Sealed electronic module provided with improved fastening device - Patent Application 20070122967

Abstract

To provide a sealed electronic module with an improved fastening device. The device includes a printed circuit board (8) having a plurality of electronic components (12), a shaped metal plate (16) that supports and fixes the printed circuit board (8) by one or more fixing devices (20), and a closing cover (24) that seals the shaped metal plate and / or the printed circuit board (8) to ensure sealing of the printed circuit board (8) from the outside of the sealed electronic module (4). The one or more fixing devices (20) that place the printed circuit board (8) on the shaped metal plate (16) have one or more mechanical joints (34), which form a form-fit between a male portion formed on the printed circuit board (8) and a female portion or seat portion formed on the shaped metal plate (16), or vice versa, and the shaped metal plate (16) does not have a through hole that communicates with the outside of the sealed electronic module (4) at the mechanical joints (34).

Description

[Technical Field]

[0001] The present invention relates to a sealed electronic module provided with an improved fastening device. [Background technology]

[0002] In the automotive field, it is known to manufacture electronic modules, such as electronic control units, housed in the engine compartment, which are subjected to high mechanical and thermal stresses during operation.

[0003] Furthermore, because the engine compartment is not sealed, the electronic modules are also susceptible to water and moisture, which, if infiltrated into the electronic modules, can cause problems with the function of the electronic components fixed to special printed circuit boards within those modules.

[0004] In electronic modules with a molded metal plate as a metal housing, the printed circuit board is usually fixed with bolts through special holes drilled in the printed circuit board and the molded metal plate, making the intrusion of moisture and / or water particularly problematic (Figure 1).

[0005] As is known, there is a gap between the threads of a bolt and a nut. The gap widens due to different thermal deformations of the bolt and the nut connected to each other. Therefore, the bolt cannot be firmly fixed. In fact, the bolt and the formed metal plate are typically made of different metal materials, and therefore have different thermal expansion coefficients.

[0006] To overcome this drawback, it is known to use, for example, thread-locking pastes or special sealing bushes, but these solutions cannot guarantee an ideal seal over the long term, taking into account that the electronic modules mentioned above must maintain their sealing for several years, even when subjected to harsh conditions of use in terms of mechanical and thermal stresses. Summary of the Invention

[0007] Therefore, there is a need in the art to look to the prior art to address the cited shortcomings and limitations.

[0008] Such a need is met by a sealed electronic module as claimed in claim 1.

[0009] Further embodiments of the invention are set forth in the dependent claims. [Brief explanation of the drawings]

[0010] Further features and advantages of the present invention will become more apparent from the following detailed description of the preferred, non-limiting embodiments. [Figure 1] FIG. 1 is a cross-sectional view of an embodiment of the prior art. [Figure 2] 1 is an exploded perspective view of a sealed electronic module according to an embodiment of the present invention; [Figure 3] 2 is a perspective view of some components of the electronic module of FIG. 1, with the closing cover omitted. FIG. [Figure 4] 3 is a cross-sectional view showing the assembled configuration of the sealed electronic module of FIG. 2. FIG. [Figure 5] FIG. 4 is a plan view of the electronic module of FIG. 3. [Figure 6a] 1A-1D are cross-sectional views illustrating successive steps for creating a joint by plastic deformation according to one embodiment of the present invention. [Figure 6b] 1A-1D are cross-sectional views illustrating successive steps for creating a joint by plastic deformation according to one embodiment of the present invention. [Figure 7] 1A-1D are cross-sectional views illustrating successive steps for creating a joint by plastic deformation according to one embodiment of the present invention. [Figure 8] 1A-1D are cross-sectional views illustrating successive steps for creating a joint by plastic deformation according to one embodiment of the present invention. [Figure 9] 1 is a perspective view of a male part of a mechanical joint according to a possible embodiment of the present invention; FIG. [Figure 10] 1A-1C are plan views of an electronic module showing different embodiments of the mechanical joint between the printed circuit board and the shaped metal plate, without the closing cover. [Figure 11] 1A-1C are plan views of an electronic module showing different embodiments of the mechanical joint between the printed circuit board and the shaped metal plate, without the closing cover. [Figure 12] 1A-1C are plan views of an electronic module showing different embodiments of the mechanical joint between the printed circuit board and the shaped metal plate, without the closing cover.

[0011] Elements or parts of elements common to the embodiments described below are designated by the same numerical reference symbols. DETAILED DESCRIPTION OF THE INVENTION

[0012] With reference to the above figures, reference number "4" generally indicates a sealed electronic module particularly suitable for use in the automotive field, but not exclusively.

