Insulation protection circuit board and method for manufacturing same, on-board electrical component, and server

Abstract

Provided are an insulation protection circuit board and an insulation protection method for a circuit board, an on-board electrical component, and a server. The present invention is an insulation protection circuit board in which a circuit board is insulation-protected by a thermoplastic resin (A) and is submerged in a cooling liquid for use, or an insulation protection circuit board in which a circuit board is insulation-protected by a sheet made of the thermoplastic resin (A), wherein the thermoplastic resin (A) is at least one resin selected from the group consisting of a crystalline resin having a glass transition temperature of 70°C or more and an amorphous resin having a glass transition temperature of 160°C or more.

Description

Insulated protection circuit board, its manufacturing method, in-vehicle electrical component, server 【0001】 The present invention relates to a circuit board insulated and protected by a thermoplastic resin, a method for insulating and protecting the circuit board, an in-vehicle electrical component, and a server. 【0002】 In recent years, in xEVs such as electric vehicles, to improve convenience such as extending the cruising range and expanding the interior space, miniaturization and weight reduction of in-vehicle electrical components have been promoted. Among them, an inverter including components such as a power module, a bus bar, and a current sensor is a core component that converts power from a battery into motor output, and technical development of so-called eAxle, which integrates an inverter, a motor, a speed reducer, etc. into one housing, is actively carried out. 【0003】 In the above-mentioned inverter, there is a means to make the inverter small and lightweight by mounting or incorporating components such as a power module, a bus bar, and a current sensor on a circuit board. However, cooling technology is important to address heat accumulation caused by integrating the control circuit and other components on one circuit board, and heat generation caused by applying a SiC (silicon carbide) semiconductor that can handle higher heat resistance and higher frequencies. 【0004】 Also in data centers, as the amount of data processed increases, the power consumption per server rack tends to increase acceleratively, and development to improve the efficiency of cooling heat generated from circuit boards and semiconductors in the server is actively carried out. 【0005】Regarding the cooling of the circuit board mentioned above, one method is to immerse the circuit board in a cooling liquid. In this case, the circuit board needs to be insulated. Typical methods of insulation include coating and potting with insulating resin, but coating carries the risk of insulation defects due to incomplete coating, and potting has the problem of insufficient cooling efficiency due to the thickness of the insulating resin. As an alternative method of insulation, insulating films and sheets can be used. For example, Patent Document 1 describes a cooling device in which a semiconductor device is housed in an imide resin film bag, the inside is evacuated, and the device is immersed in a cooling liquid. Patent Document 2 describes a cooling system in which a bag of synthetic resin such as polyethylene, polypropylene, or polyester is watertightly connected to a heat sink, and the circuit board is wrapped in the bag and immersed in a cooling liquid. Patent Document 3 describes overlay molding and covering a circuit board with a stretchable film. Patent Document 4 describes a biaxially oriented polyarylene sulfide film with a defined degree of crystallinity and high elongation at break. Patent document 5 describes decorative films using ABS, acrylic, PVC, TPU, PC, etc. as base materials. 【0006】 Japanese Patent Publication No. 4-372159, International Publication No. 2024 / 209558, Japanese Patent Publication No. 2015-228421, International Publication No. 2013-176103, Japanese Patent Publication No. 2024-146383 【0007】However, Patent Document 1 insulates semiconductor devices with bags made of imide resin film, which has a chemical structure that raises concerns about hydrolysis. There is a risk of deterioration of the bags and dielectric breakdown due to prolonged immersion in the coolant. Furthermore, although it is described that the imide resin film bags are made to adhere tightly to the semiconductor devices by reducing the pressure, imide resin film is a relatively rigid film, so simply reducing the pressure of the bags at room temperature will not result in sufficient adhesion to the semiconductor devices, and an air layer will be trapped between the semiconductor devices and the imide resin film, reducing the cooling efficiency. Patent Document 2 insulates substrates with bags made of films such as polyethylene, polypropylene, and polyester, which have low heat resistance, raising concerns about their long-term resistance to semiconductor heat generation. Furthermore, although it is described that the bags are made to adhere tightly to the substrate by reducing the pressure, even if the pressure of the bags is reduced at room temperature, the bags do not conform well to the shape of the substrate, resulting in poor adhesion, and an air layer will be trapped between the semiconductor devices and the film, reducing the cooling efficiency. Patent Document 3 does not describe means for immersing circuit boards in a coolant, nor does it describe specific film materials with excellent heat resistance and chemical resistance. Patent document 4 describes a rigid biaxially oriented polyarylene sulfide film, which lacks the shaping and conformability to circuit boards necessary for secondary processing such as vacuum forming. Patent document 5 describes decorative films based on ABS, acrylic, PVC, TPU, and PC, which have low heat and chemical resistance, and are not suitable for insulating applications where circuit boards are expected to be immersed in cooling liquid. 【0008】 Therefore, the object of the present invention is to provide thermoplastic resin sheets, multilayer sheets, and circuit boards and methods for insulating and protecting circuit boards, automotive electrical components, and servers that have excellent heat resistance and chemical resistance. 【0009】To solve the above problems, the present invention has the following configuration: (1) an insulating protective circuit board in which the circuit board is insulated and protected by a sheet made of thermoplastic resin (A). (2) an insulating protective circuit board in which the circuit board is insulated and protected by a sheet made of thermoplastic resin (A), wherein the thermoplastic resin (A) is at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher. (3) the insulating protective circuit board of (1), wherein the thermoplastic resin (A) is mainly composed of at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher. (4) the insulating protective circuit board of any one of (1) to (3), wherein the liquid absorption rate when the thermoplastic resin (A) is immersed in a cooling liquid (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less. (5) An insulating protective circuit board described in any of (1) to (4) below that satisfies condition 1 or 2 below: Condition 1: The main component of the thermoplastic resin (A) is a crystalline resin and the tensile elongation of a sheet made of the thermoplastic resin (A) at 200°C is 100% or more, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile elongation of a sheet made of the thermoplastic resin (A) at 250°C is 100% or more; Condition 2: The main component of the thermoplastic resin (A) is a crystalline resin and the tensile stress at 100% elongation at 200°C of a sheet made of the thermoplastic resin (A) is 0.1 MPa or more and 30 MPa or less, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile stress at 100% elongation at 250°C of a sheet made of the thermoplastic resin (A) is 0.1 MPa or more and 30 MPa or less. (6) An insulating protective circuit board described in any of (1) to (5) below that satisfies condition 2' below: Condition 2': The main component of the thermoplastic resin (A) is a crystalline resin and the tensile stress of a sheet made of the thermoplastic resin (A) at 150°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile stress of a sheet made of the thermoplastic resin (A) at 200°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less.