Arrangement of a printed circuit board at an interface

Abstract

Arrangement of a printed circuit board (1) to an interface (6), wherein the printed circuit board (1) comprises: - a first surface (1.1) and an opposite second surface (1.2), - a continuous, electrically conductive via (2) with a first edge (2.1) and a second edge (2.2), wherein the circuit board (1) and the interface (6) are materially bonded together by means of an intermediate layer (7), wherein a milling (5) partially surrounding the via (2) forms a flexible area (1.3) of the printed circuit board (1), wherein the printed circuit board (1) and the interface (6) in the area of ​​the via (2) and the milling (5) are free of the intermediate layer (7), and a plastic coating (10) of the printed circuit board (1) fills at least the via (2) and the milling (5) in such a way that an electrically conductive contact is established between the via (2) and the interface (6), and wherein the plastic coating (10) deforms the flexible area (1.3) of the circuit board (1) in such a way as to the interface (6) that the electrically conductive contact is established.

Description

[0001] The invention relates to an arrangement of a printed circuit board at an interface, wherein the printed circuit board comprises a first surface and an opposite second surface, as well as a continuous, electrically conductive via with a first edge and a second edge. The printed circuit board and the interface are integrally connected to one another by means of an intermediate layer.

[0002] Printed circuit boards are used, for example, in motor vehicles for the electronic control and regulation of a vehicle's transmission. These printed circuit boards are typically rigid circuit boards that electrically connect discrete components and highly integrated modules, while also serving as their carriers.

[0003] Conventional printed circuit boards consist of one or more substrate plates made of glass-fiber-reinforced, cured epoxy resin, which are copper-clad on one or both sides to form electrically conductive structures, particularly conductor tracks. In multilayer printed circuit boards, one or more of these substrate plates are pressed together using prepreg layers or prepregs, and sometimes also with copper foil. The substrate plates and prepregs form the electrically insulating substrate layers of the multilayer printed circuit board.

[0004] The insulated conductor tracks between electrically insulating substrate layers are electrically connected to each other in the circuit board through metallized holes, also known as through-holes or vias. The various manufacturing processes for through-holes are familiar to those skilled in the art. Typically, a hole is first drilled through several electrically insulating substrate layers of the circuit board, which is then cleaned. The non-conductive wall of the hole is then made conductive before being galvanically reinforced with copper.

[0005] According to the state of the art, a circuit carrier is mounted on a base plate, for example made of aluminum, whereby the base or carrier plate serves to mechanically stabilize and dissipate heat from the electronic components of the circuit carrier.

[0006] To ensure the functionality of electronic control units with corresponding circuit boards, especially transmission control units in motor vehicles, and also to meet electromagnetic requirements, a connection, especially a ground connection, of the circuit board to a customer interface, such as a transmission housing, a housing part, or a hydraulic plate, must be established. Currently, this is primarily achieved using wired connections such as cables, or mechanically detachable connections such as screw connections or nuts, or with mechanically non-detachable connections such as rivets.

[0007] Such control units are typically protected from external influences, such as transmission oil, by housing covers. Seals, adhesives, or material-to-material connections are used between the circuit board or an associated base plate and a cover.

[0008] Instead of a housing, another option for protecting the control unit from external influences is to enclose the electronics in a plastic sheath or encapsulation, for example, using an injection-molded or molded process. One possible embodiment is described in EP 1906719 A1.

[0009] The plastic enclosure surrounds all components on the populated flat side of the circuit board, protecting both the electronic components and the connecting elements, such as bonding wires, used to electrically contact the electronic components from external influences such as chips or transmission oil. The plastic enclosure thus provides the control unit with an optimal combination of electronic protection and a housing concept with a reduced installation space requirement compared to the state of the art.

[0010] Preferably, the plastic sheath is made of a curable material so that the form and material connection between the plastic sheath and the components can be produced particularly easily.

[0011] With molded electronic assemblies, contacting, especially the ground connection to an interface, is difficult using the technologies described above, such as screws or rivets, because access to the ground connection, in particular, is surrounded by molding compound. Furthermore, an additional, often complex manufacturing process is always required to create the connection between the circuit board's ground socket and a housing as an interface, which incurs costs and additional labor.

