Electronic package including a component to be cooled and associated mounting method

Abstract

The present disclosure relates to a set of electronic packaging elements (1) intended to be mounted on an electronic board (4) comprising components to be cooled (5), comprising: a frame (2), a heat sink (7) fixed inside the frame (2) by a retaining element (9), a cover (3) configured to be fixed on the frame (2) in order to retain the electronic board (4) in the box (1). The heat sink (7) is configured to be fixed on the electronic board (4) while maintaining a predetermined distance between the lower face of the heat sink (7) and the components (5), and the cover (3) is configured to be able to be fixed to the heat sink (7) by a fixing point. The retaining element (9) is connected to the heat sink (7) in order to allow a translational movement of the heat sink (7) with respect to the frame (2) in three orthogonal directions.

Description

Technical Field

[0001] The present invention relates to the field of cooling of electronic components in environments subject to strong vibrations, such as in the automotive field. Background Art

[0002] In the automotive sector, increasingly powerful electronic components are being used, particularly due to the development of new functions such as driver assistance or autonomous driving. Therefore, solutions are needed to cool these components, which can be subject to strong vibrations, while protecting them from the external environment.

[0003] The proposed cooling solution must effectively cool the component while maintaining the integrity of both it and the electronic board to which it is mounted. To this end, care must be taken to limit the stresses on the electronic board, particularly to avoid breakage of solder joints or traces, and to limit structural weaknesses by using the most rigid connections and avoiding natural resonant frequencies. Furthermore, it is desirable to limit production costs by limiting the number of assembly steps and storage costs by limiting the number of parts to be assembled.

[0004] Various solutions have been proposed in an attempt to address these problems.

[0005] A first solution consists in fixing the electronic board to a base and enclosing the electronic board and the component to be cooled in a rigid enclosure fixed to the base, in order to form an electronic package. Since the heat sink, intended to be in thermal contact with the component to be cooled, is rigidly fixed within the enclosure, a layer of thermal interface material, such as thermal paste, grease, or even a thermal pad, is placed between the heat sink and the component to ensure thermal contact. Due to the mechanical tolerances between the component and the heat sink, the thickness of the thermal interface material layer varies from one electronic package to another. Consequently, the cooling performance varies, which can lead to overheating of the component or other sensitive components on the electronic board. Consequently, this solution is unsatisfactory in terms of thermal performance.

[0006] To overcome this drawback, it has been proposed to screw heat sinks onto the electronic board on either side of the component to be cooled. This allows for a reproducible and controlled thickness of the thermal interface material applied. However, this additional mechanical connection imposes an additional constraint that can lead to localized bending of the electronic board. This second solution is unsatisfactory because it induces additional stress on the electronic board.

[0007] To overcome this drawback, in a third solution, it has been proposed to fix the heat sink directly on the electronic board. This third solution is not satisfactory because it involves an additional sub-assembly step and therefore the storage of additional elements. Moreover, since the weight of the heat sink is generally of the order of 50 to 200 grams for the intended applications, the soldered joints or printed tracks can break in the presence of vibrations. Moreover, the electronic board is subjected to dynamic stresses generated at each vertical acceleration, for example when the vehicle passes over a pothole, which also have an impact on the integrity of the electronic board in terms of cyclic fatigue.

[0008] To overcome this drawback, in a fourth solution, it has been proposed to fix the heat sink on the electronic board and on the cover. Since the cover is rigid, the structural stability of the assembly is improved. However, with this solution, the position of the electronic board inside the rigid enclosure is difficult to adjust since it is defined by the cover / electronic board / cooler assembly. Thus, for example, it is necessary to increase the new tolerances by enlarging the hole intended to receive the connector on the shelf enclosure. This solution is not viable because it is necessary to limit the entry of solid and liquid foreign bodies into the electronic package. It also poses a problem if it is envisaged to connect several electronic boards directly together by means of connectors fixed to each of them.

[0009] There is therefore a need for a cooling solution compatible with all these problems. SUMMARY

[0010] The purpose of the present disclosure is to overcome the drawbacks of the prior art

[0011] The purpose of the present disclosure is to propose a cooling solution that makes it possible to efficiently cool a component while guaranteeing good integrity of this component and of the electronic board on which it is fixed.

[0012] The purpose of the present disclosure is to limit production costs by limiting the number of assembly steps and to limit storage costs by limiting the number of parts to be assembled.

