Method for manufacturing an electronic power module

Abstract

The invention relates to a method for manufacturing a power electronics module (1) by additive manufacturing, characterized in that it comprises the following steps: - making or fixing a preform (15) of polymer material on at least one face of an insulating substrate (2a) covered with at least one metal layer (2b, 2c), called metallized substrate (2), - depositing a first metal layer (17) on the preform (15), - depositing a second metal layer (18) on the first metal layer (17) by electroforming.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an electronic power module by additive manufacturing, and an electronic power module obtained using such a method.

[0002] This invention is particularly applicable to the aerospace field where severe thermal stress may exist. Background Technology

[0003] Power electronics modules are used in converters required for the electrification of propulsion and non-propulsion systems on aircraft, so that electrical energy from a future autonomous power grid (115V AC, 230V AC, 540V DC) can be converted into several forms (AC / DC, DC / AC, AC / AC, and DC / DC).

[0004] Figure 1 A prior art power electronic module 1 is shown. It includes a substrate 2 comprising an electrically insulating layer 2a of ceramic material, on each of its opposite faces being coated with metal layers 2b, 2c. Such an assembly is referred to as a metallized substrate 2.

[0005] A top metal layer 2b forms the power circuit on which the power semiconductor component 3 is assembled. The power electronic module 1 includes electrical and / or mechanical interconnects 4, through which the power semiconductor component 3 and connector 5 are assembled to the power circuit. The power semiconductor component 3 suffers from Joule effect losses due to its defects and therefore represents a significant heat source.

[0006] The power semiconductor components 3 are electrically interconnected with each other and with connectors 5 via wiring conductors 6. A housing 7, typically made of polymer, is glued to a substrate 2 or a metal substrate 9 on which the substrate 2 is disposed using adhesive sealant 8. The housing 7 is filled with an encapsulant 10, such as gel or epoxy resin, to provide mechanical and electrical protection for the power components 3 and the wiring conductors 6.

[0007] The lower metal layer 2c of substrate 2 is attached to metal substrate 9, which has the function of dissipating heat flow and providing thermal connection with metal heat sink 11. Figure 1 As shown, the power electronic module 1 includes electrical and / or mechanical interconnects 12, and the lower metal layer 2c of the substrate 2 is bonded to the substrate 9 through the electrical and / or mechanical interconnects.

[0008] The substrate 9 is bonded to the heat sink 11 via a thermal interface material layer 13, such as hot grease, an elastomer film, or a phase change material. The thermal interface material layer 13 reduces the contact thermal resistance between the substrate 9 and the heat sink 11 to ensure better heat dissipation. The heat sink 11 has fins 14, which allow for further reduction of the latter's thermal resistance, through which a cooling fluid, such as air, passes.

[0009] Such layer stacks have several limitations when used at high temperatures.

[0010] The first limitation is high thermal resistance, which is attributed to the thermal interface material 13, especially when using a soft thermal interface material (e.g., hot grease), and to the various interfaces that separate the electrical component 3 from the coolant.

[0011] The second limitation relates to high-temperature instability, particularly limited by the operating temperature of the thermal interface 13 (approximately 50°C in the case of hot grease).

[0012] The third limitation is the limited reliability of the assembly due to thermal fatigue caused by the difference in the coefficients of thermal expansion between the materials. When rigid interface materials are used, this fatigue is a source of crack propagation in the welded joints, particularly between substrate 2 and base 9, and between base 9 and heat sink 11.

[0013] The literature proposes a technical solution based on direct cooling of metallized substrates by fluid, but these solutions have limitations, especially at the level of the exchange surface.

[0014] To overcome these drawbacks, document FR 3 061 989 proposes using additive manufacturing by melting powder beds used to directly produce housing heat sinks and electrical connectors on the underside and topside of a metallized substrate, respectively. This technique reduces the thermal resistance of the assembly and limits the number of assembly steps. However, melting the metal powder bed requires locally high temperatures during the process, resulting in high residual stresses. These stresses can cause cracking of the ceramic layer of the metallized substrate in some geometries. Furthermore, the high temperatures generated by this process limit the choice of substrate to metallized ceramic. Additionally, it is not possible to simultaneously produce components on two opposite sides of the substrate via additive manufacturing, requiring operator intervention to flip the substrate. Summary of the Invention

[0015] The present invention aims to correct these shortcomings in a simple, reliable and inexpensive manner.

[0016] For this purpose, the present invention relates to a method for manufacturing a power electronic module by additive manufacturing, characterized in that the method comprises the following steps:

[0017] - A preform of polymer material is fabricated or fixed on at least one side of an insulating substrate, the insulating substrate being covered with at least one metal layer, referred to as a metallized substrate.

[0018] - Deposit a first metal layer on the preform.

[0019] - A second metal layer is deposited on the first metal layer by electroforming.

