Printed circuit board and assembly with a printed circuit board

Abstract

Arrangement comprising a printed circuit board (1) - with a layer package (2) which has at least one conductor layer and at least one carrier layer on which the conductor layer is arranged, and - with a sealing frame (8) which is partially embedded in the layer package (2) so that a media-tight connection with the layer package (2) is formed, wherein the sealing frame (8) has a sealing groove (16) for receiving a sealing element (22) in a sealing surface facing away from the layer package (2), wherein the arrangement further comprises a wall (20) of a superior or separate structural unit against which the sealing frame (8) with the sealing surface is mounted with a sealing element (22) introduced into the sealing groove (16).

Description

The invention relates to a printed circuit board and to an assembly comprising such a printed circuit board.Printed circuit boards are usually used for the construction of electronic circuits. The printed circuit boards usually serve as a supporting structure for electrical (usually in particular electronic) components, such as transistors, microprocessors, ASICs and the like, and for providing conductor tracks, by means of which the electrical components are contacted with one another in the intended assembled state. An electronic circuit can form, for example, a control unit (also referred to as a control unit) of an engine and / or transmission of a motor vehicle. In order to protect the electrical components from mechanical and / or chemical influences and / or contamination, the printed circuit boards which carry the circuits are conventionally arranged in a housing.In motor vehicles, control units for engines and / or transmissions are usually used in the engine compartment, in or on the transmission itself. Therefore, the media tightness of the housing of these control units is of particular importance, in particular since comparatively aggressive media, such as oil vapors, gases and / or liquids, can occur in these fields of application, which can damage the electrical components and / or their contact points with the printed circuit board (for example as a result of short circuit or accelerated corrosion).DE 10 2013 215 246 A1 describes electronic module having a first printed circuit board element with at least one electronic component arranged thereon, a second printed circuit board element with at least one electrical component arranged thereon and a spacer, wherein the first printed circuit board element, the second printed circuit board element and the spacer are formed in such a way that they together completely enclose a central cavity in which the electronic component of the first printed circuit board element is accommodated. Along the outer periphery of the first circuit board element, a sealing ring is formed.To seal the housing, sealing elements, such as sealing rings, are used at the joints of the housing, i.e. between a often trough-like housing base body and a housing cover assigned to the latter. However, the use of such a two-part housing requires sufficient space ("installation space") in the region in which the electronic circuit is to be used.DE 198 32 062 C2 describes a control device for a motor vehicle having a base plate on which a circuit carrier is mounted, a housing cover which is coupled to the base plate in a sealed manner via at least one housing seal, and an electrical connection element which is led through between the base plate and the housing cover in the region of the housing seal. The base plate is surrounded by a circumferential frame element.DE 10 2015 218 050 A1 describes an electronic component comprising at least one circuit carrier which is equipped with a number of electronic components, and at least one cover element for sealing the electronic components. The circuit carrier has a number of through-openings, which are each formed around a region that can be fitted with at least one of the electronic components. An edge portion of the cover member is formed of a molding and / or injection molding material and penetrates through the through holes.DE 10 2015 218 706 A1 describes an electronic component which has: (i) a printed circuit board for receiving an electronic circuit arrangement, (ii) at least one metallically designed cover element for forming an electronic space which is closed off from an external environment and in which the electronic circuit arrangement is received, and (iii) at least one metallically designed holding element which is at least partially introduced into a printed circuit board surface and delimits the electronic space on the bottom side. A material bond is produced between a circumferential edge of the cover element and a part of the at least one holding element exposed on the printed circuit board surface.The invention is based on the object of making possible a simple and effective sealing of electrical components with a small installation space requirement.This object is achieved according to the invention by an arrangement having the features of claim 1.The arrangement according to the invention has a printed circuit board. The printed circuit board comprises a layer package which has at least one conductor track layer and at least one carrier layer on which the conductor track layer (preferably one of the conductor track layers) is arranged. Furthermore, the printed circuit board comprises a sealing frame which is partially embedded in the layer package, preferably in the carrier layer or a plurality of the carrier layers, such that a media-tight connection is formed with the layer package. The sealing frame has a sealing surface on a side facing away from the layer package, in which sealing surface a sealing groove is formed for receiving a sealing element. The printed circuit board, specifically the sealing frame, is configured to be mounted in an intended mounting state with the sealing surface, preferably with the sealing element introduced into the sealing groove there, against a (housing) wall of a superordinate or at least separate structural unit. According to the invention, the arrangement further comprises the wall on the superordinate or at least separate structural unit, against which the sealing frame is mounted with the sealing surface by means of a sealing element introduced into the sealing groove.By means of the sealing element inserted in the intended assembled state, in particular in cooperation with the housing wall, a