[0013] It is noted that sealed electronic modules may be used in a variety of fields, and therefore the application of the invention to the automotive field is preferred, but not exclusive.

[0014] The sealed electronic module 4 includes a printed circuit board 8 having a plurality of electronic components 12 thereon, and a formed metal plate 16 which serves to support and secure the printed circuit board 8 by one or more fasteners 20 .

[0015] The sealed electronic module 4 further comprises a closing cover 24. The closing cover 24 covers the formed metal plate 16 and / or the printed circuit board 8 so as to ensure hermeticity of the printed circuit board 8 from the outside of the sealed electronic module 4.

[0016] The formed metal plate is usually made of aluminum or steel. The closure cover 24 can be made of either a metal or plastic material.

[0017] The sealed electronic module 4 includes a peripheral seal gasket 28 disposed between the closure cover 24 and the molded metal plate 16 to ensure a tight seal within the sealed electronic module 4. The peripheral seal gasket 28 defines an area 32 of the printed circuit board 8 having the electronic components 12. For example, a gasket formulated with a resin or made of a polymeric material may be used as the peripheral seal gasket 28.

[0018] Advantageously, the one or more fastening devices 20 for mounting the printed circuit board 8 on the shaped metal plate 16 comprise one or more mechanical joints 34. The mechanical joints 34 form a positive connection between a male part 36 made on the printed circuit board 8 and a female part or seat 40 made on the shaped metal plate 16, or vice versa.

[0019] In other words, the male portion 36 and the female portion 40 may be provided on the molded metal plate 16 and the printed circuit board 8, respectively, or vice versa.

[0020] Advantageously, the shaped metal plate 16 does not have any through holes communicating with the outside of the sealed electronic module 4 at the mechanical joint 34. In this way, there is no possibility of water or moisture penetrating into the sealed electronic module 4 through the mechanical joint 34 between the shaped metal plate 16 and the printed circuit board 8.

[0021] According to one embodiment, the mechanical joint 34 is a joint formed by plastic deformation between a male part 36 of the formed metal plate 16 and a female part 40 of the printed circuit board 8. The mechanical joint 34 is received in the female part 40 of the printed circuit board 8, which has a through hole 48 aligned in the assembly direction XX.

[0022] The male part 36 has one or more cantilevered portions 52 that protrude at least partially from the seat along the assembly direction XX at the top 44 of the male part 36. The cantilevered portions 52 form undercuts relative to the assembly direction XX.

[0023] According to one embodiment, the cantilevered portion 52 is a crown or rim forming an undercut relative to the assembly direction XX.

[0024] Preferably, the male portion 36 and female portion 40 have opposite shapes relative to each other.

[0025] For example, the male part 36 and the female part 40 are axially symmetrical with respect to an axis of symmetry parallel to the assembly direction XX.

[0026] The male part 36 may have various shapes in cross section perpendicular to the assembly direction XX.

[0027] For example, the male portion 36 may have a flat portion (FIG. 10), a shear portion (FIG. 11), or a hex portion (FIG. 12).

[0028] The above example shapes are merely suggestive and not exhaustive, and therefore additional shapes for the male portion 36 are possible.

[0029] It is also possible to configure the male and female portions 36, 40 to snap together, for example, by providing a slightly forced or interference fit between the male and female portions, such that the top 44 of the male portion 36 is forced through and through the female portion or sheet of the printed circuit board 8, resulting in a strong mechanical joint.

[0030] According to a preferred embodiment, the male portion 36 of the mechanical joint 34 has a recess 56 opposite the associated female portion or seat 40 .

[0031] The recess allows for more precise control of the plastic deformation of the top portion 44 of the male portion 36 as well as for coupling with a possible associated punch portion, as will be described in more detail below.

[0032] Preferably, the male part 36 has the same thickness as the formed metal plate 16 in the assembly direction XX, since it is provided on the formed metal plate 16 by plastic deformation of the formed metal plate 16 itself.

[0033] Next, the method for assembling the sealed electronic module according to the present invention and the associated operations will be described.