[0012] WO 2015 / 104072 A9 discloses a printed circuit board with a metallic carrier plate and an insulating layer on a surface that electrically insulates the metallic carrier plate. The carrier plate is free of the insulating layer in at least one connection area. The carrier plate has a metallic coating in the connection area, and a semiconductor contact is electrically connected to the metallic coating of the connection area.

[0013] From CN 1 10 177 428 A and KR 10 2011 0 074 177 A, various arrangements of a printed circuit board at an interface are also known.

[0014] WO 2020 / 001 854 A1 discloses the use of a printed circuit board for transmission control and for arrangement on an interface, wherein the printed circuit board has, between a printed circuit board top side and a printed circuit board bottom side arranged at a distance from the printed circuit board top side, a plurality of spaced-apart conductor tracks which are electrically connected to one another via a first through-hole. The first through-hole is drilled out on the printed circuit board bottom side such that it is arranged so as to be recessed relative to the printed circuit board bottom side. The printed circuit board can be arranged on an interface, wherein the printed circuit board bottom side faces the interface. A second through-hole extends to the printed circuit board bottom side and has a projection relative to the printed circuit board bottom side, wherein the second through-hole is electrically connected to a ground layer arranged within the printed circuit board.The second via is not drilled and is conductively connected to the interface. The first and second vias are each formed as sleeves and encapsulated with resin.

[0015] EP 2 434 846 B1 discloses a wiring element for wiring a plurality of electrical components, comprising at least one circuit board made of a material with a first electrical conductivity, which carries at least one conductor track made of a material with a second electrical conductivity, and at least one connection element. The connection element is arranged in a contact region of the circuit board, which occupies a partial area of ​​the surface of the circuit board and is separated from the remaining surface of the circuit board on at least two sides by at least one slot. The contact region can be deformed at least partially in a direction orthogonal to the surface of the circuit board due to the flexibility of the material of the circuit board.

[0016] The object of the present invention is therefore to provide an arrangement of a circuit board of a control unit to an interface which ensures the functionality of the electronic control unit and at the same time reduces costs in terms of material and manufacturing process.

[0017] This object is achieved according to the invention by an arrangement having the features of claim 1.

[0018] In the arrangement according to the invention, the circuit board and the interface are integrally connected to one another by means of an intermediate layer, for example a laminate or a prepreg layer.

[0019] A milled hole in the circuit board partially surrounding the through-hole creates a flexible area of ​​the circuit board in the area of ​​the through-hole. In particular, the circuit board and the interface are free of the intermediate layer in the area of ​​the through-hole and milled hole, and a plastic sheath surrounding the circuit board simultaneously fills at least the through-hole and the milled hole in such a way that an electrically conductive contact is established between the lower edge of the through-hole and the intermediate layer-free area of ​​the interface.

[0020] This creates a ground connection from the circuit board of the control unit to the adjacent interface without additional materials such as cables or screws and without an additional process step, taking advantage of the fact that during the encapsulation process of the circuit board, a certain pressure must be exerted which is sufficient to deform the flexible area of ​​the circuit board in the area of ​​the via in the direction of the interface in such a way that an electrically conductive contact is created between the edge of the via and the interface, and this contact is permanently maintained under formation of the ground connection after the encapsulation material has hardened due to the adhesive effect of the plastic encapsulation.

[0021] In one embodiment, the circuit board is a multi-layer circuit board, which can increase the compactness of a corresponding electronic circuit.

[0022] In a further embodiment, the milling forming the flexible region of the circuit board is designed as a milling extending from the first surface to the opposite second surface of the circuit board.

[0023] In a further embodiment, the interface to which the circuit board is arranged can be designed as a metallic carrier plate, a housing, or a housing part. In addition to its function as an electrically conductive contact, the interface can thus also serve as a heat sink for the circuit board.

[0024] In another embodiment, the interface can be made of aluminum or die-cast aluminum, for example. Depending on the application or customer requirements, the use of a different metal would also be conceivable.

