Electrical system comprising a radiator for cooling an electrical device

Abstract

The invention relates to an electrical system (100) comprising: - an electrical device (116); - a radiator (102) having a face (110; 104) for receiving the electrical device (116), this face (110; 104) being provided with an electrically insulating layer (112) having a thickness of at least 100 μm and a dielectric strength of at least 10 kV / mm; and - a thermal interface material (114) extending over the electrically insulating layer (112), the electrical device (116) extending over the thermal interface material (114).

Description

Description TITLE: ELECTRICAL SYSTEM WITH A RADIATOR FOR COOLING AN ELECTRICAL DEVICE Technical field of the invention

[0001] The present invention relates to an electrical system with a cooling radiator of an electrical device, an electrical converter, such as an inverter or a rectifier, comprising such an electrical system and a mobility device comprising such an electrical system or such an electrical converter.

[0002] A mobility device is, for example, a motorized land vehicle, a train, an aircraft, or a drone. A motorized land vehicle is, for example, a motor vehicle, a motorcycle, a motorized bicycle, or a motorized wheelchair. Technological background

[0003] It is known to dissipate heat from an electrical device through a metallic and therefore electrically conductive radiator. In this case, a thermal interface material, i.e. thermal paste, is generally used.

[0004] The simplest way to use thermal interface material is to spread it on the heat sink, then push the electrical device into it, and then cure the thermal interface material. One problem with this solution is that it is necessary to provide sufficient distance between the electrical device and the heat sink to prevent current leakage from the electrical device to the heat sink. However, this distance is generally difficult to guarantee due to the positioning tolerances of the electrical device.

[0005] It is also known to provide an electrically insulating layer in the form of a ceramic layer. In this case, thermal interface material is provided between the radiator and the ceramic layer and between the ceramic layer and the electrical device. This solution therefore requires two layers of thermal interface material.

[0006] It may therefore be desirable to provide an electrical system which makes it possible to overcome at least some of the aforementioned problems and constraints. Summary of the invention

[0007] An electrical system is therefore proposed comprising: an electrical device; a radiator having a face for receiving the electrical device, this face being provided with an electrically insulating layer having a thickness of at least 100 pm and a dielectric hardness of at least 10 kV per mm; and a thermal interface material extending over the electrically insulating layer, the electrical device extending over the thermal interface material.

[0008] Thus, the receiving face of the radiator is provided with a coating forming an electrically insulating layer, this insulation being carried out between the component and the radiator.

[0009] The invention may further comprise one or more of the following optional features, in any technically possible combination.

[0010] Optionally, the electrically insulating layer has a thickness of at most 800 μm, preferably at most 500 μm.

[0011] Optionally also, the electrically insulating layer has a thermal conductivity of at least 1 Wm-1.K-1, preferably at least 5 Wm-1.K-1, more preferably at least 10 Wm-1.K-1, more preferably at least 30 Wm-1.K-1.

[0012] Optionally also, the thermal interface material has a thickness of at most 1 mm, preferably at most 0.5 mm.

[0013] Optionally also, the thermal interface material has a thermal conductivity of at least 3.5 Wm-1.K-1.

[0014] Optionally also, the electrical device is at least partially embedded in the thermal interface material, such that the electrical device has edges at least partially in contact with the thermal interface material.

[0015] Also optionally, the electrically insulating layer is a layer of polymerized resin.

[0016] Also optionally, the electrically insulating layer results from a surface treatment carried out on the receiving face.

[0017] Also optionally, the surface treatment is a plasma projection of ceramic in order to create the electrical insulating layer by deposition, for example a deposit of alumina AI2O3.

[0018] Also optionally, the surface treatment is nitridation.

[0019] Optionally also, the electrical system further comprises a part, such as a housing, provided with an opening into which the radiator is inserted, the radiator being fixed to this part, for example by welding.

[0020] Also provided is an electrical converter comprising an electrical system according to the invention.

[0021] A mobility device is also proposed comprising an electrical system according to the invention or an electrical converter according to the invention.

[0022] There is also provided a method of manufacturing an electrical system, comprising: producing an electrically insulating layer having a thickness of at least 100 μm and a dielectric hardness of at least 10 kV per mm, on one face of a radiator; then applying a thermal interface material to the electrically insulating layer; then placing an electrical device on the thermal interface material.