media-tight enclosure of at least one electrical component arranged on the layer stack with respect to the environment is preferably formed.Because the sealing frame is formed as part of the printed circuit board itself and embedded in the layer package of the printed circuit board in a media-tight manner, an additional housing (i.e. completely separate from the printed circuit board) which surrounds the entire printed circuit board can advantageously be dispensed with. The layer package therefore itself forms part of the enclosure.In a preferred embodiment, the sealing frame is formed from thermoplastic material, in particular injection molded. This allows a particularly high freedom of design with simultaneously simple production.In an expedient embodiment, the carrier layer of the layer package comprises a fiber-reinforced thermosetting plastic. In particular, the carrier layer is formed from a (preferably glass or aramid) fiber fabric impregnated with the thermosetting plastic (for example an epoxy resin). The layer package is thus designed in particular in the manner of an FR2 or FR5 printed circuit board.In an expedient development, the thermosetting plastic of the carrier layer and the thermoplastic of the sealing frame are selected in particular such that they have particularly good adhesion to one another. This makes it possible in a simple manner to seal the sealing frame against the layer package in a media-tight manner.In a further expedient embodiment, the sealing frame forms an annularly closed edge around at least a partial region of the layer package. The (partial) region of the layer package bordered in this way, in particular the surface of the layer package, is also referred to below as "electronics region", in relation to the spatial volume placed on the bordered area, in particular as "electronics space". In this electronics compartment, the electrical component or the electrical components to be housed are arranged in the intended mounting state.In a particularly preferred embodiment, the sealing frame-at least a part of the sealing frame-is accessible on a flat side of the (preferably plate-like) layer package of the printed circuit board. That is to say that the sealing frame is partly open on this flat side of the layer package. The electronics space defined (surrounded) by the sealing frame in this case covers a smaller area (i.e. the above-described partial area of the flat side) compared to the total area of the layer package.In a preferred development, the sealing frame projects in particular over the surface of one of the flat sides of the (in particular plate-like) layer package. The sealing frame preferably forms a web, referred to below as a "frame web", which projects beyond the surface of the layer stack. In an exemplary embodiment, this frame web is designed to project so high above the surface of the flat side that electrical components arranged on the stack of layers are projected beyond the end of the frame web facing away from the stack of layers in the intended assembled state. As a result, the printed circuit board equipped with the electrical components can be mounted in a simple manner against a flat wall of the superordinate or separate structural unit during assembly, without there being the risk of the electrical components being clamped between the wall and the layer package.In an alternative embodiment, the sealing frame protrudes in particular on the narrow sides of the (preferably plate-like) layer package. This means that the sealing frame protrudes beyond the layer package in the direction of the plane thereof. In this case, the sealing surface of the sealing frame is aligned substantially transversely (in particular perpendicularly) to the plane direction of the layer package and the sealing groove is thus opened in the plane direction of the layer package.The assembly according to the invention comprises the arrangement described above. A number of electrical components are arranged on the layer package of the printed circuit board. A sealing element, preferably a sealing ring, is introduced (inserted) into the sealing groove of the sealing frame, and the circuit board is attached with the sealing frame to a housing wall (for example a housing cover) of a superordinate or separate structural unit, so that the or at least one of the electrical components is housed in a media-tight manner with respect to the environment by means of the sealing element.The module represents, for example, a control device for an engine or a transmission (which in turn form the aforementioned structural unit) of a motor vehicle, wherein the control device is preferably connected to the engine or transmission, in particular its housing. In this case, the control device preferably forms an integral part of these structural units. In this case, the housing wall is preferably the wall of the motor or transmission housing. The electronic circuit of the control unit is formed in particular by the electrical components arranged on the printed circuit board. The printed circuit board is fastened to the housing wall, for example, by means of fastening screws.Due to the media-tight integration of the sealing frame into the layer package of the printed circuit board, an additional housing (i.e. completely separate from the printed circuit board) which surrounds the entire printed circuit board and by means of which the printed circuit board is fastened to the housing wall of the superordinate or separate structural unit can advantageously be dispensed with. This advantageously also makes it possible to save on assembly effort. The printed circuit board thus forms in particular a part of its housing (its housing), in particular a housing base, so that in the above-described mounted state the entire assembly takes up comparatively little installation space.In an optionally additional, expedient embodiment, the electronics space defined by the sealing frame on the layer package represents a trough which (in the intended assembled state) is filled by means of a casting compound preferably introduced by injection molding. The electrical components arranged in the electronics compartment are enclosed by the potting compound in a medium-tight and vibration-damped manner. The casting compound is in particular a so-called casting resin. Optionally, the potting compound is a gel which has an increased thermal conductivity compared to a conventional casting resin, with the result that the dissipation of the heat emitted by the electrical components during operation of the assembly is advantageously improved.Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Shown therein are: FIG. 1 shows a schematic sectional illustration of a printed circuit board which comprises a layer package and a sealing frame integrated therein, FIGS. 2 and 3 show in a view according to FIG. 1 in each case a further exemplary embodiment of the printed circuit board, and FIG. 4 shows a view according to FIG. 1 of an assembly comprising the printed circuit board according to FIG. 1.Corresponding parts are always provided with the same reference numerals in all figures.FIG. 1 shows a printed circuit board 1. The printed circuit board 1 comprises a layer package 2 (also referred to as a "laminate package") which is designed in the form of a planar plate and is constructed on the basis of the principle of an FR4 printed circuit board. The layer package 2 thus comprises a plurality of layers ("laminate plies") (not shown in more detail), which each serve for conducting electrical signals or for mechanical stabilization. The layers used for conducting the electrical signals and for contacting electrical or electronic components 4 (shown in dashed lines in FIG. 1 ) are referred to here and below as conductor track layers. The conductor track layers have conductor tracks (running in the plane of the layer package 2) which in the present exemplary embodiment are formed by copper. The layers for mechanical stabilization (of the conductor track layers) are referred to here and below as carrier layers. The carrier layers are formed from a glass fiber fabric impregnated with a thermosetting resin, for example an epoxy resin. The printed circuit board 1 also comprises an element formed from thermoplastic material, which is at least partially embedded in the layer package 2, specifically in the thermosetting resin of at least one of the carrier layers. This element serves to form a media-tight enclosure of the components 4 arranged on one of the flat sides 6 of the layer package 2 in the intended assembled state.In an exemplary embodiment shown in FIG. 1, the sealing frame 8 is formed by a substantially T-shaped profile which, within one of the flat sides 6 of the layer package 2, surrounds a partial region of this flat side 6 in a annularly closed manner. The partial or surface area bordered by the sealing frame 8 is also referred to here and in the following as an electronics area, the space standing on this surface area and bordered by the sealing frame 8 is referred to as an "electronics space 10".The cross beam of the T-shaped profile of the sealing frame 8 forms a foot 12 by means of which the sealing frame 8 is embedded in the layer package 2. In the exemplary embodiment shown, the foot 12 is fixed both in a materially integral and form-fitting manner in the layer package 2, specifically in the corresponding carrier layer. The resin of the corresponding carrier layer also forms a medium-tight connection with the thermoplastic material of the sealing frame 8.In the present exemplary embodiment, the vertical bar of the T-shaped profile of the sealing frame 8 forms a frame web 14 which projects perpendicularly on the flat side 6 of the layer package 2 and which surrounds the electronics chamber 10 in a annularly closed manner. In the sealing frame 8, specifically in the end of the frame web 14 facing away from the flat side 6 of the layer stack 2 (specifically the end surface referred to there as sealing surface), a sealing groove 16 is introduced. In this sealing groove 16, in the intended assembled state of the printed circuit board 1 on a housing wall 20 of a superordinate structural unit (cf. FIG. 4 ), a sealing element, specifically a sealing ring 22, is inserted.In a further exemplary embodiment illustrated in FIG. 2, a sealing frame 8 of the type described above is arranged on each of the two flat sides 6 of the layer package 2.In a further exemplary embodiment, not shown in more detail, the two sealing frames 8 according to FIG. 2 are connected to one another in one piece, specifically at their respective feet 12.In an alternative exemplary embodiment shown in FIG. 3, the sealing frame 8 is arranged circumferentially along the edges 24 of the layer package 2 running transversely to the flat sides 6. The sealing groove 16 is introduced into the sealing frame 8 in the direction of the plane of the layer package 2 circumferentially around the layer package 2.FIG. 4 shows the printed circuit board 1 in the intended mounting state. The printed circuit board 1 is part of a module 30, which represents a control device integrated into a transmission of a motor vehicle. The control device is formed by the printed circuit board 1 and the electrical or electronic components 4 contacted with its layer package 2. The transmission as a higher-order structural unit comprises a transmission housing which is indicated by the (housing) wall 20. The printed circuit board 1 is fixed to the wall 20 by means of (fastening) screws 32. The screws 32 apply the sealing pressure required for the media-tight sealing of the printed circuit board 1 against the transmission housing to the sealing ring 22 inserted into the sealing groove 16. The layer package 2 and the sealing frame 8 thus integrally form a housing (in cooperation with the wall 20) for the components 4.In the exemplary embodiment shown in FIG. 4, one of the electronic components 4 is formed by a sensor 34, which projects through a housing aperture 36 of the transmission housing in the direction of the transmission components in order to be able to record operating characteristics during operation of the transmission. The housing aperture 36 is also sealed off in a media-tight manner from the environment of the transmission by means of the printed circuit board 1.The subject matter of the invention is not limited to the exemplary embodiments described above. Rather, further embodiments of the invention can be derived from the above description by the person skilled in the art. In particular, the individual features of the invention described on the basis of the various exemplary embodiments and their design variants can also be combined with one another in another manner.List of reference characters1 Circuit board 2 Layer package 4 Component 6 Flat side 8 Sealing frame 10 Electronics compartment 12 Foot 14 Frame web 16 Sealing groove 20 Housing wall 22 Sealing ring 24 Edge 30 Assembly 32 Fastening screw 34 Sensor 36 Housing aperture