(7) An insulating protective circuit board according to any one of (1) to (6), wherein the insulating protective circuit board is insulated and protected by a multilayer sheet formed by laminating a sheet made of thermoplastic resin (A) and an adhesive layer (B). (8) An insulating protective circuit board according to any one of (1) to (7), wherein the sheet made of thermoplastic resin (A) contains a black pigment. (9) A method for manufacturing an insulating protective circuit board according to any one of (1) to (8), wherein a sheet made of thermoplastic resin (A) is spread out and set to cover the entire circuit board, and then the sheet is molded to cover the circuit board by utilizing the pressure difference between the top and bottom of the sheet to obtain a circuit board insulated and protected by thermoplastic resin (A). (10) An automotive electrical component including the insulating protective circuit board according to any one of (1) to (8). (11) An eAxle including the automotive electrical component according to (10). (12) An xEV including the automotive electrical component according to (10). (13) A server including the insulating protective circuit board according to (1) or (2). (14) A data center including the server according to (13). (15) A thermoplastic resin sheet made of thermoplastic resin (A), wherein thermoplastic resin (A) mainly contains a resin with a glass transition temperature of 70°C or higher, the degree of crystallinity of the thermoplastic resin sheet is 5% or more and 30% or less, the tensile elongation at 200°C is 100% or more, and the tensile stress at 100% elongation at 150°C is 0.1 MPa or more and 30 MPa or less. (16) The thermoplastic resin sheet according to (15), wherein the liquid absorption rate when immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less. (17) The thermoplastic resin sheet according to (15) or (16), comprising a black pigment.(18) A thermoplastic resin sheet made of thermoplastic resin (A), wherein the thermoplastic resin (A) mainly consists of at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher, and satisfies the following conditions 1 to 4: Condition 1: The main component of thermoplastic resin (A) is a crystalline resin and the tensile elongation of the thermoplastic resin sheet at 200°C is 100% or more, or the main component of thermoplastic resin (A) is an amorphous resin and the tensile elongation of the thermoplastic resin sheet at 250°C is 100% or more; Condition 2: The main component of thermoplastic resin (A) is a crystalline resin and the tensile stress of the thermoplastic resin sheet at 100% elongation at 200°C is 0.1 MPa or more and 30 MPa or less, or the main component of thermoplastic resin (A) is an amorphous resin and the tensile stress of the thermoplastic resin sheet at 100% elongation at 250°C is 0.1 MPa or more and 30 MPa or less; Condition 3: The liquid absorption rate when immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less; Condition 4: Contains a black pigment. (19) A thermoplastic resin sheet as described in (18) that satisfies the following condition 2': Condition 2': The main component of the thermoplastic resin (A) is a crystalline resin and the tensile stress of the thermoplastic resin sheet at 100% elongation at 150°C is 0.1 MPa or more and 30 MPa or less, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile stress of the thermoplastic resin sheet at 100% elongation at 200°C is 0.1 MPa or more and 30 MPa or less. (20) A multilayer sheet in which a sheet made of the thermoplastic resin (A) described in any of (15) to (17) and an adhesive layer (B) are laminated.(21) A multilayer sheet comprising a sheet made of thermoplastic resin (A) and an adhesive layer (B), wherein the thermoplastic resin (A) mainly consists of at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher, and the multilayer sheet satisfies the following conditions 1 to 3: Condition 1: The main component of the sheet made of thermoplastic resin (A) is a crystalline resin and the tensile elongation of the sheet made of thermoplastic resin (A) at 200°C is 100% or higher, or the main component of the sheet made of thermoplastic resin (A) is an amorphous resin and the tensile elongation of the sheet made of thermoplastic resin (A) at 250°C is 100% or higher; Condition 2: The main component of the sheet made of thermoplastic resin (A) is a crystalline resin, and the tensile stress of the sheet made of thermoplastic resin (A) at 100% elongation at 200°C is 0.1 MPa or more and 30 MPa or less, or the main component of the sheet made of thermoplastic resin (A) is an amorphous resin, and the tensile stress of the sheet made of thermoplastic resin (A) at 100% elongation at 250°C is 0.1 MPa or more and 30 MPa or less; Condition 3: The liquid absorption rate when the sheet made of thermoplastic resin (A) is immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less. (22) A multilayer sheet according to (21) that satisfies the following condition 2': Condition 2': The main component of the sheet made of thermoplastic resin (A) is a crystalline resin and the tensile stress of the sheet made of thermoplastic resin (A) at 150°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less, or the main component of the sheet made of thermoplastic resin (A) is an amorphous resin and the tensile stress of the sheet made of thermoplastic resin (A) at 200°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less. (23) A multilayer sheet according to (21) or (22) wherein the sheet made of thermoplastic resin (A) contains a black pigment. (24) A multilayer sheet according to any one of (21) to (23) wherein the thermoplastic resin (A) is mainly composed of a resin selected from polyphenylene sulfide, polyether ether ketone, polyphenyl sulfone, polyether sulfone, and polysulfone.(25) An insulating protective circuit board in which the circuit board is insulated and protected by a thermoplastic resin sheet described in any of (15) to (19) or a multilayer sheet described in any of (20) to (24). (26) An automotive electrical component comprising the insulating protective circuit board described in (25). (27) An automotive electrical component having an insulating protective circuit board described in (25) and a cooling device comprising a coolant, wherein the insulating protective circuit board is immersed in the coolant. (28) An eAxle comprising the automotive electrical component described in (26) or (27). (29) An xEV comprising the automotive electrical component described in (26) or (27). (30) A server comprising the insulating protective circuit board described in (25). (31) A server having an insulating protective circuit board described in (25) and a cooling device comprising a coolant, wherein the insulating protective circuit board is immersed in the coolant. A data center including the servers described in (32), (30), or (31). 【0010】 According to the present invention, it is possible to provide a thermoplastic resin sheet with excellent heat resistance and chemical resistance, which is used by immersion in a coolant, a circuit board insulated and protected by the thermoplastic resin, and a method for insulating and protecting a circuit board. The insulating and protected circuit board of the present invention enables efficient cooling of automotive electronic components and servers, thereby achieving miniaturization and weight reduction. Furthermore, the manufacturing method of the insulating and protected circuit board of the present invention achieves process efficiency through a simple method utilizing the thermoplastic resin sheet, as well as improved reliability and safety. 【0011】 The embodiments of the present invention will be described in detail below. 【0012】A circuit board is a substrate on which conductive circuits are formed and electronic components such as elements and coils are mounted. The insulating protective circuit board of the present invention requires that the circuit board be insulated and protected by a sheet made of thermoplastic resin (A) (sometimes simply called a thermoplastic resin sheet). Here, insulating protection specifically means that the entire circuit board is covered with a sheet made of thermoplastic resin (A), and that the liquid absorption rate of the thermoplastic resin (A) when immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less. As a result, the surface of the circuit board is electrically isolated from the surroundings, and the circuit board can be used safely even when immersed in a coolant. It can also protect the board from sand and dust from the outside. The insulating protective circuit board of the present invention is useful for various components, including automotive electronic components and servers. 【0013】 The insulating protective circuit board of the present invention can be used by immersing it in a coolant. By immersing it in a coolant, the circuit board that stores or generates heat can be efficiently cooled. Suitable coolants include water, ethylene / propylene glycol-based coolants such as long-life coolant (LLC), oils such as automatic transmission fluid (ATF), fluorine-based refrigerants, and insulating oils. When the insulating protective circuit board of the present invention is used in a server, water is preferred as the coolant from the viewpoint of heat transfer efficiency, specific heat, and environmental impact. When the insulating protective circuit board of the present invention is used in automotive electrical components, long-life coolant is preferred as the coolant from the viewpoint of heat transfer efficiency, specific heat, and prevention of freezing in winter. 