Electronic assembly

Abstract

The invention relates to an electronic assembly (100; 100a to 100c) comprising a circuit carrier (10) designed as a printed circuit board (12; 12a; 12b) which has components (16) connected to the circuit carrier (10) on a first side (14), wherein the circuit carrier (10) and at least some of the components (16) are covered by a rigid mass (36) made of plastic and connected to the circuit carrier (10), and wherein the circuit carrier (10) is at least indirectly connected in a heat-conducting manner to a cooling device (22) on a second side (18) of the circuit carrier (10) opposite the first side (14) and is subjected to a force in the direction of the cooling device (22) by means of at least one mechanical element (37; 38).

Description

Technical area

[0001] The invention relates to an electronic assembly which is characterized by particularly advantageous mechanical properties in connection with the cooling of heat-generating components. State of the art

[0002] From DE 10 2020 135 099 A1, an electronic assembly with the features of the preamble of claim 1 is known. The known electronic assembly is characterized by a circuit carrier in the form of a printed circuit board, on the upper side of which components, in particular heat-generating components, are arranged. A frame-shaped housing is arranged on the upper side of the printed circuit board, which has an opening in its central region in which the components are fastened to the printed circuit board. The central region is also encapsulated with a compound which can serve, among other things, to protect the components and increase the rigidity of the printed circuit board. A heat transfer element is arranged on the underside of the printed circuit board, with which the circuit carrier is connected in heat-conducting contact to a cooling device.To ensure heat-conducting contact, the circuit board is mechanically connected or clamped to the cooling device via screw connections.

[0003] Furthermore, DE 10 2018 207 966 A1 discloses a printed circuit board with a multilayer structure. Some of the layers are designed as stiffening layers and consist, for example, of an epoxy resin. The stiffening layers are arranged within the cross-section of the printed circuit board.

[0004] Most recently, it is known from DE 10 2017 208 322 A1 of the applicant to form an electronic module with a molded body, wherein a strut-shaped or grid-shaped support contour serving to stiffen the electronic module is arranged within the molded body. Disclosure of the invention

[0005] The electronic assembly according to the invention with the features of claim 1 has the advantage that its circuit board carrying the components is, on the one hand, mechanically particularly stable or rigid, and, on the other hand, enables an optimized heat transfer from at least one heat-generating component to a cooling device.

[0006] The invention is based on the idea of ​​providing stiffening elements or support contours known from the prior art in conjunction with an arrangement of the at least one heat-generating component provided on the side of the cooling device. This maximizes the flexural rigidity of the circuit board when clamping or securing it to the cooling device, and enables direct heat transfer from the at least one heat-generating component to the cooling device.

[0007] Against the background of the above explanations, an electronic assembly with the features of claim 1 therefore has a circuit carrier in the form of a printed circuit board. The circuit carrier has components connected to the circuit carrier on a first side, wherein the circuit carrier and at least some of the components are covered by a rigid mass made of plastic and connected to the circuit carrier, and wherein the circuit carrier is connected to a cooling device in a heat-conducting manner on the second side facing away from the first side and is subjected to force in the direction of the cooling device by means of at least one mechanical element. The electronic assembly according to the invention is characterized in that the circuit carrier has at least one heat-generating component on the second side, which is connected to the cooling device.

[0008] Advantageous further developments of the electronic assembly according to the invention are listed in the subclaims.

[0009] A particularly simple stiffening option, which makes it possible to dispense with separate, flat stiffening layers, especially in the cross-section of the circuit board, involves the mass arranged on the first side of the circuit board being a resin. A resin is understood, in particular, to be an epoxy resin with a relatively high degree of hardness or strength.

[0010] In a further development of the last suggestion, especially when the resin is relatively thin, it can be provided that the resin is laterally surrounded by a dam-like wall. In this case, the resin can be metered easily by filling the interior space enclosed by the wall with resin after the dam-like wall has been secured or positioned.

[0011] A further, particularly preferred embodiment of the invention, in which particularly favorable mechanical properties can be achieved, provides that the circuit carrier, together with the components and the mass, is curved in a state not connected to the cooling device, and that the at least one mechanical element exerts a force on the circuit carrier that is opposite to the curvature, so that at least the area of ​​the circuit carrier that is connected to the cooling device is flat in the state mounted with the cooling device.

