Electronic device and cooling device for said electronic device

Abstract

Title: Electronic Device and Cooling Device for this Electronic Device The present invention relates to an electronic device comprising a housing (4), one or more electronic components housed in said housing (4), the housing (4) comprising a cooling channel configured to permit heat exchange between a coolant and at least one electronic component via a wall of the housing (5) which has an external face (12) contributing to delimiting said cooling channel and an internal face (7) against which at least one component is disposed, the cooling channel (8) being delimited by the external face (12) of the housing (4) and a closing wall (6), the cooling channel comprising pins (10) which are formed to extend through the circulation of the coolant,the pins (10) being made entirely with the external face (12) of said wall of the housing (5) towards the interior of the cooling channel, the part of the cooling circuit comprising at least one means for reducing cross-section. (figure 5),

Description

Title of the invention: Electronic device and cooling device for this electronic device

[0001] The present invention relates to the field of electronic devices such as charge conversion systems for electric vehicles.

[0002] Charge conversion systems for electric vehicles include various electronic components such as power modules, coils, or capacitors, without this list being exhaustive. These electronic components generate heat during the operation of the charge conversion system.

[0003] Nowadays, electric vehicles use increasingly higher power levels to increase their performance and range. This is accompanied by increasingly significant heat production during the operation of the charging conversion systems and necessitates finding solutions to reduce thermal stress on electronic components.

[0004] In this context, electric vehicles include a cooling circuit capable of recovering heat from the vehicle's charging system. More specifically, the cooling circuit includes a section passing through a housing in which the electronic components are housed. The housing is made, for example, molded, so that raised features form a cavity defining a cooling channel within the housing. This channel is covered and sealed by a closure wall fixed to an external face of the housing so that a coolant circulates along the housing.

[0005] The channel includes a heat exchange portion defined at the point where a portion of the housing wall defining the channel is in contact, on one side of that wall opposite the channel, with at least one electronic component. Heat exchange between the electronic component and the coolant occurs through the housing wall in this heat exchange portion.

[0006] The casing includes pins extending from the wall in this exchange portion, these pins being evenly spaced from each other and increasing the contact area of ​​the coolant with the casing material. The rods extend from the outer face such that their free ends are oriented towards one side of the closing wall. It is known to position the pins as high as possible so that their free ends are close to the closing wall without touching it, which prevents the closing wall from being properly attached to the housing. Ensuring a minimum spacing between the free ends of the pins and the The closing wall reduces the amount of fluid passing through the channel without coming into contact with the pins.

[0007] The pins are molded with the housing during injection molding. The sealing wall covering the cavity seals the cooling circuit by being attached to the housing by friction welding. The sealing wall can also be screwed in place.

[0008] This cooling solution is simple to implement but can be improved insofar as the inventors have observed that the cooling of the electronic elements may not be sufficient and may lead to overheating of the electronic elements if the operating power of the electronic system is increased.

[0009] The present invention falls within this context and aims to provide a cooling circuit allowing for more efficient heat exchange.

[0010] The present invention proposes an electronic device comprising a housing, at least one electronic component housed in said housing, the housing comprising a cooling channel configured to allow heat exchange between a coolant and the at least one electronic component via a wall of the housing which has an external face contributing to delimiting said cooling channel and an internal face against which the at least one electronic component is disposed, the cooling channel being delimited by the external face of the housing and a closing wall which is fixed to the housing to seal said cooling channel, the cooling channel comprising at least one exchange portion inside which are formed pins to traverse the flow of the coolant and improve the heat exchange between the coolant and the at least one electronic component,the pins being made in one piece with the outer face of said housing wall towards the inside of the cooling channel, the part of the cooling circuit comprising at least one means of reducing the cross-section in the exchange part being configured to locally form areas with reduced cross-section allowing to increase the velocity of the coolant intended to be in contact with the pins.

[0011] The electronic device may, for example, be a charge conversion system capable of equipping an electric motor vehicle. Such a charge conversion system functions to transform alternating current supplied by a home charging station into direct current usable by the electrical components of the electric vehicle, and in particular the propulsion components of the electric vehicle. The electronic device is characterized here by the presence of a cooling channel configured to cool an electronic component.

