Arrangement for potential equalization in a control unit

Abstract

Arrangement for potential equalization in a control unit (1) for a motor vehicle, comprising a. at least one electrical component (3) on a circuit carrier (4), b. a base plate (2) on which the circuit carrier (4) is arranged, c. at least one foil conductor (5) with an electrical contact area (7), wherein the foil conductor (5) is permanently connected to a carrier plate (6), and the foil conductor (5) electrically connects the circuit carrier (4) to at least one component provided outside the control unit (1), and d. at least two electrical connecting elements, one of which is a first connecting element that electrically connects the circuit carrier (4) to the flexible foil conductor (5), wherein the at least two connecting elements are led through an opening (10) in the base plate (2), and the carrier plate (6), covering the opening (10) in a media-tight manner, is electrically connected to the base plate (2), characterized in that the flexible foil conductor (5) in the contact area (7) has at least one recess (9) such that, in order to establish a potential equalization between the circuit carrier (4) and the base plate (2), a second connecting element (8) of the at least two electrical connecting elements is directly electrically connected to the carrier plate (6) through a recess (9).

Description

[0001] The invention relates to an arrangement for potential equalization in a control unit for a motor vehicle, a control unit with a corresponding arrangement, and a method for establishing potential equalization in a control unit.

[0002] For reasons of electromagnetic compatibility, a control unit in a motor vehicle requires, in particular, a ground connection of the circuit carrier of the control unit to the control unit housing or to the control unit base plate, which is usually made of aluminum.

[0003] Such a ground connection is primarily necessary to compensate for the ground offset between the transmission housing, i.e. the ground on the vehicle, and the control unit. Ground here refers to the electrical reference potential for signal and operating voltages in the vehicle or control unit. Up to now, this has generally been achieved by directly bonding the circuit board to an aluminum base plate of the control unit. For this to happen, the bonding surface must be machined before the bond is created. This incurs additional manufacturing costs, as otherwise no further processing is necessary. One difficulty is that the bonding surface may be contaminated or that the bonding surface does not meet the surface roughness requirements, meaning that a secure bond cannot be guaranteed, which may require repairs.

[0004] Typically, the ground bond is applied directly to the die-cast aluminum base plate. To ensure bondability to the base plate, a mechanically machined surface, such as a milled surface, is required. Above all, the base plate must be washed with perchloroethylene, for example, and especially degreased, to meet the strict cleanliness and surface finish requirements. This is an expensive and particularly environmentally harmful process.

[0005] WO 2009 / 007252 A2 discloses a control device comprising an electrically conductive base plate, an electrically conductive cover plate, and a circuit board arranged between the base plate and the cover plate. The circuit board has a first contact point electrically coupled to the cover plate, and the circuit board has a second contact point electrically coupled to the first contact point and the base plate.

[0006] From WO 2008 / 113 323 A1 it is known to provide a conductor track in a supply line to the electrical component for potential equalization between an electrical component and its housing.

[0007] WO 2004 / 091270 A1 describes a control unit with an arrangement for electrically connecting at least one electrical assembly on a circuit carrier, which is arranged on a base plate inside a housing, to at least one electrical component provided outside the housing by means of a separate flexible foil conductor. The separate foil conductor is arranged on the side of the base plate opposite the circuit carrier, between the base plate and a separate carrier plate. The carrier plate covers the opening in the base plate in a media-tight manner. The electrical connection is established by means of a bonding wire through an opening in the base plate.

[0008] The invention is therefore based on the object of creating an arrangement for potential equalization in such a control unit for a motor vehicle and a method for its production, in which the potential equalization of the circuit carrier to the control unit housing is simplified.

[0009] This object is solved by the features of claims 1, 10 and 11.

[0010] The core of the invention is that, in order to create potential equalization between the circuit carrier and the base plate, at least one connecting element is electrically connected directly to the carrier plate and thus to the base plate through a recess in the contact area of ​​the conductor carrier. As a rule, the conductor carrier on the carrier plate completely covers the opening in the base plate. This is particularly useful for reasons of tightness. Since the carrier plate must be mechanically and / or chemically pretreated before the connection between the conductor carrier and the carrier plate, which, like the base plate, is made of aluminum or an aluminum alloy, for example, and thus the conditions regarding the surface quality for bondability are also created, no additional manufacturing step is required to create the potential equalization.The conductor carrier is designed in particular as a flexible foil or as a printed circuit board.

