Examples 1 to 4 and Comparative Examples 1 and 2 in Figure 2(b) are locations that were randomly and independently selected separately in each capacitor, as described above. In the figure, PET indicates a sleeve made of polyethylene terephthalate, PVC indicates a sleeve made of polyvinyl chloride, and PO indicates a sleeve made of polyolefin.

[0066] The graphs shown in Figures 2(c) and 2(d) are plots of the height difference h data shown in Figure 2(b). Figure 2(c) is a graph plotting all the data from Figure 2(b), and Figure 2(d) is a graph plotting the average values ​​of A, B, and C for each capacitor in Figure 2(b).

[0067] As can be seen from the results shown in Figures 2(b), 2(c), and 2(d), when capacitors according to Examples 1 to 4 using PET or PVC sleeves were used, there was almost no change in appearance and almost no height difference h occurred even when immersed in a hydrocarbon-based liquid immersion cooling refrigerant 2000 at a high temperature of 70°C or 80°C for 2000 hours. The absence of a height difference h indicates that the sleeve in the capacitor did not deform, and there was almost no lifting or peeling of the sleeve from the outer case. In other words, it can be seen that capacitors with polyethylene terephthalate or polyvinyl chloride sleeves are less prone to peeling even when cooled by liquid immersion cooling with a hydrocarbon-based liquid immersion cooling refrigerant.

[0068] On the other hand, when capacitors according to Comparative Examples 1 and 2, which use polyolefin sleeves, were immersed in hydrocarbon-based immersion cooling refrigerant 2000 at high temperatures of 70°C or 80°C for 2000 hours, a significant change in appearance occurred. Not only was the height difference h large overall and on average, but the variation in height difference h among individual capacitors was also remarkably large. The occurrence of a large height difference h suggests that the sleeve in that capacitor was significantly deformed, and that significant lifting or delamination of the sleeve from the outer casing occurred. In other words, it can be understood that capacitors with polyolefin sleeves are relatively prone to delamination when cooled by immersion cooling with hydrocarbon-based immersion cooling refrigerants.

[0069] Furthermore, the characters printed on the outer surface of the condenser sleeves of Examples 1 to 4 and Comparative Examples 1 and 2 after immersion in hydrocarbon-based immersion cooling refrigerant 2000 at a high temperature of 70°C or 80°C for 2000 hours were also observed and compared. Figure 3 is a table showing the observation results of the printing state on the sleeve surface after immersion in hydrocarbon-based immersion cooling refrigerant 2000 for 2000 hours. In the figure, PET indicates a polyethylene terephthalate sleeve, PVC indicates a polyvinyl chloride sleeve, and PO indicates a polyolefin sleeve.

[0070] In Figure 3, Comparative Examples 1 and 2, which were capacitors fitted with polyolefin sleeves, showed blurring of the printed characters on the sleeve surface at both 70°C and 80°C. On the other hand, in Examples 1 to 4, which were fitted with polyethylene terephthalate and polyvinyl chloride sleeves, no blurring of the printed characters on the sleeves was observed at any temperature. This indicates that polyethylene terephthalate and polyvinyl chloride sleeves are remarkably suitable for capacitors used in liquid immersion cooling, particularly those using hydrocarbon-based refrigerants, and possess remarkable durability and practicality that exceeds initial expectations.

[0071] The capacitors, electronic components, immersion cooling, and their manufacturing, molding, structure, and configuration described above are not limited to the specific descriptions illustrating numerical values, structures, configurations, and procedures in the examples, but are broadly applicable to any electronic components, and the structure, materials, process content, sequence, and procedures can be appropriately changed, arranged, and modified within the scope of the technical concept of the present invention, which is obvious to those skilled in the art. [Industrial applicability]

[0072] This invention is suitable for various capacitors and other electronic components protected by an outer sleeve. [Explanation of Symbols]

[0073] 100... Lead wire, 200... Sealing body, 300... Sleeve, 400... Case, 500... Capacitor element, 600... Lead wire, 700... Lead wire, 800... Lead weld, 900... Round bar, 1000... Capacitor, 2000... Hydrocarbon-based immersion coolant, 3000... Sealed container, 5000... Capacitor.

Claims

1. A liquid-immersion cooled condenser that is cooled by liquid immersion with a refrigerant, The device comprises a capacitor element, an electrolyte, a case housing the capacitor element and the electrolyte, a sealing body sealing the opening of the case, and a sleeve covering at least a portion of the outer surface of the case. The sleeve is formed of polyvinyl chloride or polyethylene terephthalate. A liquid immersion cooling capacitor characterized by the following features.

2. In the immersion cooling capacitor according to claim 1, The aforementioned refrigerant is a hydrocarbon-based refrigerant for immersion cooling. A liquid immersion cooling capacitor characterized by the following features.

3. A method for manufacturing a liquid immersion cooling capacitor, comprising a capacitor element, an electrolyte, a case housing the capacitor element and the electrolyte, and a sealing body sealing the opening of the case, wherein the capacitor is subjected to liquid immersion cooling using a refrigerant, A step of housing the capacitor element and the electrolyte in the case and sealing the opening with the sealing body, The process includes the step of covering at least a portion of the outer surface of the sealed case with a sleeve made of polyvinyl chloride or polyethylene terephthalate. A method for manufacturing an immersion cooling capacitor, characterized by the following features.

4. In the method for manufacturing an immersion cooling capacitor according to claim 3, The aforementioned refrigerant is a hydrocarbon-based refrigerant for immersion cooling. A method for manufacturing an immersion cooling capacitor, characterized by the following:

5. The casing and A circuit board equipped with at least an immersion cooling capacitor is disposed inside the aforementioned housing, An electronic device in which a hydrocarbon-based immersion cooling refrigerant is filled inside the aforementioned enclosure, The immersion cooling condenser is positioned immersed in the hydrocarbon-based immersion cooling refrigerant. The immersion cooling capacitor is the immersion cooling capacitor described in claim 1 or claim 2. An electronic device characterized by the following features.

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