[0025] In a further embodiment, the continuous, electrically conductive through-plating consists in particular of copper or a copper alloy, wherein the through-plating can be designed as a plated socket or can also be designed as a separate, socket-shaped part.

[0026] In another embodiment, the milling, which partially surrounds the via and forms a flexible area of ​​the circuit board, runs concentrically to the via. However, a U-shaped or spoon-shaped milling geometry would also be conceivable.

[0027] In a further embodiment, the intermediate layer is designed as an insulating prepreg layer or as a laminate.

[0028] The plastic casing can be a thermoset material with electrically insulating properties, preventing short circuits between the electronic components. The thermoset material is, for example, an epoxy-based polymer.

[0029] The plastic casing can also be a thermoplastic.

[0030] The drawings show: Fig. 1 a plan view of an arrangement of a printed circuit board at an interface, Fig. 2 a section through an arrangement of Fig. 1 in level AA, Fig. 3 shows another section through an arrangement of Fig. 1 in level AA, Fig. 4 shows another section through an arrangement of Fig. 1 in level AA.

[0031] Fig. Figure 1 shows a top view of an arrangement of a printed circuit board 1 at an interface. The upper first edge 2.1 of the through-hole 2 with the corresponding drill hole 4 is partially surrounded by a milling 5. The milling 5, which partially surrounds the through-hole 2 and, in this case, occupies an angular range of approximately 270° with respect to the thickness of the printed circuit board 1, forms a flexible region 1.3 of the printed circuit board 1 around the through-hole 2. The respective required angular range depends in particular on the thickness of the printed circuit board 1, its material properties, and the diameter of the through-hole 2. Fig. 1, the milling 5 runs essentially concentrically to the through-plating 2. However, a U-shaped or spoon-shaped milling geometry would also be conceivable.

[0032] Fig. 3 shows a section through the arrangement of Fig. 1 in plane AA. The printed circuit board 1 comprises an upper first surface 1.1 and an opposite, lower second surface 1.2. The printed circuit board 1 is a multilayer printed circuit board with several internal conductor tracks or conductor lines 8 and an internal ground layer 9.

[0033] The continuous, electrically conductive through-plating 2 terminates at the first surface 1.1 of the printed circuit board 1 with a first edge 2.1 and at the second surface 1.2 of the printed circuit board 1 with the second edge 2.2. Fig. 2, the electrically conductive edges 2.1 and 2.2 are virtually placed on the surfaces 1.1 and 1.2 of the circuit board 1. It would also be conceivable for the first edge 2.1, in particular, to be flush with the first surface 1.1 of the circuit board 1. For cost reasons, the through-hole 2 is usually made of copper or a copper alloy such as brass.

[0034] The through-hole 2 can be designed as a plated socket, with the wall of the borehole 4 being galvanically metallized, for example. Alternatively, the through-hole 2 can also be designed as a separate, socket-shaped part, for example as an insert or press-in part.

[0035] The printed circuit board 1 is integrally connected to an interface 6 by means of an intermediate layer 7, for example a laminate or a prepreg layer.

[0036] The interface 6 can be designed as a metallic carrier plate or as a housing, for example, a gear housing, or as a housing part, for example, a hydraulic plate. In addition to its function as an electrically conductive contact, the interface 6 can thus also serve, in particular, as a heat sink for the circuit board 1.

[0037] A milling 5 which is continuous with respect to the thickness of the printed circuit board 1 partially surrounds the through-hole 2 with the corresponding drill hole 4 and thereby forms a flexible area 1.3 of the printed circuit board 1 around the through-hole 2.

[0038] The second surface 1.2, the circuit board 1 and the interface 6 are free of the intermediate layer 7 in the area of ​​the through-hole 2, including the second edge 2.2 and the milling 5.

[0039] Fig. 2 shows a section through the arrangement of Fig. 3, with the difference that the milling 5 is designed as a type of blind hole, whereby the depth of the blind hole is sufficient to form the flexible area 1.3 of the circuit board 1.

[0040] Fig. 4 shows how Fig. 3 a section through the arrangement of Fig.1 in plane AA, wherein the circuit board 1 is surrounded by a plastic sheath 10 from the upper first surface 1.1. The plastic sheath 10 can be, for example, a thermoset or a thermoplastic.