【0014】The thermoplastic resin (A) used in the embodiments of the present invention preferably has as its main component at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher, i.e., a super engineering plastic. In the present invention, the main component refers to the component with the highest content (parts by weight) of the thermoplastic resin contained in the sheet made of thermoplastic resin (A). By insulating and protecting the circuit board with at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher, excellent heat resistance and chemical resistance insulation protection can be achieved, and a circuit board that can withstand immersion in a coolant can be obtained. 【0015】 Examples of crystalline resins with a glass transition temperature of 70°C or higher include polyphenylene sulfide (sometimes abbreviated as PPS), aromatic polyamide, liquid crystal polymer, polyether ether ketone (sometimes abbreviated as PEEK), and polytetrafluoroethylene. Examples of amorphous resins with a glass transition temperature of 160°C or higher include polyphenyl sulfone (sometimes abbreviated as PPSU), polyether sulfone (sometimes abbreviated as PES), polysulfone (sometimes abbreviated as PSU), polyetherimide, and polyamideimide. Among these, any resin selected from polyphenylene sulfide, polyether ether ketone, polyphenyl sulfone, polyether sulfone, and polysulfone is preferred from the viewpoint of durability to coolant, liquid absorption rate, and environmental impact. 【0016】The thermoplastic resin (A) used in the embodiments of the present invention may contain other resin components, as long as the effects of the present invention are not impaired. Specific examples of other resin components include polyester resins such as polyamide, polyethylene terephthalate, polybutylene terephthalate, polycyclohexyldimethylene terephthalate, and polynaphthalene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene, polyamide-imide, polyacetal, polyimide, polyetherimide, polyketone resin, liquid crystal polymer, polyetherketone resin, polythioetherketone resin, polyetheretherketone resin, olefin-based elastomer, and silicone-based elastomer. 【0017】 The sheet made of the thermoplastic resin (A) used in the embodiments of the present invention preferably satisfies the following condition 1: The main component of the thermoplastic resin (A) is a crystalline resin and the tensile elongation of the sheet made of the thermoplastic resin (A) at 200°C is 100% or more, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile elongation of the sheet made of the thermoplastic resin (A) at 250°C is 100% or more. 【0018】 It is more preferable that the tensile elongation is 150% or more, and even more preferable that it is 200% or more. 【0019】 A sheet made of thermoplastic resin (A) more preferably satisfies the following condition 1': Condition 1': The main component of thermoplastic resin (A) is a crystalline resin and the tensile elongation of the sheet made of thermoplastic resin (A) at 150°C is 50% or more, or the main component of thermoplastic resin (A) is an amorphous resin and the tensile elongation of the sheet made of thermoplastic resin (A) at 200°C is 50% or more. The tensile elongation is more preferably 100% or more, more preferably 150% or more, and even more preferably 200% or more. 【0020】 By satisfying these conditions, when a sheet made of thermoplastic resin (A) is molded to cover a circuit board, the sheet does not tear and conforms to and covers the mounted components on top of the circuit board. This makes it easier to obtain a circuit board that is highly reliable and has high cooling efficiency when immersed in a coolant. 【0021】 To obtain such a sheet, it is preferable that the main component of the sheet is a resin selected from PPS, PEEK, PPSU, PES, and PSU. Specifically, examples include unstretched sheets press-molded from these resins, unstretched sheets obtained by extruding these resins, which have been heated and melted in an extruder, through a T-die, taking them back with a cooling roll for molding, and then winding them up, and tubes obtained by blowing these resins, which have been heated and melted in an extruder, through a circular die while simultaneously blowing air into them for inflation molding. 【0022】 The sheet made of the thermoplastic resin (A) used in the embodiments of the present invention preferably satisfies the following condition 2. Condition 2: The main component of the thermoplastic resin (A) is a crystalline resin and the tensile stress of the sheet made of the thermoplastic resin (A) at 100% elongation at 200°C is 0.1 MPa or more and 30 MPa or less, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile stress of the sheet made of the thermoplastic resin (A) at 100% elongation at 250°C is 0.1 MPa or more and 30 MPa or less. The tensile stress is more preferably 25 MPa or less, more preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less. 【0023】 A sheet made of thermoplastic resin (A) more preferably satisfies the following condition 2': Condition 2': The main component of thermoplastic resin (A) is a crystalline resin and the tensile stress of a sheet made of thermoplastic resin (A) at 150°C when 100% elongated is 0.1 MPa or more and 30 MPa or less, or the main component of thermoplastic resin (A) is an amorphous resin and the tensile stress of a sheet made of thermoplastic resin (A) at 200°C when 100% elongated is 0.1 MPa or more and 30 MPa or less. The tensile stress is more preferably 25 MPa or less, more preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less. 【0024】When the tensile stress is above the lower limit, the sagging of the sheet during heating can be reduced, making it easier to shape the sheet onto the substrate. When the tensile stress is below the upper limit, when the heated sheet is molded to cover the circuit board, it becomes easier to stretch the sheet uniformly overall, resulting in improved shape-following ability. 【0025】 The sheet made of thermoplastic resin (A) used in the embodiments of the present invention preferably satisfies the following condition 3. Condition 3: When the sheet made of thermoplastic resin (A) is immersed in a cooling liquid (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours, the liquid absorption rate is 0% or more and 10% or less. 【0026】 The upper limit of the liquid absorption rate is more preferably 8% or less, even more preferably 6% or less, particularly preferably 4% or less, and especially preferably 3% or less. The method for measuring the liquid absorption rate will be described later. Note that if the liquid absorption rate is less than 0%, it indicates that some of the thermoplastic resin (A) is dissolved in the coolant. By insulating and protecting the circuit board with thermoplastic resin (A) that has a liquid absorption rate of 0% or more and 10% or less when immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours, dielectric breakdown can be made less likely to occur when the insulated circuit board is immersed in the coolant. Here, the mixture of ethylene glycol and pure water in a weight ratio of 1:1 is used as a test coolant that mimics the composition of a long-life coolant. 【0027】 To obtain such a sheet, it is preferable that the main component of the sheet is a resin selected from PPS, PEEK, PPSU, PES, and PSU. Specifically, examples include unstretched sheets press-molded from these resins, unstretched sheets obtained by extruding these resins, which have been heated and melted in an extruder, through a T-die, taking them back with a cooling roll for molding, and then winding them up, and tubes obtained by blowing these resins, which have been heated and melted in an extruder, through a circular die while simultaneously blowing air into them for inflation molding. 【0028】The sheet made of thermoplastic resin (A) used in the embodiment of the present invention preferably contains a black pigment. By using a sheet containing a black pigment, when the sheet is heated using an infrared (IR) heater, the absorption wavelength band of the sheet is broadened, allowing for efficient absorption of infrared rays, which in turn increases the heating rate and shortens the molding process time. 【0029】 In the present invention, a preferred method for manufacturing an insulating protective circuit board involves spreading a sheet made of thermoplastic resin (A) to cover the entire circuit board, and then using the pressure difference between the top and bottom of the sheet to mold the sheet so that it covers the circuit board, thereby insulating and protecting it with the thermoplastic resin (A). By molding the circuit board to cover it with a sheet made of thermoplastic resin (A), drying and curing treatments are unnecessary compared to methods of coating or potting the resin, thus enabling a simple, solvent-free, and environmentally friendly insulating treatment. Furthermore, because the sheet made of thermoplastic resin (A) is flexible, the insulating resin is less likely to crack compared to cases where the resin is coated or potted, resulting in a highly reliable insulating protective circuit board. Methods for molding a sheet made of thermoplastic resin (A) to cover a circuit board using a pressure difference include, for example, a molding method in which the sheet is spread out and set above the circuit board to cover the entire circuit board, a pressure difference is created in the upper and lower spaces surrounding the set sheet, and the heated and softened sheet is molded onto the circuit board; a molding method in which the sheet is spread out and set above the circuit board to cover the circuit board, a vacuum is drawn through a hole in the base at the bottom of the circuit board and a hole in the circuit board, and the heated and softened sheet is molded onto the circuit board; and a molding method in which the circuit board is set inside a tube or bag made of the sheet, and a pressure difference is created by reducing the pressure inside the tube or bag. 