CN107787148B

CN107787148B - Device for fixing printed circuit board

Info

Publication number: CN107787148B
Application number: CN201710731099.6A
Authority: CN
Inventors: 丹尼尔·威尔; 克里斯蒂安·迈尔
Original assignee: Lisa Draexlmaier GmbH
Current assignee: Lisa Draexlmaier GmbH
Priority date: 2016-08-26
Filing date: 2017-08-23
Publication date: 2021-04-16
Anticipated expiration: 2037-08-23
Also published as: DE102016115898A1; CN107787148A; DE102016115898B4

Abstract

The invention relates to a device for fixing printed circuit boards, in particular printed circuit boards which are subjected to strong vibrations in the construction of motor vehicles. To this end, the apparatus for fixing a printed circuit board according to the present invention comprises: the support comprises a housing, for example, which at least partially covers the printed circuit board, a circuit board holder for enclosing the printed circuit board, and screws for connecting the support with the circuit board holder. To compensate for tolerances, the bracket has a receiving portion for the screw, which contains a screw portion and a wedge portion. The circuit board holder also has two j aws that surround the printed circuit board on its underside and upper side, and screw domes for receiving the wedge portions.

Description

Device for fixing printed circuit board

Technical Field

The invention relates to a device for fixing printed circuit boards to a carrier, in particular a printed circuit board carrier, which is subjected to strong vibrations, for example in the construction of a motor vehicle.

Background

In motor vehicles, electrical circuits are used to an ever increasing extent. In addition to electrical functionality and weight, the circuit must also be able to handle environmental mechanical requirements. This also includes the fastening in and on the vehicle by means of a bracket. To protect the electrical circuit from undesired external influences, such as contamination and moisture, the electrical circuit is often surrounded by a housing, which covers at least a part of the electrical circuit. The circuitry is typically implemented on a printed circuit board such that the housing surrounds the printed circuit board. The housing can also serve as a holder for fixing the printed circuit board.

The printed circuit board with the circuit must therefore be fixed to the carrier in such a way that damage during use in the motor vehicle, in particular damage due to shocks and vibrations, is avoided over the lifetime.

Furthermore, there is a requirement that expansion of the printed circuit board of more than 500 μm/m is not allowed during mounting and operation.

Furthermore, there is a demand for space, low cost, space-optimized design and mountable printed circuit board connections, since a large number of further printed circuit boards and mechanical and electrical components are usually formed next to the printed circuit board.

Disclosure of Invention

The object of the invention is therefore to compensate for tolerances in the dimensions of the printed circuit board during the fixing, in particular during the connection of the printed circuit board to further components.

To this end, the apparatus for fixing a printed circuit board according to the present invention comprises: a support, in particular a part of the housing which at least partially covers the printed circuit board, a circuit board holder for enclosing the printed circuit board and a screw for connecting the housing with the circuit board holder. To compensate for tolerances, the housing has a receptacle for the screw, which receptacle has a screw portion and a wedge portion. The circuit board holder in turn has two j aws which surround the printed circuit board on its underside and upper side and have screw domes for receiving the wedge portions.

The circuit board holder is connected with the printed circuit board. This is typically a detachable plug connection and is used for tolerance compensation in the x, y direction in the plane of the printed circuit board.

The screw stud and the wedge part of the receptacle are now fitted in the holder and tolerance compensation in the z-direction is carried out when the screw is screwed in. For this purpose, the screw is inserted into the receptacle of the holder and screwed there until it reaches the wedge part located therebelow. Thereby, the wedges are spread apart and the circuit board holder (and thus also the printed circuit board) is fixed on the holder in the z-direction. The device can thus compensate for tolerances in all directions and can also compensate for the large tolerances in dimensions and, if necessary, stresses that result during z-deflection. The fixation is as stress-free as possible. If the current/voltage sensor is present on a printed circuit board, a higher measurement accuracy is achieved during the lifetime. Furthermore, the mounting of the printed circuit board is simple and inexpensive, without the need for additional compensation elements in addition to the board holder to compensate for tolerances.

According to an advantageous development of the invention, the screw arch has a rotationally symmetrical hollow space, in particular with a diameter of 3 to 10mm, in particular 5 to 8mm, and a length of 4 to 15mm, in particular 6 to 12 mm. Due to the symmetry and the dimensioning of the hollow space, depending on the size and weight of the printed circuit board, a plurality of fastenings can be realized, which allow a large tolerance range and require low forces during the screwing-in process.

Additional improvements of the present invention are achieved when a precession portion is disposed between the j aw and the screw arch. After the screw has partially spread the wedge, according to this refinement, screwing in continues until the screw penetrates into the screwed-in portion and there results a form-fitting connection. In order that no pressure occurs between the screwing in of the screw part and the screw-in part, the thread is formed by the screw, i.e. the screw part and the screw-in part in this case do not have a preformed thread.