[0013] A set of electronic package elements is proposed, intended to be mounted on an electronic board comprising a component to be cooled, in which:

[0014] - said set comprises:

[0015] * a rigid shelf containing a heat sink intended to cool the component, said heat sink being fixed inside the shelf,

[0016] * a rigid cover configured to be fixed on the shelf and on the electronic board, so as to retain the electronic board in the electronic package,

[0017] the heat sink is configured to be fixed to the electronic board while maintaining a predetermined distance between the face of the heat sink intended to be in thermal contact with the component to be cooled and said component, and

[0018] The cover is configured to be fixable to the radiator via fixing points.

[0019] Furthermore, the heat sink is secured by a retainer integral with the interior of the frame, the retainer being resiliently connected to the heat sink to allow translational movement of the heat sink relative to the frame in three orthogonal directions.

[0020] According to another aspect, an electronic package is provided, comprising:

[0021] - a set of electronic packaging components as described above, and

[0022] - electronic boards on which the components to be cooled are mounted,

[0023] in

[0024] -The electronic board is fixed to the inner surface of the cover, which is fixed to the frame,

[0025] - the face of the heat sink intended to be in thermal contact with the component to be cooled is fixed to the electronic board so as to maintain a predetermined distance between said face of the heat sink and the component, said face of the heat sink also being fixed to the cover at fixing points, and

[0026] - A layer of thermal interface material is placed between said face of the heat sink and the component.

[0027] According to another aspect, a method for mounting an electronic package is provided, the method comprising the following steps:

[0028] a. Providing a set of electronic packaging components as described above,

[0029] b. providing an electronic board including components to be cooled,

[0030] c. placing the rack in a holding device suitable for assembling electronic packages,

[0031] d. Apply a layer of thermal interface material on one side of the heat sink or one side of the component,

[0032] e. Place one side of the electronic board in contact with the frame,

[0033] f. Place the cover in contact with the electronic board,

[0034] g. Fix the electronic board on the rack,

[0035] h. Fix the cover on the frame,

[0036] i. fixing the surface of the heat sink to the electronic board so as to maintain a predetermined distance between the surface of the heat sink and the component, and

[0037] j. Fix the face of the radiator to the cover at the fixing points.

[0038] The features disclosed in the following paragraphs may be optionally implemented. They may be implemented independently of each other or in combination with each other:

[0039] - the holder is connected to the heat sink by at least three elastically deformable arms configured to allow translational movement of the heat sink in three orthogonal directions;

[0040] - each elastically deformable arm extends substantially in a plane, and wherein one end of each arm is connected to the heat sink by a pivot joint perpendicular to the plane;

[0041] - the heat sink comprises a plurality of cooling fins parallel to the reference plane, and the holder comprises two mutually opposite walls extending parallel to the reference plane and a wall perpendicular to the reference plane, the two opposite walls being elastically connected to the heat sink, and the perpendicular wall being adapted to accommodate a fan;

[0042] - Steps g and h of the method are performed simultaneously, and then steps i and j of the method are performed simultaneously.

[0043] The proposed solution offers many advantages.

[0044] Because the distance between the face of the heat sink and the face of the component to be cooled, which faces are intended to be in thermal contact with each other, is controlled, it is possible to apply a thickness of thermal interface material which is reproducible and as thin as possible to ensure good cooling performance. Furthermore, the electronic boards are not subjected to additional stresses during assembly which could damage the electrical contacts or the tracks. Dynamic stresses caused by vibrations on the boards are also limited. The proposed solution also limits the number of parts to be stored and the number of assembly steps, since the heat sink is already mounted in the enclosure. Therefore, when mounting the box, all that is required is to fix the electronic boards to the heat sink and the cover, and to fix the cover to the enclosure. Furthermore, the proposed solution makes it possible to control the position of the electronic boards relative to the rack.

[0045] The use of elastically deformable arms has the advantage of allowing fluid movement of the heat sink in three directions without risk of clogging and without generating acoustic noise, as opposed to what can be obtained by using prismatic connections (i.e. by using, for example, cascade slides). Furthermore, the elastically deformable arms make it possible to limit the stresses exerted on the electronic board by applying only a slight tension thereon.

[0046] Furthermore, the use of an intermediate component allows for the integration of new functionalities. For example, a fan can be placed on the intermediate component to generate airflow from one end to the other through the spaces between the fins of the heat sink. This configuration allows for greater flexibility in the positioning and orientation of the heat sink relative to the enclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Other features, details, and advantages will become apparent from reading the following detailed description and from examining the accompanying drawings, in which:

[0048] [ Figure 1 ] shows a cross-sectional view of an electronic package according to one embodiment;

[0049] [ Figure 2 ] shows the Figure 1 A first perspective view of a heat sink connected to a holder of a first embodiment;

[0050] [ Figure 3 ] shows Figure 2 a second perspective view of the heat sink and the retaining member;

[0051] [ Figure 4 ] shows a perspective view of a heat sink connected to a holder according to a second embodiment. DETAILED DESCRIPTION

[0052] The following drawings and descriptions essentially contain elements of distinct characteristics, and therefore, they serve not only to clarify the understanding of the present disclosure but also to contribute to its definition, if necessary.