[0012] The cooling channel may, for example, be part of a cooling circuit configured to exchange heat with the various heating elements of the vehicle. The cooling circuit is configured to include a heat exchanger outside the electronic device in which the coolant transfers the heat recovered inside the electronic device to an external element.

[0013] The cooling channel is formed by the combination of a cavity formed by the relief of the housing intended to house the electronic components and a closing wall configured to seal the channel by being fixed to the housing. The cooling channel includes a heat exchange portion, which is an area of ​​the housing in which studs are provided to allow the flow of the coolant to pass through and to increase the surface area for heat exchange between the coolant and the housing material, and in which, according to the invention, at least one cross-section reduction means is provided to allow the fluid velocity to be increased in the vicinity of the studs.

[0014] By increasing the speed of the coolant, the portion of the coolant heated by the calories recovered from the electronic components, through the wall of the housing in contact with said electronic components, is more rapidly transferred to the outside of the housing.

[0015] It should be understood that in this invention, the means for reducing the cross-section are different from the pins whose function is to extend the heat exchange surface. Of course, the pins pass through the coolant flow in the exchange section and reduce the cross-section of the cooling channel for the passage of the coolant, but one object of the invention is to provide additional means specifically or primarily dedicated to the function of reducing the cross-section.

[0016] The pins are molded with the housing and extend from one face of a housing wall opposite the face against which the electronic components are arranged towards the inside of the cooling channel. The pins may be of similar shape, these pins being positioned so that each pin is equidistant from the pins surrounding it. The pins may also be positioned in a staggered pattern, so that the oblique lines they help to form have pins arranged at regular intervals, forming guide lines for the coolant.

[0017] According to an optional feature of the invention, the cooling channel comprises a liquid inlet, a liquid outlet, at least one exchange portion provided with said pins, and a guide portion which is interposed between the liquid inlet and at least one exchange portion, the closing wall being configured to cover at least the exchange portion and the guiding portion.

[0018] As mentioned, the housing and its cooling channel are part of a cooling circuit specific to the entire electric vehicle and the inlet and outlet of the liquid are arranged in the housing to allow the connection of the cooling channel with the rest of the cooling circuit.

[0019] The guide portion included in the cooling channel makes the flow of coolant linear before guiding it into the exchange portion.

[0020] The exchange part is the part in which the heat produced by the electronic components is transferred to the coolant by passing through the wall of the housing against which the electronic components are arranged.

[0021] According to an optional feature of the invention, at least one means of reducing the cross-section includes a deformation of the closing wall towards the inside of the cooling channel in the exchange part.

[0022] The deformation is arranged on the closing wall in such a way that the distance between the outer face of the envelope from which the pins emerge and the closing wall is smaller at the level of this deformation than at the level of the rest of the closing wall.

[0023] The deformation can, for example, be achieved by stamping using a die in the shape of the desired deformation. The deformation is made on the closing wall so that the deformation at least partially overlaps the heat exchange portion of the channel and faces at least some of the pins of said heat exchange portion. Since the deformation is oriented towards the inside of the channel, it reduces the cross-sectional area through which the coolant flows in the cooling circuit. With the cross-sectional area reduced, the velocity of the coolant increases in the cooling circuit.

[0024] According to an optional feature of the invention, the deformation forms a bowl whose bottom wall is equidistant from each free end of a plurality of pins present in the exchange portion. The free end of each pin is the end opposite the outer face of the housing from which the pins extend.

[0025] According to an optional feature of the invention, the pins have different heights depending on their positioning relative to the bowl. Indeed, the space between the pins and the closing wall must be equivalent throughout the exchange portion and must be minimal to reduce the amount of coolant that passes through the channel without coming into contact with the pins.

[0026] According to an optional feature of the invention, at least one cross-section reduction means is formed on the closing wall and comprises pins additional protruding from the face of the closing wall that faces the cooling channel in the exchange part.

[0027] The additional pins can be made in one part with the closing wall by continuity of material.

[0028] According to an optional feature of the invention, the additional pins each extend between the pins present in the exchange part.

[0029] The additional pins of the closing wall are similar to the pins included in the channel. The additional pins of the wall are arranged such that when the closing wall is in position in the receiving area, the pins and the additional pins have a similar spacing with respect to each other without being in contact with each other.