Advantageously, the wedge part consists of three to six, in particular three or four, spreading arms which are arranged in the wedge part around the opening for the screw. For an even distribution of the force, the spreading arms are advantageously arranged rotationally symmetrically around the opening.

The possibility of flexibly coping with the available installation space is obtained if the screw domes of the circuit board holder and the j aws are connected to one another by webs and thus form an integral injection molded part. The screw arch and the j aws therefore do not have to overlap but can be separated from each other in the x and/or y direction. Tabs are used for such compensation.

The effectiveness of the device according to the invention is further improved in the following way.

The spreading of the wedge is supported by the diameter of the screw being larger than the diameter of the tubular opening in the helical portion.

If the screw is longer than the sum of the height of the screw arch and the height of the receiving portion, the screw penetrates into the bottom of the screw arch after the passage of the screw arch, i.e. into the screwed-in portion located therebelow, and the stability of the connection is further increased. The screw is advantageously a self-tapping screw.

The retention of the printed circuit board in the j aws is improved by orienting the j aws parallel to the printed circuit board and having at least one of the j aws with a support rib directed toward the printed circuit board. This support rib can be narrow and made of a material that can be ground off when the printed circuit board is pushed in between the jaws, so that a play-free and fixed retention of the printed circuit board is achieved.

This is further simplified when the height of the support ribs is smaller than the height of the printed circuit board and the height and/or width of the support ribs decreases towards the centre of the printed circuit board. In addition to a high degree of matching, a guiding aid for the printed circuit board is therefore also ensured.

Particularly in the case of longer j aws (length greater than width), it is advantageous for at least one of the j aws to have a support rib projecting away from the printed circuit board. The support ribs thus do not come into contact with the printed circuit board, but serve to ensure a pressing force of the j aws onto the printed circuit board over the entire length. In a pair of jaws, for example, one of the jaws can have a support rib and the other jaw can have a support rib.

The fastening is further improved by providing the circuit board holder with a further pair of jaws for enclosing the printed circuit board, which are also integrally connected with the screw arch, for example by means of tabs. Thus, there are two fixation points.

In addition to the j aws in the circuit board holder, further fixing points can be provided, which are advantageously provided on the side of the printed circuit board opposite the circuit board holder. The j aws and the attachment points should therefore be as far apart as possible from each other.

If a screwable component, for example a measuring resistor or a fuse, which is soldered to the printed circuit board, is selected as a fastening point, no additional fastening device is required.

Drawings

The invention is explained in detail below on the basis of examples, wherein the figures are:

figure 1 shows a device according to the invention in a perspective view,

figure 2 shows the device according to the invention in a cross-sectional view,

figure 3 shows a circuit-board holder which,

FIG. 4 shows a top view of a circuit board holder with a j aw, an

Fig. 5 shows further fastening points via a screwable measuring resistor.

Detailed Description

The printed circuit board 1 according to fig. 1 is oriented in a plane formed by the x/y-direction. On the printed circuit board 1, an electrical circuit is arranged, which is built up from electrical and electronic components connected to one another by conductor circuits. The electronic components include current/voltage sensors and the like, which react to stress and vibration within the printed circuit board 1. It is therefore important that the printed circuit board 1 is fixed to further components of the vehicle quickly, safely and inexpensively, and that no strain of the printed circuit board is allowed upon mounting.

The fastening is to take place, for example, on a support realized here by a housing 2, which housing 2 is only partially depicted as a disk in fig. 1. The function of the housing 2 is to cover the printed circuit board 1 on the upper side and to fix the printed circuit board 1 to the vehicle. For fastening the printed circuit board 1 to the housing 2, the housing 2 contains receptacles 5 for screws 4. The screws 4 are guided from the side facing away from the printed circuit board 1 through the receptacles 5 and rest with their screw heads on the receptacles 5. The screw 4 is sufficiently long that said screw 4 reaches through the receiving portion 5 into the circuit board holder 3 and there clamps a portion of the receiving portion 5, as will be explained further in connection with fig. 2, to the circuit board holder 3 acting as a wedge.

Because the receiving portions 5 can project into the circuit board holder 3 at different depths, tolerance compensation in the z direction between the circuit board holder 3 and thus the printed circuit board 1 and the housing 2 is achieved. Tolerance compensation in the x and y directions is achieved between the printed circuit board 1 and the housing 2 by the circuit board holder 3 itself. For this purpose, the circuit board holder 3 has

jaws

31, 32, as shown in fig. 2, which

jaws

31, 32 enclose the printed circuit board 1. The j aws 31, 32 are oriented in the plane of the printed circuit board 1 such that the printed circuit board 1 in the

j aws

31, 32 is movable within a tolerance range in this plane.