[0020] The manufacturing process can be carried out on a metallized insulating substrate to obtain cooling, electrical connection and / or mechanical protection elements for power electronic modules via additive manufacturing.

[0021] This type of method allows for the parallel production of several components (such as radiators, housings, and power connectors).

[0022] For a single power electronic module, all of the above-described components or combinations or groups of components may be printed simultaneously or sequentially using the methods described.

[0023] The preform can be fabricated using additive manufacturing. The preform can be fabricated or fixed on at least two opposite sides of a metallized substrate.

[0024] The second layer can have a thickness ranging from several micrometers to several millimeters, depending on the requirements. The thickness of the second layer can vary depending on the voltage applied and the bias time applied during the electroforming deposition step.

[0025] During electroforming, all or part of the metal substrate and the first metal layer may be immersed in an electrolytic bath containing metal ions, such as copper in ionic form. Electrodes are electrically connected to the first metal layer, and a potential is applied to the electrodes to deposit the filler metal from the electrolytic bath onto the first metal layer. Non-metallic regions of the substrate not at the electrode potential are then left uncovered with the filler metal.

[0026] The method may include the step of dissolving the polymer preform by chemical or thermal means.

[0027] This makes it possible to create recessed areas, connectors, or channels in the resulting power electronic modules. Specifically, channels can facilitate heat exchange for cooling the assembly, for example, by means of a cooling airflow or liquid coolant.

[0028] The method may include the step of assembling an active component, such as a semiconductor power component, onto a metallized substrate.

[0029] Active components can be bonded to a metallized substrate by sintering, bonding, or sintering.

[0030] At least two active components can be connected to each other via wires.

[0031] The method may include the step of protecting at least one region of the metallized substrate before depositing the first metal layer.

[0032] The area to be protected may be covered with a film made of, for example, a polymer. The film may be removed during the dissolution step of the preform.

[0033] The metallized substrate may contain at least one ceramic insulating layer.

[0034] The metal layer of the metallized substrate can be bonded to the insulating layer by active metal brazing (AMB), direct bonding of copper (DBC), or direct bonding of aluminum (DBA).

[0035] The insulating layer can also be a polymer layer.

[0036] The thickness of the first metal layer can be less than 5 micrometers, preferably less than 1 micrometer.

[0037] The first metal layer can be deposited on the preform via chemical reduction through spraying.

[0038] A power electronic module may include a housing, a metallized substrate, and active components housed within the housing, the method comprising the step of filling the housing at least partially with an electrically insulating material.

[0039] The insulating material is, for example, a gel based on silicone or epoxy resin.

[0040] The present invention also relates to a power electronic module obtained by the above method, comprising a metallized substrate and an active component mounted on a first surface of the metallized substrate, wherein a heat sink including a cooling channel extends from a second surface of the metallized substrate opposite to the first surface.

[0041] The power electronic module may include at least one connector electrically connected to the metallized substrate.

[0042] The connector may be formed from a conductive member extending from a first side of a metallized substrate.

[0043] The outer casing may also extend from the first side of the metallized substrate. The metal components of the outer casing can be fabricated during the electroforming step.

[0044] The present invention also includes an aircraft having at least one power electronic module of the type described above. Attached Figure Description

[0045] Figure 1 This is a schematic diagram illustrating a prior art power electronic module.

[0046] Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 Various steps of a method for manufacturing a power electronic module according to an embodiment of the present invention are shown. Detailed Implementation

[0047] Figures 2 to 6 Various manufacturing steps of a power electronic module 1 according to an embodiment of the present invention are illustrated schematically.

[0048] exist Figure 2In the first step shown, a preform 15 of polymer material is fabricated on two opposite sides of the metallized substrate 2 by additive manufacturing. The preform 15 can be fabricated directly on the metallized substrate 2, or it can be attached to the metallized substrate 2 after the preform 15 has been fabricated. In the latter case, the preform 15 can be bonded to the metallized substrate 2.

[0049] The metallized substrate 2 includes an electrically insulating layer 2a of ceramic material, on each of its opposite sides coated with metal layers 2b and 2c, such as copper. The metal layers 2b and 2c of the metallized substrate 2 can be bonded to the insulating layer 2a by active metal brazing (AMB), direct copper bonding (DBC), or direct aluminum bonding (DBA).

[0050] Metal layers 2b and 2c can form orbitals that are separate from each other.

[0051] The polymer material protective film 16 can cover at least a portion of the conductor track of the top layer 2b.

[0052] Alternatively, the electrically insulating layer 2a may be made of a polymer material (in the case of an insulating metal substrate—IMS).

[0053] like Figure 3 As shown, a first metal layer 17, such as copper, is then deposited on the preform 15, for example, by chemical reduction via spraying. The thickness of the first layer 17 is, for example, less than 1 micrometer.