[0030] According to an optional feature of the invention, said additional pins extend from the deformation of the closing wall, both the additional pins and the means for reducing the section forming the deformation.

[0031] According to an optional feature of the invention, at least one means for reducing the cross-section comprises at least one rib extending from said outer face between two pins.

[0032] The rib between the pins is configured to achieve a reduction in cross-section and to direct the flow of coolant into the channel, while increasing the contact area between the exchange part and the coolant.

[0033] According to an optional feature of the invention, the rib has a height less than the height of the pins, the height being measured in a direction perpendicular to said external face.

[0034] According to an optional feature of the invention, at least one group of ribs is configured to form parallel lines of ribs forming a fluid circulation channel along the outer face.

[0035] The arrangement of the ribs allows the flow to be directed into areas of the channel where the circulation of the coolant is restricted without the diffuser.

[0036] Other features and advantages of the invention will become apparent later from the following description on the one hand, and from several illustrative and non-limiting examples given by reference to the accompanying schematic drawings on the other hand, in which:

[0037] Fig. 1 is a schematic representation of an electronic device according to the invention, seen from below, which makes visible a closing wall of a cooling channel;

[0038] Fig. 2 is a schematic representation of a first embodiment of the cooling channel, the closing wall having been removed here to make the pins present in the channel visible;

[0039] Fig. 3 is a schematic representation of a first embodiment of the closing wall;

[0040] Fig. 4 is a schematic representation of a second embodiment of the closing wall;

[0041] Fig. 5 is a cross-sectional view of a combination of the first embodiment of the cooling channel and the second embodiment of the closing wall;

[0042] The [Fig.6] is a schematic representation of a third embodiment of the closing wall;

[0043] Fig. 7 is a schematic representation of a second embodiment of the cooling channel, the closing wall having also been removed to make visible the pins present in said channel.

[0044] Figure 1 is a schematic representation of the electronic device according to the invention, presented here by way of non-limiting example in the form of a charge conversion system 2 intended for use in an electric vehicle. The charge conversion system 2 comprises a housing 4 having compartments for at least one electronic component such as a coil, a capacitor, or a power module, not shown here. The compartments are arranged on an inner face 7 visible in Figure 5 of a wall of the housing 5, here the lower wall 5 visible in Figures 2, 5, and 7.

[0045] The electronic device is equipped with a cooling system for the electronic components, with a cooling channel 8 extending along the housing 4. More specifically, the cooling channel 8 extends along an outer face 12 of the bottom wall 5, this outer face 12 being opposite the inner face 7 against which the electronic components are in contact. The bottom wall 5 forms a heat exchange wall through which the heat produced by the electronic components passes from the inner face 7 to the outer face 12 to be absorbed by a coolant circulating in the cooling channel 8 along the bottom wall 5.

[0046] The cooling channel 8 is delimited by a liquid inlet 16 and a liquid outlet 18 between which the cooling fluid, such as oil or glycol water, circulates. The recovered heat is removed from the electronic device through the liquid outlet. Thus, the cooling channel 8 cools the electronic components to limit their temperature rise.

[0047] The cooling channel 8 represents a portion of a cooling circuit that is part of a cooling circuit for the entire vehicle, not shown in the figures. The coolant is heated in the housing 4 as described above and then leaves the housing to exchange heat with a radiator on board the vehicle to cool down before returning through the cooling channel 8.

[0048] The casing 4 is formed, for example by injection molding, with reliefs forming at least one cavity 22 on the side of the outer face 12 of the casing wall 5. This cavity 22, visible in Figures 2, 5, and 7, defines the cooling channel 8 described in more detail later in the specification. The reliefs on the outer face 12 are formed to create a periphery 20 surrounding the cavity 22 and defining a receiving area 24 for a closing wall 6, said closing wall participating in the delimitation of the cooling channel 8 with the outer face 12 of the bottom wall by being integral with it.

[0049] The closing wall 6 is fixed to the housing 4. The closing wall 6 has a thickness substantially equal to the corresponding dimension of the receiving area 24 such that when the housing 4 and the closing wall 6 are fixed to each other, the outer face of the closing wall 6 and the outer face of the bottom wall of the housing 4 are substantially in the same plane, thus achieving the flatness necessary for friction stir welding. The closing wall 6 has a shape substantially similar to the shape of the cavity 22 of the cooling channel 8 in the housing 4.

