EMC housing

Abstract

The present disclosure provides EMC enclosures. An electromagnetic compatible (EMC) enclosure having a first part (2) and a second part (3) for forming an enclosure when assembled together. The first part (2) and the second part (3) comprise a first interface surface (4) and a second interface surface (5), respectively, for compressing a gasket (9) inserted between the interface surfaces (4, 5) when the first part and the second part are assembled together. At least one of the first interface surface (4) and the second interface surface (5) comprises a plurality of undercut regions (7) for reducing compression of the gasket (9) in the regions when the first part (2) and the second part (3) are assembled together.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to electromagnetic compatibility (EMC) housings for electromagnetic interference (EMI) shielding and motor vehicle electronics housings. BACKGROUND

[0002] Electronic units typically generate electromagnetic radiation during operation, which can interfere with the operation of other nearby electronic devices. This potential for EMI is particularly problematic in motor vehicle applications, as electromagnetic interference can potentially compromise the operation of the vehicle's electronic control units when they are performing safety-critical operations. Therefore, it is necessary to ensure that motor vehicle electronics such as head unit and domain controllers are electromagnetically compatible (EMC) to ensure that they are isolated from external electromagnetic noise, while not radiating electromagnetic fields that can affect other devices.

[0003] To meet EMC requirements, motor vehicle electronics are typically encased in a die-cast metal EMI shielding housing that forms an electrical ground barrier for absorbing electromagnetic radiation. Such housings are typically provided in two separable parts to allow the housing to be opened during assembly and to facilitate access to the device for subsequent maintenance. The second part of the housing will therefore typically form a removable panel or cover that is secured to the first part by screws, which parts fit together at opposing interfaces. An elastomeric conductive EMI shielding gasket will also be provided between the interface surfaces to seal between the panels. For the shielding gasket to work effectively, it must be compressed within a specific compression range. In practice, however, the interface surfaces rarely fit together perfectly due to inherent manufacturing tolerances, casting defects and thermal differences. At the same time, the rigidity of the cover part is often insufficient to properly compress the gasket across the interface between the parts. These factors mean that the compression rate around the gasket is often non-uniform.

[0004] In this regard, Figure 1An isometric view of a conventional automotive EMC enclosure 1 is shown having a base portion 2 covered by a cover portion 3 to enclose a printed circuit board (PCB) 6. The cover portion 3 is shown in exaggerated distortion for illustration purposes, being enlarged by a factor of 20. As shown, the base portion interface surface 4 and the cover portion interface surface 5 are separated from each other in a plurality of areas, creating gaps in the enclosure. In these areas, the gasket disposed between the interface surfaces can not be sufficiently compressed into the desired compression range to form an effective EMI shield. As such, electromagnetic radiation can leak through or be emitted from the enclosure in these areas. Furthermore, EMI shielding cannot be improved by tightening the screw fasteners that secure the cover portion 3 to the base portion 2, as while this helps to compress the components together, its effectiveness is limited by the stiffness of the cover portion 3, and it also results in a large force being applied to the PCB 6. Thus, the load on the PCB 6 can cause strain on electronic components and interconnects, and ultimately has the potential to cause component failure or reliability issues.

[0005] To address the above problems, new EMI shielding gaskets have been investigated that are more compressible and thus can provide a more uniform seal between the components of an EMC enclosure. For example, more complex gasket shapes can be formed by molding, die cutting, or selective deposition dispensing processes. However, these more complex manufacturing techniques are largely impractical for automotive applications, as they would have a significant detrimental impact on overall production time, resulting in an unacceptable increase in production costs.

[0006] Therefore, there remains a need to address the above problems in the related art. SUMMARY

[0007] According to a first aspect, there is provided an electromagnetic compatibility, EMC, enclosure, the EMC enclosure comprising: a first portion and a second portion for forming an outer shell when assembled together, wherein the first and second portions comprise a first interface surface and a second interface surface, respectively, for compressing a gasket inserted between the first and second interface surfaces when the first and second portions are assembled together, and wherein at least one of the first and second interface surfaces comprises a plurality of undercut regions for reducing compression of the gasket in the undercut regions when the first and second portions are assembled together.