[0012] In order to enable a homogeneous transfer of force from the circuit carrier to the cooling device, several mechanical elements designed as fastening screws are provided, which connect the circuit carrier to the cooling device, particularly in the edge areas of the circuit carrier. Because a central area of ​​the circuit carrier is free of fastening screws, the central area can be optimally used to create the layout or arrange the electronic components.

[0013] In a first refinement of the last proposal, it can be provided that the fastening screws are located outside the ground. Alternatively, it can also be provided that at least one fastening screw is located in the area of ​​the ground and clamps the circuit board against the cooling device by means of a sleeve-shaped spacer element.

[0014] In order to avoid the electronic assembly having to be additionally arranged in a separate housing so that the assembly is protected against the influence of media, it can furthermore be provided in a further embodiment of the invention that the circuit carrier is sealed against the cooling device on the side facing the cooling device by means of a sealing element running around the edge.

[0015] In a further development of this proposal, the sealing element is preferably arranged in a recess with a U-shaped cross-section. This recess can either be formed in a separate element or monolithically with the cooling device, for example, through additive manufacturing of the cooling device.

[0016] Optimized heat transfer and effectiveness of the cooling device is achieved by the cooling device being flat on the side facing the circuit board. This ensures a large heat transfer surface from the at least one heat-generating component to the cooling device.

[0017] A preferred structural design of the cooling device provides that it is designed as a so-called vapor chamber, in which an evaporable coolant is arranged in a channel of the cooling device and evaporates in the region of the heat-generating component and condenses in another region of the cooling device.

[0018] Finally, depending on the specific design of the layout or the required application of force in the direction of the cooling device, it can also be provided that the mass leaves free at least a partial area of ​​the circuit carrier in which components and / or fastening elements are arranged.

[0019] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings. Short description of the drawings Fig. 1 to Fig. 4 show cross-sections through differently designed electronic components, Fig. 5 a view in the direction of the plane VV of the Fig. 4 and Fig. 6 and Fig. 7 Top views of different geometries of resin reinforcement elements used to stiffen the circuit board. Embodiments of the invention

[0020] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0021] In the Fig. 1 shows an electronic assembly 100 which is a component of a control unit not shown, for example a control unit for automotive applications.

[0022] The electronic assembly 100 comprises a circuit carrier 10 in the form of a printed circuit board 12, which, according to the prior art, can also be designed, in particular, as a multilayer printed circuit board 12. The printed circuit board 12 serves to arrange an electronic circuit comprising a plurality of electrical or electronic components 16 on a first side 14 of the printed circuit board 12. Furthermore, at least one heat-generating component 20 is arranged on the second side 18 of the printed circuit board 12, opposite the first side 14.

[0023] The heat-generating component 20 is, for example, a power semiconductor or similar device, which in the illustrated embodiment is shown as a flat component 20 having a constant thickness or height. While the components 16 arranged on the first side 14 of the circuit board 12 are uncritical with regard to their heat generation, the at least one component 20 arranged on the second side 18 of the circuit board 12 must be cooled by additional cooling measures during operation in order to ensure proper functioning of the assembly 100. A cooling device 22 is used for this purpose, which in the illustrated embodiment is designed as a flat cooling device 22 with at least one channel 24 for forming a so-called vapor chamber 26. Alternatively, the cooling device 22 can, however, also have, for example, cooling fins or similar elements in a manner known per se.

[0024] In the illustrated embodiment, the cooling device 22 completely covers the at least one heat-generating component 20 and projects laterally at least as far as the edge regions of the circuit board 12. In order to enable a heat-conducting contact between the at least one heat-generating component 20 and the cooling device 22 formed flat on the side of the at least one heat-generating component 20, a heat transfer medium 28, for example a heat-conductive adhesive, is also typically arranged between the at least one heat-generating component 20 and the cooling device 22.

