Modular plastic housing with embedded heat sink

Description

[0001] The invention relates to a module housing made of plastic, in particular thermoset, with an embedded heat sink that can be mounted on a heat sink.

[0002] Electrical and electronic devices or modules are frequently housed in a thermoset plastic casing. Like thermoplastic casings, these offer advantages over metallic casings, including low weight, good electrical insulation properties, and the ability to produce a wide variety of shapes with a very high surface quality through primary molding.

[0003] The housing can be a separate structure enclosing internal device or module components, or it can be a single piece of material directly encasing these components. Housing components, such as screw sleeves (which must be made of metal), or device or module components requiring an interface with the environment (such as a heat sink), can be placed in the mold during housing production and cast or pressed in using the plastic.

[0004] Compared to thermoplastic housings, those made of thermoset plastics are more dimensionally stable and heat-resistant, which is particularly advantageous for devices and modules that generate a lot of heat during operation. However, for applications where the housing may be subject to mechanical stress, thermoset plastics have the disadvantage of being brittle and therefore easily breakable.

[0005] EP 2 175 708 A1 discloses an electronic module with a heat sink. The electronic module comprises a housing which is attached to a conductive plate by means of a screw connection.

[0006] EP 1 006 766 A1 shows an electronic device with a two-part housing for accommodating an electronic circuit.

[0007] In DE 20 2017 104 164 U1 a mounting system and a cooling device for COM modules is shown.

[0008] It is common practice to manufacture housings for modules (hereinafter referred to as module housings), particularly for electronic circuit modules, from thermoset plastics. These circuit modules essentially contain a printed circuit board populated with electronic components and a heat sink to dissipate the heat generated by these components. To transfer the heat absorbed by the heat sink via thermal conduction, it must be in good surface contact with an external heat sink, requiring a pressing force and only minimal flatness tolerance. The better the surface contact, the faster the heat is dissipated from the heat sink.

[0009] The relative position of the heat sink within the module housing is determined by the design of the circuit module. The heat sink is typically positioned relative to the components such that it is in direct or indirect contact with the heat sink via a short thermal conductor at the end face of the module housing. This results in the heat sink being arranged in a variety of relative positions within the module housing towards its edge. Facing away from the circuit module and outwards, the heat sink has a flat, embedded surface on all sides. This surface is brought into contact with a support that serves as an external heat sink by screwing the module housing to the support, either directly or indirectly, via two mounting sleeves that are also embedded in the module housing.

[0010] In Fig. 1a and 1bA module housing of this type, in accordance with the state of the art, is shown. To ensure a good, force-fit connection between the heat sink and the heat sink, the two screw sleeves are arranged relative to the heat sink such that an imaginary line connecting them runs across the free planar surface of the heat sink.

[0011] For optimal heat dissipation from the heat sink, the heat sink typically has a contact surface adapted in size and shape to the free planar surface of the heat sink. When the heat sink is properly mounted, the mounting sleeves, which are embedded at a distance from the heat sink, are positioned opposite mounting bushings. These bushings can be located in the support serving as the heat sink or in components rigidly connected to the support. To ensure that the heat sink exerts a pressing force against the support during installation, the contact surfaces on the support are dimensioned or toleranced in their relative heights for both the heat sink and the mounting sleeves such that tightening the screws driven into the support through the mounting sleeves generates a pressing force from the heat sink onto the support.This creates bending stresses in the module housing along the imaginary connection line, which can lead to cracking in a brittle plastic.

[0012] The object of the invention is to improve a plastic module housing with an embedded heat sink in such a way that it can be attached to a support without bending stresses.

[0013] This problem is solved for a module housing made of plastic, in particular thermoset plastic, with an embedded heat sink and at least one embedded screw-in sleeve, which has a collar with an externally exposed screw-in surface and is intended for mounting the module housing on a support serving as an external heat sink, by connecting the heat sink and the at least one screw-in sleeve to each other, forming a monolithic body, whereby heat is extracted from the heat sink by conduction to the support, at least via the screw-in surface. When the module housing is screwed onto the support, a clamping force is transmitted into the support via the screw-in surface of the at least one screw-in sleeve, which generates an equal and opposite force. This opposing force is absorbed by the monolithic body formed by the heat sink and the at least one screw-in sleeve.Since the heat sink bends only negligibly as a result of the counterforce, which can be distributed differently depending on the position of the monolithic body on the support, the bending stresses introduced into the plastic are also negligible at most.

[0014] Monolithic means that the body consists of a single, inseparable unit.

[0015] From a stress-related perspective, it is advantageous to have exactly one mounting sleeve, with the mounting surface being dimensioned or toleranced to be raised above the heat sink. When mounting the module housing to the support, only the mounting surface then makes contact with the support, thus completely preventing the introduction of bending stresses into the module housing. Furthermore, to minimize flatness tolerances, only the mounting surface requires final surface finishing. Alternatively, the support can be designed so that only the mounting surface makes contact with the support, even if the heat sink is not recessed relative to the mounting surface. Heat dissipation solely through conduction via the mounting surface has the particular advantage that, to minimize flatness tolerances, only the mounting surface requires final surface finishing.Even if additional surface areas of the monolithic body are brought into contact with the support, besides the mounting surface, virtually no bending stresses are introduced into the plastic. To achieve optimal heat dissipation from the heat sink to the mounting sleeve, the cross-section of a monolithic connection is adapted in height and / or width to the height of the heat sink and the outer diameter of the mounting sleeve.