The housing 2 and the circuit board holder 3 are made of plastic and manufactured in an injection molding method. PA6 GF30 proved to be an advantageous material. The screw 4 is a screw 4 for screwing directly into plastic, for example an EJOT Delta PT of dimensions 40 × 20 (nominal diameter 4 mm).

The function of the device can be better explained by means of the sectional illustration of fig. 2. The printed circuit board 1 is clamped between the

j aws

31, 32 and is thus fixed in the x and y directions. For this purpose, the

jaws

31, 32 enclose the printed circuit board 1 on the upper side O and the lower side U of the printed circuit board 1. The j aws 31, 32 are part of an integrally formed circuit board holder 3, which circuit board holder 3 furthermore contains screw studs 33, which screw studs 33 have a rotationally symmetrical hollow space 34 and a screwed-in portion 35. The screw bosses 35 connect the screw posts 33 to the

j aws

31, 32, optionally via tabs 38, as shown in fig. 3.

In order to fix the housing 2 in the circuit board holder 3, the wedge portion 52 of the receiving portion 5 must extend into the screw stud 33. For this purpose, the housing 2 must not rest on the screw domes 33, and tolerance compensation in the z direction can be achieved within a range determined by the length of the wedge portion 52 and the depth of the hollow spaces 34 in the screw domes 33.

The screw 4 is screwed into the screw part 51 with an opening 56, the diameter of said opening 56 being dimensioned narrower than the diameter of the screw 4. Here, a thread is tapped in the screw part 51. This thread is not formed over the entire length of the surface of the screw part 51 projecting perpendicularly out of the housing 2, but only over a part thereof. The remainder of the bore 56 in the helical portion 51 can have a larger diameter.

If the screw 4 is screwed further in, said screw 4 reaches the wedge portion 52 of the receiving portion 5 of the housing 2. The wedge part 52 is formed by three spreading arms 53 to 55 which are arranged rotationally symmetrically around an opening 56 which also passes through the wedge part 52. The opening 56 is also narrower than the diameter of the screw 4 at this location.

The wedge portion 52 has a minimum of three spreading arms 53 to 55, but can also contain a greater number of spreading arms. The spreader arms 53 to 55 are used for radial force distribution. More arms (e.g. up to six) result in a more even force distribution but also in a lower load capacity of the wedge portion 52, since it is determined by the tool that the channel between the spreader arms 53-55 must have a certain minimum width (e.g. 1 mm).

The hollow space 34 in the screw arch 33 has, for example, an inner diameter of 6.6mm, which is obtained due to the structure of the wedge portion 52 (in terms of demolding and load-bearing capacity). The length of the hollow space 34 in the screw arch 33 depends on the actual design of the wedge part 52 (offset 2mm in z-direction) and the combination of the screws 4 used. Thus obtaining a length of 10 mm.

In the dimensioning of the screw 4, it should be longer than the sum of the height H1 of the screw stud 33 and the height H2 of the receiving portion 5. Thus, when the screw 4 reaches the wedge 52 and the spreader arms 53 to 55 spread apart, the screw 4 clamps the spreader arms 53 to 55 within the screw arch 33 and precisely to a height for tolerance compensation in the z-direction. Thereby, a force-fit connection is produced between the housing 2 and the circuit board holder 3.

Since the screw 4 is sufficiently long, the screw 4 can penetrate further until the screw head abuts on the receiving portion 5 and further penetrates into the circuit board holder 3 to reach the screw-in portion 35. In the screwed-in portion 35, the screw 4 forms a further thread and thus achieves a form-fitting connection between the circuit board holder 3 and the housing 2.

An exemplary circuit board holder 3 is shown in fig. 4. In addition to the screw stud 33 with the hollow space 34 located inside and the screw-in portion 35 located thereunder, the circuit board holder 3 also contains a tab 38, which tab 38 connects the screw-in portion 35 with the two pairs of

jaws

31, 32 and 36, 37. The tabs 38 give a minimum spacing between the

j aws

31, 32, 36, 37. Due to the shape of the web 38 and the placement of the threaded portion 35 on the web 38, it is possible to adapt a plurality of fastening options to the available installation space and the fastening point 6 in the housing 2.