[0023] Optionally, the method further comprises embedding at least a portion of the electrical device into the thermal interface material, such that the electrical device has edges at least partially in contact with the thermal interface material.

[0024] Also optionally, the production of the electrical insulating layer involves the application of a layer of resin, then polymerization of the resin.

[0025] Also optionally, the production of the electrical insulating layer includes a surface treatment on the face of the radiator.

[0026] Also optionally, the surface treatment is electrolytic plasma oxidation.

[0027] Also optionally, the surface treatment is nitridation.

[0028] Also optionally, to make the electrical insulating layer on the face of the radiator, the electrical insulating layer is made on one face of a plate, the method further comprising cutting a piece of the plate, this piece forming the radiator with the electrically insulating layer.

[0029] Optionally also, the method further comprises: inserting the radiator into an opening of a part; and fixing the radiator to the part, for example by welding edges of the radiator to edges of the housing opposite each other.

[0030] Optionally also, the method further comprises stripping a portion of the insulating layer extending over at least a portion of a periphery of the radiator, in order to leave this or these portions of the periphery visible, and the fixing of the radiator to the part is carried out by welding, through the portion or portions left visible, edges of the radiator to edges of the housing opposite. Brief description of the figures

[0031] The invention will be better understood with the aid of the following description, given solely by way of example and with reference to the appended drawings in which: Figure 1 is a side sectional view of a first electrical system according to the invention, Figure 2 is a block diagram of a method for manufacturing the electrical system of Figure 1, Figure 3 is a side sectional view of a first intermediate state of the electrical system during its manufacture according to the method of Figure 2, Figure 4 is a side sectional view of a second intermediate state of the electrical system during its manufacture according to the method of Figure 2, Figure 5 is a side sectional view of a third intermediate state of the electrical system during its manufacture according to the method of Figure 2, Figure 6 is a side sectional view of a second electrical system according to the invention,Figure 7 is a block diagram of a manufacturing process of the electrical system of Figure 6, Figure 8 is a side sectional view of a first intermediate state of the electrical system during its manufacture according to the method of Figure 7, Figure 9 is a side sectional view of a second intermediate state of the electrical system during its manufacture according to the method of Figure 7, Figure 10 is a side sectional view of a third intermediate state of the electrical system during its manufacture according to the method of Figure 7, Figure 11 is a side sectional view of a fourth intermediate state of the electrical system during its manufacture according to the method of Figure 7, Figure 12 is a three-dimensional view of a part of the electrical system manufactured according to the method of Figure 7, Figure 13 is a side sectional view of a fifth intermediate state of the electrical system during its manufacture according to the method of Figure 7,and Figure 14 is a side sectional view of a sixth intermediate state of the electrical system during its manufacture according to the method of Figure 7., Detailed description of the invention

[0032] With reference to Figure 1, a first electrical system 100 according to the invention will now be described.

[0033] The electrical system 100 firstly comprises a radiator 102, for example made of aluminium or an aluminium alloy, for example an AISi12 aluminium alloy (the addition of silicon to the aluminium is useful for the foundry process). The radiator 102 has a face conventionally oriented upwards and called the upper face 104.

[0034] The radiator 102 has, for example, a recess 106 in the upper face 104. The recess 106 has a bottom 110, for example also oriented upwards. As will be apparent later, the bottom 110 forms a face for receiving an electrical device.

[0035] The bottom 110 is provided with an electrically insulating layer 112. The latter has a thickness of at least 100 μm and a dielectric hardness of at least 10 kV per mm. Thus, the electrically insulating layer 112 is capable of withstanding a potential difference of at least 1 kV DC. For example, 200 μm of thickness is necessary to ensure 3 kV DC with 15 kV per mm. For example, 125 μm of thickness is necessary to ensure 5 kV DC with 40 kV per mm.

[0036] Preferably, the electrically insulating layer 112 has a thickness of at most 800 μm, preferably at most 500 μm. Thus, heat transfer through the electrically insulating layer 112 is always possible. The electrically insulating layer 112 has, for example, a thermal conductivity of at least 1 W. 1 .K -1 , preferably at least 5 W.rrr 1 . K' 1 , preferably at least 10 W.rrr 1 . K' 1 , preferably at least 30 W.rrr 1 . K' 1 .

[0037] The electrically insulating layer 112 may be, for example, a layer of polymerized resin. In this case, the thickness is preferably at least 200 μm, for example between 300 μm and 400 μm.