[0011] Because the carrier plate is mechanically and electrically connected to the base plate, in particular by riveting, screwing, welding, gluing, soldering or caulking, when a connecting element is contacted through a recess in the contact area of ​​the conductor carrier with the carrier plate, the base plate is also electrically connected to the circuit carrier and the potential equalization is established.

[0012] For example, the base plate is designed as part of the control unit's housing, which eliminates the manufacturing step of connecting a separate base plate to the housing when assembling the housing.

[0013] In particular, the circuit carrier is a printed circuit board made of fiber-reinforced plastic or, for applications at higher temperatures, of ceramic. The circuit board can be single-layer or multi-layer. Special printed circuit boards can also be designed using thick-film, LTCC, HDI, HTCC, or DCB technology.

[0014] In particular, the conductor carrier is connected to the carrier plate at one end by a material bond, such as gluing or lamination. If the external electrical components are arranged in an electrically conductive manner in the area of ​​the other end of the conductor carrier before the carrier plate is attached to the base plate, this creates a finished module consisting of external components, conductor carrier, and carrier plate, which can be connected to the base plate, particularly in an oil-tight manner, through the respective opening in the area of ​​the relevant assembly on the circuit carrier.

[0015] To increase the seal between the module consisting of the circuit carrier and carrier plate on the one hand, and the base plate on the other, a seal is advantageously arranged between the circuit carrier and the base plate so that it follows the edge of the opening on the side of the base plate opposite the circuit carrier. The seal can be molded on or provided as a separate part. Advantageously, the seal extends along its entire circumference on the foil.

[0016] In the event that the seal is designed as a separate part, for example, as an insert seal, it is advantageous for handling during manufacture of the arrangement according to the invention if a groove for receiving the seal is provided on the side of the base plate opposite the circuit carrier at the edge of the opening. It would also be conceivable for a liquid seal to be injected into the groove.

[0017] In particular, the base plate has a stepped recess surrounding the opening in the area of ​​the opening to accommodate the support plate. If the outer surface of the support plate is flush with the outer surface of the base plate, the compactness of the arrangement according to the invention and thus of the control unit housing is increased.

[0018] In the method for producing a potential equalization according to the invention in a control unit for a motor vehicle, a control unit is first provided with a circuit carrier and a base plate in which, depending on the application, at least one opening is located near the circuit carrier, between the circuit carrier and the housing wall. Furthermore, a separate conductor carrier with an electrical contact area at at least one end is provided for each opening, wherein the conductor carrier is permanently connected to a carrier plate, for example by gluing or lamination. The carrier plate is then joined to the base plate in such a way that the carrier plate is mechanically and electrically connected to the conductor carrier, covering the opening in a media-tight manner, and to the base plate.In particular, the carrier plate and base plate are made of metal, for example, aluminum, and the connection is made by riveting, screwing, welding, gluing, soldering, or caulking. An electrically conductive contact is then established between the circuit carrier, with the components located thereon, and the base plate using a connecting element. The connecting element, for example a bonding wire, is guided from the circuit carrier through the opening in the base plate and through a recess in the contact area of ​​the conductor carrier directly to the carrier plate, or vice versa. The fact that the carrier plate is electrically connected to the base plate of the control unit housing achieves potential equalization between the circuit carrier and the housing.

[0019] Further features, advantages, and details can be found in the following description, in which preferred embodiments are explained in more detail with reference to the figures. They show: Fig. 1 an arrangement for potential equalisation, where the support plate is larger than the opening in the base plate, Fig. 2 an arrangement such as Fig. 1, whereby the support plate is recessed flush with the base plate, Fig. 3 a perspective view of a cable carrier, Fig. 4 a schematic representation of a layer structure of a conductor carrier with contacting area, and Fig. 5 a schematic representation of a layer structure of a conductor carrier with a recess in the contacting area.

