Screw connection for screwing with a mounting interface, comprising a printed circuit board, at least one screw and a washer element

Abstract

Screw connection for screwing to a mounting interface (8), comprising a printed circuit board (9), at least one screw (10) having a screw thread (13) and a screw head (11), wherein the screw thread (13) is passed through a screw passage (14) formed in the printed circuit board (9), and a washer (1) arranged between the screw head (11) and the printed circuit board (9), wherein the washer (1) is connected to the printed circuit board (9) in a rotationally secure and captive manner, wherein the washer (1) is connected to the printed circuit board (9) by positive locking and / or frictional locking, and wherein the washer (1) is fixed to the printed circuit board (9) by overmolding with a plastic compound (17).

Description

[0001] The present invention relates to a screw connection for screwing with a mounting interface, comprising a printed circuit board, at least one screw having a screw thread and a screw head, wherein the screw thread is passed through a screw passage formed in the printed circuit board, and a washer element arranged between the screw head and the printed circuit board.

[0002] Printed circuit boards (PCBs) are typically connected to another structure, referred to collectively as the mounting interface, by means of screws. For example, a PCB functioning as a transmission control unit is screwed directly to a corresponding interface on the transmission using one or more screws. Tightening these screws can involve high torques. This can damage the PCB surface in the area of ​​the mounting surface due to the friction of the rotating screw head. The PCB surface can be the PCB itself or a coating applied to the board, for example, to provide a ground connection or meet electromagnetic compatibility requirements.If a coating is present, it can be damaged by the rotating screw head. Such damaged areas are particularly susceptible to corrosion. This is especially true if the circuit board, as is often the case in a gearbox, is exposed to aggressive media such as gear oil and / or hydraulic oil. This can cause pre-damaged areas of the coating to detach further, and connected conductor tracks can be chemically attacked, potentially permanently damaging the circuit board and rendering it unusable. In particular, already damaged areas can be further damaged if the circuit board is subsequently re-screwed.

[0003] It is generally known to place simple washers between the screw head and the circuit board; however, this carries the risk that the washer will rotate when the screw is tightened and itself damage the circuit board. This risk is particularly high with serrated washers.

[0004] US Patent 2019 / 0260143 A1 discloses a washer element that is positioned between a surface of the busbar and the screw head when screwing a busbar to a printed circuit board. An anti-rotation feature on the washer element, in the form of protruding pins that engage in recesses in the printed circuit board, prevents the washer element from rotating when the screw is tightened. A disadvantage of such a washer element is that it can detach from the assembly if the screw is not yet fully tightened and the assembly is rotated during installation.

[0005] The present invention therefore aims to provide a screw assembly comprising a printed circuit board, at least one screw and a washer element for screwing together with a mounting interface, which in particular also offers reliable protection of the screwing surfaces on the printed circuit board during re-screwing and which overcomes the disadvantages of the prior art.

[0006] According to claim 1, the invention comprises a screw assembly for screw connection with a mounting interface, comprising a printed circuit board, at least one screw having a screw thread and a screw head, wherein the screw thread extends through a screw hole formed in the printed circuit board, and a washer element arranged between the screw head and the printed circuit board. The invention is characterized in that the washer element is connected to the printed circuit board in a rotationally secure and captive manner.

[0007] In other words, the invention provides that the screw assembly includes a washer element which is arranged between the screw head and the printed circuit board (PCB). The washer element thus serves as a bearing surface for the screw and, according to the invention, is connected to the PCB in a rotationally secure manner, so that the washer element does not rotate when the screw is tightened, thus protecting the surface of the PCB from damage caused by a rotating screw head. Furthermore, according to the invention, the washer element is also securely connected to the PCB. This has the advantage that even if the screw assembly needs to be rotated during assembly, the washer element remains firmly connected to the PCB and does not detach from the PCB even if the screw is not yet fully tightened.In this way, the surface of the printed circuit board can be reliably protected from damage and subsequent corrosion. Furthermore, it has been shown that if a failure occurs, for example due to an excessive tightening torque, the screw head breaks off, but the printed circuit board remains undamaged. This represents a further advantage of the screw connection according to the invention.

