Device and method for fastening a printed circuit board to a substrate

Abstract

A device and a method for attaching a printed circuit board to a carrier, preferably in a motor vehicle, comprising at least the printed circuit board and an elastic fastening element for attachment to a counterpart of the carrier, characterized in that the elastic fastening element is electrically conductive and is soldered onto the printed circuit board.

Description

[0001] The invention relates to a device and a method for fastening a printed circuit board to a carrier according to the preamble of the independent claims. State of the art

[0002] US7385830B2 discloses a device for mounting a printed circuit board (PCB) onto a carrier board. The device for mounting a PCB with through-holes comprises a carrier board and a plurality of clips mounted on the PCB. The carrier board has a plurality of standoffs corresponding to the through-holes of the PCB. Each clip has a resilient section and defines a mounting opening for the standoffs sliding within it. When the standoffs press against the resilient sections of the clips, the PCB is clamped onto the carrier board.

[0003] The current state of the art is only partially suitable for time-saving, potentially automated assembly, as the standoffs must first be inserted into the through-holes of the circuit board, and then the circuit board must be moved laterally so that the standoff heads snap into the mounting opening of the clips. Therefore, several successive steps are necessary during assembly. Furthermore, this type of assembly, which requires the standoff heads to snap into place, necessitates a complex standoff geometry. Disclosure of the invention

[0004] The device according to the features of claim 1 enables both mechanical fastening of the printed circuit board to the substrate and an electrically conductive connection of the printed circuit board to the substrate. Because both properties are provided by a single fastening element, this device is particularly space-saving. This allows for flexible and efficient use of the printed circuit board, especially with regard to the placement of electronic components and the arrangement of conductor tracks within the printed circuit board.

[0005] Since the mounting element is electrically conductive and soldered to the circuit board, the circuit traces of the circuit board can be electrically connected to the mounting element. This is particularly advantageous when an electrically conductive connection between the circuit board and the substrate is necessary, which is provided in a very space-saving manner by the mounting element. A further advantage is that the mounting element is elastically designed. This allows for particularly simple assembly in just one manufacturing step. During assembly, the mounting element is elastically deformed and returns to its original shape after the counterpart snaps into place. This fixes the circuit board to the substrate without requiring any additional movement of the circuit board, such as lateral movement, to engage the counterpart in the mounting element.

[0006] This type of fastening is particularly advantageous because no screw connections and therefore no additional screw stations are needed in production.

[0007] In a further development, it is proposed that the elastic fastening element be implemented as a metallic spring element. Because the elastic fastening element is made entirely of a metallic material, it enables a particularly reliable electrically conductive connection to the counterpart. Furthermore, metal is characterized by high elasticity compared to other materials, such as plastic. This simplifies assembly, as the fastening element can be deformed more easily and reversibly.

[0008] The metallic material also has a positive effect on service life. Compared to plastic fasteners, a metallic spring element retains its elasticity longer, thus ensuring a durable attachment of the circuit board to the substrate. The spring element design is also advantageous because it allows for a mechanical connection of the circuit board to the substrate that can be released manually or automatically. This device is particularly well-suited for automotive applications, where high demands are placed on durability. Furthermore, the high production volumes in the automotive sector necessitate time-saving and cost-effective assembly.

[0009] In a further development, the elastic fastening element is provided with at least one planar contact surface with the printed circuit board (PCB), which is soldered to the PCB surface. This contact surface comprises a base area of ​​at least a rectangular shape and / or two parallel, opposing ribs projecting from the rectangular base area. The planar contact surface ensures a reliable connection between the fastening element and the PCB. This is due to the relatively large solder area available. This enables both an electrically conductive and a mechanical connection between the fastening element and the PCB. The stability of the fastening element is further increased by the parallel, opposing ribs.

[0010] In a practical further development, a recess is provided in the printed circuit board to accommodate the counterpart. This is particularly advantageous when the fastening element is not located directly on the sides of the circuit board. If the fastening element is positioned inwards from the sides of the circuit board, the recess provides the necessary space to receive the counterpart of the carrier.

[0011] In a suitable further development, it is provided that the printed circuit board has at least one recess that is at least partially surrounded by a contact surface of the fastening element. This at least partial enclosure of the recess by the fastening element increases the stability of the fastening.

[0012] In a further development, the elastic fastening element is provided to have at least one fastening section extending transversely to a planar contact surface, which includes at least one protrusion that projects towards a recess in the printed circuit board or over an edge of the printed circuit board. This is particularly advantageous for mounting the printed circuit board on the substrate and for securing the counterpart to the fastening element. During assembly, the counterpart is guided along the fastening element by means of this fastening section. The fastening section is elastically deformed in the process. Once the counterpart is in its final position, the fastening element returns to its original shape. The counterpart is secured in its final position by means of the fastening area and, in particular, by means of the protrusion.