【0030】In embodiments of the present invention, if the thermoplastic resin (A) is a crystalline resin, the sheet made of the thermoplastic resin (A) preferably has a degree of crystallinity of 5% to 30%, more preferably 10% to 25%, and even more preferably 15% to 20%. By using a sheet with a degree of crystallinity of 5% or more, the liquid absorption rate when immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours can be set to 0% to 10%. By using a sheet with a degree of crystallinity of 30% or less, the tensile elongation at 200°C can be set to 50% or more, and the tensile stress at 100% elongation at 200°C can be set to 30 MPa or less. 【0031】 In embodiments of the present invention, the sheet made of thermoplastic resin (A) preferably constitutes a multilayer sheet laminated with an adhesive layer (B), and the circuit board is preferably insulated and protected by this multilayer sheet. Here, the sheet made of thermoplastic resin (A) may also be referred to as the thermoplastic resin substrate (A). 【0032】Examples of adhesives that constitute the adhesive layer (B) include acrylic, epoxy, olefin, urethane, silicone, rubber, polyimide, polyamide-imide, polyetherimide, and polyethersulfone adhesives or tacks (hereinafter, adhesives and tacks are collectively referred to simply as adhesives). In particular, when the temperature at which the circuit board insulated and protected by the thermoplastic resin (A) is used as the final product is high, it is desirable that the heat resistance temperature of the adhesive layer (B) be high. For example, when the final product is an automotive electrical component, eAxle, xEV, server, data center, etc., the operating temperature of the circuit board may be 100°C or higher. In such cases, the heat resistance temperature of the adhesive layer (B) is preferably 100°C or higher, more preferably 150°C or higher, even more preferably 190°C or higher, and in some cases 230°C or higher may be required. When such high-temperature use is anticipated, among the adhesives that constitute the adhesive layer (B) described above, polyimide adhesives, polyamide-imide adhesives, polyetherimide adhesives, and polyethersulfone adhesives are particularly preferred as suitable adhesives. Among these, polyamide-imide adhesives are preferred because their heat resistance temperature can be controlled by their molecular structure. As adhesives, it is preferable to select those with a glass transition temperature of 150°C or higher, more preferably 190°C or higher, and it is also possible to select those with a glass transition temperature of 230°C or higher. Specific examples of such polyamide-imide adhesives include the thermoplastic polyamide-imide adhesives manufactured by Resonaq Corporation (SF-10D-30, SF-21C-01, SF-32A-1010). 【0033】When a sheet made of thermoplastic resin (A) is coated onto a circuit board and then heated, the sheet may shrink and peel off the circuit board. By using a multilayer sheet having a sheet made of thermoplastic resin (A) and an adhesive layer (B), it is possible to prevent the sheet made of thermoplastic resin (A) from peeling off the circuit board even when heated. Therefore, it is preferable that the adhesive layer (B) has a high adhesive strength such that the multilayer sheet does not peel off the circuit board when heated. On the other hand, when the insulating protective circuit board of the present invention is used in a server, the multilayer sheet may be peeled off the circuit board for periodic maintenance. Therefore, it is preferable that the adhesive strength between the circuit board and the adhesive layer (B) is low enough so that mounted components on the circuit board do not fall off when the multilayer sheet is peeled off the circuit board. 【0034】 Furthermore, it is preferable that the adhesive layer (B) has a high tensile elongation and low tensile stress when heated, such that after spreading and setting the multilayer sheet to cover the entire circuit board, the multilayer sheet can be molded to cover the circuit board by utilizing the pressure difference. 【0035】 Methods for laminating the adhesive layer (B) onto a sheet made of thermoplastic resin (A) include applying a liquid obtained by dissolving or dispersing the adhesive layer (B) material in water or an organic solvent onto the sheet made of thermoplastic resin (A) and drying the water or organic solvent in a hot air oven, or pressing or heat-pressing the sheet-like adhesive layer (B) onto the sheet made of thermoplastic resin (A). 【0036】 Applicable applications of the insulating protection circuit board of the present invention include, for example, power semiconductors such as power modules, electrical and electronic components such as sensors, servers, and printed circuit boards, automotive electrical components such as inverters, electric control units, and eAxles, and various applications such as xEVs, internal combustion engine vehicles, and data centers. 【0037】 The insulating protective circuit board of the present invention is preferably used by immersing it in a cooling liquid. Specific embodiments are shown below. 【0038】The insulating protective circuit board of the present invention is suitable for use in an automotive electrical component having an insulating protective circuit board and a cooling device including a coolant, wherein the insulating protective circuit board is immersed in the coolant. For example, in an inverter, when a circuit board on which power semiconductors such as Si (silicon) semiconductors, SiC (silicon carbide) semiconductors, and GaN (gallium nitride) semiconductors are mounted is used as an automotive electrical component, immersing the circuit board in a coolant such as LLC or ATF allows for efficient cooling of the heat generated from the power semiconductors from the entire surface of the circuit board, potentially improving the performance of the inverter. By using the insulating protective circuit board of the present invention as the circuit board, the surface of the circuit board is electrically isolated from the surroundings, and the circuit board can be used safely even when immersed in a coolant. Furthermore, components mounted on the circuit board can be protected from contamination by the coolant, potentially preventing circuit board failure. 【0039】 The insulating protective circuit board of the present invention can be suitably used in a server having an insulating protective circuit board and a cooling device including a coolant, wherein the insulating protective circuit board is immersed in the coolant. When a circuit board equipped with semiconductor chips such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit) is used in a server, immersing it in a coolant such as water or oil can efficiently cool the heat generated from the semiconductor chips from the entire surface of the circuit board, potentially improving the performance of the server. By using the insulating protective circuit board of the present invention as the circuit board, the surface of the circuit board is electrically isolated from the surroundings, and the circuit board can be used safely even when immersed in a coolant. Furthermore, when maintaining the circuit board, the top of the circuit board can be exposed simply by peeling off a sheet made of thermoplastic resin (A), eliminating the need to remove a high-viscosity, non-volatile coolant such as oil, potentially simplifying maintenance. 【0040】The automotive electrical component including the insulating protection circuit board of the present invention can be suitably used in eAxle and xEV. For example, in inverters used in these applications, power semiconductors are generally cooled indirectly by attaching a metal heat sink to the power semiconductor via an insulating sheet and cooling the heat sink with a coolant. However, the design of the coolant circuit within the inverter and the design of fins to improve the cooling efficiency of the heat sink can be complex and require a great deal of effort. By using an inverter including the insulating protection circuit board of the present invention, the inverter can be used safely even when immersed in a coolant, eliminating the need for a heat sink. This simplifies the design of the coolant circuit within the inverter, potentially leading to weight reduction and reduced manufacturing costs for eAxle and xEV equipped with that inverter. 