[0034] In particular, the assembly method of the sealed electronic module 4 is as follows: providing a printed circuit board 8 having a plurality of electronic components 12; providing a formed metal plate 16 which serves to support and secure a printed circuit board 8 by one or more fastening devices 20; providing a closing cover 24 to cover the shaped metal plate 16 and / or the printed circuit board 8 so as to ensure hermeticity of the printed circuit board 8 against the exterior of the sealed electronic module 4; cold-forming the formed metal plate 16 using a punch to preform one or more fastening devices 20 for mounting the printed circuit board 8 on the formed metal plate 16, thereby obtaining a male part 36 that does not have a through-hole communicating with the outside; providing one or more holes or seats 40 in the printed circuit board 8 to serve as female portions 40; Engaging the male part 36 in the hole or seat 40 in the assembly direction XX (FIGS. 6a-6b) so that the top 44 of the male part 36 at least partially protrudes from the seat 40 along the assembly direction XX; plastically deforming the top 44 of the male part 36 to create the mechanical joint 34 by an undercut relative to the assembly direction XX; Includes:

[0035] According to a possible embodiment, the plastic deformation is effected by using a first punch 60 arranged on the lower surface 64 of the formed metal plate 16 opposite the associated printed circuit board 8 and a second punch 68 arranged on the upper surface 72 of the formed metal plate 16 opposite the lower surface 64.

[0036] Preferably, the first punch portion 60 and the second punch portion 68 have a size or area 76 that is greater than the size or area of ​​the male portion 36, said size being measured on a projection plane perpendicular to the assembly direction XX.

[0037] According to a possible embodiment, the second punch portion 68 has a flat beam-like abutment face 80 suitable for deforming the top portion 44 of the male portion 36 .

[0038] According to a possible embodiment, the first punch element 60 has a stepped beam-like striking surface 84 that is the opposite shape to the lower surface 64 of the formed metal sheet 16 .

[0039] Preferably, the step of preparing the shaped metal plate 16 includes: providing an initial flat formed metal plate 16 having a thickness S; preforming one or more male portions 36 of the formed metal plate 16 by plastic deformation of the formed metal plate 16 by punching, so that the male portions 36 have substantially the same thickness S as the formed metal plate 16; Includes:

[0040] Preferably, the preformed male part 36 has, at the top 44, a recess 88a or a protrusion 88b intended to be inserted into a corresponding seat of the printed circuit board 8. Such recess 88a or protrusion 88b facilitates subsequent plastic deformation of the top 44 so as to create a cantilevered part 52 in which a locking undercut is formed between the printed circuit board 8 and the formed metal plate 16.

[0041] In particular, by using a male part 36 having a non-flat top 44, particularly a male part 36 having a recess 88a or a protrusion 88b, the force exerted by the beam-shaped striking surface 80 of the second punch part 68 is advantageously concentrated on a limited surface.

[0042] In this way, plastic deformation of the top 44 of the male part 36 is obtained, creating an undercut, so that a limited force can be applied to the second punch part to fix the printed circuit board 8 to the formed metal plate 16. In practice, it is important to expose the printed circuit board 8 to as little compressive load as possible, in order not to impair the operation of the delicate electronic components 12 applied to the printed circuit board 8.

[0043] In particular, when a male part 36 having a recess 88a formed in the top 44 is used (Figure 6a), the beam-shaped striking surface 80 of the second punch part 68 will collide directly (and substantially exclusively) with the peripheral edge of the top 44 of the male part 36, which can easily deform by plastic flow around the portion of the printed circuit board 8 adjacent to the through hole 48.

[0044] When a male part 36 having a protrusion 88b on its top 44 is used (Figure 6b), the beam-shaped striking surface 80 of the second punch part 68 will directly (and substantially exclusively) impact the central part of the top 44 of the male part 36, which will be radially ejected towards the edge and will plastically flow around the part of the printed circuit board 8 adjacent to the through hole 48, thereby easily deforming.

[0045] As can be seen from what has been described, the present invention overcomes the shortcomings of the prior art.

[0046] In particular, the sealed electronic module of the present invention is water and moisture-proof because the device for fastening the printed circuit board to the molded metal plate does not have any holes through the molded metal plate, so there is no possibility of water or moisture passing through the joint between the sealed closure cover and the molded metal plate.

[0047] Advantageously, the plastic deformation fixation device can fix the printed circuit board in place without excessive mechanical stress that would impair the functionality of the printed circuit board. In fact, the controlled deformation joint of the present invention can withstand forces of several hundred Newtons (typically less than 500 N) without damaging or deforming the printed circuit board or the electronic components thereon.

[0048] For this purpose, a particular shape of the male part of the mechanical joint can be used to minimize the force that must be applied to the punch to plastically deform the top of the male part and create the undercut that secures the printed circuit board to the formed metal plate.

[0049] Furthermore, the controlled deformation joint is particularly resistant to the thermal and mechanical stresses (vibrations) to which electronic modules are subjected in automotive applications.

