Electronic module and method of manufacturing thereof

Abstract

An electronic module includes an electronic unit (2), a metal heat sink (3) having a plurality of protruding cooling fins (6), and a metal housing (7) connected to the heat sink (3), wherein a cavity (9) having an inlet (12) and an outlet (13) is formed between the heat sink (3) and the housing (7), the cooling fins (6) extending into the cavity, wherein the surface (10) of the housing (20) defining the cavity (9) is provided with a non-metallic anti-corrosion coating (14) at least in the area facing the cooling fins (6).

Description

Technical Field

[0001] The present invention relates to an electronic module comprising an electronic unit and a metal heat sink having a plurality of protruding cooling fins, and a metal housing connected to the heat sink, wherein a cavity having an inlet and an outlet is formed between the heat sink and the housing, and the cooling fins extend therein. Background Technology

[0002] Such electronic modules are typically constructed as power modules, with electronic units comprising one or more power components, such as high-power transistors, capacitors, etc. The components of these electronic units generate heat during operation, especially when they are power components, thus requiring appropriate cooling. For this purpose, in addition to the electronic units typically embedded in potting material, the electronic module also features a metal heat sink with multiple protruding cooling fins, such as pins or ribs, often referred to as pins or fins. Connected to the metal heat sink is a housing, also made of metal, which, together with the heat sink, defines a cavity in which a coolant inlet opening leads and a coolant outlet exits, allowing the electronic module to be integrated into a cooling circuit. The cooling fins extend into the cavity, into which coolant, such as water or a water-glycol mixture, flows, thereby allowing the heat generated at the power components to be transferred via the heat sink and the cooling fins to the fluid coolant and carried away by it.

[0003] After the electronic module is manufactured in the factory using modular components, it undergoes functional testing at the end of the production line, typically where it is connected to its associated assembly, such as a motor. This functional test is called a test. The cooling of the electronic module is also tested here, i.e., the coolant circulates in the loop and inevitably flows through the cavity. After the test, the assembly, along with the electronic module, or, in the case of disassembly, the electronic module, is usually not immediately installed but stored for a period of time.

[0004] After testing, a certain amount of coolant remains in the cooling circuit, or cavity, which is divided into relatively long, serpentine cooling channels by the cooling fins, extending from the inlet to the outlet. As described above, the cooling fins extend from the surface of the cooling element defining the cavity into the cavity and up to the opposite surface of the housing, separated from it only by a narrow gap. The radiator and therefore the cooling fins are made of metal, such as copper, with its surface sometimes coated with nickel or a nickel-containing electroplating layer. Conversely, the housing, also made of metal, is usually made of another, less expensive material, mostly aluminum. It is usually made by a die-casting process, such as aluminum die-casting. The problem is that when the residual coolant comes into contact with air or oxygen in the air, corrosion occurs in the narrow gap region between the cooling fins and the housing surface, for example, a gap region only a fraction of a millimeter wide. This corrosion originates from the different metals and the residual coolant present in the gap region, which solidifies due to a chemical reaction with air or air oxygen, resulting in a kind of "gelling". Such corrosion is certainly detrimental, as it damages the cooling structure and the housing. To address this issue, DE 10 2020 214 397 A1 suggests heat treatment of the electronic module after end-of-line testing, i.e., heating and drying, to evaporate any coolant residue that may be present in the cavity. However, this heat treatment is complex.

[0005] The problem upon which this invention is based is to provide an improved electronic module compared to the present invention. Summary of the Invention

[0006] To address this issue, in electronic modules of the type described at the beginning, the present invention specifies that the housing surface defining the cavity is provided with a non-metallic anti-corrosion coating at least in the area facing the cooling fins.