[0050] Friction stir welding provides a better seal than traditional welding. Furthermore, friction stir welding may require post-weld treatment. The sealing wall can also be screwed in place and fitted with a sealing gasket.

[0051] The cooling channel 8 also includes a guide part 26 and at least one exchange part 14, visible in [Fig.1] by dotted lines because they are covered by the closing wall 6.

[0052] As will be detailed, the exchange part 14 includes pins which are arranged across the flow of coolant and it includes according to the invention at least one means for reducing cross-section, here formed by a bowl.

[0053] Different embodiments of the structure of the cooling channel 8 will be described later, as well as different embodiments of the closing wall 6 with reference to figures 2 to 7, detailing the shape of the cavity 22 in the envelope 4, the shape of the closing wall 6 and detailing the means of reducing the cross-section carried by at least one wall delimiting the cooling channel in the exchange part 14.

[0054] Fig. 2 is a schematic representation of a first embodiment of the cooling channel 8.

[0055] The liquid inlet 16 and the liquid outlet 18 of the cooling channel 8 are connected to the rest of the cooling circuit not shown here so that the temperature of the coolant at the liquid inlet 16 is lower than the temperature of the coolant at the liquid outlet 18, the temperature of the coolant at the inlet 16 of the cooling channel 8 being lower than the overall temperature in the exchange part 14.

[0056] With the closing wall removed in [Fig. 2], the cavity 22 formed in the outer face 12 of the wall of the housing 4 is visible. The cavity 22 is configured to continuously form the exchange portion 14 and the guiding portion 26. The absence of the closing wall 6 also makes visible the previously mentioned periphery 20, surrounding the cavity 22, and the receiving area 24 formed by this periphery 20.

[0057] The exchange part 14 is distinguished from the guide part 26 by the height of the cavity in the two parts, the exchange part 14 having a height greater than that of the guide part 26.

[0058] In addition, the exchange part 14 is defined by the presence of pins 10 through the cooling channel 8 in order to improve in a specific area the heat exchange between the coolant and the wall delimiting the cooling channel.

[0059] Each pin 10 protrudes from the outer face 12 of the housing wall, in the exchange part 14 of the cooling channel 8, extending from the outer face 12 to a free end 11, at a distance dl from the closing wall 6, as can be seen in [Fig.5].

[0060] The pins 10 are arranged in successive rows where each pin is equidistant from the adjacent pins, and each row is equidistant from the adjacent rows. The arrangement of the pins 10 is shown here by way of non-limiting example, but it should be noted that such an arrangement is defined in such a way that the pins 10 are sufficient to increase the exchange surface area while being sufficiently spaced from each other so that the coolant can flow between them with a maximum surface area for each pin 10 and without excessive pressure loss.

[0061] The guide portion 26 is a portion of the cooling channel in which the coolant is directed from the liquid inlet 16 to the heat exchange portion 14. The guide portion 26 includes two guides 28 for directing the flow of the coolant. The two guides 28 are parallel to the edges of the cooling channel 8 in the guide portion 26 in order to make the flow laminar. the flow of coolant entering the exchange portion 14 of the cooling channel 8.

[0062] Figure 3 is a schematic representation of a first embodiment of the closing wall 6. In the first embodiment, the closing wall 6 includes a deformation 30 extending inward into the cooling channel 8. The deformation 30 of the closing wall 6 covers at least part of the heat exchange portion 14 of the cooling channel 8 when the closing wall 6 is attached to the casing 4. The deformation 30 constitutes the means of reducing the cross-section in this first embodiment. This feature makes it possible to increase the velocity of the coolant as it passes through the cooling channel 8.Increasing the speed in the cooling channel 8 allows for better heat exchange between the pins 10 and the coolant, since the coolant heated by the recovered heat is discharged more quickly towards the liquid outlet 18 of the cooling channel 8.