[0013] In a further development, the elastic fastening element is provided to include at least one section parallel to the printed circuit board or inclined towards the board, which interacts with a counterpart. This section of the fastening element enables a positive-locking or force-locking connection between the fastening element and the counterpart. This connection can therefore be easily disassembled without complex processes, which is particularly advantageous when replacing the printed circuit board, for example, during repairs.

[0014] In a further development, comprising the counterpart, it is provided that the counterpart projects vertically from the carrier towards the printed circuit board (PCB) relative to a planar base plate of the carrier, and that the counterpart has a hook-shaped bend at its end facing the PCB. The hook-shaped bend allows the counterpart to snap onto the fastening element, thereby fixing the PCB to the carrier.

[0015] In a further development, encompassing the counterpart, it is provided that the counterpart is realized as an overmolded part, wherein a signal line made of electrically conductive material is surrounded by an insulating overmolding, and the counterpart is exposed at an exposed contact surface to the fastening element. The advantage here is that the counterpart thus fulfills two functions: firstly, the mechanical fastening of the printed circuit board to the substrate; and secondly, an electrically conductive connection between the printed circuit board and the substrate.

[0016] In a suitable further development, including the counterpart, it is provided that the counterpart is designed to be connectable to a ground potential and / or a signal line. This allows, for example, an EMC grounding function to be provided when the counterpart is connected to a metal ground.

[0017] In a suitable further development, encompassing the counterpart, it is provided that the counterpart is made of an electrically conductive material and / or, in particular, is implemented as an electrically conductive metal part. By designing it as a complete metal part, a particularly reliable electrically conductive connection between the circuit board and the substrate is possible, since the contact area can be larger than, for example, with an overmolded signal conductor with an exposed contact surface.

[0018] The method according to the features of claim 12 enables the printed circuit board (PCB) to be attached to the substrate in a single manufacturing step. This is particularly advantageous because it saves time and therefore costs in production. Furthermore, single-step assembly is less prone to errors than fastening methods that require multiple steps. Another advantage is that, because the fastening element is soldered to the PCB, it can be soldered to the PCB along with electronic components in the same manufacturing step. No additional manufacturing processes or stations are required. Assembly can be performed either manually or automatically. In summary, these aspects enable faster and therefore more cost-effective assembly. Brief description of the drawing

[0019] They show: Fig. 1 an elastic fastening element soldered onto a printed circuit board, Fig. 2 a detailed view of the elastic fastening element, Fig. 3 the printed circuit board mounted on a carrier with the fastening element and a counterpart of the carrier, Fig. 4 possible arrangements of the fastening element on the circuit board, Fig. 5. Mounting the circuit board on the carrier using a fastening element and counterpart, Fig. 6 possible embodiments of the counterpart. embodiment of the invention

[0020] Fig. Figure 1 shows an elastic fastening element 4, which is soldered onto a printed circuit board 2. In the present embodiment, the fastening element 4 is arranged on one side of the printed circuit board 2. From this side of the printed circuit board 2, the fastening element 4 is recessed inwards. In the area of ​​the fastening element 4, the printed circuit board 2 has a recess 10, the depth of which extends from the side of the printed circuit board 2 to the fastening element 4 and the width of which is less than the side of the fastening element 4 facing the recess 10.

[0021] The fastening element has a planar contact surface 3. This contact surface 3 comprises a rectangular base surface 8 and, in the present embodiment, two parallel webs 9. The two webs 9 project from one long side of the base surface 8, so that the planar contact surface 3 has a U-shape. Alternatively, a contact surface 3 with a rectangular shape and no webs is also possible.

[0022] The contact surface 3 of the fastening element 4 at least partially encompasses the recess 10 of the printed circuit board 2. In the present embodiment, this recess 10 is rectangular and is surrounded on three sides of its rectangular area by the printed circuit board 2 and the contact surface 3 of the fastening element 4. Alternatively, the recess 10 can also be rounded. Furthermore, it is also possible for the recess 10 to be surrounded on four sides by the printed circuit board 2.

[0023] A fastening section 7 of the fastening element 4 is arranged transversely to the contact surface 3 of the fastening element 4. This fastening section 7 serves to receive a counterpart 13 of a carrier 6 and thus to fasten the printed circuit board 2 to the carrier 6, as shown in Fig. Figure 3 shows this in more detail. For this purpose, the mounting section 7 has a protrusion 5 that projects beyond the recess 10 of the circuit board 2. Further details of the mounting element 4 and the mounting of the circuit board 2 are described below.

[0024] Fig. Figure 2 shows a detailed view of the elastic fastening element 4. The planar contact surface 3 is visible, which here consists of a rectangular base surface 8 and two parallel, opposing webs 9. The fastening area 7 is located centrally between the two webs 9 on one long side of the base surface 8.