[0025] In the region of the first side 14, the circuit board 12 further comprises a dam 30 with a wall 32 that laterally surrounds most or all of the components 16. The wall 32 or the dam 30 is connected, for example, glued, to the first side 14 of the circuit board 12. The interior space 34 enclosed by the wall 32 is filled with a mass 36, which is particularly formed as an epoxy resin mass and which, when cured, has a relatively high strength or hardness. The mass 36 covers the components 16 within the interior space 34 and has a height h.

[0026] By adjusting the amount of mass 36 or the height h, the mass 36 used to stiffen the printed circuit board 12 can be adapted to the respective application.

[0027] In order to enable secure contact or heat-conducting contact between the at least one heat-generating component 20 and the (under) side of the cooling device 22 facing it, the circuit board 12 is subjected to a compressive force F in the direction of the cooling device 22 in the region of the mass 36, preferably centered relative to the at least one heat-generating component 20. The compressive force F can be generated, for example, by a spring element 37 in the form of a compression spring, which acts directly on the mass 36 and which is supported, for example, on a housing wall (not shown) of the assembly 100 on the side facing away from the mass 36.

[0028] The Fig. The assembly 100a shown in Figure 2 is characterized in that the printed circuit board 12 is connected to the cooling device 22 outside the wall 32 by means of several fastening screws 38, or the printed circuit board 12 is clamped in the direction of the cooling device 22. It is particularly preferred if, before the printed circuit board 12 is fastened to the cooling device 22, the printed circuit board 12, together with the components 16 and 20 as well as the mass 36, has a curved shape, which is illustrated by the dashed line 40, which represents the center plane of the printed circuit board 12. By fastening the printed circuit board 12 to the cooling device 22 by means of the fastening screws 38, the curvature is reduced in such a way that, ideally, the printed circuit board 12 is completely flat, but at least in the area between the at least one heat-generating component 20 and the cooling device 22, in order to ensure that the component 20 rests flatly on the cooling device 22 orto achieve a gap minimization between the mentioned elements.

[0029] In the Fig. In the assembly 100b shown in Figure 3, the fastening screws 38 are not arranged outside the wall 32 or the mass 36, but rather within the area enclosed by the wall 32. For this purpose, the fastening screws 38 are guided within sleeve-shaped spacers 42 so that their screw heads can be axially supported on the spacers 32.

[0030] It should be noted that it is not necessary to arrange all fastening screws 32 within the area enclosed by the wall 32. Instead, fastening screws 38 can be arranged in a modification of the Fig. 3, the housing 100 can also be arranged at least partially outside the wall 32, as in the assembly 100a.

[0031] The Fig. 4 and Fig. The assembly 100c shown in Figure 5, in a modification of the assembly 100b, is characterized in that the printed circuit board 12 has a connector 44 for electrically contacting the assembly 100c. In particular, the assembly 100c forms a unit that does not require additional protection against external media influences. For this purpose, a seal 48 is arranged in the space 46 between the cooling device 22 and the printed circuit board 12, which seal 48 extends around the edge of the printed circuit board 12 and, in the exemplary embodiment, is arranged in a recess 50 with a U-shaped cross section.

[0032] To form the recess 50, either a separate element 52 connected to the cooling device 22 or an element formed monolithically with the cooling device 22 can be provided. This can be achieved, for example, by producing the cooling device 22 using an additive printing process, for example, the so-called SLM process.

[0033] In the Fig. 5 shows the sealing contour 54, which extends outside of the through-holes 56 for the fastening screws 38 in the circuit board 12. This creates a circumferentially sealed arrangement of the intermediate space 46.

[0034] Most recently, in the Fig. 6 and Fig. 7 shows top views from the direction of the first side 14 of printed circuit boards 12a, 12b with reinforcing elements 58, 60. The reinforcing elements 58, 60 are designed in particular as prefabricated components and are connected to the printed circuit board 12a, 12b, for example by gluing with the mass 36, which in the illustration of the Fig. 6 and Fig. 7 is not shown, as are the components 16.