[0038] Alternatively, the electrically insulating layer 112 may result from a surface treatment carried out on the bottom 110.

[0039] For example, the surface treatment may be electrolytic plasma oxidation (EPO) or plasma electrolytic oxidation (PEO), also referred to as microarc oxidation (MAO). This is an electrochemical surface treatment designed to convert the metal of the radiator 102 to its oxide, both inward and outward from the original surface 110. The oxide coating produced is thick, largely crystalline, and, due to the inward oxide production, is highly adherent to the radiator 102.

[0040] Specifically, electrolytic plasma oxidation is similar to anodizing, but uses a higher potential, so that discharges occur and the resulting plasma changes the structure of the oxide layer.

[0041] In another example, the surface treatment may be a ceramic plasma spraying to spray a ceramic plasma, in order to produce the electrically insulating layer 112 by deposition, for example a deposition of alumina AI2O3. For example, ceramic powder is introduced into a high-temperature plasma flame to be melted (plastic state) and / or fused, and accelerated and sprayed against the receiving face 110 to be coated. After impact, the sprayed particles accumulate by crushing to form a lamellae coating, which is held on the substrate mainly by mechanical anchoring. This coating forms the electrically insulating layer 112, for example without oxidation of the receiving face 110. The plasma spraying is for example an atmospheric plasma spraying (APS).

[0042] In another example, the surface treatment may be nitridation, for example by means of a plasma (i.e., plasma nitridation, from the English “plasma nitriding”). In this surface treatment, intense electric fields are used to ionize a nitrogen gas, for example pure nitrogen, forming a plasma which is projected onto the surface 110 to be treated. An example of nitridation is for example described in the article “Mechanical Properties of Aluminum Nitride Layer Formed by Duplex Coating of Barrel Nitriding and Plasma Nitriding” by Yoshidal et al, Plasma Process. Polym. 2009.

[0043] The electrical system 100 further comprises a thermal interface material 114 (for example a thermal paste, an adhesive, a resin, a potting, for example in the form of a fluid resin to be polymerized, or a thermal grease) extending over the bottom 110, for example also in the recess 106.

[0044] The thermal interface material 114 has a thickness of at most 1 mm, preferably at most 0.5 mm and a thermal conductivity of at least 1 W.rrr 1 .K- 1 , preferably at least 3.5 W.rrr 1 .K- 1 The thermal interface material 114 is, for example, but not limited to, TGF 3600.

[0045] The electrical system 100 further comprises at least one electrical device 116 (three in the illustrated example) extending over the thermal interface material 114. Each electrical device 116 is thus placed after formation of the electrical insulating layer 112. Thus, the electrical device 116 is not fixed to the latter, nor to the radiator 102, which facilitates the possible disassembly and / or repair of the electrical device 116.

[0046] Preferably, the electrical device 116 is at least partly embedded in the thermal interface material 114, but without reaching the electrically insulating layer 112 (for example, remaining at least 1 mm from the electrically insulating layer 112) so that the electrical device 116 has edges 118 (i.e., side faces) at least partly in contact with the thermal interface material 114.

[0047] The electrical device 116 may be, for example, an isolated electrical component, such as a controllable semiconductor switch. Alternatively, the electrical device 116 may be a power module grouping several electrical components, such as a controllable semiconductor switch. For example, the power module implements at least one switching arm. In the latter case, the switching arm comprises two controllable semiconductor switches, connected to each other at a midpoint.

[0048] Each semiconductor switch is for example a metal-oxide gate field effect transistor (from the English "Metal Oxide Semiconductor Field Effect Transistor" also designated by the acronym MOSFET) or a silicon metal-oxide gate field effect transistor (from the English "Silicon Metal Oxide Semiconductor Field Effect Transistor" also designated by the acronym Si MOSFET) or a silicon carbide metal-oxide gate field effect transistor (from the English "Silicon Carbide Metal Oxide Semiconductor Field Effect Transistor" also designated by the acronym SiC MOSFET) or an insulated gate bipolar transistor (from the English "Insulated Gate Bipolar Transistor" also designated by the acronym IGBT) or a gallium nitride field effect transistor (from the English "Gallium Nitride Field Effect Transistor" also designated by the acronym GaN FET).

[0049] With reference to Figures 2 to 5, a method 200 for manufacturing the electrical system 100 will now be described.