[0025] The connection of the fastening area 7 to the base surface 8 consists of a short, flat rectangular area 20, which lies in a plane with the contact surface 3 of the fastening element 4. Extending from this area 20 is a guide area 19, which guides the counterpart 13 of the carrier 6 into the fastening area 7 of the fastening element 4.

[0026] The guide area 19 extends diagonally upwards from the base surface 8, with the angle to the plane of the base surface 8 preferably being in the range of 30° to 60°, for example 45°. In general, it can be realized with any angle between > 0° and 90°, whereby the angle can be calculated depending on the application requirements. The projection 5 adjoins the upper end of the guide area 19. The guide area 19 is preferably designed as a flat, rectangular plane whose width corresponds approximately to the distance between the two webs 9 or is slightly less than this distance.

[0027] The protrusion 5 has a semicircular curve shape in cross-section, which points back from the upper end of the guide area 19 towards the base surface 8.

[0028] A straight section 11 adjoins this protrusion. This preferably rectangular, flat section 11 preferably runs parallel to the base surface 8 or alternatively inclines slightly towards the base surface 8. A locking area 18 is arranged transversely to this section 11, projecting straight upwards from the section 11. The locking area 18, together with the section 11 and the protrusion 5, serves to fasten the counterpart 13. Further details regarding the fastening of the counterpart 13 to the fastening element 4 are described in the Fig. 3 included

[0029] Fig. Figure 3 shows the printed circuit board 2 mounted on the carrier 6, with the fastening element 4 and the counterpart 13 of the carrier 6. The printed circuit board 2 is positioned parallel to the carrier 6. A fastening element 4 is soldered onto the printed circuit board 2. The recess 10 in the printed circuit board 2 is located in the area between the two parallel, opposing ribs 9 of the fastening element 4. The counterpart 13 is located on the carrier 6 below the printed circuit board 2 and projects transversely upwards from the surface of the carrier 6 towards the printed circuit board 2. A hook-shaped section 15 is located at the end of the counterpart 13 facing the printed circuit board.

[0030] The counterpart 13 of the carrier 6 rests with its hook-shaped section 15 on the section 11 and the protrusion 5 of the fastening element 4 on and against the locking area 18. The locking area 18 prevents the counterpart 13 from tilting or shifting and thus ensures a reliable connection between the counterpart 13 and the fastening element 4.

[0031] For a particularly reliable fastening of the circuit board 2 to the carrier 6, several fastening elements 4 can be arranged on the circuit board 2 and several counterparts 13 on the carrier 6.

[0032] Fig. Figure 4 shows possible arrangements of the fastening element 4 on the circuit board 2.

[0033] The fastening element 4 can, for example, be attached directly to one side of the circuit board. In this case, no recess 10 is necessary, since the fastening area 7 projects beyond the side of the circuit board 2, thus providing space for the counterpart 13 to pass through the side of the circuit board 2. Therefore, no parallel, opposing webs 9 are required for the fastening element 4. A simpler geometry for the fastening element 4, for example with only a rectangular base 8, can be used here.

[0034] Alternatively, the fastening element 4 can be positioned slightly recessed from one side of the circuit board 2. For this purpose, the recess 10 for the passage of the counterpart 13 on the circuit board 2 is necessary, with the fastening area 7 of the fastening element 4 projecting into the recess 10.

[0035] Another possibility is to position the fastening element 4 at any location on the circuit board 2. In this case, the recess 10 for the passage of the counterpart 13 in this area on the circuit board 2 is necessary, so that the recess 10 is surrounded on four sides by the circuit board 2.

[0036] Fig. Figure 5 shows the mounting of the circuit board 2 on the carrier 6 using the fastening element 4 and the counterpart 13. Three steps 101, 102, and 103, which are carried out during assembly, are shown here as examples.

[0037] In step 101, the support 6 is shown with its counterpart 13 arranged transversely to it. Above the support 6, parallel to it, is the circuit board 2, on which the fastening element 4 is soldered. The circuit board 2 is aligned above the support 6 such that the fastening element 4 is positioned above its counterpart 13. As indicated by the arrow, the circuit board 2 is guided towards the support 6.

[0038] Step 102 shows how the counterpart 13 slides through the recess 10 of the circuit board 2. The hook-shaped section 15 of the counterpart 13 presses against the guide area 19 of the fastening element 4. This elastically deforms the fastening area 7 of the fastening element 4 and pushes it away from the recess 10 of the circuit board 2.