[0008] According to one embodiment of the invention, the washer is designed as a washer, wherein the washer has a through-hole that is aligned with the screw hole in the circuit board. The outer contour of the washer can be designed in different ways. For example, it can be essentially circular, but it can also have irregularities in the form of indentations and / or protrusions or notches.

[0009] According to the invention, the support element can be connected to the circuit board in a twist-proof and loss-proof manner by means of a positive locking mechanism.

[0010] For example, the washer can have at least one locking element that creates a positive connection with the printed circuit board (PCB). This locking element can be, for instance, an angled locking arm extending from the outer contour of a washer, which engages in a corresponding opening in the PCB. There may be only one locking arm, or there may be several, for example, two or three angled locking arms, extending from the outer contour of the washer at regular or irregular intervals. By locking such a washer with one or more locking elements into the PCB, the washer is securely and permanently attached to the PCB, preventing rotation and loss.Rotational stability means that the engaged shim cannot be rotated significantly relative to the circuit board. "Not significantly" in this context means that, due to the small amount of play required for locking, the shim can still rotate by a minimal angle of a few degrees relative to the circuit board, but this rotation is limited to the smallest possible angle by the stop of the locking arm against the circuit board.

[0011] According to a further embodiment of the invention, it can also be provided that the support element is connected to the circuit board in a rotationally secure and loss-proof manner by frictional engagement.

[0012] For example, the support element can have at least one press-fit element, which creates the frictional connection with the printed circuit board. This press-fit element can be a protruding structure on the support element, such as a pin or a knurled section, which is pressed into a corresponding recess of slightly smaller dimensions in the printed circuit board. The press-fit process plastically deforms the material involved. The resulting restoring forces ensure a permanent and secure connection between the support element and the printed circuit board. In particular, the support element is thus secured to the printed circuit board in a rotationally fixed and loss-proof manner.

[0013] In principle, it is also possible for the underlay element to be connected to the circuit board in a twist-proof and loss-proof manner by gluing, i.e. by material bonding.

[0014] It can also be provided that, in addition to the described connection methods, the support element is fixed to the circuit board by overmolding it with a plastic compound. For example, a plastic overmolding is used instead of an outer housing and applied to the entire circuit board in such a way that all electronic components of the circuit board are completely embedded in plastic. In this way, the support element can also be enclosed in the plastic compound, thus providing additional fixation. This is particularly advantageous if, due to space constraints, the support element only has a single locking element and the locked support element therefore still has a certain degree of freedom of movement. Here, the overmolding with the plastic compound ensures that the support element lies flat on the circuit board and cannot rotate relative to it.

[0015] In particular, it may be provided that the outer contour of the support element is irregularly shaped in such a way that, through interaction with the plastic compound, additional resistance to rotation of the support element relative to the circuit board is achieved. The plastic compound acts like a stop.

[0016] One aspect of the invention provides for a coating to be formed on the printed circuit board between the circuit board and the support element. Such a coating can be applied to the circuit board, for example, due to a required ground connection or electromagnetic compatibility requirements. The support element, which is mounted in a rotationally secure and captive manner, effectively protects the coating from damage.

[0017] The washer according to the invention is designed as a sheet metal part and is, for example, made of steel. In principle, the friction coefficients can be specifically influenced by the choice of material and the surface finish of the washer. The surface of the washer facing the screw head is preferably smooth, so that when the screw is tightened, only a minimal proportion of the applied torque has to be used to overcome frictional forces.

[0018] The invention will be explained in more detail below with reference to exemplary embodiments and the accompanying drawings. These show: Fig. 1: An embodiment of a shim as part of the screw assembly according to the invention in a perspective view; Fig. 2: in a sectional view, a first embodiment of the screw connection according to the invention is screwed in its operating position to a mounting interface; Fig. 3: in a sectional view, a further embodiment of the screw connection according to the invention is shown screwed in the operating position to a mounting interface; Fig. 4: in a sectional view, a further embodiment of the screw connection according to the invention is shown screwed in the operating position with a mounting interface.