[0050] In particular, such vibrations do not cause the joints made to break or even loosen, as would be the case with prior art bolted connections.

[0051] Furthermore, the thermal stresses experienced by the joint will not loosen the joint or create the possibility of infiltration as with prior art bolted joints.

[0052] In fact, the joint is very strong: even if thermal expansion occurs, there is no risk of water or moisture entering the joint, since the joint does not have any through holes that could allow the electronic module to communicate with the outside environment.

[0053] The advantage of the joint of the present invention is given by the fact that it is only intended to provide a mechanical connection between the printed circuit board and the formed metal plate and does not have a sealing function, whereas in known solutions the bolted joint has both a mechanical connection function and a sealing function.

[0054] The solution of the present invention does not provide an additional sealing device compared to the prior art solutions, and therefore does not increase the number of parts and therefore the assembly / production costs of the electronic module. In fact, the hermeticity is left to the peripheral sealing gasket between the printed circuit board and the closing cover, which is provided in prior art sealed electronic modules.

[0055] Furthermore, the joints of the present invention may be easily deformed to allow opening and disassembly of the electronic module during maintenance work, and such deformation may be of a reversible type.

[0056] Finally, the present invention also allows to reduce the overall size or thickness of the electronic module compared to known solutions that use connecting bolts between the shaped metal plate and the printed circuit board: in fact, while in the bolt solutions the thickness of the printed circuit board is added to the thickness of the shaped metal plate with its respective raised portions for accommodating the bolt threads and the nut threads, in the present invention the raised plate portions of the shaped metal plate are accommodated in holes or seats in the printed circuit board, so the overall thickness of the module does not increase.

[0057] Those skilled in the art may make several modifications and adjustments to the above-described electronic module and its assembly method to meet their specific and additional needs, all of which fall within the scope of protection defined in the following claims.

Claims

1. a printed circuit board (8) having a plurality of electronic components (12); a formed metal plate (16) serving to support and fix the printed circuit board (8) by means of one or more fixing devices (20); a closing cover (24) for covering the formed metal plate and / or the printed circuit board (8) so as to ensure the sealing of the printed circuit board (8) against the exterior of the sealed electronic module (4); Equipped with The one or more fixing devices (20) for mounting the printed circuit board (8) on the formed metal plate (16) have one or more mechanical joints (34); The mechanical joint (34) forms a bond between a male portion (36) made on the formed metal plate (16) and a female portion or seat (40) made on the printed circuit board (8); The formed metal plate (16) does not have a through hole communicating with the outside of the sealed electronic module (4) at the mechanical joint (34), A preformed male part (36) is provided before the formation of the mechanical joint (34), The preformed male part (36) has a recess (88a) or a protrusion (88b) on the tip surface of the male part, which is inserted into the female part or seat part (40) of the printed circuit board (8). Sealed electronic module.

2. the mechanical joint (34) is a mechanical joint (34) formed by plastic deformation between a male portion (36) of the formed metal plate (16) and a female portion (40) of the printed circuit board (8); 2. The sealed electronic module of claim 1, wherein the mechanical joints (34) are housed in female parts (40) of the printed circuit board (8) having through holes along an assembly direction (X-X).

3. the male part (36) has, at its top (44), one or more cantilevered beams (52) that at least partially protrude from the seat (40) along the assembly direction (X-X); The sealed electronic module of claim 2, wherein the cantilever portion forms an undercut portion relative to the assembly direction (XX).

4. The sealed electronic module of claim 3, wherein said cantilevered portion (52) is a crown or rim portion that forms said undercut portion relative to said assembly direction (XX).

5. The sealed electronic module of any one of claims 1 to 4, wherein the male portion (36) has a shape that matches the shape of the female portion (40).

6. The sealed electronic module according to any one of claims 1 to 5, wherein the male part (36) and the female part (40) are axially symmetrical about an axis of symmetry parallel to an assembly direction (XX).

7. 7. The sealed electronic module of claim 1, further comprising a peripheral seal gasket (28) disposed between the closure cover (24) and the formed metal plate (16), the peripheral seal gasket defining an area (32) of the printed circuit board (8) having the electronic components (12).

8. 8. A sealed electronic module according to any one of claims 1 to 7, wherein the male part (36) of the mechanical joint (34) has a recess (56) on the opposite side to the possibly associated female part or seat (40).

9. 9. The sealed electronic module according to claim 1, wherein the male portion (36) is made in the formed metal plate (16) by plastic deformation of the formed metal plate (16) and has the same thickness (S) as the formed metal plate (16) in the assembly direction (X-X).

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