【0041】 A server incorporating the insulating protective circuit board of the present invention can be suitably used in data centers. In servers used in data centers, when the circuit board is cooled by immersion in a coolant, it is common to use insulating liquids such as low-boiling-point fluorine-based refrigerants or oil as the coolant. However, fluorine-based refrigerants raise concerns about their harmful effects on human health, and their high specific gravity may prevent high-density server deployment due to weight limitations in data center buildings. Oil, on the other hand, has high viscosity, resulting in low cooling efficiency, and its low volatility may worsen server maintainability. By using a server incorporating the insulating protective circuit board of the present invention, the insulating protective circuit board can be cooled by immersion in conductive water, potentially enabling highly efficient server cooling with minimal environmental impact. 【0042】 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the descriptions in these examples. 【0043】 The evaluation and measurement methods used in the examples are shown below. 【0044】[Liquid Absorption Rate] A sheet made of the thermoplastic resin (A) was punched into a size of 50 mm × 8 mm and immersed in a coolant prepared by mixing ethylene glycol and pure water at a weight ratio of 1:1 in an autoclave container, and heat-treated in an oven at 150°C for 250 hours. The liquid absorption rate was calculated by the following formula from the weights of the punched sheet before and after the heat treatment. In the case where the liquid absorption rate is less than 0%, it indicates that a part of the thermoplastic resin (A) is dissolved in the coolant. Liquid Absorption Rate (%) = (Sheet weight after heat treatment - Sheet weight before immersion in coolant) / (Sheet weight before immersion in coolant) × 100 【0045】 [Tensile Elongation at 250°C, 200°C and 150°C] A sheet of the thermoplastic resin (A) was punched into a size of 50 mm × 8 mm to obtain test pieces. Using an Instron tensile testing machine (“INSTRON” (registered trademark) 5985), the test pieces were pulled at a test speed of 500 mm / min in each constant temperature bath at 250°C, 200°C and 150°C respectively, and the tensile elongation when the sheet broke was calculated as follows. Let the distance between the chucks before the test be A (20 mm) and the distance between the chucks at the time of sheet break be B (mm). Tensile Elongation (%) = (B - A) / A × 100 【0046】 [Tensile Stress at 100% Elongation at 250°C, 200°C and 150°C] A sheet of the thermoplastic resin (A) was punched into a size of 50 mm × 8 mm to obtain test pieces. Using an Instron tensile testing machine (“INSTRON” (registered trademark) 5985), the test pieces were pulled at a test speed of 500 mm / min in each constant temperature bath at 250°C, 200°C and 150°C respectively, and the tensile stress when the sheet was elongated by 100% was read. 【0047】[Crystallinity] Using approximately 10 mg of a sheet made of the thermoplastic resin (A) as a sample, the heat of fusion (ΔHm) and the heat of exothermic cold crystallization (ΔHcc) observed when the temperature was raised from 50°C to 340°C at a heating rate of 20°C / min with nitrogen as the carrier gas using a DSC (Q200) manufactured by TA Instruments were observed, and the crystallinity was calculated using the following formula. Crystallinity (%) = (ΔHm - ΔHcc) / Heat of fusion of fully crystalline thermoplastic resin (A) × 100 ÷ Content of thermoplastic resin (A) Here, the heat of fusion of fully crystalline thermoplastic resin (A) was 146.2 [J / g] when the thermoplastic resin (A) was PPS (cited from International Polymer Processing, 1988, Vol.3, No.2, pp.79-85). Similarly, when the thermoplastic resin (A) was other than PPS, the value of the heat of fusion at full crystallization of the thermoplastic resin (A) described in known academic papers and technical reports was used. 【0048】 The materials used in the examples are shown below. 【0049】 (Synthesis Example 1) PPS1 An autoclave equipped with a stirrer and a bottom plug valve was charged with 8.27 kg (70.00 mol) of 47.5% sodium hydrosulfide, 2.94 kg (70.63 mol) of 96% sodium hydroxide, 11.45 kg (115.50 mol) of N-methyl-2-pyrrolidone (NMP), 2.24 kg (27.30 mol) of sodium acetate, and 5.50 kg of ion-exchanged water, and gradually heated to 245°C over about 3 hours while passing nitrogen at normal pressure. After 9.77 kg of water and 0.28 kg of NMP were distilled off, the reaction vessel was cooled to 200°C. The amount of hydrogen sulfide scattered was 0.02 mol per mole of the charged alkali metal sulfide. 【0050】Subsequently, 10.36 kg (70.46 mol) of p-dichlorobenzene, 0.04 kg (0.20 mol) of 1,2,4-trichlorobenzene, and 9.37 kg (94.50 mol) of NMP were added. The reaction vessel was sealed under nitrogen gas, and the temperature was raised from 200°C to 270°C at a rate of 0.6°C / min while stirring at 240 rpm. The reaction was then carried out at 270°C for 140 minutes. After that, the mixture was cooled from 270°C to 250°C over 15 minutes. Then, it was gradually cooled from 250°C to 220°C over 75 minutes, and then rapidly cooled to near room temperature before the contents were removed. 【0051】 The obtained contents were diluted with approximately 35 liters of NMP to form a slurry, which was stirred at 85°C for 30 minutes. The slurry was then filtered through an 80-mesh wire mesh (mesh opening 0.175 mm) to obtain solid material. The obtained solid material was similarly washed and filtered with approximately 35 liters of NMP. The obtained solid material was diluted with 70 liters of deionized water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh to recover the solid material. This process was repeated a total of three times. The obtained solid material and 36 g of calcium acetate were diluted with 70 liters of deionized water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh. The obtained solid material was then diluted with 70 liters of deionized water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh to recover the solid material. The solid material thus obtained was dried under a nitrogen atmosphere at 120°C to obtain PPS1 with a glass transition temperature of 90°C. 【0052】 (Synthesis Example 2) PPS2 In an autoclave equipped with a stirrer, 8.27 kg (70.00 mol) of 47.5% sodium hydroxide, 2.96 kg (70.97 mol) of 96% sodium hydroxide, 11.43 kg (115.50 mol) of N-methyl-2-pyrrolidone (NMP), 2.58 kg (31.50 mol) of sodium acetate, and 10.50 kg of deionized water were charged. The mixture was gradually heated to 245°C over approximately 3 hours under atmospheric pressure while passing nitrogen through it. After distilling off 14.80 kg of water and 0.28 kg of NMP, the reaction vessel was cooled to 160°C. The amount of residual water in the system per mole of alkali metal sulfide charged was 1.06 mol, including the water consumed in the hydrolysis of NMP. The amount of hydrogen sulfide released was 0.02 mol per mole of alkali metal sulfide charged. 【0053】Next, 10.24 kg (69.63 mol) of p-dichlorobenzene, 0.55 g (0.003 mol) of 1,2,4-trichlorobenzene, and 9.00 kg (91.00 mol) of NMP were added. The reaction vessel was sealed under nitrogen gas and heated to 238°C at a rate of 0.6°C / min while stirring at 240 rpm. After the reaction was carried out at 238°C for 95 minutes, the temperature was raised to 270°C at a rate of 0.8°C / min. After the reaction was carried out at 270°C for 100 minutes, the mixture was cooled to 250°C at a rate of 1.3°C / min while injecting 1.26 kg (70 mol) of water over 15 minutes. After that, it was cooled to 200°C at a rate of 1.0°C / min and then rapidly cooled to near room temperature. 【0054】 The contents were removed, diluted with 26.3 kg of NMP, and the solvent and solids were filtered off using a sieve (80 mesh). The resulting particles were washed and filtered with 31.90 kg of NMP. These were then washed and filtered several times with 56.00 kg of deionized water, and finally washed and filtered with 70.00 kg of 0.05 wt% calcium acetate aqueous solution. Subsequently, the obtained hydrated PPS particles were dried with hot air at 80°C and then dried under reduced pressure at 120°C to obtain PPS2 with a glass transition temperature of 90°C. 【0055】 Sheet 1 of thermoplastic resin (A) The PPS1 obtained in Synthesis Example 1 was sandwiched between "Kapton" (registered trademark) films and melted under a pressure of 4 MPa using a press heated to 320°C. Next, the "Kapton" (registered trademark) film containing the molten PPS was transferred to a press heated to 150°C and held without pressure to crystallize. The "Kapton" (registered trademark) film was peeled off to obtain an unstretched PPS sheet (Sheet 1 of thermoplastic resin (A)) with a thickness of 200 μm. The obtained Sheet 1 of thermoplastic resin (A) had a liquid absorption rate of 0.2%, a tensile elongation of 224% at 200°C, a tensile elongation of 181% at 150°C, a tensile stress of 20 MPa at 100% elongation at 200°C, a tensile stress of 26 MPa at 150°C at 100% elongation, and a crystallinity of 21.7%. 