[0008] In this way, the force required to compress the gasket overall is reduced. At the same time, this can be achieved without the need to modify the gasket itself. Thus, the gasket can be compressed sufficiently to achieve the required EMI shielding effect over its entire length, but without exerting excessive strain on the electronic components housed therein. In this way, electromagnetic compatibility can be achieved without increasing the manufacturing or production costs.

[0009] In embodiments, the undercut region is between 40% and 60% of the respective interface surface. In this way, the force required to achieve sufficient compression for EMI shielding can be reduced proportionally.

[0010] In embodiments, a plurality of undercut regions form a relief pattern in the respective interface surface. In this way, a more uniform degree of compression can be achieved over the entire interface surface.

[0011] In embodiments, the undercut region is interspersed between protruding regions of the respective interface surface.

[0012] In embodiments, the spacing between the protruding regions is between 5mm and 20mm, wherein the spacing defines the undercut region. In embodiments, the spacing between the protruding regions is between 6mm and 14mm.

[0013] In embodiments, the length of the protruding regions is between 5mm and 20mm. In embodiments, the length of the protruding regions is between 6mm and 14mm.

[0014] In embodiments, the EMC housing further comprises the gasket. In embodiments, the gasket comprises an electrically conductive elastomeric material.

[0015] In embodiments, the gasket is deposited on the first interface surface. In embodiments, a segment of the gasket is allocated to the first interface surface.

[0016] In embodiments, the first interface surface is configured to press the gasket against the second interface surface when the first part and the second part are assembled together.

[0017] In embodiments, the first interface surface is configured to press the gasket against a circuit board inserted between the first interface surface and the second interface surface when the first part and the second part are assembled together. In this way, the gasket or a segment of the gasket can form a resilient support for supporting the circuit board.

[0018] In embodiments, the EMC housing further comprises a further gasket.

[0019] In embodiments, the second interface surface is configured to press the further gasket against a circuit board inserted between the first interface surface and the second interface surface when the first part and the second part are assembled together.

[0020] In an embodiment, the gasket is an electromagnetic interference, EMI, shielding gasket.

[0021] In an embodiment, the housing is a motor vehicle electronics housing.

[0022] In an embodiment, the first portion and the second portion are configured to form an enclosure around a motor vehicle electronic control unit when assembled together. BRIEF DESCRIPTION OF DRAWINGS

[0023] Illustrative embodiments will now be described, with reference to the accompanying drawings, wherein:

[0024] Figure 1 An isometric view of a conventional motor vehicle EMC housing is shown, with the distortion of the cover portion magnified by a factor of 20;

[0025] Figure 2 An isometric view of a base portion of a motor vehicle EMC housing according to an illustrative embodiment is shown;

[0026] Figure 3 An enlarged isometric view of a side interface surface segment of the base portion shown in Figure 2

[0027] An enlarged side view of a side interface surface segment of the base portion shown in Figure 4 Figure 3 An enlarged isometric view of a side interface surface segment and gasket in an assembled EMC housing of a first embodiment is shown;

[0028] Figure 5 An enlarged isometric view of an end interface surface segment of the base portion shown in

[0029] Figure 6 Figure 2 An enlarged isometric view of an end interface surface segment of the base portion shown in

[0030] Figure 7 An enlarged side view of an end segment of an interface surface and gasket in an assembled EMC housing of a first embodiment is shown; and

[0031] Figure 8 A plan view of a protruding compression area of a gasket in an EMC housing of a first embodiment is shown. DETAILED DESCRIPTION

[0032] Reference will now be made to Figures 2 to 8 An illustrative embodiment is described.

[0033] As with Figure 1 ​​The conventional housing shown, the motor vehicle EMC housing according to the exemplary first embodiment, comprises a base portion 2 and a cover portion 3 which are assembled together with a gasket 9 interposed therebetween to form the assembled EMC housing.