[0020] Fig. 1 shows an arrangement for establishing potential equalization in a control unit for a motor vehicle. A circuit carrier 4 with an electrical assembly 3 is arranged on the base plate 2, which is part of a control unit housing (not shown). The circuit carrier 4 can be, for example, a conventional printed circuit board made of fiber-reinforced plastic or ceramic. The electrical assembly 3 can be, for example, an integrated circuit or an active or passive electrical component. In the immediate vicinity of the circuit carrier 4, there is an opening 10 in the base plate 2. This opening 10 is completely covered on the side of the base plate 2 opposite the circuit carrier 4 by a carrier plate 6, sealing it off from the outside.A conductor carrier 5, here embodied, for example, as a flexible foil conductor or so-called flex foil made of polyimide, is arranged between the base plate 2 and the carrier plate 6. The foil conductor 5 normally has the function of electrically connecting the circuit carrier 4, in a manner not shown, to at least one component provided outside the control unit 1. For this purpose, an electrical contact area is located in the area of ​​the opening 10 on the foil conductor 5, which can be contacted by means of the electrical connecting element 8 and thus establishes an electrically conductive connection between the circuit carrier 4 and the foil conductor 5, or a component provided outside the control unit 1.

[0021] In Fig. 1, a portion of the contact area of ​​the foil conductor 5 is removed, forming a recess 9, so that the carrier plate 6 can be directly electrically contacted through the recess 9 by the bonding wire 8. Because the carrier plate 6 is connected both mechanically and electrically to the base plate 2 by means of the connecting elements 11, for example rivets or screws, the circuit carrier is also connected to the base plate 2 and thus to the control unit housing by the bonding wire 8, establishing potential equalization.

[0022] Fig. Figure 2 shows an arrangement according to the invention, wherein the base plate 2 has on its outer side in the region of the opening 10 a stepped recess 13 surrounding the opening 10. This recess 13 receives the carrier plate 6, flush with the base plate 2. In order to increase the sealing effect between the base plate 2 and the foil conductor 5, a seal 12 surrounding the opening 10 is arranged between the foil conductor 5 on the carrier plate 6 and the base plate 2. This seal 12 can be designed as an insert seal or as an injection-molded liquid seal. The seal is arranged here in a groove 14 in the base plate. The carrier plate 6 is in Fig. 2 is connected to the base plate 2 both mechanically and electrically by means of a caulking.

[0023] Fig. 3 shows a carrier plate 6 and a flexible foil conductor 5, which is permanently connected to the carrier foil 5. The foil conductor 5 has a substantially rectangular shape. A rectangular contacting region 7 essentially consists of several electrical contact points 18 and at least one, in this case two, recesses 9 of different sizes. The contacting region 7, or the electrical contact points 18, are arranged substantially centrally with respect to the carrier plate 6 arranged on the opposite surface of the foil conductor 5. The electrical contact points 18 are connected, in a manner not shown, to a contacting region at the other end of the foil conductor 5 via electrical conductor tracks.

[0024] The electrical contact points 18 are used to contact a bonding wire 8 made of Fig. 1 or Fig. 2 on the flexible foil conductor, wherein the carrier plate 6 opposite the electrical contact points 18 ensures sufficient stability due to mechanical effects of a bonding process.

[0025] One in Fig. The foil conductor 5 shown in Figure 4 is permanently connected to a carrier plate 6 by means of an adhesive layer 16. The foil conductor 5 essentially has a centrally arranged electrically conductive layer 15 and an upper and a lower protective layer 17, wherein the protective layers 17 are each connected to the electrically conductive layer 15 via an adhesive layer 16. In sections, an upper protective layer 17 with a corresponding adhesive layer 16 is removed to create electrical contact points 18. This allows a contacting layer forming an electrical contact point 18 to be arranged directly on the electrically conductive layer 15, so that there is electrical contact between the contact point 18 and the electrically conductive layer 15. The contacting layer is preferably made of a nickel-gold compound, wherein the layer thickness of the contacting layer is in particular less than 20 µm.The electrically conductive layer 15 is a copper foil and has a layer thickness of, in particular, 50 to 200 µm. Polyimide, with a layer thickness of, in particular, less than 100 µm, is primarily used for the protective layer 17. An acrylic-based adhesive, such as Pyralux®, with layer thicknesses of generally less than 100 µm, is used as the adhesive layer 16. The carrier plate 6 is predominantly made of aluminum or one of its alloys. The thickness of the carrier plate 6 is preferably between 1 and 4 mm.