[0007] In the electronic module according to the invention, the housing surface defining the cavity and susceptible to corrosion as described above is provided with a non-metallic anti-corrosion coating, wherein the anti-corrosion coating is provided at least in the region facing the cooling fins. The anti-corrosion coating is made of a non-metallic material, preferably plastic, which separates the two metal components from each other in this region, that is, separates the cooling fins, made of a more expensive material, from the housing surface, made of a less expensive material, thereby preventing galvanic corrosion caused by coolant residue and its reaction with air or air oxygen through the connection between the cooling fins and the housing surface in this region. Therefore, after testing, coolant residue can remain in the cavity without problems because the housing material will not corrode even after a long period of time due to the protection of the anti-corrosion coating.

[0008] As described above, the anti-corrosion coating is preferably made of plastic, such as thermoplastic polymers like fluoropolymers, as well as other thermoplastic polymers and thermosetting polymers.

[0009] The anti-corrosion coating can be applied to the housing surface in various forms. According to the invention, the anti-corrosion coating can be a pre-fabricated coating element disposed on the surface of the housing. The coating element is, for example, a film or sheet of a correspondingly sized form, which is, for example, adhered to the housing surface. The dimensions of the coating element are designed to at least cover the area of ​​the housing surface facing the cooling fins, but preferably extend beyond that area.

[0010] Alternatively, the anti-corrosion coating can be applied as a cured coating. The anti-corrosion coating is thus applied to the housing surface using a liquid material, such as a polymer, and subsequently cured, similar to painting. This application can be performed on the housing itself alone, or it can be done after the electronic module is completed by filling the cavity, draining excess material, and then curing.

[0011] The cooling fins can also be spaced apart from the anti-corrosion coating by a narrow gap of only a fraction of a millimeter. However, they can also be attached to the anti-corrosion coating.

[0012] It is advantageous to have a seal extending around the cavity and laterally defining the cavity between the radiator and the housing. This seal completely seals the cavity on all sides, including the surface facing the radiator and the surface facing the housing, ensuring that the coolant only wets the surfaces of the radiator or cooling fins that are not in contact with each other on the housing surface, and not the connection area where the radiator directly contacts the housing. The seal can be, for example, an annular sealing ring made of a suitable sealing material; polymeric materials, such as thermoplastics or elastomers, can also be used.

[0013] In addition to the electronic module itself, the present invention also relates to a method for manufacturing such an electronic module, comprising the following steps: - Apply prefabricated coating elements as a non-metallic anti-corrosion coating to the surface of the housing defining the cavity. - Connect the housing to the radiator such that cooling fins protruding from the radiator extend into the cavity and terminate near the cladding element.

[0014] In a variation of this method, to form the non-metallic anti-corrosion coating, a prefabricated coating element, as described above, for example in the form of a plastic film or small plastic sheet, is used and placed onto and fixed thereto, for example, by adhesive bonding. In a next step, the housing is connected to the heat sink, thereby closing the cavity and allowing the cooling fins to extend into the cavity and, correspondingly, terminate adjacent to or abut against the coating element via a very narrow gap, as described above, only a fraction of a millimeter wide.

[0015] If a seal is to be provided in the cavity that laterally defines the cavity, such a seal can be provided on the housing before or after the application of the coating element.

[0016] As an alternative to the aforementioned variant, the present invention provides a method for manufacturing such an electronic module, comprising the following steps: - The housing is connected to a heat sink replica including cooling fins, the heat sink replica being identical to the heat sink of the electronic module, such that cooling fins protruding from the heat sink replica extend into the cavity and terminate adjacent to the surface of the housing, wherein, prior to connection, a seal is provided on the housing or the heat sink replica, the seal laterally defining the cavity after the housing and the heat sink replica are connected. - Fill the cavity with a curable fluid. - The fluid is discharged, wherein the surface of the housing defining the cavity is covered with a fluid layer. - Allow the fluid to solidify to form the anti-corrosion coating and remove the radiator assembly, or vice versa. - Connect the housing to the radiator such that cooling fins protruding from the radiator extend into the cavity and terminate near the anti-corrosion coating, wherein, if necessary, a seal is provided on the housing or the radiator prior to connection, the seal laterally defining the cavity after the housing and the radiator are connected.