[0034] Figure 2 A perspective view of the base portion 2 of a motor vehicle EMC housing according to the illustrative embodiment is shown. The base portion 2 comprises a first interface surface 4 which cooperates with a corresponding second interface surface 5 on the cover portion 3 when the base portion and the cover portion are assembled together. The first interface surface 4 comprises two side interface surface segments 4a which extend along the sides of the housing and two end interface surface segments 4b which extend along the ends of the housing. As discussed in further detail below, the side segments and the end segments of the first interface surface have shaped surface profiles in the form of flat undulations which extend along their lengths. In Figure 2 the undulations are visible in the side interface surface segments 4a as raised regions 8 interspersed with undercut regions 7. Corresponding undulations are formed on the end interface surface segments 4b, although not visible in Figure 2 because the second segment 9b of the gasket has been deposited on top of them.

[0035] Turning first to the side interface surface segments 4a, Figure 3 and Figure 4 enlarged isometric and side views of one of the interface surfaces are shown respectively. The interface surface has an undulating profile in which the flat bottom of the undercut region 7 lies in a different plane than the flat top of the raised region 8. In this way, a repeating pattern of raised and undercut is provided in which a space 71 is defined between the planes of these structures by the undercut region 7.

[0036] In this regard, Figure 5 an enlarged isometric view of the side interface surface segments 4a and the gasket 9 in the assembled EMC housing is shown. The gasket 9 is formed as an elongated body of electrically conductive elastomeric material and the raised regions 8 form seats on which the gasket 9 sits. The space 71 formed by the undercut regions 7 provides areas into which adjacent regions of the gasket 9 move when the assembly is compressed. The side segments of the second interface surface 5 provided on the cover portion 3 have flat surfaces for pressing the gasket 9 into the first interface surface 4. In this way, in the first segment 9a of the gasket, the raised regions 8 of the first interface surface 4 will protrude into the gasket material when the base portion 2 and the cover portion 3 are brought together by the screw fixation means. At the same time, although the gasket material will contact the surfaces of the undercut regions 7, the gasket material in these regions will be substantially uncompressed due to the space 71.

[0037] Figure 6An enlarged isometric view of the end interface surface section 4b of the base portion 2 is shown, which forms a resilient support for the PCB 6. In this regard, the end interface surface section 4b has a relief corresponding to the relief provided in the side interface surface section 4a, with the same repeating pattern of undercut regions 7 and protruding regions 8. In this case, a second section 9b of the gasket is deposited directly on the first interface surface 4 of the base portion 2 and forms a lower compressible support for the PCB 6. As shown, the second section 9b of the gasket takes a contoured profile corresponding to the first interface surface 4 on which it is deposited, with the gasket 9 protruding in regions on the protruding regions 8 of the first interface surface 4 and recessed in regions on the undercut regions 7 of the first interface surface 4.

[0038] The end section of the second interface surface 5 provided on the cover portion 3 also has a relief corresponding to the relief on the end interface surface section 4b of the first interface surface 4 shown. Figure 6 That is, in contrast to the flat side sections of the second interface surface 5, the end section of this surface is provided with a pattern of protruding regions 8 and undercut regions 7. At the same time, a second gasket 10 is also deposited directly on this second interface surface 5 to produce a corresponding contoured profile, which serves to form an upper compressible support for the PCB 6. Thus, the end sections of the first and second interface surfaces 4, 5 are substantially mirror-symmetrical to each other, although the positions of the protruding regions and undercut regions need not be precisely matched.

[0039] Figure 7 An enlarged side view of the end interface surface sections 4b, 5b of the interface surfaces and gaskets 9, 10 in the assembled EMC housing of the first embodiment is shown. The PCB 6 is sandwiched between the gaskets 9, 10, with the regions of the gaskets 9, 10 associated with the protruding regions of the first and second interface surfaces forming compression regions 91, 101. In this way, the gaskets 9, 10 are compressed into the PCB 6 by the respective interface surfaces, which serves to clamp the PCB 6 in place. Since the PCB 6 is resiliently held between the gaskets 9, 10, the forces and strains exerted on the PCB 6 are also minimised, thereby mitigating the risk of damage to the PCB 6.