[0050] During a step 202, illustrated in FIG. 3, the electrically insulating layer 112 is produced on the bottom 110 of the recess 106 of the radiator 102.

[0051] For example, during this step 202, a layer of material, for example of a material different from the thermal interface material 114, for example a resin, is applied. Preferably the material (the resin) is deposited in the liquid state, which allows it to be well distributed in the recess 106 and to reach the desired thickness, for example between 300 μm and 400 μm. The material (the resin) is then crosslinked or polymerized, for example by heating, in order to be hardened to reach for example a Shore OO hardness of at least 60, preferably at least 70, more preferably at least 80. The material used for the electrically insulating layer 112 is for example, in a non-limiting manner, TIA227 from Momentive.

[0052] Alternatively, a surface treatment is carried out on the bottom 110, for example electrolytic plasma oxidation or nitridation.

[0053] During a step 204, illustrated in FIG. 4, the thermal interface material 114 is applied to the electrically insulating layer 112.

[0054] During a step 206, illustrated in FIG. 5, the electrical device 116 is placed on the thermal interface material 114. Preferably, the electrical device 116 is embedded at least partially into the thermal interface material 114, but without reaching the electrically insulating layer 112.

[0055] With reference to Figure 6, a second electrical system 600 according to the invention will now be described.

[0056] The elements common to the first electrical system 100 will be designated by the same references and will not be described again.

[0057] The second electrical system 600 differs from the first electrical system 100 in that it does not have a recess, so that the upper face 104 this time plays the role of a face for receiving an electrical device.

[0058] Furthermore, the radiator 102 is integrated into a larger part 602, such as a larger radiator or a housing delimiting for example an interior space in which each component 116 extends. Hereinafter, this part 602 will be called a housing. The housing 602 thus has a through opening 604, into which the radiator 102 is inserted. The latter is fixed to the housing 602 by welds 606 between edges of the radiator 102 and edges of the housing 602 facing each other.

[0059] With reference to Figures 7 to 14, a method 700 for manufacturing the electrical system 600 will now be described.

[0060] During a step 702, illustrated in FIG. 8, the electrically insulating layer 112 is produced on one face of a plate 802, a part of which will form the radiator 102, as will be explained below. This makes it possible to produce the electrically insulating layer 112 over a large surface area. Indeed, the face 104 of the radiator 102 may be small, so that it may be difficult to produce the electrically insulating layer 112. This is particularly true in the case of nitridation.

[0061] Thus, during a step 704, illustrated in FIG. 9, the plate 802 covered with the electrically insulating layer 112 is cut into pieces, one of which forms the radiator 102.

[0062] During a step 706, illustrated in FIG. 10, a portion of the electrically insulating layer 112 extending over at least a portion 1002 of a periphery of the radiator 102 is stripped, for example by scraping. This makes it possible to leave this portion 1002 of the periphery visible.

[0063] During a step 708, illustrated in FIG. 11, the thermal interface material 114 is applied to the electrically insulating layer 112.

[0064] During a step 710, illustrated in FIG. 12, the housing 602 provided with the opening 604 is obtained.

[0065] In a step 712, illustrated in FIG. 13, the radiator 102 is inserted into the opening 604 of the housing 602.

[0066] During a step 714, illustrated in FIG. 14, the welds 606 between the edges of the radiator 102 and the edges of the housing 602 opposite each other are preferably made through the part or parts 1002 left visible, to avoid damaging the electrically insulating layer 112.

[0067] During a step 716, the electrical device 116 is placed on the thermal interface material 114. Preferably, the electrical device 116 is pushed at least partially into the thermal interface material 114, but without reaching the electrically insulating layer 112. The result is illustrated in FIG. 6.

[0068] In conclusion, it will be noted that the invention is not limited to the embodiments described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in light of the teaching which has just been disclosed to them.

[0069] In the detailed presentation of the invention given above, the terms used should not be interpreted as limiting the invention to the embodiments set forth in this description, but should be interpreted to include all equivalents whose prediction is within the reach of those skilled in the art by applying their general knowledge to the implementation of the teaching just disclosed to them.