[0054] Next, a second metal layer 18, such as copper, is deposited on the first metal layer 17, as... Figure 4 As shown in the image. This type of deposition can be achieved through electroforming.

[0055] The second layer 18 may have a thickness between several micrometers and several millimeters, depending on the voltage and bias time applied during the electroforming deposition step.

[0056] During electroforming, the metallized substrate 2 and the first metal layer 17 are wholly or partially immersed in an electrolytic bath containing metal ions, such as copper in ionic form. The bath may be a low-temperature bath, i.e., at a temperature below 100°C. Electrodes are electrically connected to the first metal layer 17, and a potential is applied to the electrodes to deposit the filler metal from the electrolytic bath onto the first metal layer 17. Non-metallic regions of the substrate 2 not at the electrode potential are then left uncovered with the filler metal. According to one embodiment, at least a portion of the first metal layer 17 is covered with a protective film to prevent the deposition of a second metal layer 18 in the covered region.

[0057] The second metal layer 17 may specifically define the connector 5, housing component 7, or cooling channel 19 of the heat sink or radiator 11.

[0058] like Figure 5 As shown in the diagram, the preform 15 is then removed in a chemical or thermal dissolution step.

[0059] In the case of chemical dissolution, the ABS preform 15 can be dissolved in an acetone bath at a temperature of 50°C using ultrasound.

[0060] Alternatively, to dissolve the PLA preform 15, a 35% sodium bicarbonate bath can be used at a temperature of 60°C, and stirring can be performed to promote dissolution.

[0061] Therefore, recessed areas, connectors 5, or channels 19 may be created, which are intended to facilitate heat exchange for purposes such as cooling the assembly by means of airflow or liquid coolant.

[0062] Membrane 16 can also be removed during the dissolution step.

[0063] The power semiconductor component 3 is then bonded to the corresponding track on the metallized substrate 2 via electrical and / or mechanical interconnects 4, such as... Figure 6 As seen in the diagram. The power components 3 are then electrically interconnected with each other and / or with the connector 11 by means of wiring wires 6. The housing 7 is then filled with an electrical encapsulant or insulator 10, such as gel or epoxy resin, to provide mechanical and electrical protection for the power components 3 and the wiring wires 6.

[0064] This type of method offers the following advantages:

[0065] The excellent thermal performance is particularly attributed to the reduction in the interface between the semiconductor component 3 and the heat sink 11, as well as the possibility of producing heat sinks 11 with complex geometries.

[0066] -Potentially usable at extremely high temperatures -Reliability is improved by eliminating welding on large surfaces.

[0067] - This is attributed to the increased mass power density of the converter due to the reduced mass of the heat sink 11.

[0068] - Reduced the number of manufacturing steps and manufacturing time.

[0069] - Compared to the same production process using additive manufacturing techniques that require extremely high local temperatures to melt or sinter metal powders, residual stress is reduced.

[0070] -The channels 19 of the heat sink 11 are sealed because there is no porosity or gaps in the electrodeposited material 18.

[0071] - Electroforming offers high precision in terms of surface reproducibility. This allows for highly flexible surface texturing via polymer preforms 15 with complex geometries obtained through additive manufacturing, thus significantly increasing the exchange surface area and consequently improving performance in terms of heat dissipation.

[0072] - A single assembly is obtained at low temperature (<80°C) and in a single stage, which includes several functions (heat sink 11, housing 7, connector 5) on both sides of the metallized insulating substrate 2, without the need for additional joints.

Claims

1. A method for manufacturing a power electronic module (1) by additive manufacturing, characterized in that, The method includes the following steps: - A preform (15) of polymer material is fabricated or fixed on at least one surface of a metallized substrate (2) by additive manufacturing, the metallized substrate (2) comprising an insulating substrate (2a) covered with at least one metal layer (2b, 2c), the step of which is performed by additive manufacturing to obtain cooling, electrical connection and / or mechanical protection elements for a power electronic module. - A first metal layer (17) is deposited on the preform (15). - A second metal layer (18) is deposited on the first metal layer (17) by electroforming. The method then includes the step of dissolving the preform of the polymer material (15) by chemical or thermal means.

2. The method according to claim 1, characterized in that, The method includes the step of assembling an active component (3) on the metallized substrate (2).

3. The method according to claim 1 or 2, characterized in that, The method includes the step of protecting at least one region of the metallized substrate (2) before depositing the first metal layer (17).

4. The method according to claim 1 or 2, characterized in that, The metallized substrate (2) includes at least one ceramic insulating layer.

5. The method according to claim 1 or 2, characterized in that, The thickness of the first metal layer (17) is less than 5 micrometers.

6. The method according to claim 2, characterized in that, The power electronic module (1) includes a housing (7), in which the metallized substrate (2) and the active component (3) are housed, and the method includes the step of filling the housing at least partially with an electrically insulating material (10).

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