Liquid immersion cooling device

Abstract

Provided is a liquid immersion cooling device in which deterioration of a first resin layer of an electronic member due to a coolant is suppressed.　A liquid immersion cooling device according to the present invention comprises: a coolant; a container that internally has the coolant; and an electronic member that is at least partially in contact with the coolant in the container. At least a part of the surface of the electronic member has a first resin layer which contains at least one substance that is selected from the group consisting of a vinyl chloride resin, an epoxy resin, a polyimide resin, a silicone resin, an olefin resin, an ethylene propylene diene rubber, an ethylene vinyl acetate copolymer, and a polyester resin. A second resin layer which contains at least one resin that is selected from the group consisting of a fluorine-containing resin and a (meth)acrylic resin is disposed on at least a part of the surface of the first resin layer.

Description

liquid immersion cooling device

[0001] The present invention relates to an immersion cooling device.

[0002] Air cooling, immersion cooling, and the like are known as methods for cooling electronic components that constitute servers, supercomputers, etc., and in recent years, immersion cooling has attracted attention due to its excellent cooling efficiency. Patent Document 1 discloses a method for cooling a substrate placed in a container with a coolant using an immersion cooling device that includes a container that stores a coolant therein, a pump unit that includes a heat exchanger and a liquid pump, and a cooling device that includes a fan.

[0003] JP 2023-000068 A

[0004] The present inventors have found that when an immersion cooling apparatus such as that described in Patent Document 1 is used, the resin layer of the electronic component may be deteriorated by the coolant. Such deterioration of the resin layer of the electronic component may lead to damage to the electronic component itself.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an immersion cooling device in which deterioration of the resin layer of an electronic component due to a coolant is suppressed.

[0006] As a result of intensive research into the above-mentioned problems, the present inventors have found that by disposing a second resin layer containing at least one resin selected from the group consisting of a fluorine-containing resin and a (meth)acrylic resin on a first resin layer of an electronic component, deterioration of the resin layer of the electronic component due to a coolant can be suppressed, and have arrived at the present invention.

[0007] That is, the inventors have found that the above-mentioned problems can be solved by the following configuration. [1] An immersion cooling apparatus including a coolant, a container containing the coolant, and an electronic component at least a portion of which is in contact with the coolant in the container, wherein at least a portion of the surface of the electronic component has a first resin layer containing at least one resin selected from the group consisting of vinyl chloride resin, epoxy resin, polyimide resin, silicone resin, olefin resin, ethylene propylene diene rubber, ethylene vinyl acetate copolymer, and polyester resin, and a second resin layer containing at least one resin selected from the group consisting of fluorine-containing resin and (meth)acrylic resin is disposed on at least a portion of the surface of the first resin layer. [2] The immersion cooling apparatus according to [1], wherein the second resin layer contains the fluorine-containing resin. [3] The immersion cooling apparatus according to [1] or [2], wherein the electronic component includes a component selected from the group consisting of a printed circuit board and a cable, and at least a portion of the surface of the component is constituted by the first resin layer. [4] The immersion cooling apparatus according to any one of [1] to [3], wherein the fluororesin contains units based on a fluoroolefin. [5] The immersion cooling apparatus according to any one of [1] to [4], wherein the fluororesin contains units based on chlorotrifluoroethylene and units based on a vinyl ether. [6] The immersion cooling apparatus according to any one of [1] to [5], wherein the second resin layer has a thickness of 50 nm to 100 μm. [7] The immersion cooling apparatus according to any one of [1] to [6], wherein the coolant has a normal boiling point of 45 to 450°C. [8] The immersion cooling apparatus according to any one of [1] to [7], wherein the coolant is at least one selected from the group consisting of fluorine-containing compounds and hydrocarbon compounds. [9] The immersion cooling apparatus according to any one of [1] to [8], wherein the coolant has a GWP of 0 to 7500.

[0008] According to the present invention, it is possible to provide an immersion cooling device in which deterioration of the resin layer of an electronic component due to a coolant is suppressed.

[0009] 1 is a schematic diagram illustrating an embodiment of an immersion cooling apparatus of the present invention.

[0010] The meanings of terms used in the present invention are as follows. A numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits. In the numerical ranges described in this specification in stages, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another staged numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the Examples. In this specification, each component may be used alone or in combination with two or more substances corresponding to the component. Here, when two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. A unit is a collective term for an atomic group based on one molecule of the above-mentioned monomer that is formed directly by polymerization of the monomer, and an atomic group obtained by chemically converting a portion of the above-mentioned atomic group. The content (mol %) of each unit relative to the total units contained in the resin can be determined by analyzing the resin using nuclear magnetic resonance spectroscopy, and can also be determined from the amounts of components used in producing the resin. (Meth)acrylic resin is a general term for acrylic resin and methacrylic resin. The thickness of the second resin layer is a value measured using a probe-type film thickness gauge (SWT9300, manufactured by Sanko Electronics Research Institute).

[0011] The immersion cooling apparatus of the present invention includes a coolant, a container containing the coolant, and an electronic component at least a portion of which is in contact with the coolant within the container. At least a portion of the surface of the electronic component has a first resin layer containing at least one resin selected from the group consisting of vinyl chloride resin, epoxy resin, polyimide resin, silicone resin, olefin resin, ethylene propylene diene rubber, ethylene vinyl acetate copolymer, and polyester resin. A second resin layer containing at least one resin selected from the group consisting of fluorine-containing resin and (meth)acrylic resin is disposed on at least a portion of the surface of the first resin layer. The immersion cooling apparatus of the present invention can suppress deterioration of the first resin layer of the electronic component due to the coolant. The reason for this is presumably because the first resin layer is protected by the second resin layer containing a specific resin.