[0019] Fig. Figure 1 shows a variant embodiment of a support element designated as 1 in its entirety, which is a component of the element described in the Fig. The screw connection shown in Figures 2 to 4 is formed by the washer element 1. This element is manufactured as a sheet metal part from steel and is designed as a washer with a central through-hole 2. The outer contour 3 of the washer element 1 is essentially circular, but it exhibits irregularities in the form of a notch 4 and a flattened area 5. The significance of these irregularities will be discussed in more detail below.

[0020] Extending from the outer contour 3 of the support element 1 is a locking element 6 designed as an angled locking arm. The locking element 6 is designed to engage in a corresponding opening in the printed circuit board 9 within the screw connection described in more detail below and to lock the printed circuit board 9 into place. Towards its free end, the locking element 6 splits into two parallel sections 6a, 6b, each with recesses 7a, 7b. When the locking element 6 is inserted into the opening of the printed circuit board 9, the sections 6a, 6b can be compressed like a spring element. As soon as the printed circuit board 9 rests against the locking element 6 in the area of ​​the recesses 7a, 7b, the sections 6a, 6b relax and return to their initial position due to the restoring forces.

[0021] The washer 1, which is snapped into the circuit board 9, is thus connected to the circuit board 9 in a form-fit manner, preventing rotation and loss. "Preventing rotation" means that the snapped-in washer 1 cannot be rotated significantly relative to the circuit board 9. "Not significant" means that, due to the small amount of play required for the locking mechanism, the washer 1 can rotate by a minimal angle of a few degrees relative to the circuit board 9, but this rotation is limited to the smallest possible angle by the stop of the locking arm against the circuit board 9. Furthermore, due to the locking mechanism between the washer 1 and the circuit board 9, the washer 1 is also secured against loss; that is, even if the screw connection is rotated during assembly, the washer 1 remains in its intended position.

[0022] In the Fig. In the embodiment shown in Figure 1, only one locking element 6 is formed. Alternatively, several locking elements 6, for example two, three or more, can be provided along the outer contour 3 of the support element 1, which can be arranged at the same or different distances from each other.

[0023] Fig. Figure 2 shows a first embodiment of the screw assembly according to the invention in a sectional view, screwed to a mounting interface 8 in its operating position. The screw assembly comprises a printed circuit board 9 with a screw feedthrough 14, a screw 10 having a screw head 11 and a screw shank 12 with a screw thread 13 formed in its surface (not visible in the figures), and a washer 1 arranged between the screw head 11 and the printed circuit board 9. The screw assembly is screwed to a mounting interface 8, which can be, for example, a gearbox interface and which, for this purpose, has a suitable screw-in opening 15 with an internal thread for screwing in the screw 10. In the illustrated embodiment, a metal spacer bushing 16 is also arranged between the printed circuit board 9 and the mounting interface 8. Fig. The section shown in Figure 2 only depicts one screw connection. In principle, the circuit board 9 can be connected to the mounting interface 8 by several identical screw connections.

[0024] The support element 1 is basically the same as the one above, with reference to Fig. The support element 1 described in section 1 is designed and arranged on the circuit board 9 such that the through-hole 2 formed in the support element 1 is aligned with the screw through-hole 14 in the circuit board 9. However, the ... Fig. 2. The supporting element shown is 1. Two locking elements designed as locking arms are 6. These extend through as shown in the Fig. As can be seen in Figure 2, the circuit board 9 and lock into place, thereby forming a positive-locking connection between the circuit board 9 and the washer 1 in the manner described above. The washer 1 is thus securely and securely connected to the circuit board 9 and cannot detach from it even if rotation of the screw assembly is required during assembly.

[0025] When screw 10 is tightened during the fastening process with the mounting interface 8, for example with a tightening torque of 5 Nm, the screw head 11 rotates only on the surface of the washer 1, and not directly on the surface of the circuit board 9. At the same time, the washer 1 is prevented from rotating due to the anti-rotation connection to the circuit board 9. In this way, the surface of the circuit board 9 is effectively protected from damage. In particular, the screw assembly can be disassembled and subsequently re-tightened during reuse of the entire electrical component without damaging the circuit board 9.

[0026] In the Fig. Figure 3 shows a further embodiment of the screw connection according to the invention, screwed together in the operating position with a mounting interface 8. The embodiment according to Fig. 3 differs from the embodiment shown in the above only in that Fig. 2, that the support element 1 is additionally fixed to the circuit board 9 by overmolding with a plastic compound 17.