[0016] According to the invention, the screw-in sleeve is completely connected to the heat sink over a height of the heat sink in the direction of a cylindrical axis of the screw-in sleeve, whereby a cross-section of the monolithic connection between the heat sink and the screw-in sleeve in the direction of the height of the heat sink is optimized for heat extraction.

[0017] Alternatively or additionally, the screw-in sleeve is connected to the heat sink over a width that corresponds at least to the outer diameter of the screw-in sleeve, thus optimizing the cross-section of the monolithic connection between the heat sink and the screw-in sleeve in the direction of the width of the heat sink for heat dissipation.

[0018] For optimal transmission of the pressure force, the screw-on surface is preferably designed to be largely ring-shaped.

[0019] For optimal heat dissipation, the mounting surface preferably has an outer diameter that is at least twice as large as the inner diameter of the mounting surface.

[0020] Preferably, a module housing according to the invention can be used in an electrical assembly. For example, the electrical assembly is an inverter and / or a gearbox.

[0021] Advantageously, an electrical assembly with a module housing according to the invention is used in a motor vehicle, in particular an electric vehicle. This enables the use of a module housing according to the invention in the automotive industry.

[0022] The invention will now be explained in more detail using an exemplary embodiment with reference to the drawings. The drawings show: Fig. 1a and 1bein module housing according to the prior art in a top view and in a sectional view and Fig. 2a to 2bein module housing according to the invention in a top view, in a sectional view and a perspective view.

[0023] Equivalent to the state of the art, as presented in the Fig. 1a - 1bThe module housing according to the invention consists of plastic, preferably thermoset. A heat sink 1 and at least one screw-in sleeve 2 are embedded within it. While, according to the prior art, heat is extracted from the heat sink 1 directly via a free base surface of the heat sink (thermal interface), and the at least one screw-in sleeve 2 only functions as a mechanical interface, the at least one screw-in sleeve 2 of a module housing according to the invention represents both a mechanical and a thermal interface. For this purpose, the at least one screw-in sleeve 2, forming a monolithic body 0, is connected to the heat sink 1.

[0024] According to the in the Fig. 2a - 2cIn the illustrated embodiment, the monolithic body has exactly one screw-in sleeve 2 with a collar 21 having an externally exposed screw-in surface 211, which comes into contact with a support 3 serving as an external heat sink when the module housing is mounted. In the illustrated embodiment, the screw-in surface 211 is an integral part of a flat base surface that extends over the entire monolithic body 0.

[0025] If the module housing is mounted on a support 3, as shown, which presents a contact surface 31 to the module housing, the dimensions of which are limited to the mounting surface, heat dissipation occurs by conduction, and force is also applied exclusively via the mounting surface 211. Here, only a perfectly flat mounting surface is advantageous. If the contact surface 31 on the support 3 is dimensioned larger, up to a size equal to the base area of ​​the monolithic body 0 (not shown in the drawings), heat dissipation occurs across the entire base surface by conduction, which, however, places high demands on the flatness of the base surface and the contact surface 31. To ensure that the entire base surface is pressed evenly against a contact surface 31 on the support 3, one or even two additional mounting sleeves 2 formed in the monolithic body can be provided. Reference sign

[0026] 0 monolithic body 1 heat sink 2 mounting sleeve 20 cylinder axis 21 collar 211 mounting surface 22 cylinder axis 3 support 31 contact surface h height of the heat sink d outer diameter of the mounting sleeve

Claims

1. Module housing made of plastic, with an embedded cooling element (1) and at least one embedded screw-on sleeve (2), which has a collar (21) with an outwardly exposed screw-on surface (211) and is intended for mounting the module housing on a support (3) serving as an external heat sink, wherein the cooling element (1) and the at least one screw-on sleeve (2) form a monolithic element (0), whereby heat is extracted from the cooling element (1) to the support (3) by heat conduction at least via the screw-on surface, wherein there is precisely one screw-on sleeve (2), and the screw-on surface (211) is raised in relation to the cooling element (1) such that, when the module housing is mounted, only the screw-on surface (211) comes to bear against the support (3), characterized in that the screw-on sleeve (2) is completely connected to the cooling element (1) over the height of the cooling element (h) in the direction of a cylindrical axis (20) of the screw-on sleeve, whereby a cross section of the monolithic connection between the cooling element (1) and the screw-on sleeve (2) in the direction of the height of the cooling element (h) is optimized for the heat extraction.

2. Module housing made of plastic, with an embedded cooling element, according to the preceding claim, characterized in that the screw-on sleeve is connected to the cooling element (1) over a width which corresponds at least to an outer diameter of the screw-on sleeve (d), whereby a cross section of the monolithic connection between the cooling element (1) and the screw-on sleeve (2) in the direction of the width of the cooling element (1) is optimized for the heat extraction.

3. Module housing made of plastic, with an embedded cooling element, according to one of the preceding claims, characterized in that the screw-on surface (211) is annular.

4. Module housing made of plastic, with an embedded cooling element, according to Claim 3, characterized in that the screw-on surface (211) has an outer diameter which is at least twice the size of the inner diameter of the screw-on surface (211).

5. Module housing made of plastic, with an embedded cooling element, according to one of the preceding claims, characterized in that the plastic is a thermosetting polymer.

6. Electrical assembly comprising a module housing according to one of the preceding claims.

7. Motor vehicle with a control comprising an electrical assembly according to Claim 6.