[0063] The deformation 30 of the closing wall 6 forms a basin extending into the interior of the cooling channel 8. In other words, the closing wall 6 has a second side 62, visible on [Fig.3] and opposite to the first side 61 mentioned previously, and the deformation 30 forms a hollow relief on the first side 61 and a convex relief on the second side 62.

[0064] When the first embodiment of the closing wall 6 is placed on the first embodiment of the casing 4, the pins 10 extending from the outer face 12 through the cavity 22 of the cooling channel 8 can be classified into two distinct sets, since the deformation 30 does not cover all the pins. A first set of pins comprises the pins 10 whose free end 11 faces the bowl of the deformation 30, and a second set of pins comprises the pins 10 that are arranged at the periphery of the first set of pins and are not covered by the deformation. Consequently, the pins of the first set of pins have a height less than the height of the pins of the second set, the height of each pin 10 being measured along a direction perpendicular to the closing wall 6 when it is fixed to the casing 4.

[0065] Fig. 4 is a schematic representation of a second embodiment of the closing wall 6 in which the closing wall 6 of the cooling channel 8 includes additional pins 32 arranged uniformly on the part of the closing wall 6 which covers the exchange part 14 when the closing wall 6 is fixed to the casing 4.

[0066] The additional pins 32 are arranged on the second side 62 of the closing wall 6 facing the cooling channel 8 when said wall The closure wall 6 covers the cavity 22 of said cooling channel 8. In addition, the additional pins 32 are arranged on the second side 62 of the closure wall 6 so as not to come into contact with the pins 10 present in the cooling channel 8, when the closure wall 6 is fixed to the casing 4, as can be seen in [Fig.5].

[0067] Thus, the additional pins 32 limit the area where the coolant can pass between the pins 10, thereby drastically increasing the efficiency of the heat exchange between the coolant circulating in the exchange section 14 and the pins, while simultaneously reducing the cross-sectional area of ​​the coolant flow to increase its velocity. The additional pins 32 constitute the means of reducing the cross-sectional area.

[0068] The additional pins 32 of the closing wall 6 have a shape similar to that of the pins 10. The height of the additional pins 32 is less than that of the pins 10, in order to ensure that the free end 33 of these additional pins does not come into contact with the bottom of the cavity when the closing wall 6 is attached to the housing 4 and prevent the proper closure of the closing wall. The height of the additional pins 32 is measured in a direction perpendicular to the closing wall, so that the additional pins 32 are substantially parallel to the pins 10 when the closing wall 6 is attached to the housing 4.

[0069] Figure 5 is a cross-sectional view of a detail of the electronic device formed by a closing wall 6 according to the second embodiment and a housing 4 according to the first embodiment. The cross-sectional view of Figure 5 is perpendicular to the direction of flow of the coolant in the heat exchange portion 14.

[0070] As mentioned previously, the spacing between the pins 10 and the additional pins 32 can be seen in [Fig. 5] when the closing wall 6 is placed on the housing 4. Thus, the pins 10 and the additional pins 32 do not come into contact with each other. Channels are formed between the pins 10 and the additional pins 32.

[0071] The difference between the height of the pins and the height of the additional pins implies that the distance dl between the free end 11 of the pins 10 and the second side 62 of the closing wall 6 is less than the distance d2 between the free end 33 of the additional pins 32 and the bottom of the cavity 22.

[0072] As mentioned, the closing wall 6 has a thickness tl substantially equal to the height of the receiving area 24. The thickness of the closing wall 6 and the height of the receiving area 24 are defined along an axis perpendicular to the first side 61 and / or the second side 62 of the closing wall 6.

[0073] As mentioned, [Fig. 5] shows the inner face 7 on which the electronic components are arranged, said electronic components not being illustrated here. The inner face 7 has a flat portion, but this is not limiting for the purposes of the invention.

[0074] Fig. 6 is a schematic representation of a third embodiment of the closing wall 6. The third embodiment of the closing wall is a combination of the first and second embodiments of the closing wall 6 described previously, so that the closing wall 6 comprises two types of means for reducing the cross-section, namely the additional pins 32 and the deformation 30.

[0075] In this third embodiment, the additional pins 32 extend from the second side 62 of the closing wall 6 into a region limited to the basin formed by the deformation 30. It should be understood that some additional pins can be arranged from the closing wall outside this region with a difference in height of the additional pins depending on their location on or next to the deformation, so that their free ends are equidistant from the bottom of the cavity when the closing wall is fixed to the casing.