【0056】Sheet 2 of Thermoplastic Resin (A) The PPS1 obtained in Synthesis Example 1 was sandwiched between "Kapton" (registered trademark) films and melted under a pressure of 4 MPa using a press heated to 320°C. Next, the "Kapton" (registered trademark) film containing the molten PPS was transferred to a press heated to 120°C and held without pressure to crystallize. The "Kapton" (registered trademark) film was peeled off to obtain an unstretched PPS sheet (Sheet 2 of Thermoplastic Resin (A)) with a thickness of 150 μm. The obtained Sheet 2 of Thermoplastic Resin (A) had a liquid absorption rate of 0.1%, a tensile elongation of 450% at 200°C, a tensile elongation of 414% at 150°C, a tensile stress of 5 MPa at 100% elongation at 200°C, a tensile stress of 8 MPa at 100% elongation at 150°C, and a crystallinity of 19.9%. 【0057】 For the thermoplastic resin (A) sheet 3, using a TEX30α twin-screw extruder manufactured by Japan Steel Works Ltd., set to a cylinder temperature of 300°C and a screw rotation speed of 200 rpm, 0.3 parts by weight of carbon black was added to 100 parts by weight of PPS1 obtained in Synthesis Example 1 through the raw material supply port and melted. The resin extruded from the extruder was pelletized using a strand cutter, and then dried overnight with hot air at 120°C to obtain black PPS1 pellets. The obtained black PPS1 pellets were sandwiched between "Kapton" (registered trademark) films and melted under a pressure of 4 MPa using a press heated to 320°C. Next, the "Kapton" (registered trademark) film containing the molten PPS was transferred to a press heated to 120°C and held without pressure to crystallize. The "Kapton" (registered trademark) film was peeled off to obtain an unstretched PPS sheet (thermoplastic resin (A) sheet 3) with a thickness of 150 μm. The obtained thermoplastic resin (A) sheet 3 had a liquid absorption rate of 0.1%, a tensile elongation of 439% at 200°C, a tensile elongation of 401% at 150°C, a tensile stress of 5 MPa at 100% elongation at 200°C, a tensile stress of 8 MPa at 150°C, and a crystallinity of 19.9%. 【0058】Sheet 4 of thermoplastic resin (A): PPSU pellets (BASF Japan Ltd.'s "Ultrason"® P3010) with a glass transition temperature of 220°C were sandwiched between "Kapton"® films and melted under a pressure of 4 MPa using a press heated to 370°C. Next, the "Kapton"® film containing the molten PPSU was transferred to a press at room temperature and held without pressure to solidify. The "Kapton"® film was peeled off to obtain a PPSU sheet (sheet 4 of thermoplastic resin (A)) with a thickness of 150 μm. The obtained sheet 4 of thermoplastic resin (A) had a liquid absorption rate of 1.4%, a tensile elongation of 380% at 250°C, and a tensile stress of 2 MPa at 100% elongation at 250°C. 【0059】 For the thermoplastic resin (A) sheet 5, using a TEX30α twin-screw extruder manufactured by Japan Steel Works Ltd., with the cylinder temperature set to 300°C and the screw rotation speed to 200 rpm, the PPS2 obtained in Synthesis Example 2 was fed in through the raw material supply port and melted. The resin extruded from the extruder was pelletized using a strand cutter, and then dried overnight with hot air at 120°C to obtain PPS2 pellets. The obtained PPS2 pellets were supplied to a single-screw extruder and melted at 310°C. The molten resin was filtered through a stainless steel fiber sintered filter with an average mesh opening of 10 μm, and then extruded into a sheet from a 900 mm wide T-die. Next, this sheet was wrapped around a cooling roll with a surface temperature of 100°C while being pressed with a rubber nip roll, and cooled and solidified to obtain a PPS sheet (thermoplastic resin (A) sheet 5) with a thickness of 150 μm. The obtained thermoplastic resin (A) sheet 5 had a liquid absorption rate of 0.1%, a tensile elongation of 441% at 200°C, a tensile elongation of 400% at 150°C, a tensile stress of 5 MPa at 100% elongation at 200°C, a tensile stress of 8 MPa at 150°C, and a crystallinity of 19.5%. 【0060】For the thermoplastic resin (A) sheet 6, using a TEX30α twin-screw extruder manufactured by Japan Steel Works Ltd., with the cylinder temperature set to 300°C and the screw rotation speed to 200 rpm, 0.3 parts by weight of carbon black was added to 100 parts by weight of PPS2 obtained in Synthesis Example 2 through the raw material supply port and melted. The resin extruded from the extruder was pelletized using a strand cutter, and then dried overnight with hot air at 120°C to obtain black PPS2 pellets. The obtained PPS2 pellets were supplied to a single-screw extruder and melted at 310°C. The molten resin was filtered through a stainless steel fiber sintered filter with an average mesh opening of 10 μm, and then extruded into a sheet from a 900 mm wide T-die. Next, this sheet was wrapped around a cooling roll with a surface temperature of 100°C while being pressed with a rubber nip roll and cooled and solidified to obtain a PPS sheet (thermoplastic resin (A) sheet 6) with a thickness of 150 μm. The obtained thermoplastic resin (A) sheet 6 had a liquid absorption rate of 0.1%, a tensile elongation of 439% at 200°C, a tensile elongation of 398% at 150°C, a tensile stress of 5 MPa at 100% elongation at 200°C, a tensile stress of 8 MPa at 150°C, and a crystallinity of 19.6%. 【0061】 Sheet 7 of thermoplastic resin (A) The PPS1 obtained in Synthesis Example 1 was sandwiched between "Kapton" (registered trademark) films and melted using a press heated to 320°C under a pressure of 4 MPa. Next, the "Kapton" (registered trademark) film containing the molten PPS was rapidly cooled by immersion in ice water to obtain an amorphous PPS sheet. The obtained amorphous PPS sheet was stretched to 3.5 times x 3.5 times at 103°C using an automatic biaxial stretching machine (IMC-11A9) manufactured by Imoto Seisakusho, and then heat-treated at 265°C while holding the sheet to crystallize it, thereby obtaining a biaxially oriented PPS sheet (Sheet 7 of thermoplastic resin (A)). The obtained thermoplastic resin (A) sheet 7 had a liquid absorption rate of 0.5%, a tensile elongation of 26% at 200°C, a tensile elongation of 23% at 150°C, a tensile stress at fracture of 38 MPa at 200°C, a tensile stress at fracture of 49 MPa at 150°C, and a crystallinity of 31.4%. 【0062】A sheet of thermoplastic resin (A) was prepared by sandwiching polyetherimide (PEI) pellets ("Ultem"® Resin 1000, manufactured by SABIC Japan LLC) with a glass transition temperature of 215°C between "Kapton"® films and melting them under a pressure of 4 MPa using a press heated to 370°C. The "Kapton"® films containing the molten PEI were then transferred to a press at room temperature and allowed to solidify without pressure. The "Kapton"® films were peeled off to obtain a PEI sheet (sheet 8 of thermoplastic resin (A)) with a thickness of 150 μm. The obtained sheet 8 of thermoplastic resin (A) had a liquid absorption rate of -1.0%, a tensile elongation of 390% at 250°C, and a tensile stress of 2 MPa at 100% elongation at 250°C. 【0063】 A thermoplastic polyimide (PI) pellet ("Surprim"® TO65, manufactured by Mitsubishi Gas Chemical Company, Inc.) with a glass transition temperature of 185°C was sandwiched between "Kapton"® films and melted under a pressure of 4 MPa using a press heated to 355°C. Next, the "Kapton"® film containing the molten PI was transferred to a press at room temperature and held without pressure to solidify. The "Kapton"® film was peeled off to obtain a PI sheet (thermoplastic resin (A) sheet 9) with a thickness of 150 μm. The obtained thermoplastic resin (A) sheet 9 had a liquid absorption rate of -2.0%, a tensile elongation of 370% at 250°C, and a tensile stress of 2 MPa at 100% elongation at 250°C. 【0064】A sheet of thermoplastic resin (A) was prepared by sandwiching acrylic (PMMA) pellets ("Acrypet"® VH, manufactured by Mitsubishi Chemical Corporation) with a glass transition temperature of 100°C between "Kapton"® films and melting them under a pressure of 4 MPa using a press heated to 200°C. Next, the "Kapton"® film containing the molten PMMA was transferred to a press at room temperature and held without pressure to solidify. The "Kapton"® film was peeled off to obtain a PMMA sheet (sheet of thermoplastic resin (A)) with a thickness of 150 μm. The obtained sheet of thermoplastic resin (A) 10 had a liquid absorption rate of 14.0%, a tensile elongation of 480% at 150°C, and a tensile stress of 3 MPa at 100% elongation at 150°C. 【0065】 The following experiment was conducted using a circuit board with capacitors and IC chips mounted on a printed circuit board measuring 150 mm in width and 110 mm in length. 