[0026] Fig. 5 shows a Fig. 4 with a carrier plate 6, wherein in the region of an electrical contact point 18 the foil conductor 5 with its layers 15, 16, 17 and the adhesive layer 16 connecting the foil conductor 5 to the carrier plate 6 are removed. Through this recess 9 formed thereby, as in Fig. 1 and Fig.2, in order to form a potential equalization between circuit carrier 4 and base plate 2, the carrier plate 6 can be connected directly to a bonding wire 8. List of reference symbols 1 control unit 2 base plate 3 electrical component 4 circuit carriers 5 cable carriers 6 Carrier plate 7 electrical contact area 8 electrical connecting element 9 Recess 10 Breakthrough 11 Fastener, screw, caulking 12 Seal 13 Deepening 14 grooves 15 copper foil 16 adhesive layer 17 Protective layer 18 electrical contact point

Claims

[1] Arrangement for potential equalization in a control unit (1) for a motor vehicle, comprising a. at least one electrical component (3) on a circuit carrier (4), b. a base plate (2) on which the circuit carrier (4) is arranged, c. at least one foil conductor (5) with an electrical contacting area (7), wherein the foil conductor (5) is permanently connected to a carrier plate (6), and the foil conductor (5) electrically connects the circuit carrier (4) to at least one component provided outside the control unit (1), and d. at least two electrical connecting elements, of which a first connecting element electrically connects the circuit carrier (4) to the flexible foil conductor (5), wherein the at least two connecting elements are guided through an opening (10) in the base plate (2), and the support plate (6), covering the opening (10) in a media-tight manner, is electrically connected to the base plate (2), characterized by that the flexible foil conductor (5) has at least one recess (9) in the contacting area (7) such that, in order to establish potential equalization between the circuit carrier (4) and the base plate (2), a second connecting element (8) of the at least two electrical connecting elements is electrically conductively connected directly to the carrier plate (6) through a recess (9). [2] Arrangement according to claim 1, characterized by that the foil conductor (5) is designed as a flexible foil. [3] Arrangement according to claim 1 or 2, characterized by that the carrier plate (6) is mechanically and electrically connected to the base plate (2). [4] Arrangement according to one of the preceding claims, characterized by that the base plate (2) is designed as part of the housing of the control unit (1). [5] . Arrangement according to one of the preceding claims, characterized by that the circuit carrier (4) comprises a printed circuit board. [6] Arrangement according to one of the preceding claims, characterized by that the foil conductor (5) is permanently connected to the carrier plate (6) by a material connection. [7] Arrangement according to one of the preceding claims, characterized by that a seal (12) is arranged between the foil conductor (5) and the base plate (2) in such a way that it follows the edge of the opening (10) on the side of the base plate (2) opposite the circuit carrier (4). [8] . Arrangement according to claim 7 , characterized bythat on the side of the base plate (2) opposite the circuit carrier, a groove (14) for receiving the seal (12) is provided at the edge of the opening (10). [9] . Arrangement according to one of the preceding claims, characterized by that the base plate (2) in the region of the opening (10) has a step-shaped recess (13) surrounding the opening (10) for receiving the carrier plate (6). [10] Control unit (1) for a motor vehicle comprising a housing with a base plate (2) on which a control unit is arranged, which comprises at least one electrical component (3) on a circuit carrier (4), with at least one separate conductor carrier (5) with an electrical contacting area (7), wherein the conductor carrier (5) is permanently connected to a carrier plate (6), and the conductor carrier (5) electrically connects the circuit carrier (4) to at least one component provided outside the control unit (1), and with at least two electrical connecting elements, wherein a first electrical connecting element electrically connects the circuit carrier (4) to the conductor carrier (5), wherein the at least two connecting elements are guided through an opening (10) in the base plate (2), and the carrier plate (6), covering the opening (10) in a media-tight manner, is electrically connected to the base plate (2), characterized by , that the conductor carrier (5) has at least one recess (9) in the contacting area (7) such that, in order to establish potential equalization between the circuit carrier (4) and the base plate (2), a second connecting element (8) of the at least two electrical connecting elements is electrically conductively connected directly to the carrier plate (6) through a recess (9). [11] Method for establishing a potential equalization in a control unit (1) for a motor vehicle, comprising the following steps: a. Providing a control unit (1) with i. a circuit carrier (4) and ii. a base plate (2) with an opening (10), b. Providing a separate conductor carrier (5) with an electrical contacting area (7), wherein the conductor carrier (5) is permanently connected to a carrier plate (6), and c. Joining the support plate (6) to the base plate (2) in such a way that the support plate (6), covering the opening (10) in a media-tight manner, is mechanically and electrically connected to the base plate (2), d. Establishing an electrical contact between the circuit carrier (4) and the base plate by means of a connecting element (8) which directly contacts the carrier plate (6) through a recess (9) in the contacting area (7) of the conductor carrier (5).

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