[0012] The immersion cooling apparatus of the present invention will be described with reference to the drawings.

[0013] 1 is a schematic diagram showing one embodiment of the immersion cooling apparatus of the present invention. The immersion cooling apparatus 1 includes a coolant L, a container 10 storing the coolant L, a plurality of electronic components 20 arranged inside the container 10 so as to be immersed in the coolant L, a heat exchange pump unit 30 connected to the container 10 via a coolant supply pipe 31 and a coolant return pipe 32, and a cooler 40 connected to the heat exchange pump unit 30 via a cold water supply pipe 41 and a cold water return pipe 42.

[0014] The container 10 has an openable and closable lid 10a at the top. The inside of the container 10 is filled with a coolant L to a height sufficient to immerse at least a portion of the electronic component 20. The coolant L is used to cool the electronic component 20. A preferred embodiment of the coolant L will be described later.

[0015] A plurality of electronic components 20 are arranged inside the container 10, and the plurality of electronic components 20 are arranged at predetermined intervals. In the example of Fig. 1, nine electronic components 20 are arranged in parallel, but the arrangement and number of the electronic components 20 are not particularly limited.

[0016] The electronic component 20 has an electronic component main body 20a and a cable 20b connected to the electronic component main body 20a. A specific example of the electronic component main body 20a is a processing board (e.g., a motherboard) in a server or the like. The processing board has, for example, a printed circuit board and electronic components mounted on the printed circuit board (e.g., a CPU, a power supply unit, memory, storage such as a hard disk or SSD (Solid State Drive), and a communication unit). Specific examples of the cable 20b include a power cable and a communication cable.

[0017] 1 shows an example in which the entire electronic component body 20a and at least a part of the cable 20b are immersed in the coolant, but this is not limiting. For example, a part of the electronic component body 20a may be immersed in the coolant L, or the entire cable 11b may be immersed in the coolant L.

[0018] At least a portion of the surface of the electronic component 20 is made of a first resin layer (not shown). The first resin layer contains at least one selected from the group consisting of vinyl chloride resin, epoxy resin, polyimide resin, silicone resin, olefin resin (e.g., polyethylene resin, polypropylene resin), ethylene propylene diene rubber, ethylene vinyl acetate copolymer, and polyester resin. In order to more significantly exhibit the effects of the present invention, vinyl chloride resin, ethylene propylene diene rubber, ethylene vinyl acetate copolymer, or polyester resin is preferred, and vinyl chloride resin is more preferred.

[0019] The electronic component 20 preferably includes a component selected from the group consisting of a printed circuit board and a cable, and at least a portion of the surface of the component is formed by the first resin layer. Here, the first resin layer of the cable corresponds to, for example, the resin coating when the cable is formed of a copper wire and a resin coating covering the copper wire. Also, the first resin layer of the printed circuit board corresponds to, for example, the protective layer (e.g., a sealing resin) when the protective layer is disposed on the surface of the printed circuit board.

[0020] When a label on which characters or symbols for identification or performance indication are printed is attached to a component such as a cable or a printed circuit board, the label itself may be the first resin layer. When the label is the first resin layer, a second resin layer (described later) is disposed on the surface of the label, thereby preventing the label itself and the characters or symbols printed on the label from being lost due to the coolant.

[0021] The first resin layer may contain a component other than the resin described above. Specific examples of components other than resin include plasticizers. The type of plasticizer is not particularly limited. For example, when the resin contained in the first resin layer is a vinyl chloride resin, specific examples of plasticizers that may be contained in the first resin layer include phthalate esters (bis(2-ethylhexyl) phthalate, diisononyl phthalate, diisodecyl phthalate, dibutyl phthalate, etc.), adipate esters (dioctyl adipate, diisononyl adipate, etc.), trimellitate esters (trioctyl trimellitate, etc.), polyesters, phosphate esters (tricresyl phosphate, etc.), citric acid esters (tributyl acetyl citrate, etc.), epoxidized vegetable oils (epoxidized soybean oil, epoxidized linseed oil, etc.), sebacate esters, azelaate esters, maleate esters, benzoate esters, etc. Here, if the first resin layer comes into contact with a coolant, components such as plasticizers may leach out of the first resin layer, causing deterioration of the first resin layer. Furthermore, the leachable plasticizer may adhere to the circuit board, causing malfunctions. Furthermore, if the leachable resin floats or adheres within the immersion cooling device, it may be necessary to replace the filter more frequently or other problems may occur. To address these problems, a second resin layer (described below) is disposed on the surface of the first resin layer of the electronic component 20, which suppresses the leachable components such as plasticizers from leaching out, thereby suppressing deterioration of the first resin layer.

[0022] A second resin layer (not shown) is disposed on at least a portion of the surface of the first resin layer. That is, the electronic component 20, the first resin layer, and the second resin layer are laminated in this order. The second resin layer is preferably disposed in a portion of the first resin layer that may come into contact with at least one coolant L selected from the group consisting of liquids and gases. The second resin layer may also be disposed on the entire surface of the first resin layer. Another layer may also be included between the first resin layer and the second resin layer.

[0023] At least a portion of the second resin layer on the surface of the first resin layer is in contact with a coolant, which may be liquid or gas.