Claims

Arrangement, comprising a printed circuit board (1) - with a layer package (2) which has at least one conductor track layer and at least one carrier layer on which the conductor track layer is arranged, and - with a sealing frame (8) which is partially embedded in the layer package (2) such that a medium-tight connection is formed with the layer package (2), wherein the sealing frame (8) has a sealing groove (16) in a sealing surface facing away from the layer package (2) for receiving a sealing element (22), wherein the arrangement further has a wall (20) of a superordinate or separate structural unit, against which the sealing frame (8) is mounted with the sealing surface with a sealing element (22) introduced into the sealing groove (16).An assembly according to claim 1, wherein the sealing frame (8) is formed of thermoplastic material.Arrangement according to Claim 1 or 2, wherein the carrier layer of the layer package (2) comprises a fibre-reinforced thermosetting plastic.Arrangement according to one of Claims 1 to 3, wherein the sealing frame (8) forms an annularly closed edge around at least one partial region of the layer package (2).Arrangement according to one of Claims 1 to 4, wherein the sealing frame (8) projects beyond the surface of the layer package (2) on a flat side (6) of the latter.Arrangement according to one of Claims 1 to 4, wherein the sealing frame (8) projects on the narrow sides (24) of the layer package (2).Assembly (30) with an arrangement according to one of Claims 1 to 6, wherein a number of electrical components (4) is arranged on the layer package (2) of the printed circuit board (1), wherein a sealing element (22) is introduced into the sealing groove (16) of the sealing frame (8), and wherein the printed circuit board (1) is mounted with the sealing frame (8) against the wall (20), such that the number of electrical components (4) is housed in a media-tight manner with respect to the environment by means of the sealing element (22).

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