【0066】 [Example 1] Using a TOM molding machine (NGF-0406-T) manufactured by Fuse Vacuum Co., Ltd., a sheet 1 of thermoplastic resin (A) cut to A4 size was placed on the frame, and the circuit board was set on the lifting table. Then the upper and lower boxes were closed and the upper and lower boxes were vacuumed. Next, the sheet was heated to 200°C for 145 seconds using an IR heater, and then the lifting table was raised while the upper box was pressurized to 0.2 MPa to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Then, using the same procedure, insulating protection was applied to the opposite side of the circuit board, obtaining an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and then the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0067】[Example 2] Using a TOM molding machine (NGF-0406-T) manufactured by Fuse Vacuum Co., Ltd., a sheet 1 of thermoplastic resin (A) cut to A4 size was placed on the frame, and the circuit board was set on the lifting table. Then the upper and lower boxes were closed and the upper and lower boxes were vacuumed. Next, the sheet was heated to 150°C for 47 seconds using an IR heater, and then the lifting table was raised while the upper box was pressurized to 0.2 MPa to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Then, using the same procedure, insulating protection was applied to the opposite side of the circuit board, obtaining an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and then the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0068】 [Example 3] Using a TOM molding machine (NGF-0406-T) manufactured by Fuse Vacuum Co., Ltd., a sheet 3 of thermoplastic resin (A) cut to A4 size was placed on the frame, and the circuit board was set on the lifting table. Then the upper and lower boxes were closed and the upper and lower boxes were vacuumed. Next, the sheet was heated to 200°C for 80 seconds using an IR heater, and then the lifting table was raised while the upper box was pressurized to 0.2 MPa to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Then, using the same procedure, insulating protection was applied to the opposite side of the circuit board, obtaining an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and then the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0069】[Example 4] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 1 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 264°C from both sides using an IR heater for 21 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Subsequently, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0070】 [Example 5] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 2 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 206°C from both sides using an IR heater for 15 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Next, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Then, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0071】[Example 6] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 3 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 206°C from both sides using an IR heater for 10 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Next, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Then, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0072】 [Example 7] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 4 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 300°C from both sides using an IR heater for 18 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Subsequently, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 340°C, and the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0073】[Example 8] An acrylic adhesive (X3(50)) manufactured by Nichiei Shinka Co., Ltd. was bonded to a thermoplastic resin (A) sheet 3 cut to A4 size, and then heat-treated at 80°C for 5 minutes using a hot air oven. Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., the sheet 3 with the adhesive bonded to it was placed on the frame, and the circuit board was set on the lifting table. Next, the sheet was heated to 232°C from both sides using an IR heater for 12 seconds, then the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, thus providing insulating protection to one side of the circuit board. Then, using the same procedure, insulating protection was applied to the opposite side of the circuit board, obtaining an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and then the excess sheet was removed by trimming. In this embodiment, the insulating protective circuit board is covered with an insulating thermoplastic resin, so it can be used safely even when immersed in a coolant. Furthermore, because the thermoplastic resin (A) sheet and the circuit board are bonded together, the thermoplastic resin (A) sheet does not peel off the circuit board even when heat-treated in a hot air oven at 150°C for 10 minutes, making it possible to use it as a circuit board with higher heat resistance and cooling efficiency with a coolant. 【0074】 [Example 9] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 5 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 231°C from both sides using an IR heater for 12 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Subsequently, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0075】 [Example 10] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 6 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 231°C from both sides using an IR heater for 9 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Subsequently, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and the excess sheet was removed by trimming. The insulating protected circuit board of this example can be used safely even when immersed in a coolant because the circuit board is covered with insulating thermoplastic resin. 【0076】 [Example 11] An acrylic adhesive (X3(50)) manufactured by Nichiei Shinka Co., Ltd. was bonded to a thermoplastic resin (A) sheet 6 cut to A4 size, and then heat-treated at 80°C for 5 minutes using a hot air oven. Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., the sheet 6 with the adhesive bonded to it was placed on the frame, and the circuit board was set on the lifting table. Next, the sheet was heated to 231°C from both sides using an IR heater for 9 seconds, then the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, thus providing insulating protection to one side of the circuit board. Then, using the same procedure, insulating protection was applied to the opposite side of the circuit board, obtaining an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 275°C, and then the excess sheet was removed by trimming. In this embodiment, the insulating protective circuit board is covered with an insulating thermoplastic resin, so it can be used safely even when immersed in a coolant. Furthermore, because the thermoplastic resin (A) sheet and the circuit board are bonded together, the thermoplastic resin (A) sheet does not peel off the circuit board even when heat-treated in a hot air oven at 150°C for 10 minutes, making it possible to use it as a circuit board with higher heat resistance and cooling efficiency with a coolant. 【0077】 [Comparative Example 1] Using a TOM molding machine (NGF-0406-T) manufactured by Fuse Vacuum Co., Ltd., a sheet 7 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Subsequently, the sheet was heated to 200°C from both sides with an IR heater for 146 seconds. After moving the lifting table to the position of the sheet, it was raised, and an attempt was made to vacuum the area below the circuit board to make the sheet adhere tightly to the circuit board. However, the sheet could not be stretched and broke, and insulation protection could not be achieved. 【0078】 [Comparative Example 2] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 8 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 300°C from both sides using an IR heater for 20 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Subsequently, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 340°C, and the excess sheet was removed by trimming. In this comparative example, the insulating protected circuit board had insufficient insulating protection because the thermoplastic resin (A) dissolved in the LLC. 【0079】[Comparative Example 3] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 9 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 300°C from both sides using an IR heater for 21 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Subsequently, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 340°C, and the excess sheet was removed by trimming. In this comparative example, the insulating protected circuit board had insufficient insulating protection because the thermoplastic resin (A) dissolved in the LLC. 【0080】 [Comparative Example 4] Using a vacuum pressure forming machine (KFS-062-20) manufactured by Asano Research Institute Co., Ltd., a sheet 10 of thermoplastic resin (A) cut to A4 size was placed on the frame, and a circuit board was set on the lifting table. Next, the sheet was heated to 150°C from both sides using an IR heater for 7 seconds. Then, the lifting table was moved to the position of the sheet and raised, and the area below the circuit board was vacuumed to make the sheet adhere tightly to the circuit board, providing insulating protection to one side of the circuit board. Subsequently, the opposite side of the circuit board was also provided with insulating protection using the same procedure, resulting in an insulating protected circuit board with insulating protection on both sides. Next, the sheet that protruded around the insulating protected circuit board was heat-sealed at 190°C, and the excess sheet was removed by trimming. The circuit board in this comparative example could not be insulated because it was covered with thermoplastic resin (A), which absorbs a lot of liquid from LLC. 【0081】 【0082】