[0041] The plastic sheath 10, which surrounds the printed circuit board 1, simultaneously fills at least the through-plating 2 or the corresponding drill hole 4 and the milling 5 in such a way that an electrically conductive contact is established between the lower second edge 2.2 of the through-plating 2 and the interlayer-free area of ​​the interface 6.

[0042] This is due to the fact that during the enveloping process of the printed circuit board 1 with the plastic enveloping 10, a certain pressure must be exerted which is then sufficient to deform the flexible region 1.3 of the printed circuit board 1 in the region of the through-hole 2 in the direction of the region of the interface 6, which is free of intermediate layers, in such a way that an electrically conductive contact is established between the edge 2.2 of the through-hole 2 and the interface 6, and after the curing of the plastic enveloping 10, remains permanently due to its adhesive effect after the curing of the enveloping 10.

[0043] Under certain circumstances, especially with thicker printed circuit boards 1, the contact between the edge 2.2 and the interface 6 can also be additionally established by mechanical support on the encapsulating tool.

[0044] This creates a ground connection from the circuit board 1 to the adjacent interface 6 without additional materials such as cables or screws and without an additional process step. List of reference symbols 1 printed circuit board, printed circuit board base material 1.1 First surface of the circuit board 1.2 Second surface of the circuit board 1.3 Flexible area 2 through-hole plating 2.1 First edge of the via 2.2 Second edge of the via 4 borehole 5 Milling 6 Interface 7 Intermediate layer, laminate 8 conductor track, conductor path 9 Ground position of the circuit board 10 plastic wrapping

Claims

[1] Arrangement of a printed circuit board (1) to an interface (6), wherein the printed circuit board (1) comprises: - a first surface (1.1) and an opposite second surface (1.2), - a continuous, electrically conductive through-plating (2) with a first edge (2.1) and a second edge (2.2), wherein the printed circuit board (1) and the interface (6) are integrally connected to one another by means of an intermediate layer (7), wherein a milling (5) partially surrounding the through-hole (2) forms a flexible region (1.3) of the printed circuit board (1), wherein the printed circuit board (1) and the interface (6) are free of the intermediate layer (7) in the region of the through-plating (2) and the milling (5), and a plastic sheath (10) of the printed circuit board (1) fills at least the through-plating (2) and the milling (5) in such a way that an electrically conductive contact is established between the through-plating (2) and the interface (6), and wherein the plastic sheath (10) deforms the flexible region (1.3) of the printed circuit board (1) in the direction of the interface (6) in such a way that the electrically conductive contact is established. [2] Arrangement of a printed circuit board (1) according to claim 1, characterized by that the circuit board (1) is a multilayer circuit board. [3] Arrangement of a printed circuit board (1) according to claim 1 or 2, characterized bythat the milling (5) forming the flexible region (1.3) of the printed circuit board (1) is designed as a milling (5) extending from the first surface (1.1) to the opposite second surface (1.2) of the printed circuit board (1) [4] Arrangement of a printed circuit board (1) according to one of the preceding claims, characterized by that the interface (6) is designed as a metallic carrier plate or as a housing or as a housing part. [5] Arrangement of a printed circuit board (1) according to claim 4, characterized by that the interface (6) is made of aluminum or die-cast aluminum. [6] Arrangement of a printed circuit board (1) according to one of the preceding claims, characterized by that the continuous, electrically conductive through-plating (2) is made of copper or a copper alloy. [7] Arrangement of a printed circuit board (1) according to one of the preceding claims, characterized bythat the through-hole connection (2) is designed as a plated socket. [8] Arrangement of a printed circuit board (1) according to one of the preceding claims, characterized by that the milling (5) surrounds the through-plating (2) partially concentrically to the through-plating (2). [9] Arrangement of a printed circuit board (1) according to one of the preceding claims, characterized by that the intermediate layer (7) is designed as an insulating prepreg layer or as a laminate. [10] Arrangement of a printed circuit board (1) according to one of the preceding claims, characterized by that the plastic covering (10) is made of duroplast or thermoplastic.

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