Claims

Claims [1] Electrical system (100; 600) comprising: an electrical device (116); a radiator (102) having a face (110; 104) for receiving the electrical device (116), this face (110; 104) being provided with an electrically insulating layer (112) having a thickness of at least 100 pm and a dielectric hardness of at least 10 kV per mm; and a thermal interface material (114) extending over the electrically insulating layer (112), the electrical device (116) extending over the thermal interface material (114). [2] Electrical system (100; 600) according to claim 1, wherein the electrically insulating layer (112) has a thickness of at most 800 pm, preferably at most 500 pm. [3] Electrical system (100; 600) according to claim 1 or 2, wherein the electrically insulating layer (112) has a thermal conductivity of at least 1 W.nr 1 .K' 1 , preferably at least 5 W.nr1 .K' 1 , preferably at least 10 W.nr 1 .K' 1 , preferably at least 30 W.nr 1 .K' 1 . [4] Electrical system (100; 600) according to any one of claims 1 to 5. 3, wherein the thermal interface material (114) has a thickness of at most 1 mm, preferably at most 0.5 mm. [5] Electrical system (100; 600) according to any one of claims 1 to 5. 4, wherein the thermal interface material (114) has a thermal conductivity of at least 3.5 W.nr 1 .K' 1 . [6] Electrical system (100; 600) according to any one of claims 1 to 5. 5, wherein the electrical device (116) is at least partially embedded in the thermal interface material (114), such that the electrical device (116) has edges (118) at least partially in contact with the thermal interface material (114). [7] Electrical system (100; 600) according to any one of claims 1 to 6, wherein the electrically insulating layer (112) is a layer of polymerized resin. [8] Electrical system (100; 600) according to any one of claims 1 to 6, in which the electrically insulating layer (112) results from a surface treatment carried out on the receiving face (110; 104). [9] Electrical system (100; 600) according to claim 8, wherein the surface treatment is a plasma projection of ceramic in order to produce the electrical insulating layer (112) by deposition, for example a deposition of alumina AI2O3. [10] Electrical system (100; 600) according to claim 8, wherein the surface treatment is nitridation. [11] Electrical system (600) according to any one of claims 1 to 10, further comprising a part (602), such as a housing, provided with an opening (604) into which the radiator (112) is inserted, the radiator (112) being fixed to this part (602), for example by welding. [12] Electrical converter comprising an electrical system (100; 600) according to any one of claims 1 to 11. [13] Mobility device comprising an electrical system (100; 600) according to any one of claims 1 to 11 or an electrical converter according to claim 12. [14] Method (200; 700) for manufacturing an electrical system (100; 600), comprising: a production (202; 702) of an electrically insulating layer (112) having a thickness of at least 100 μm and a dielectric hardness of at least 10 kV per mm, on a face (110; 104) of a radiator (102); then an application (204; 708) of a thermal interface material (114) on the electrically insulating layer (112); then a placement (206; 716) of an electrical device (116) on the thermal interface material (114). [15] The method (200; 700) of claim 14, further comprising embedding at least a portion of the electrical device (116) into the thermal interface material (114), such that the electrical device (116) has edges (118) at least partially in contact with the thermal interface material (114). [16] Method (200; 700) according to claim 14 or 15, wherein the production (202; 702) of the electrically insulating layer (112) comprises an application of a layer of resin, then a polymerization of the resin. [17] Method (200; 700) according to claim 14 or 15, wherein the production of the electrically insulating layer (112) comprises a surface treatment on the face (110; 104) of the radiator (102). [18] The method (200; 700) of claim 17, wherein the surface treatment is electrolytic plasma oxidation. [19] Method (200; 700) according to claim 17, wherein the surface treatment is nitridation. [20] Method (700) according to any one of claims 14 to 19, in which, to produce the electrically insulating layer (112) on the face (104) of the radiator (112), the electrically insulating layer (112) is produced on one face of a plate (802), the method (700) further comprising a cutting (704) of a piece of the plate (802), this piece forming the radiator (112) with the electrically insulating layer (112). [21] A method (700) according to any one of claims 14 to 20, further comprising: inserting (712) the radiator (112) into an opening (604) of a part (602); and attaching (714) the radiator (112) to the part (602), for example by welding edges of the radiator (112) to facing edges of the housing (602). [22] Method (700) according to claims 20 and 21 taken together, further comprising stripping (706) a portion of the insulating layer (112) extending over at least a portion (1002) of a periphery of the radiator (102), in order to leave this or these portions (1002) of the periphery visible, and in which the fixing (714) of the radiator (112) to the part (602) is carried out by welding, through the or parts (1002) left visible, from edges of the radiator (112) to edges of the housing (602) opposite.

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