Claims

1. An insulated circuit board in which the circuit board is insulated and protected by a sheet made of thermoplastic resin (A).

2. An insulating protective circuit board in which the circuit board is insulated and protected by a sheet made of thermoplastic resin (A), wherein the thermoplastic resin (A) is at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher.

3. The insulating protective circuit board according to claim 1, wherein the thermoplastic resin (A) is mainly composed of at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher.

4. The insulating protective circuit board according to claim 1 or 2, wherein the thermoplastic resin (A) has a liquid absorption rate of 0% or more and 10% or less when immersed in a cooling liquid (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours.

5. The insulating protective circuit board according to claim 4, satisfying either condition 1 or 2 below: Condition 1: The main component of the thermoplastic resin (A) is a crystalline resin and the tensile elongation of a sheet made of the thermoplastic resin (A) at 200°C is 100% or more, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile elongation of a sheet made of the thermoplastic resin (A) at 250°C is 100% or more; Condition 2: The main component of the thermoplastic resin (A) is a crystalline resin and the tensile stress at 100% elongation at 200°C of a sheet made of the thermoplastic resin (A) is 0.1 MPa or more and 30 MPa or less, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile stress at 100% elongation at 250°C of a sheet made of the thermoplastic resin (A) is 0.1 MPa or more and 30 MPa or less.

6. The insulating protective circuit board according to claim 5, satisfying the following condition 2': Condition 2': The main component of the thermoplastic resin (A) is a crystalline resin, and the tensile stress of a sheet made of the thermoplastic resin (A) at 150°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less, or the main component of the thermoplastic resin (A) is an amorphous resin, and the tensile stress of a sheet made of the thermoplastic resin (A) at 200°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less.

7. An insulating protective circuit board according to claim 6, wherein the circuit board is insulated and protected by a multilayer sheet comprising a sheet made of thermoplastic resin (A) and an adhesive layer (B) laminated together.

8. The insulating protective circuit board according to claim 7, wherein the sheet made of thermoplastic resin (A) contains a black pigment.

9. A method for manufacturing an insulating and protected circuit board according to claim 1 or 2, comprising spreading and setting a sheet made of thermoplastic resin (A) so as to cover the entire circuit board, and then using the pressure difference between the top and bottom of the sheet to mold the sheet so that it covers the circuit board, thereby obtaining a circuit board that is insulated and protected by thermoplastic resin (A).

10. An automotive electrical component comprising an insulating protective circuit board according to claim 1 or 2.

11. An eAxle comprising the automotive electrical component described in claim 10.

12. xEV including the in-vehicle electrical component described in claim 10.

13. A server comprising an insulating protective circuit board according to claim 1 or 2.

14. A data center including the server described in claim 13.

15. A thermoplastic resin sheet made of a thermoplastic resin (A), wherein the thermoplastic resin (A) mainly contains a resin with a glass transition temperature of 70°C or higher, the degree of crystallinity of the thermoplastic resin sheet is 5% or more and 30% or less, the tensile elongation at 200°C is 100% or more, and the tensile stress at 100% elongation at 150°C is 0.1 MPa or more and 30 MPa or less.

16. The thermoplastic resin sheet according to claim 15, wherein the liquid absorption rate when immersed in a cooling liquid (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less.

17. The thermoplastic resin sheet according to claim 15, comprising a black pigment.

18. A thermoplastic resin sheet made of a thermoplastic resin (A), wherein the thermoplastic resin (A) mainly consists of at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher, and satisfies the following conditions 1 to 4: Condition 1: The main component of the thermoplastic resin (A) is a crystalline resin and the tensile elongation of the thermoplastic resin sheet at 200°C is 100% or higher, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile elongation of the thermoplastic resin sheet at 250°C is 100% or higher; Condition 2: The main component of thermoplastic resin (A) is a crystalline resin, and the tensile stress of the thermoplastic resin sheet at 100% elongation at 200°C is 0.1 MPa or more and 30 MPa or less, or the main component of thermoplastic resin (A) is an amorphous resin, and the tensile stress of the thermoplastic resin sheet at 100% elongation at 250°C is 0.1 MPa or more and 30 MPa or less; Condition 3: The liquid absorption rate when immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less; Condition 4: Contains a black pigment.

19. A thermoplastic resin sheet according to claim 18 that satisfies the following condition 2': Condition 2': The main component of the thermoplastic resin (A) is a crystalline resin and the tensile stress of the thermoplastic resin sheet at 150°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less, or the main component of the thermoplastic resin (A) is an amorphous resin and the tensile stress of the thermoplastic resin sheet at 200°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less.

20. A multilayer sheet comprising a thermoplastic resin sheet according to claim 15 and an adhesive layer (B) laminated together.

21. A multilayer sheet comprising a sheet made of thermoplastic resin (A) and an adhesive layer (B), wherein the thermoplastic resin (A) mainly consists of at least one resin selected from the group consisting of crystalline resins with a glass transition temperature of 70°C or higher and amorphous resins with a glass transition temperature of 160°C or higher, and the multilayer sheet satisfies the following conditions 1 to 3: Condition 1: The main component of the sheet made of thermoplastic resin (A) is a crystalline resin and the tensile elongation of the sheet made of thermoplastic resin (A) at 200°C is 100% or higher, or the main component of the sheet made of thermoplastic resin (A) is an amorphous resin and the tensile elongation of the sheet made of thermoplastic resin (A) at 250°C is 100% or higher; Condition 2: The main component of the sheet made of thermoplastic resin (A) is a crystalline resin, and the tensile stress of the sheet made of thermoplastic resin (A) at 100% elongation at 200°C is 0.1 MPa or more and 30 MPa or less, or the main component of the sheet made of thermoplastic resin (A) is an amorphous resin, and the tensile stress of the sheet made of thermoplastic resin (A) at 100% elongation at 250°C is 0.1 MPa or more and 30 MPa or less; Condition 3: The liquid absorption rate when the sheet made of thermoplastic resin (A) is immersed in a coolant (a mixture of ethylene glycol and pure water in a weight ratio of 1:1) at 150°C for 250 hours is 0% or more and 10% or less.

22. A multilayer sheet according to claim 21 that satisfies the following condition 2': Condition 2': The main component of the sheet made of thermoplastic resin (A) is a crystalline resin and the tensile stress of the sheet made of thermoplastic resin (A) at 150°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less, or the main component of the sheet made of thermoplastic resin (A) is an amorphous resin and the tensile stress of the sheet made of thermoplastic resin (A) at 200°C when it is 100% elongated is 0.1 MPa or more and 30 MPa or less.

23. The multilayer sheet according to claim 21, wherein the sheet is made of thermoplastic resin (A) and contains a black pigment.

24. The multilayer sheet according to claim 21, wherein the thermoplastic resin (A) is mainly composed of a resin selected from polyphenylene sulfide, polyether ether ketone, polyphenyl sulfone, polyether sulfone, and polysulfone.

25. An insulated and protected circuit board in which the circuit board is insulated and protected with a thermoplastic resin sheet according to any one of claims 15 to 19 or a multilayer sheet according to any one of claims 20 to 24.

26. An automotive electrical component comprising an insulating protective circuit board as described in claim 25.

27. An in-vehicle electrical component having a cooling device including an insulating protective circuit board and a coolant according to claim 25, wherein the insulating protective circuit board is immersed in the coolant.

28. An eAxle comprising the automotive electrical component described in claim 26.

29. xEV including the in-vehicle electrical component described in claim 26.

30. A server comprising an insulating protective circuit board as described in claim 25.

31. A server having a cooling device including an insulating protective circuit board and a coolant according to claim 25, wherein the insulating protective circuit board is immersed in the coolant.

32. A data center including the server described in claim 30.

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