[0053] Now refer to Figure 1 , which shows an electronic package according to one embodiment. Electronic package 1 includes a frame 2, a cover 3, an electronic board 4, a heat sink 7, and a holder 9. A component 5 to be cooled is mounted on the electronic board 4. A layer of thermal interface material 6 (e.g., thermal paste, grease, or a thermal pad) is placed between the lower surface of heat sink 7 and the upper surface of component 5 to ensure thermal contact between heat sink 7 and component 5 and allow heat generated by component 5 to dissipate toward heat sink 7.

[0054] The cover 3 is configured to be fixed to the frame 2 and the electronic board 4 in order to retain the electronic board 4 in the electronic package 1. Therefore, the cover 3 includes two recesses 31, each for receiving a screw 81, making it possible to fix the electronic board 4 and the cover 3 to the frame 2. It should be noted that both the frame 2 and the cover 3 are rigid in order to ensure good integrity of the component 5 and the electronic board 4. The frame 2 and the cover 3 are made of sheet metal, for example.

[0055] The shelf 2 comprises a heat sink 7 intended to cool the component 5. Unlike the prior art described in the introduction, the heat sink 7 is fixed to the shelf 2 by means of a retainer 9. The retainer 9 is fixed integrally inside the shelf by, for example, screwing, crimping, riveting or welding, so as to ensure good rigidity of the shelf / retainer assembly. Furthermore, the retainer 9 is elastically connected to the heat sink 7 to allow translational movement of the heat sink 7 relative to the shelf 2 in three orthogonal directions. This reduces the stresses to which the board is subjected, in particular during assembly, and thus reduces the breaking of printed tracks or electrical contacts. It also limits the dynamic stresses when the electronic package is subjected to strong vibrations, for example when a vehicle passes over a pothole, and thus limits the cyclic fatigue to which the electronic board is subjected. By way of example, it is possible to provide a few millimetres of translational movement of the heat sink relative to the shelf in three orthogonal directions, for example 2 mm. This improves the management of tolerances, in particular when it is wished to place several electronic boards side by side and to connect them directly to one another by means of connectors fixed to each board.

[0056] Advantageously, the retainer 9 is connected to the heat sink 7 by means of at least three elastically deformable arms 91 (only two of which are visible here), which are configured to allow translational movement of the heat sink 7 in three orthogonal directions. In the embodiment described here, two elastically deformable arms 91 are connected to two opposite faces of the retainer 9. In a variant embodiment, an opposite face is connected to a single elastically deformable arm.

[0057] The heat sink 7 is configured to be fixed on the electronic board 4 while maintaining a predetermined distance between the lower face of the heat sink 7 and the component 5, so as to guarantee the reproducibility of the cooling and thus its performance. To this end, the heat sink 7 comprises three threaded sleeves 71 and two centring pins 72, more particularly visible in Figure 3 . The centring pins 72 make it possible to centre the heat sink 7 on the electronic board 4 on either side of the component 5. It will be noted that the cover 3 has three recesses 32 (only two of which are visible here), which are intended to allow the fixing screws 82 to be mounted on the electronic board 4 and on the threaded sleeves 71.

[0058] It should be noted that one of the recesses 32 is configured to fix the cover 3 to the heat sink 7 by means of an additional fixing point, so as to limit the stresses applied to the electronic board when it is fixed at a predetermined distance from the heat sink by means of the threaded sleeves.

[0059] Figure 2 and 3 The configuration of the retainer 9 and the heat sink 7 is shown more precisely according to two different perspective views.

[0060] Reference is made to Figure 2The heat sink 7 includes a base 74 and cooling fins 75. The base 74 includes a bottom wall and two side walls. The cooling fins 75 are arranged on the bottom wall and oriented parallel to the side walls. The heat sink also includes the aforementioned threaded sleeve 71 and centering pin 72 on one side of the bottom wall, as well as a boss for holding / maintaining the thermal interface material layer 6.

[0061] The holder 9 described here is made of synthetic material and comprises reinforcements 93 on its two opposite walls 94. In a variant embodiment, when the holder 9 is rigid, it does not comprise any reinforcements.