[0024] Components that can be contained in the second resin layer and preferred embodiments of the second resin layer will be described later.

[0025] The heat exchange pump unit 30 is connected to the vessel 10 via a coolant supply pipe 31 and a coolant return pipe 32. The heat exchange pump unit 30 also has a heat exchanger 34 and a liquid pump 35 inside. The upstream end 31b of the coolant supply pipe 31 is connected to the heat exchanger 34, and the downstream end 31a of the coolant supply pipe 31 is connected to the side wall of the vessel 10. The upstream end 32a of the coolant return pipe 32 is connected to the side wall of the vessel 10, and the downstream end 32b of the coolant return pipe 32 is connected to the liquid pump 35.

[0026] The heat exchanger 34 exchanges heat between the cold water supplied from the cooler 40 and the coolant L supplied from the liquid pump 35 via the coolant discharge pipe 33. This cools the coolant L. The liquid pump 35 may be driven by, for example, an electric motor, and the discharge rate may be adjusted by a control unit (not shown).

[0027] The cooler 40 is connected to the heat exchange pump unit 30 via a cold water supply pipe 41 and a cold water return pipe 42. The cooler 40 also has a fan 43. The cooler 40 exchanges heat between the cold water and outside air taken in by the fan 43. This cools the cold water. The start, stop, rotation speed, etc. of the fan 43 are controlled by, for example, a control unit (not shown).

[0028] The electronic components 20 are cooled by heat exchange with the coolant L stored in the container 10. The coolant L warmed by the exhaust heat of the electronic components 20 is supplied to the heat exchanger 34 by the liquid pump 35 in the heat exchange pump unit 30, and then exchanges heat with cold water or outside air supplied from the cooler 40 to the heat exchanger 34. The coolant L cooled by heat exchange is supplied again into the container 10.

[0029] 1 shows a so-called single-phase immersion cooling apparatus in which the coolant L is used in a liquid state, but the present invention is not limited to this, and the immersion cooling apparatus of the present invention may also be a so-called two-phase immersion cooling apparatus that utilizes a cooling cycle of vaporization and liquefaction of the coolant L. When a two-phase immersion cooling apparatus is used, the liquid coolant L may be in contact with the second resin layer, or the vaporized coolant L may be in contact with the second resin layer.

[0030] Next, a preferred embodiment of the coolant L will be described.

[0031] The normal boiling point of the coolant L is preferably 45 to 500°C, more preferably 50 to 450°C, and even more preferably 50 to 430°C. If the normal boiling point of the solvent L is 45°C or higher, particularly in the case of a two-phase immersion cooling apparatus, not only cold water but also outside air can be used to cool the coolant L, which is advantageous in that power consumption can be further reduced and heat of vaporization can be utilized, thereby further reducing power consumption. If the normal boiling point of the solvent L is 500°C or lower, particularly in the case of a single-phase immersion cooling apparatus, the viscosity of the coolant L does not increase, which is advantageous in that the coolant L can be circulated efficiently. Note that the normal boiling point means the boiling point at 1 atmosphere.

[0032] The GWP of a refrigerant is preferably 0 to 7500, more preferably 0 to 5000, and even more preferably 0 to 150. GWP means global warming potential, and unless otherwise specified, is the 100-year value from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (2007). When a refrigerant is a mixture of two or more types, the GWP of the refrigerant is the weighted average of the composition masses of each component. The lower the GWP, the smaller the impact of the refrigerant on global warming.

[0033] As the coolant L, at least one selected from the group consisting of fluorine-containing compounds and hydrocarbon compounds is preferred in terms of increasing the heat exchange efficiency with the electronic component 20. Two or more coolants may be used in combination. Fluorine-containing compounds are more preferred in terms of non-flammability. When used indoors, non-flammability is preferred in terms of the Fire Service Act. Fluorine-containing compounds are also more preferred in terms of easy drainage and low stickiness. In particular, when the coolant L is a fluorine-containing compound and the second resin layer disposed on the first resin layer of the electronic component 20 contains a fluorine-containing resin, the coolant L has excellent wettability with respect to the second resin layer, thereby further improving the heat exchange efficiency. Hydrocarbon compounds are more preferred in terms of low dielectric constant. When CPUs and GPUs become highly efficient, their clock speeds increase and their frequencies become higher. At this time, if the coolant has a low dielectric constant, malfunctions are less likely to occur.

[0034] Commercially available fluorine-containing compounds can be used, such as Opteon 2P50 (48.9°C, hydrofluoroolefin) manufactured by Chemours, Galden HT55 (55°C, perfluoropolyether) manufactured by Solvay, AMOLEA AS-300 (55°C, hydrochlorofluoroolefin), Asahiklin AE-3000 (56°C, hydrofluoroether), Asahiklin AC-6000 (115°C, hydrofluorocarbon) manufactured by AGC, Novec 7100 (61°C, hydrofluoroether), FC-3284 (50°C, perfluorocarbon), FC-3283 (128°C, perfluorocarbon), Novec 7300 (98°C, hydrofluoroether), Novec 7700 (167°C, hydrofluoroether), Novec Examples of suitable solvents include Fluorinert FC-40 (165°C, perfluorocarbon), Fluorinert 7500 (128°C, hydrofluoroether), and Fluorinert FC-40 (165°C, perfluorocarbon). The temperature in parentheses indicates the standard boiling point.