The j aws 31, 32, 36, 37 are shown enlarged in fig. 4. One

jaw

31, 36 of each pair of jaws has a support rib 39 and the

other jaw

32, 37 has a support rib 40. The support ribs 39 are thus located between the

jaws

31, 32 and 36, 37 and can be easily removed when the printed circuit board 1 is pushed on, and therefore also as the

other jaws

32, 37 always rest on the printed circuit board 1 and result in a secure clamping connection. As a guide aid and for easier removal, the support ribs 39 taper toward the printed circuit board 1. The support ribs 40 are formed in a triangular shape, located on the opposite outer sides of the j aws and ensure that the

j aws

32, 37 are not bent over by the printed circuit board 1.

Fig. 5 finally shows the other end of the printed circuit board 1, which preferably lies opposite the circuit board holder 3 in the mounted position. The measuring resistor 61 is soldered to the printed circuit board 1 in two places as a fixing point 6 for the printed circuit board 1. Between these two welded connections there is an electrical resistance close to the illustrated gap.

The two parts of the measuring resistor have one

screw hole

62, 63 each for screwing the measuring resistor together with the bracket 2 or another part of the vehicle. The printed circuit board 1 is therefore connected on the vehicle in a stable and vibration-proof manner via the two pairs of

jaws

31, 32, 36, 37 and the fastening points 6, and at the same time tolerance compensation during installation is achieved.

List of reference numerals

1 printed circuit board

2 support, casing

3 Circuit board holder

4 screw

5 receiving part

6 fixed point

31. 32, 36, 37 jaw

33 screw arch post

34 hollow space

35 screw-in part

38 tab

39 support rib

40 support rib

51 helical part

52 wedge portion

53 to 55 spreading arms

56 opening hole

61 Member of measuring resistance

62. 63 screw hole

Height of H1 screw arch column

Height of H2 receiving part

Upper side of O

Lower side of U

Claims

1. An apparatus for fixing a printed circuit board (1) with:

-a support (2),

a circuit board holder (3) for enclosing a printed circuit board (1),

screw (4) for connecting a carrier (2) to a circuit board holder (3), wherein

The bracket (2) has a receiving portion (5) for the screw (4), said receiving portion comprising a screw portion (51) and a wedge portion (52),

the circuit board retainer (3) comprises two jaws (31, 32) which surround the printed circuit board (1) on the lower side (U) and the upper side (O) of the printed circuit board (1) and which have screw domes (33) for receiving wedge portions (52).

2. The device according to claim 1, wherein the screw stud (33) has a hollow space (34) with rotational symmetry.

3. The apparatus of claim 2, wherein the screw arch (33) has a diameter of 3 to 10 mm.

4. The apparatus of claim 2, wherein the screw arch (33) has a diameter of 5 to 8 mm.

5. The apparatus of claim 2, wherein the screw arch (33) has a length of 4 to 15 mm.

6. The apparatus of claim 2, wherein the screw arch (33) has a length of 6 to 12 mm.

7. The apparatus of claim 1 or 2, wherein a precession portion (35) is arranged between the j aws (31, 32) and the screw arch (33).

8. Apparatus according to claim 1 or 2, wherein the wedge part (52) consists of three to six spread arms (53-55) arranged around an opening (56) for a screw (4) in the wedge part (52).

9. The apparatus of claim 8, wherein the arms are arranged rotationally symmetrically about the aperture (56).

10. The device according to claim 1 or 2, wherein the screw stud (33) and the j aws (31, 32, 36, 37) are connected to one another by a web (38) and form an integral injection-molded part.

11. The device according to claim 1 or 2, wherein the diameter of the screw (4) is larger than the diameter of a tubular opening (56) in the helical portion (51).

12. The device according to claim 1 or 2, wherein the screw (4) is longer than the sum of the height (H1) of the screw arch (33) and the height (H2) of the receiving portion (5).

13. The device according to claim 1 or 2, wherein the j aws (31, 32) are oriented parallel to the printed circuit board (1) and at least one j aws (31) has a support rib (39) directed towards the printed circuit board (1).

14. Apparatus according to claim 13, wherein the height of the support ribs (39) is smaller than the height of the printed circuit board (1) and the height and/or width of the support ribs (39) decreases towards the center of the printed circuit board (1).

15. The apparatus of claim 13, wherein at least one j aw (32) has a support rib (40) projecting away from the printed circuit board (1).

16. The device according to claim 1 or 2, wherein the circuit board holder (3) has a further pair of j aws (36, 37) for enclosing the printed circuit board (1), the further pair of j aws (36, 37) also being integrally connected with the screw arch (33).

17. Device according to claim 1 or 2, with further fixing points (6) on the opposite side of the printed circuit board (1) to the circuit board holder (3).

18. The device according to claim 17, wherein the fixing point (6) is formed by a screwable member (61), the member (61) being soldered to the printed circuit board (1).

19. Apparatus according to claim 18, wherein said member (61) is a measuring resistance with two screw holes (62, 63).