[0062] Each elastically deformable arm 91 is made of, for example, a synthetic material and is configured to be deformable in three orthogonal directions so as to allow the heat sink to translate a predetermined distance, for example 2 mm in a plane parallel to the bottom wall of the base and 2 mm in a direction perpendicular to the plane.

[0063] Each elastically deformable arm 91 is connected by one end thereof to the wall 94 of the holder 9 and by the other end to the side wall of the base 74. Between these two ends, each elastically deformable arm 91 is folded and includes several inflection points. These inflection points make it possible to reduce the rigidity of the arm at local points and, in the case of some of these inflection points, in directions contained in different planes, thereby allowing translational movement of the heat sink relative to the holder and, therefore, relative to the frame, in three orthogonal directions.

[0064] In the example described here, each elastically deformable arm 91 extends substantially in one plane and comprises several points of inflection making it possible to reduce the rigidity and allow translational movement of the radiator 7 in this plane. Furthermore, each arm 91 comprises a portion perpendicular to the plane of the arm, which portion defines a right angle with the rest of the arm, thus allowing translational movement of the radiator perpendicular to the plane of the arm.

[0065] Advantageously, each end 92 of the elastically deformable arm 91 is connected to the radiator 7 by a pivot joint to facilitate the movement of the radiator caused by the deformation of the arm. In the example described here, each end 92 of the elastically deformable arm comprises an eyelet for receiving a bolt 73. Advantageously, the bolt 73 is oriented perpendicular to the plane of the arm.

[0066] It will be noted that the use of elastically deformable arms offers certain advantages over the use of prismatic connectors. In particular, it allows the noise generated to be limited, allows the fluid to flow without risk of clogging, and allows a slight tension to be applied to the electronic board, which compensates for the force applied by screwing the electronic board onto the threaded sleeve.

[0067] It will be noted that the presence of the holder 9 makes it easier to integrate certain functions within the electronic package. For example, in addition to two walls 94 opposite each other to which the elastically deformable arms 91 are connected, the holder 9 may comprise a vertical wall 95 suitable for housing the fan 10. It will be noted that the wall 95 is perpendicular to the plane defined by the cooling fins 75 so as to optimize the circulation of the air flow through the heat sink, as shown in FIG. Figure 4 The presence of the retainer 9 makes it possible to relax the constraints on the positioning of the radiator (and more specifically the orientation of the cooling fins relative to the rack). In fact, without the retainer, the position and orientation of the radiator are limited by the position of the fan on the chassis.

[0068] Advantageously, the electronic package 1 is mounted as follows:

[0069] a. Provided are a frame 2 and a cover 3 comprising a heat sink 7 and fixing screws 81 and 82,

[0070] b. providing an electronic board 4 comprising a component 5 to be cooled and adapted to be mounted on the cover,

[0071] c. The rack 2 comprising the heat sink 7 is placed in a holding device suitable for mounting the electronic package,

[0072] d. a layer of thermal interface material 6 is applied to the face of the heat sink 7 intended to be in thermal contact with the component 5 to be cooled, or to the face of the component 5 intended to be in thermal contact with the heat sink, depending on the orientation of the rack in the holding device,

[0073] e. One side of the electronic board 4 is placed in contact with the frame 2,

[0074] f. The cover 3 is placed in contact with the electronic board 4,

[0075] g. The electronic board 4 is fixed on the frame 2,

[0076] h. Cover 3 is fixed on frame 2,

[0077] i. The surface of the heat sink 7 is fixed to the electronic board 4 so as to maintain a predetermined distance between the surface of the heat sink 7 and the component 5, and

[0078] j. The face of the heat sink 7 is fixed to the cover 3 at fixing points.

[0079] These different steps can be performed in the order described here, or for some cases, can be performed in a different order.Similarly, these steps can be performed sequentially, or for some cases, can be performed simultaneously.

[0080] In the embodiment described here, the rack 2 containing the heat sink 7 is preferably placed in the holding device so that the face of the heat sink 7 intended for thermal contact with the component 5 is oriented upward. In this case, the layer of thermal interface material 6 is deposited on the face of the heat sink intended for thermal contact with the component 5 to be cooled. Furthermore, step g of fixing the electronic board 4 to the rack 2 and step h of fixing the cover 3 to the rack 2 are performed simultaneously by introducing and tightening each fixing screw 81 into a corresponding recess 31. Similarly, step i of fixing the face of the heat sink 7 to the electronic board 4 and step j of fixing said face of the heat sink 7 to the cover 3 at the fixing point are performed simultaneously by fixing the fixing screw 82 in the recess 32.