[0017] In a variation of this method, the anti-corrosion coating is formed by coating the surface of the housing. For this purpose, a radiator replica, including cooling fins, is first attached to the housing. The radiator replica is geometrically identical to the radiator to be subsequently fixed. Similarly, a seal is provided within the cavity. The formed cavity is then filled with a liquid material forming the coating, which is drained, for example, after a certain holding time. This results in a fluid layer covering the surface of the housing defining the cavity. Subsequently, while the radiator replica is still installed, the fluid can be cured while the anti-corrosion coating of this form is being formed, with the radiator replica removed after curing. Alternatively, it is conceivable to remove the radiator replica after draining the fluid, and only then does the coating cure. In any case, after removing the heat sink replica, the cavity surface is now provided with the coated housing connected to the actual heat sink of the electronic unit, such that the cooling fins protruding from the heat sink extend into the cavity and either terminate near the anti-corrosion coating, i.e., the coating area, via a still-present narrow gap, or abut against it. Of course, before this, the seal is inserted into the cavity if necessary. Attached Figure Description

[0018] The present invention will now be described with reference to one embodiment and in conjunction with the accompanying drawings. The drawings are schematic representations. Detailed Implementation

[0019] The diagram illustrates an electronic module 1, comprising an electronic unit 2, preferably a power electronic device, which includes multiple high-performance power components such as transistors and capacitors, typically mounted on a printed circuit board. The power electronic device 2 is housed within a corresponding recess in a metal heat sink 3, for example, copper, and encapsulated with a potting material 4. During operation, the power components generate heat, which is dissipated through the heat sink 3.

[0020] On the lower side 5 of the radiator, a plurality of cooling fins 6 are arranged in a protruding manner, preferably ribs, i.e., fins, which can form a quasi-serpentine cooling channel in the assembly diagram.

[0021] In addition, a housing 7 is provided, which is connected to the heat sink 3 by fastening elements 8, shown only schematically here, particularly by screws. The housing 7 is also made of metal, but of a different and less expensive metal than that of the heat sink 3. The heat sink 3 is, for example, made of copper, and preferably has an additional coating, such as nickel or a nickel-based coating, on its lower side 5 and the cooling fins 6. Conversely, the housing 7 is, for example, made of aluminum, and is therefore an aluminum die-cast housing.

[0022] A cavity 9 is formed by the heat sink 3 and the housing 7, which is defined upward by the surface of the lower side 5 and downward by the surface 10 of the housing 7. The cavity 9 is laterally defined and sealed by a surrounding seal 11, such as a sealing ring, preferably made of a suitable elastic plastic material, wherein the seal 11 extends to the lower side 5, thus also sealing the connection area between the heat sink 3 and the housing 7.

[0023] The housing 7 has an inlet 12 leading to the cavity 9 and an outlet 13 extending from the cavity 9. Both the inlet 12 and the cavity 13 are preferably configured as elongated slits within the housing 7. Through the inlet 12 and the outlet 13, the electronic module 1 can be connected to a coolant circuit in which a coolant, such as a water-glycol mixture, circulates in a hermetically sealed manner. The coolant flows into the cavity 9 via the inlet 12, flows through the cavity along a serpentine channel defined by the ribbed cooling fins 6, and exits again from the outlet 13.

[0024] The cooling fins 6 extend toward the surface 10 of the housing, wherein the surface 10 is covered with a non-metallic anti-corrosion coating 14. The anti-corrosion coating 14 is disposed at least in the region of the surface 10 adjacent to the ends of the cooling fins 6. The anti-corrosion coating 14 is, for example, a pre-formed coating element disposed on, or particularly adhered thereto, the surface 10. The coating element can be a cut film or a correspondingly sized piece. As a plastic material, any thermoplastic or thermosetting plastic can be used, which is chemically stable enough that the coolant used will not corrode it, and thermally stable enough to withstand the temperatures present in the cavity or within the coolant. Alternatively, the anti-corrosion coating 14 can also be achieved by an applied coating, which is first applied to the surface 10 in fluid form and then cured.