[0035] Among fluorine-containing compounds, fluorine-containing olefin-based compounds (e.g., hydrofluoroolefins, hydrochlorofluoroolefins, etc.) have low GWP and are environmentally desirable, but they are easily decomposed and tend to generate acids. Therefore, the first resin layer is easily attacked by the acids, and deterioration may be more pronounced compared to other types of coolants. However, by providing a second resin layer, even when a fluorine-containing olefin-based compound is used as the coolant, it is possible to achieve both a reduction in environmental impact and suppression of deterioration of the resin layer of the electronic component due to the coolant.

[0036] Commercially available hydrocarbon compounds can be used, such as Synfluid PAO 8 manufactured by Chevron Phillips Chemical Company, and Hitherm P 100 and ENEOS IX series manufactured by Eneos Corporation. The larger the molecular weight of a hydrocarbon compound, the less likely it is to deteriorate the resin layer when used as a coolant.

[0037] Components that may be contained in the second resin layer disposed on the surface of the first resin layer and preferred embodiments of the second resin layer will be described below.

[0038] The second resin layer contains at least one selected from the group consisting of a fluorine-containing resin and a (meth)acrylic resin, and preferably contains a fluorine-containing resin in view of better effects of the present invention.

[0039] The fluororesin preferably has a unit based on a fluoroolefin (hereinafter also referred to as "unit F-1") in order to obtain better effects of the present invention. A fluoroolefin is an olefin in which one or more hydrogen atoms have been substituted with a fluorine atom. In a fluoroolefin, one or more hydrogen atoms not substituted with a fluorine atom may be substituted with a chlorine atom. The number of carbon atoms in the fluoroolefin is preferably 2 to 8, more preferably 2 to 4. Specific examples of fluoroolefins include CF ２ =CF ２ (TFE), CF ２ =CFCl (chlorotrifluoroethylene), CF ２ = CHF, CH ２ =CF ２ (VDF), CF ２ =CFCF ３ , C.F. ２ = CHCF ３ , C.F. ３ CH=CHF, CF ３ CF=CH ２ , formula CH ２ =CX ｆ１ (CF ２ ) ｎ１ Y ｆ１ (In the formula, X ｆ１ and Y ｆ１ are each independently a hydrogen atom or a fluorine atom, and n1 is an integer of 2 to 10.) From the viewpoint of superior adhesion, CF ２ =CF ２ , C.H. ２ =CF ２ , C.F. ２ = CFCl, CF ３ CH=CHF, CF ３ CF=CH ２ is preferred, and CF ２ =CF ２ or CF ２ =CFCl is more preferred, CF ２ =CFCl is more preferred.

[0040] When the fluororesin contains the unit F-1, the content of the unit F-1 is preferably from 20 to 100 mol %, more preferably from 30 to 70 mol %, and still more preferably from 40 to 60 mol %, based on all units contained in the fluororesin, from the viewpoint of adhesion.

[0041] The fluorine-containing resin may contain a unit having at least one of an aliphatic hydrocarbon ring and an aromatic ring (hereinafter also referred to as "unit F-2"). The unit F-2 is preferably a unit based on a monomer having at least one of an aliphatic hydrocarbon ring and an aromatic ring (hereinafter also referred to as "monomer f2"). The unit F-2 is preferably a unit not containing a fluorine atom.

[0042] Specific examples of the aliphatic hydrocarbon ring include monocyclic aliphatic hydrocarbons such as cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane; polycyclic aliphatic hydrocarbons such as 4-cyclohexylcyclohexane and decahydronaphthalene; aliphatic hydrocarbons having a bridged ring structure such as norbornane and a 1-adamantyl group; and aliphatic hydrocarbons having a spiro ring structure such as a spiro[3.4]octyl group. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, toluene, xylene, naphthalene, phenol, and benzoic acid; and aromatic heterocycles such as furan, thiophene, pyrrole, and pyridine.

[0043] As the monomer f2, vinyl ether, vinyl ester, allyl ether, allyl ester, or (meth)acrylic acid ester having at least one of an aliphatic hydrocarbon ring and an aromatic ring is preferable. Specific examples of the monomer f2 include cyclohexyl (meth)acrylate, cyclohexyl vinyl ether, cyclohexanedimethanol monovinyl ether (CH ２ =CHO-CH ２ -cycloC ６ H １０ -CH ２ OH), CH ２ =CHCH ２ O-CH ２ -cycloC ６ H１０ -CH ２ OH, CH ２ =CHO-CH ２ -cycloC ６ H １０ -CH ２ -(OCH ２ CH ２ ) １５ OH, benzoic acid vinyl ester, tert-butyl benzoic acid vinyl ester, and benzyl (meth)acrylate. ６ H １０ "-" represents a cyclohexylene group, and "-cycloC ６ H １０ The bonding site of "-" is usually 1,4-.

[0044] When the fluororesin contains units F-2, the content of units F-2 is preferably from 1 to 50 mol %, more preferably from 5 to 45 mol %, and still more preferably from 10 to 40 mol %, based on all units contained in the fluororesin.

[0045] The fluorine-containing resin may contain a unit having neither an aliphatic hydrocarbon ring nor an aromatic ring, and having at least one of a hydroxy group and a carboxy group (hereinafter also referred to as "unit F-3"). Unit F-3 is preferably a unit having no fluorine atom.