[0081] This reduces the number of steps to be performed when mounting the electronic package. Furthermore, by performing steps g and h before performing steps i and j, the stress applied to the electronic board is limited because the electronic board 4 is secured to the rigid frame 2 and the rigid cover 3 before the heat sink 7 is secured to the electronic board 4.

[0082] Furthermore, when the electronic board has appropriate holes, the board's position can be centered relative to the frame. This reduces the tolerances applied to the frame for connector positioning, which limits the intrusion of solid and liquid foreign matter into the electronic package. Furthermore, because the electronic board's position is defined relative to the frame, several electronic boards can be easily connected directly together using connectors attached to each board.

[0083] It should also be noted that because the heat sink is mounted on a rack, the number of parts to be stored is reduced, and therefore the costs associated with the storage and assembly of the electronic packages are reduced.

[0084] The present disclosure is not limited to the examples of electronic packages described above, but encompasses all variants that a person skilled in the art may consider within the framework of the protection sought.

Claims

1. A set of electronic packaging components intended to be mounted on an electronic board (4) comprising a component (5) to be cooled, wherein: -The group of electronic packaging components includes: a rigid frame (2) containing a radiator (7) intended to cool the component (5), said radiator (7) being fixed inside said frame (2), a rigid cover (3) configured to be fixed to the frame (2) and to the electronic board (4) so ​​as to retain the electronic board (4) in the electronic package (1), - the heat sink (7) is configured to be fixed to the electronic board (4) while maintaining a predetermined distance between the face of the heat sink (7) intended to be in thermal contact with the component (5) to be cooled and the component (5), and - the cover (3) is configured to be fixed to the radiator (7) via fixing points, Characterized in that the radiator (7) is fixed by a retaining member (9) integral with the interior of the frame (2), and the retaining member (9) is elastically connected to the radiator (7) to allow the radiator (7) to move in translation in three orthogonal directions relative to the frame (2).

2. A set of electronic packaging components according to claim 1, wherein the retaining member (9) is connected to the heat sink (7) by at least three elastically deformable arms (91), and the elastically deformable arms (91) are configured to allow translational movement of the heat sink (7) in three orthogonal directions.

3. A set of electronic packaging components according to claim 2, wherein each elastically deformable arm (91) extends substantially in a plane, and wherein one end (92) of each arm (91) is connected to the heat sink (7) by a pivot joint perpendicular to the plane.

4. A set of electronic packaging components according to any one of claims 1 to 3, wherein: - the heat sink (7) comprises a plurality of cooling fins (75) parallel to the reference plane, and - the holder (9) comprises two mutually opposite walls (94) extending parallel to a reference plane and a wall (95) perpendicular to the reference plane, the two mutually opposite walls (94) being elastically connected to the radiator (7), and the wall (95) perpendicular to the reference plane being suitable for accommodating a fan (10).

5. An electronic package comprising: - a set of electronic packaging components according to any one of claims 1 to 4, and - an electronic board (4) on which the components to be cooled (5) are mounted, in - the electronic board (4) is fixed on the inner surface of the cover (3), and the cover (3) is fixed on the frame (2), - the face of the heat sink (7) intended to be in thermal contact with the component (5) to be cooled is fixed to the electronic board (4) so ​​as to maintain a predetermined distance between the face of the heat sink (7) and the component (5), the face of the heat sink (7) also being fixed to the cover (3) at a fixing point, and - A layer of thermal interface material (6) is placed between said face of said heat sink (7) and the component (5).

6. A method for mounting an electronic package, the method comprising the steps of: a. providing a group of electronic packaging components according to any one of claims 1 to 4, b. providing an electronic board (4) comprising a component to be cooled (5), c. placing the rack (2) in a holding device suitable for assembling an electronic package, d. applying a thermal interface material layer (6) on one side of the heat sink (7) or one side of the component (5), e. placing one side of the electronic board (4) in contact with the frame (2), f. placing the cover (3) in contact with the electronic board (4), g. fixing the electronic board (4) on the frame (2), h. fixing the cover (3) on the frame (2), i. fixing the face of the heat sink (7) on the electronic board (4) so ​​as to maintain a predetermined distance between the face of the heat sink (7) and the component (5), and j. Fixing the face of the heat sink (7) to the cover (3) at the fixing points.

7. The method of mounting an electronic package according to claim 6, wherein steps g and h are performed simultaneously, and then steps i and j are performed simultaneously.

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