[0027] The plastic compound 17 is applied to the entire circuit board 9 in such a way that all electronic components of the circuit board 9 are completely embedded in the plastic compound 17. In this way, the support element 1 is also enclosed in the plastic compound 17, thus providing additional fixation.

[0028] Since the outer contour of the support element 1, as shown in the Fig. As shown in Figure 1, irregularities in the form of an indentation 4 and a flattened area 5 are present, and in combination with the plastic compound 17, an additional anti-rotation device is provided in relation to the circuit board 9, since the plastic compound 17 fills the irregularly shaped areas or is directly adjacent to them and thus acts like a stop.

[0029] In the Fig. Figure 4 shows a further embodiment of the screw connection according to the invention, screwed together in the operating position with a mounting interface 8. The embodiment according to Fig. 3 differs from the embodiment shown in the above only in that Fig. 2, that an additional metallic coating 18 is applied to the circuit board 9 in the area of ​​the contact surface of the support element 1. Such a coating 18 can also be applied in principle to the one described in the Fig. The embodiment shown in Figure 3 is provided with plastic overmolding. A metallic coating 18 can be applied to the circuit board 9, for example, due to a required ground connection or an electromagnetic compatibility requirement.

[0030] Alternatively to the one in the Fig.In addition to the washer 1 shown in Figure 1 with one or more locking elements 6, a washer 1 (not shown) can also be used in the screw connection according to the invention, which is connected to the circuit board 9 via a friction-fit connection. For this purpose, at least one press-fit element, for example a pin or a knurled section, can be formed on the washer 1, which is pressed into a corresponding recess of slightly smaller dimensions formed in the circuit board 9. This secures the washer 1 to the circuit board 9 in a rotationally fixed and loss-proof manner. Here, too, as described above for the washer 1 with locking element 6, additional fixation can be achieved by means of a plastic overmolding. Reference symbol list 1 support element 2. Feedthrough opening 3 outer contour 4 notches 5 flattened area 6 locking element Section 6a Section 6b 7a Exclusion 7b Exclusion 8 Installation interface 9 printed circuit board 10 screws 11 screw head 12 screw shaft 13 screw threads 14 screw feedthrough 15 Screw-in opening 16 Spacer bushing 17 Plastic compound 18 coating 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 2019 / 0260143 A1

[0004]

Claims

[1] Screw connection for screwing with a mounting interface (8), comprising a printed circuit board (9), at least one screw (10) having a screw thread (13) and a screw head (11), wherein the screw thread (13) is passed through a screw passage (14) formed in the printed circuit board (9), and a washer (1) arranged between the screw head (11) and the printed circuit board (9), characterized by , that the support element (1) is connected to the circuit board (9) in a manner that prevents rotation and loss. [2] Screw connection according to claim 1, characterized by , that the support element (1) is designed as a washer, wherein the washer has a through-hole (2) aligned with the screw through-hole (14) in the circuit board (9). [3] Screw connection according to claim 1 or 2, characterized by , that the support element (1) is connected to the circuit board (9) by positive locking. [4] Screw connection according to claim 3, characterized by , that at least one locking element (6) is formed on the support element (1), via which the positive locking connection with the circuit board (9) is effected. [5] Screw connection according to any one of claims 1 to 4, characterized by , that the support element (1) is connected to the circuit board (9) by friction. [6] Screw connection according to claim 5, characterized by , that at least one press-fit element is formed on the support element (1), via which the friction-fit connection with the circuit board (9) is effected. [7] Screw connection according to one of claims 3 to 6, characterized by , that the support element (1) is fixed to the circuit board (9) by overmolding with a plastic compound (17). [8] Screw connection according to claim 7, characterized by, that an outer contour (3) of the support element (1) is irregularly formed in such a way that, by interaction with the plastic mass (17), the support element (1) is prevented from rotating relative to the circuit board (9). [9] Screw connection according to any one of claims 1 to 8, characterized by , that a coating (18) is formed on the circuit board (9) between the circuit board (9) and the support element (1). [10] Screw connection according to any one of claims 1 to 9, characterized by , that the support element (1) is designed as a sheet metal part.

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