[0046] Unit F-3 may be a unit based on a monomer having at least one of a hydroxy group and a carboxy group (hereinafter also referred to as "monomer f3"), or may be a unit obtained by converting a group convertible to a hydroxy group or a carboxy group in a fluororesin containing a unit having this group to at least one of a hydroxy group and a carboxy group. Examples of such units include units obtained by reacting a fluororesin containing a unit having a hydroxy group with a polycarboxylic acid or an acid anhydride thereof to convert some or all of the hydroxy groups to carboxy groups. At least a portion of the hydroxy groups or carboxy groups in monomer f3 may be crosslinked with a curing agent (for example, a compound having two or more isocyanate groups in one molecule, a compound having two or more epoxy groups in one molecule), or may remain without crosslinking with the curing agent.

[0047] Examples of the monomer f3 having a hydroxy group include vinyl ethers, vinyl esters, allyl ethers, allyl esters, (meth)acrylic acid esters, and allyl alcohols, all of which have a hydroxy group. Specific examples of the monomer f3 having a hydroxy group include CH ２ =CHOCH ２ CH ２ OH, CH ２ =CHCH ２ OCH ２ CH ２ OH, CH ２ =CHOCH ２ CH ２ CH ２ CH ２ OH and CH ２ =CHCH ２ OCH ２ CH ２ CH ２ CH ２ OH, and from the viewpoint of copolymerizability with fluoroolefin, CH ２ =CHCH ２ OCH ２ CH ２ OH or CH ２ =CHOCH ２ CH ２ CH ２ CH ２OH is preferred.

[0048] Examples of the monomer f3 having a carboxy group include unsaturated carboxylic acids, (meth)acrylic acid, and monomers obtained by reacting the hydroxy group of the above-mentioned monomer having a hydroxy group with a carboxylic acid anhydride. Specific examples of the monomer f3 having a carboxy group include CH ２ =CHCOOH, CH(CH ３ )=CHCOOH, CH ２ =C(CH ３ ) COOH, HOOCCH=CHCOOH, CH ２ =CH(CH ２ ) ｎ１１ COOH (where n11 is an integer of 1 to 10), CH ２ = CHO(CH ２ ) ｎ１２ OC(O)CH ２ CH ２ COOH (where n12 is an integer of 1 to 10). From the viewpoint of copolymerizability with fluoroolefin, CH ２ =CH(CH ２ ) ｎ１１ COOH or CH ２ = CHO(CH ２ ) ｎ１２ OC(O)CH ２ CH ２ COOH is preferred.

[0049] When the fluororesin contains units F-3, the content of units F-3 is preferably more than 0 mol % and not more than 30 mol %, more preferably from 1 to 15 mol %, and still more preferably from 1.5 to 5 mol %.

[0050] The fluorine-containing resin may contain units (hereinafter also referred to as units F-4) based on a monomer (hereinafter also referred to as monomer f4) that has neither an aliphatic hydrocarbon ring nor an aromatic ring and does not have a hydroxy group or a carboxy group. Units F-4 are preferably units that do not have a fluorine atom. Units F-4 may have a crosslinkable group other than a hydroxy group or a carboxy group. Specific examples of such groups include an amino group, an epoxy group, an oxetanyl group, and a hydrolyzable silyl group.

[0051] Examples of the monomer f4 include one or more selected from the group consisting of alkenes, vinyl ethers, vinyl esters, allyl ethers, allyl esters, and (meth)acrylic acid esters. From the viewpoints of copolymerizability with fluoroolefins and weather resistance of the fluorine-containing resin, at least one of vinyl ethers and vinyl esters is preferred, and vinyl ethers are more preferred.

[0052] Specific examples of the monomer f4 include ethylene, propylene, 1-butene, ethyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, vinyl acetate, vinyl pivalate, vinyl neononanoate (manufactured by HEXION, trade name "VEOVA 9"), vinyl neodecanoate (manufactured by HEXION, trade name "VEOVA 10"), and tert-butyl (meth)acrylate.

[0053] When the fluororesin contains units F-4, the content of units F-4 is preferably from 10 to 40 mol %, more preferably from 20 to 30 mol %, based on all units contained in the fluororesin.

[0054] In order to obtain a more excellent effect of the present invention, the fluorine-containing resin preferably has units based on a fluoroolefin, more preferably has units based on chlorotrifluoroethylene, and even more preferably has units based on chlorotrifluoroethylene and units based on vinyl ether. Here, a fluorine-containing resin having units based on chlorotrifluoroethylene and units based on vinyl ether has excellent wettability with both fluorine-containing and hydrocarbon compound coolants. More specifically, a fluorine-containing resin having units based on chlorotrifluoroethylene and units based on vinyl ether has excellent wettability with fluorine-containing compound coolants because both are fluorine-based, and also has excellent wettability with hydrocarbon compound coolants because the oil repellency of the fluorine-containing resin having units based on chlorotrifluoroethylene and units based on vinyl ether is not too high. Therefore, the heat exchange efficiency is increased, and the cooling efficiency of electronic components by the coolant is further improved.

[0055] Two or more types of fluorine-containing resins may be used in combination. When the second resin layer contains a fluorine-containing resin, the content of the fluorine-containing resin is preferably 50 to 90 mass %, more preferably 60 to 80 mass %, based on the total mass of the second resin layer.

[0056] Fluorine-containing resins are produced by known methods. For example, they can be obtained by copolymerizing each monomer in the presence of a solvent and a radical polymerization initiator. Methods for producing fluorine-containing resins include solution polymerization and emulsion polymerization. During or after the production of the fluorine-containing resin, a polymerization stabilizer, a polymerization inhibitor, a surfactant, and the like may be used, if necessary.