[0040] Figure 8A plan view of the protruding regions of the gasket 6 in the EMC housing of the first embodiment is shown. As shown, when the housing is closed, the overall length of the gasket which is substantially compressed is reduced. In this embodiment, each protruding region 8 is 10mm long interspersed with a 10mm undercut region. Thus, the length of the gasket after compression is effectively reduced by approximately 50%. However, it will be appreciated that the length of the protruding regions 8 and undercut regions 7 and the spacing therebetween can be adjusted to optimise the amount of compression. Advantageously, the force required to compress the gasket 9 is reduced due to the discontinuity in the compressed gasket region caused by the undercut regions 7. This therefore allows a higher degree of compression to be achieved in the gasket, with the compression in the required range being achieved more evenly around the entire interface between the sections 2, 3. At the same time, the discontinuity does not compromise the EMI shielding performance of the gasket. Furthermore, the lower compression force means that the PCB 6 is subjected to a lower load. Moreover, there is no significant increase in production costs as the underlying gasket manufacturing techniques can still be used. That is, it is not necessary to change the deposition or moulding process to obtain a complex gasket shape to increase compression. Rather, the moulds used to mould the housing components can simply be constructed to include the required interface surface profiles which are used to adjust the compressibility on the gasket.

[0041] It will be appreciated that the above embodiments have been shown for the purposes of illustration only. In practice, the embodiments can be applied to many different configurations, the detailed embodiments being readily implemented by the skilled person.

Claims

1. An electromagnetic compatibility, EMC, enclosure, the EMC enclosure comprising: a first part and a second part for forming an enclosure when assembled together, wherein the first and second parts comprise a first and second interface surface, respectively, for compressing a gasket inserted between the first and second interface surfaces when the first and second parts are assembled together, and wherein the first and second interface surfaces comprise a protruding area for the gasket to rest on and a plurality of undercut areas for reducing compression of the gasket in the undercut areas when the first and second parts are assembled together, the undercut areas being arranged adjacent to each of the protruding areas forming a space such that a portion of the gasket contacts the undercut areas when the gasket is compressed and gasket material in the plurality of undercut areas is not compressed due to the space, the first and second interface surfaces comprising the protruding area and the plurality of undercut areas being mirror-symmetrical to each other.

2. The EMC housing of claim 1, wherein, The plurality of undercut areas is between 40% and 60% of the respective interface surface.

3. The EMC housing according to claim 1 or 2, wherein, The plurality of undercut areas forms a relief pattern in the respective interface surface.

4. The EMC housing according to claim 1 or 2, wherein, The plurality of undercut areas is interspersed between the protruding areas of the respective interface surface.

5. The EMC housing of claim 4, wherein, The spacing between the protruding areas is between 5 mm and 20 mm, wherein the spacing defines the plurality of undercut areas.

6. The EMC enclosure of claim 4, wherein, The length of the protruding areas is between 5 mm and 20 mm.

7. The EMC enclosure of claim 1 or 2, further comprising the gasket.

8. The EMC housing of claim 7, wherein, The gasket is dispensed onto the first interface surface.

9. The EMC housing according to claim 1 or 2, wherein, The first interface surface is for pressing the gasket against the second interface surface when the first and second parts are assembled together.

10. The EMC housing according to claim 1 or 2, wherein, The first interface surface is for pressing the gasket against a circuit board inserted between the first and second interface surfaces when the first and second parts are assembled together.

11. The EMC enclosure of claim 1 or 2, further comprising another gasket.

12. The EMC enclosure of claim 11, wherein, The second interface surface is for pressing the other gasket against a circuit board inserted between the first and second interface surfaces when the first and second parts are assembled together.

13. The EMC housing according to claim 1 or 2, wherein, The gasket is an electromagnetic interference, EMI, shielding gasket.

14. The EMC housing of claim 1 or 2, wherein, The EMC enclosure is a motor vehicle electronics enclosure.

15. The EMC enclosure of claim 14, wherein, The first and second parts are configured to form an enclosure around a motor vehicle electronic control unit when assembled together.

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