[0039] In step 103, the counterpart 13 has reached its final position on the fastening element 4. The hook-shaped section 15 of the counterpart 13 rests on the protrusion 5 and the section 11 and is held in its final position by the locking area 18. It can be seen that the printed circuit board 2 does not rest directly on the carrier 6, but that there is a gap between the printed circuit board 2 and the carrier 6. This gap can be achieved and maintained by various means. For example, the printed circuit board 2 can be held by a profile or by spacers, which are preferably arranged on the carrier 6.

[0040] Fig.Figure 6 shows possible embodiments of the counterpart 13. Depending on the application, the counterpart 13 can be made of different materials. For purely mechanical fastening of the circuit board 2 to the carrier 6, the counterpart 13 can be made of plastic. If a mechanical and electrically conductive connection between the circuit board 2 and the carrier 6 is required, the counterpart 13 can be made entirely of metal or of an electrically conductive component overmolded with electrically insulating material. In the latter case, a signal line 16 made of electrically conductive material is surrounded by an insulating overmolding 12. The counterpart 13 is exposed by the overmolding 12 at an exposed contact surface 14.

[0041] The present device and method are preferably used in a control unit of a motor vehicle characterized by high stress and demanding service life requirements. However, its use is not limited to this. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] US 7385830B2

[0002]

Claims

[1] A device for attaching a printed circuit board (2) to a carrier (6), preferably in a motor vehicle, comprising at least the printed circuit board (2) and an elastic fastening element (4) for attachment to a counterpart (13) of the carrier (6), characterized by , that the elastic fastening element (4) is electrically conductive and is soldered onto the circuit board (2). [2] Device according to any one of the preceding claims, characterized by that the elastic fastening element (4) is realized as a metallic spring element. [3] Device according to any one of the preceding claims, characterized by, that the elastic fastening element (4) has at least one planar contact surface (3) to the printed circuit board (2) which is soldered to the surface of the printed circuit board (2), wherein the contact surface (3) comprises at least one rectangular base surface (8) and / or two parallel opposing webs (9) projecting from the rectangular base surface (8). [4] Device according to any one of the preceding claims, characterized by , that a recess (10) of the circuit board (2) is formed for the insertion of the counterpart (13). [5] Device according to any one of the preceding claims, characterized by that the circuit board (2) has at least one recess (10) which is at least partially surrounded by a contact surface (3) of the fastening element (4). [6] Device according to any one of the preceding claims, characterized by, that the elastic fastening element (4) has at least one fastening section (7) extending transversely to a planar contact surface (3), which includes at least one protrusion (5) projecting in the direction of a recess (10) of the printed circuit board (2) or over an edge of the printed circuit board (2). [7] Device according to any one of the preceding claims, characterized by , that the elastic fastening element (4) comprises at least one section (11) parallel to the printed circuit board (2) or inclined towards the printed circuit board (2), which interacts with a counterpart (13). [8] Device according to any one of the preceding claims, characterized by , that the elastic fastening element (4) comprises at least one locking area (18) which interacts with a counterpart (13). [9] Device according to any of the preceding claims and comprising the counterpart (13), characterized by, that the counterpart (13) projects vertically from the support (6) towards the printed circuit board (2) to a planar base plate (17) of the support (6) and that the counterpart (13) has a hook-shaped section (15) at its end facing the printed circuit board (2). [10] Device according to any of the preceding claims and comprising the counterpart (13), characterized by , that the counterpart (13) is realized as an overmolded part, wherein a signal line (16) made of electrically conductive material is surrounded by an insulating overmolding (12) and at an exposed contact surface (14) to the fastening element (4) the counterpart (13) is exposed from the overmolding (12). [11] Device according to any of the preceding claims and comprising the counterpart (13), characterized by , that the counterpart (13) is designed to be connectable to a ground potential and / or a signal line. [12] Device according to any of the preceding claims and comprising the counterpart (13), characterized by , that the counterpart (13) is made of an electrically conductive material and / or is realized in particular as an electrically conductive metal part. [13] Method for attaching a printed circuit board (2) to a carrier (6), preferably in a motor vehicle, comprising at least the printed circuit board (2) and an elastic fastening element (4) for attachment to a counterpart (13) of the carrier (6), characterized by , that the elastic fastening element (4) is electrically conductive and is soldered onto the circuit board (2) in the same manufacturing step together with electronic components. [14] Method according to claim 13, characterized by, that during assembly the printed circuit board (2) with the elastic fastening element (4) is aligned parallel to the base plate (16) of a carrier (6) over the counterpart (13) and that the printed circuit board (2) is pressed in the direction of the carrier (6) and that the counterpart (13) is connected to the elastic fastening element (4) in a form-fitting and / or force-fitting manner. [15] Method according to claim 13, characterized by , that during disassembly the protrusion (5) of the elastic fastening element (4) is released from a hook-shaped bend (15) of the counterpart (13) and the circuit board (2) is removed from a support (6).

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