[0057] As the fluorine-containing resin, commercially available products may be used, and examples thereof include the "Lumiflon" series (manufactured by AGC), the "Fluon" series (manufactured by AGC), the "Kynar" series (manufactured by Arkema), the "Zeffle" series (manufactured by Daikin Industries, Ltd.), the "Eterflon" series (manufactured by Eternal), and the "Zendura" series (manufactured by Honeywell).

[0058] The (meth)acrylic resin is a polymer containing units based on a (meth)acrylic acid ester or a crosslinked product thereof. Examples of the (meth)acrylic acid ester include alkyl (meth)acrylates and aryl (meth)acrylates. Specific examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate.

[0059] The (meth)acrylic acid ester may have a reactive group such as a hydroxy group, a carboxy group, an amino group, an epoxy group, an oxetanyl group, a hydrolyzable silyl group, etc. The reactive group may remain unreacted, or may be crosslinked intramolecularly or by a curing agent having a group capable of reacting with the reactive group.

[0060] As the (meth)acrylic resin, commercially available products may be used, and a specific example thereof is ACRYDIC A-801 (acrylic resin having a hydroxy group) manufactured by DIC Corporation.

[0061] Two or more types of (meth)acrylic resins may be used in combination. When the second resin layer contains a (meth)acrylic resin, the content of the (meth)acrylic resin is preferably 20 to 90% by mass, and more preferably 30 to 80% by mass, based on the total mass of the second resin layer.

[0062] The second resin layer may contain additives in addition to the various resins described above, such as a curing agent, a curing catalyst, an ultraviolet absorber, a matting agent, a leveling agent, a surface conditioner, a degassing agent, a filler, a thickener, a dispersant, a surfactant, an antistatic agent, a rust inhibitor, a silane coupling agent, an antifouling agent, a stain-reducing treatment agent, a colorant, and a plasticizer.

[0063] The second resin layer preferably contains a curing agent. When the second resin layer contains a fluorine-containing resin having units F-3 based on a hydroxyl group-containing monomer f3 and a curing agent, the ratio of the molar amount of isocyanate groups in the curing agent to the molar amount of hydroxyl groups in the fluorine-containing resin is preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and particularly preferably 90% or more. It is also preferably 230% or less, more preferably 200% or less, even more preferably 150% or less, and particularly preferably 105% or less. It is also preferably 30 to 230%, more preferably 40 to 200%, even more preferably 40 to 150%, particularly preferably 50 to 150%, and most preferably 90 to 105%. When the ratio is equal to or greater than the lower limit, the solvent resistance of the coating film is superior. When the ratio is equal to or less than the upper limit, the non-stickiness is superior. Here, the above ratio is calculated based on the amounts of the fluorine-containing resin and the curing agent charged.

[0064] The thickness of the second resin layer is preferably 50 nm to 100 μm, more preferably 100 nm to 80 μm, even more preferably 500 nm to 40 μm, and particularly preferably 800 nm to 20 μm. If the thickness of the second resin layer is 50 nm or more, the effects of the present invention are more excellent. If the thickness of the second resin layer is 100 μm or less, the flexibility of the electronic component is not impaired and resistance to deterioration by the coolant L is excellent.

[0065] The method for forming the second resin layer is not particularly limited, but examples include a method in which a coating composition is applied onto a first resin layer of an electronic component to form a second resin layer on at least a portion of the surface of the first resin layer.

[0066] The coating composition is preferably a composition containing a resin. Examples of the resin include the resins that can be contained in the second resin layer (at least one of a fluorine-containing resin and a (meth)acrylic resin). In addition to the resin, the coating composition may also contain various components that can be contained in the second resin layer, and a liquid medium (e.g., water, an organic solvent).

[0067] The coating composition may be a coating composition in which the resin is dissolved or dispersed in a liquid medium, or may be a coating composition that is substantially free of a liquid medium (e.g., a powder coating composition). Examples of liquid media include organic solvents and water, and examples of coating compositions that are dissolved or dispersed in a liquid medium include coating compositions that are dissolved in organic solvents (e.g., solvent-based coating compositions) and coating compositions that are dispersed in water (e.g., aqueous coating compositions). A coating composition that is substantially free of a liquid medium means that the content of the liquid medium is 0.1 mass% or less relative to the total mass of the coating composition.

[0068] Examples of organic solvents include ketone-based solvents, ester-based solvents, hydrocarbon-based solvents, alcohol-based solvents, glycol ether-based solvents, and glycol ester-based solvents. Specific examples of ketone-based solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and diacetone alcohol. Specific examples of ester-based solvents include ethyl acetate and butyl acetate. Specific examples of hydrocarbon-based solvents include hexane, heptane, cyclohexane, xylene, ethylbenzene, toluene, ExxonMobil's Solvesso 100 and ExxonMobil's Solvesso 150, and aromatic hydrocarbon solvents (e.g., mineral spirits). Specific examples of alcohol-based solvents include butyl alcohol. Specific examples of glycol ether-based solvents include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monopropyl ether. Specific examples of glycol ester-based solvents include 1-methoxypropyl-2-acetate.

[0069] When the coating composition contains a liquid medium, the content of the liquid medium is preferably 10 to 95 mass %, more preferably 20 to 90 mass %, based on the total mass of the coating composition, and the content of the resin is preferably 50 to 80 mass %, more preferably 60 to 80 mass %, based on the total solid content of the coating composition.