[0035] In the case of the printed circuit board 12a with the reinforcing element 58, it can be seen that this serves to stiffen the printed circuit board 12a by increasing the section modulus, wherein the fastening of the printed circuit board 12a with the cooling device 22 (not shown) takes place by applying force or fastening outside the stiffening element 58. The stiffening element 58 has, in particular, four laterally projecting arm regions 62 and a central region 64 formed without a reinforcing element 58. The fastening of the printed circuit board 12a with the cooling device 22 by means of the fastening screws 38 takes place outside the stiffening element 58 via through openings 66 in the printed circuit board 12a.

[0036] In contrast, the stiffening element 60 in the circuit board 12b is designed as a full-surface stiffening element 60, i.e., the central region 64 is also provided with the material of the reinforcing element 60. The force is introduced into the reinforcing element 60 in the central region 64 by means of the spring element 37, which is shown only symbolically. The through-openings 66 shown outside the reinforcing element 60 in the circuit board 12b can serve to support the circuit board 12b relative to the cooling device 22. For this purpose, spacer sleeves or similar elements can be provided, which can be fixed via through-openings 66 using fastening screws (not shown).

[0037] The electronic assembly 100, 100a to 100c described so far can be modified or altered in a variety of ways without deviating from the inventive concept. In particular, it is not necessary for the mass 36 to be completely filled with the mass 36 in the area of ​​the components 16, especially if a separate housing is provided for encapsulating the assembly 100. Rather, areas on the first side 14 of the printed circuit board 12 can also be left free of the mass 36 in order to arrange components 16 in these areas, for example. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 135 099 A1

[0002] DE 10 2018 207 966 A1

[0003] DE 10 2017 208 322 A1

[0004]

Claims

[1] Electronic assembly (100; 100a to 100c), with a circuit carrier (10) designed as a printed circuit board (12; 12a; 12b), which has components (16) connected to the circuit carrier (10) on a first side (14), wherein the circuit carrier (10) and at least some of the components (16) are covered by a rigid mass (36) made of plastic and connected to the circuit carrier (10), and wherein the circuit carrier (10) is at least indirectly connected to a cooling device (22) in a heat-conducting manner on a second side (18) of the circuit carrier (10) opposite the first side (14) and is subjected to a force in the direction of the cooling device (22) by means of at least one mechanical element (37; 38), characterized by that the circuit carrier (10) has on the second side (18) at least one heat-generating component (20) which is connected to the cooling device (22). [2] Assembly according to claim 1, characterized bythat the mass (36) is a resin, in particular an epoxy resin. [3] Assembly according to claim 1 or 2, characterized by that the mass (36) is laterally surrounded by a dam-like wall (32). [4] Assembly according to one of claims 1 to 3, characterized by that the circuit carrier (10) together with the components (16, 20) and the mass (36) is curved when not connected to the cooling device (22), and that the at least one mechanical element (38) exerts a force opposite to the curvature, so that at least the region of the circuit carrier (10) which is connected to the cooling device (22) is flat in the assembled state. [5] Assembly according to one of claims 1 to 4, characterized bythat several mechanical elements (38) designed as fastening screws are provided which connect the circuit carrier (10) to the cooling device (22), in particular in edge regions of the circuit carrier (10). [6] Assembly according to claim 5, characterized by that the fastening screws are arranged outside the mass (36). [7] Assembly according to claim 5, characterized by that at least one fastening screw is arranged in the region of the mass (36) and clamps the circuit carrier (10) against the cooling device (22) by means of a sleeve-shaped spacer element (42). [8] Assembly according to one of claims 1 to 7, characterized by that the circuit carrier (10) is sealed against the cooling device (22) on the side facing the cooling device (22) by means of a sealing element (48) running around the edge. [9] Assembly according to claim 8, characterized bythat the sealing element (48) is arranged in a recess (50) which is U-shaped in cross section. [10] Assembly according to one of claims 1 to 9, characterized by that the cooling device (22) is flat on the side facing the circuit carrier (10) at least in the region of the at least one heat-generating component (20) [11] Assembly according to one of claims 1 to 10, characterized by that the cooling device (22) is designed as a vapor chamber (26). [12] Assembly according to one of claims 1 to 11, characterized by that the mass (36) leaves free at least a partial area of ​​the circuit carrier (10) in which components (16) and / or fastening elements are arranged.

Images