[0025] Regardless, the cooling fins 6 extend close to the anti-corrosion coating 14 and are separated from it only by a very narrow gap 15, for example, only a fraction of a millimeter, or even against the impact-resistant coating made of polymer material, i.e., in contact with it. The anti-corrosion coating 14 prevents corrosion in the narrow gap 15 area between the cooling fins 6 and the metal housing 7, in which the housing 7, made of less valuable metal, would be corroded. Such corrosion would be caused by coolant residue remaining in the cavity or channel after functional testing of the manufactured electronic module 1. Through this residual coolant, combined with the chemical reaction of air or air oxygen entering the cavity 9, the cooling fins 6 would come into contact with the uncoated surface 10. However, this is effectively prevented by the non-metallic anti-corrosion coating 14, which effectively protects and encapsulates the surface 10. This allows for end-of-line testing after manufacturing and also allows for extended storage of the electronic module 1 before final assembly, as any tendency to corrode is suppressed.

[0026] Explanation of reference numerals in the attached figures 1 Electronic Module 2 electronic units 3. Radiator 4. Potting materials 5. Lower side 6 Cooling fins 7. Casing 8 Fastening components 9 cavities 10 Surface 11. Seals 12 entrances 13 Exports 14 Anti-corrosion coating 15. Gap.

Claims

1. An electronic module comprising an electronic unit (2), a metal heat sink (3) having a plurality of protruding cooling fins (6), and a metal housing (7) connected to said heat sink (3), wherein, A cavity (9) with an inlet (12) and an outlet (13) is formed between the radiator (3) and the housing (7), and the cooling fins (6) extend into the cavity. The cavity is characterized in that the surface (10) of the housing (20) defining the cavity (9) is provided with a non-metallic anti-corrosion coating (14) at least in the area facing the cooling fins (6).

2. The electronic module according to claim 1, characterized in that, The anti-corrosion coating (14) is made of plastic.

3. The electronic module according to claim 1 or 2, characterized in that, The anti-corrosion coating (14) is a pre-fabricated coating element, which is disposed on the surface (10) of the housing (7).

4. The electronic module according to claim 1 or 2, characterized in that, The anti-corrosion coating (14) is applied in the form of a cured coating.

5. The electronic module according to any one of the preceding claims, characterized in that, A seal (11) is provided between the radiator (3) and the housing (7) to surround the cavity (9) and laterally define the cavity (9).

6. A method for manufacturing an electronic module according to any one of claims 1 to 5, comprising the steps of: - Apply a pre-fabricated coating element as a non-metallic anti-corrosion coating (14) to the surface (10) of the housing (7) defining the cavity (9); and - Connect the housing (7) to the radiator (3) such that the cooling fins (6) protruding from the radiator (3) extend into the cavity (9) and terminate near the cladding element.

7. The method according to claim 6, characterized in that, Before or after the application of the coating element, a seal (11) is provided on the housing (7), the seal laterally defining the cavity (9) after the housing (7) is connected to the heat sink (3).

8. A method for manufacturing an electronic module according to any one of claims 1 to 5, comprising the steps of: - Connect the housing (7) to a heat sink assembly including cooling fins, the heat sink assembly being identical to the heat sink (3) of the electronic module (1), such that cooling fins protruding from the heat sink assembly extend into the cavity (9) and terminate at a surface (10) adjacent to the housing (7), wherein, Before connection, a seal (11) is provided on the housing (7) or on the radiator replica, the seal laterally defining the cavity (9) after the housing (7) and the radiator replica are connected; - Fill the cavity (9) with a curable fluid; - The fluid is discharged such that the surface (10) of the housing (7) defining the cavity (9) is covered with a fluid layer; - Solidify the fluid to form the anti-corrosion coating (14) and remove the radiator assembly, or vice versa; - Connect the housing (7) to the radiator (3) such that cooling fins (6) protruding from the radiator (3) extend into the cavity (9) and terminate near the anti-corrosion coating (14), wherein, if necessary, a seal (11) is provided on the housing (7) or the radiator (3) before connection, the seal laterally defining the cavity (9) after the housing (7) and the radiator (3) are connected.

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