[0070] When the coating composition is an aqueous coating composition or a solvent-based coating composition, specific examples of the application method include spray coating, squeegee coating, flow coating, bar coating, spin coating, dip coating, screen printing, gravure printing, die coating, inkjet printing, curtain coating, and methods using a brush and spatula. When the coating composition is a powder coating composition, specific examples of the application method include electrostatic coating, electrostatic spraying, electrostatic immersion, atomization, fluidized bed immersion, spraying, spraying, thermal spraying, and plasma thermal spraying. If necessary, a treatment of drying to remove the solvent after application may be performed. The drying temperature is preferably 20 to 140°C, and the drying time is preferably 1 to 60 minutes.

[0071] The present invention will be described in detail below with reference to examples. Examples 1 to 3 are working examples, and Example 4 is a comparative example. However, the present invention is not limited to these examples.

[0072] [Abbreviations, etc.] CTFE: chlorotrifluoroethylene CHVE: cyclohexyl vinyl ether EVE: ethyl vinyl ether HBVE: 4-hydroxybutyl vinyl ether 2-EHVE: 2-ethylhexyl vinyl ether Fluorine-containing resin F1: Fluorine-containing resin having a molar ratio of CTFE units / CHVE units / EVE units / HBVE units = 50 / 15 / 25 / 10 Acrylic resin A1: ACRYDIC A-801 (manufactured by DIC Corporation) Curing agent: Coronate HX (trade name, manufactured by Tosoh Corporation, isocyanurate of hexamethylene diisocyanate) Curing catalyst: 10,000-fold diluted solution of dibutyltin dilaurate (DBTDL) with butyl acetate (manufactured by Kanto Chemical Co., Ltd.)

[0073] [Example 1] Coating composition 1 was prepared by mixing the various components shown in Table 1 below. In coating composition 1, the ratio of the molar amount of isocyanate groups in the curing agent to the molar amount of hydroxy groups in the fluorine-containing resin was 52%. Next, coating composition 1 was applied to the surface of a polyvinyl chloride film (product name "Achilles Flat", manufactured by Achilles Corporation) using a doctor blade to form a coating film. The resulting coating film was dried at 80°C for 30 minutes to obtain evaluation sample 1 in which a second resin layer was formed on the surface of the polyvinyl chloride film. The thickness of the second resin layer was 40 μm.

[0074] [Example 2] Evaluation sample 2, in which a second resin layer was formed on the surface of a polyvinyl chloride film, was obtained in the same manner as in Example 1, except that the coating amount of coating composition 1 was adjusted so that the thickness of the second resin layer was 20 μm.

[0075] [Example 3] Coating composition 2 was prepared by mixing the various components shown in Table 1 below. In coating composition 2, the ratio of the molar amount of isocyanate groups in the curing agent to the molar amount of hydroxy groups in the fluorine-containing resin was 52%. Except for using coating composition 2 instead of coating composition 1, evaluation sample 3 was obtained in the same manner as in Example 1, in which a second resin layer was formed on the surface of a polyvinyl chloride film. The thickness of the second resin layer was 40 μm.

[0076] Example 4 A polyvinyl chloride film (product name "Achilles Flat", manufactured by Achilles Corporation) was used as evaluation sample 4.

[0077] [Evaluation of Deterioration State] A coolant was dripped onto the surface of the evaluation sample according to the drip method described in JIS K 5600-6-1 (2016). After 24 hours, the deterioration state of the evaluation sample was visually inspected and evaluated according to the following criteria. The results are shown in Table 1. Evaluation results of C or higher were deemed acceptable for practical use. For evaluation samples 1 to 3, the coolant was dripped onto the surface of the second resin layer, and for evaluation sample 4, the coolant was dripped onto the surface of the polyvinyl chloride film. Asahiklin AE-3000 (manufactured by AGC), AMOLEA AS-300 (manufactured by AGC), and hexane were used as the coolants dripped onto the evaluation samples. (Evaluation Criteria) A: No change was observed on the surface. B: Some roughness was observed on the surface. C: Some deformation was observed on a portion of the surface. D: Deformation was observed over the entire surface.

[0078]

[0079] As shown in Table 1, when a component having a second resin layer containing a fluorine-containing resin or a (meth)acrylic resin on its surface was used, it was confirmed that the component located below the second resin layer was less susceptible to deterioration by the coolant (Examples 1 to 3). Therefore, it can be said that by arranging the second resin layer on the first resin layer of an electronic component in an immersion cooling apparatus, deterioration of the first resin layer by the coolant is less likely to occur.

[0080] Other embodiments of the present invention will be described as reference examples. <Preparation of Coating Composition 3 and Coating Composition 4> Coating composition 3 was prepared by adding 21 parts by mass of Coronate HX to 100 parts by mass of LF200MEK (manufactured by AGC) containing a fluororesin with a molar ratio of CTFE units / CHVE units / EVE units / HBVE units of 50 / 15 / 25 / 10. In coating composition 3, the ratio of the molar amount of isocyanate groups in the curing agent to the molar amount of hydroxy groups in the fluororesin was 150%. Coating composition 4 was prepared by adding 14 parts by mass of Coronate HX to 100 parts by mass of LF800 (manufactured by AGC) containing a fluororesin with a molar ratio of CTFE units / CHVE units / HBVE units / 2-EHVE units of 50 / 26 / 9 / 15. In Coating Composition 4, the ratio of the molar amount of isocyanate groups in the curing agent to the molar amount of hydroxy groups in the fluorine-containing resin was 100%.

[0081] Reference Example 1 A 30 cm section from the end of a polyvinyl chloride-coated PanZone (product name) Cat 6 cable assembly LAN cable (manufactured by Panduit Corporation) was immersed in Coating Composition 3, pulled out, and then heated with a hair dryer for 10 minutes before coating. It was confirmed that the coated portion of Coating Composition 3 was not sticky. Similarly, a 30 cm section from the opposite end was coated with Coating Composition 4. This LAN cable was immersed in IX Series (a hydrocarbon compound manufactured by ENEOS Corporation) and left at room temperature for six months. The LAN cable was then removed and wiped with Kimwipes (manufactured by Nippon Paper Crecia Co., Ltd.) to check for any changes in each section before and after immersion. As a result, the sections coated with Coating Composition 3 or Coating Composition 4 maintained their flexibility without breaking at sharp angles when bent, and the bent sections did not turn white. On the other hand, the portion not coated with coating composition 3 or coating composition 4 broke at an acute angle when bent, lost flexibility, and the bent portion also turned white.

[0082] Reference Example 2 Two polyester film barcode labels were attached to the surface of a 5 cm square stainless steel plate, and the surface of one of the labels was coated with Coating Composition 3 and heated with a dryer for 5 minutes. It was confirmed that the coated area was not sticky. This stainless steel plate was immersed in IX Series (a hydrocarbon compound manufactured by ENEOS Corporation) and left at room temperature for half a year. The stainless steel plate was then removed and wiped with a Kimwipe to check for any changes before and after immersion. As a result, the barcode on the label coated with Coating Composition 3 could be read without ink bleeding even when rubbed with a Kimwipe. On the other hand, the label without Coating Composition 3 had ink bleeding when rubbed with a Kimwipe, making it impossible to read the barcode.

[0083] Reference Example 3: A polyvinyl chloride film barcode label was attached to one end of a PanZone (product name) Cat6 cable assembly LAN cable (manufactured by Panduit Corporation Japan Branch), and Coating Composition 3 was applied to the surface and heated for 5 minutes with a hair dryer. It was confirmed that the coated area was not sticky. On the other end of the LAN cable, only a polyvinyl chloride film barcode label was attached, and no coating composition was applied. This LAN cable was immersed in IX Series (a hydrocarbon compound manufactured by ENEOS Corporation) and left at room temperature for six months. The LAN cable was then removed and wiped with a Kimwipe to check for any changes in each area before and after immersion. As a result, the barcode on the label coated with Coating Composition 3 could be read without ink bleeding, even when rubbed with a Kimwipe. On the other hand, when the label that was not coated with Coating Composition 3 was rubbed with Kimwipe, the ink bled, the barcode could not be read, and the label itself became slightly hard and deteriorated.

[0084] The entire contents of the specifications, claims, drawings and abstracts of Japanese Patent Application No. 2024-072204 filed on April 26, 2024, and Japanese Patent Application No. 2024-154227 filed on September 6, 2024 are hereby incorporated by reference as the disclosure of the specification of the present invention.

[0085] REFERENCE SIGNS LIST 1 immersion cooling device 10 container 10a lid 20 electronic component 20a electronic component body 20b cable 30 heat exchange pump unit 31 coolant supply pipe 31a downstream end 31b upstream end 32 coolant return pipe 32a upstream end 32b downstream end 33 coolant discharge pipe 34 heat exchanger 35 liquid pump 40 cooler 41 cold water supply pipe 42 cold water return pipe 43 fan L coolant

Claims

1. An immersion cooling device comprising a coolant, a container having the coolant therein, and an electronic component at least a portion of which is in contact with the coolant within the container, wherein at least a portion of the surface of the electronic component has a first resin layer comprising at least one resin selected from the group consisting of vinyl chloride resin, epoxy resin, polyimide resin, silicone resin, olefin resin, ethylene propylene diene rubber, ethylene vinyl acetate copolymer, and polyester resin, and a second resin layer comprising at least one resin selected from the group consisting of fluorine-containing resin and (meth)acrylic resin disposed on at least a portion of the surface of the first resin layer.

2. The immersion cooling apparatus according to claim 1, wherein the second resin layer contains the fluorine-containing resin.

3. The immersion cooling apparatus according to claim 1 or 2, wherein the electronic component includes a component selected from the group consisting of a printed circuit board and a cable, and at least a portion of the surface of the component is made of the first resin layer.

4. The immersion cooling apparatus according to claim 1 or 2, wherein the fluorine-containing resin contains units based on a fluoroolefin.

5. The immersion cooling apparatus according to claim 1 or 2, wherein the fluorine-containing resin contains a unit based on chlorotrifluoroethylene and a unit based on vinyl ether.

6. The immersion cooling apparatus according to claim 1 or 2, wherein the second resin layer has a thickness of 50 nm to 100 μm.

7. The immersion cooling apparatus according to claim 1 or 2, wherein the normal boiling point of the coolant is 45 to 450°C.

8. The immersion cooling apparatus according to claim 1 or 2, wherein the coolant is at least one selected from the group consisting of fluorine-containing compounds and hydrocarbon compounds.

9. The immersion cooling apparatus of claim 1 or 2, wherein the coolant has a GWP of 0 to 7500.

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