[0076] Consequently, due to the deformation when the closing wall 6 is fixed to the housing 4, the pins of the exchange part 14 have, as in the second embodiment, two different pin heights 10 to maintain the same space between the upper part of the pins 10 and the closing wall 6.

[0077] The use of the deformation 30 and the additional pins 32 increases the reduction of the coolant passage cross-section in the exchange part 14, which makes it possible to increase the speed of the coolant passing through the cooling channel 8.

[0078] Fig. 7 is a schematic representation of a second embodiment of the housing 4 in which the cooling channel 8 includes ribs 34 extending from the outer face 12 between the pins 10. The ribs 34 are produced by continuity of material with the housing 4 and therefore extend from the outer face 12 in the cavity 22 of the cooling channel 8 towards the interior of said cooling channel 8.

[0079] The height of the ribs is substantially less than the height of the pins, these heights being measured perpendicular to the external face 12 in the exchange part 14. By way of non-limiting example, the height of the ribs can be on the order of 20% of the height of the pins.

[0080] The ribs 34 form a means of reducing the cross-section in the cooling channel 8; this feature increases the velocity of the coolant as it passes through the cooling channel 8. The increase The speed in the cooling channel 8 allows for better heat exchange between the pins 10 and the coolant.

[0081] The ribs 34 also allow the flow of coolant to be directed into the exchange part 14 in order to distribute the coolant as best as possible in the cooling channel 8. The ribs 34 form oblique rows which direct the fluid towards the lateral edges of the cooling channel 8. The efficiency of the heat exchange in the cooling channel 8 is then more uniform.

[0082] Finally, the ribs 34 also allow the contact area between the external face 12 of the cavity 22 and the coolant to be increased.

[0083] It can be observed that not all pins are connected to an adjacent pin by a rib 34. More specifically, the pins located near the liquid outlet 18 are not connected by ribs in order to prevent the coolant from flowing in a direction other than that of the outlet and because there is no electronic component located on the inner face 7 of the housing near this liquid outlet 18.

[0084] Of course, the invention is not limited to the examples just described and many adaptations can be made to these examples without going out of the scope of the invention.

[0085] The invention, as described above, achieves its intended purpose and provides a load conversion system. Variations not described here could be implemented without departing from the scope of the invention, since, according to the invention, they include a coolant passage section optimized to increase the coolant velocity according to the invention.

Claims

Demands

1. Electronic device comprising a housing (4), at least one electronic component housed in said housing (4), the housing (4) comprising a cooling channel (8) configured to permit heat exchange between a coolant and the at least one electronic component via a wall of the housing (5) which has an external face (12) contributing to delimiting said cooling channel (8) and an internal face (7) against which the at least one electronic component is disposed, the cooling channel (8) being delimited by the external face (12) of the housing (4) and a closing wall (6) which is fixed to the housing (4) to seal said cooling channel (8),the cooling channel (8) comprising at least one heat exchange portion (14) within which pins (10) are formed to extend through the coolant circulation and improve heat exchange between the coolant and at least one electronic component, the pins (10) being made integrally with the external face (12) of said housing wall (5) facing the interior of the cooling channel (8), the portion of the cooling circuit comprising at least one cross-section reduction means in the heat exchange portion (14) being configured to locally form areas with reduced cross-section allowing to increase the velocity of the coolant intended to be in contact with the pins (10).

2. Electronic device according to the preceding claim in which the cooling channel (8) comprises a liquid inlet (16), a liquid outlet (18), at least one exchange portion (14) provided with said lugs (10), and a guide portion (28) which is interposed between the liquid inlet (16) and at least one exchange portion (14), the closing wall (6) being configured to cover at least the exchange portion (14) and the guide portion (28).

3. Electronic device according to any one of the preceding claims wherein said at least one section reduction means comprises a deformation (30) of the closing wall (6) towards the interior of the cooling channel (8) in the exchange part (14).

4. Electronic device according to the preceding claim, wherein the deformation (30) forms a bowl whose bottom wall is equidistant from each free end of a plurality of pins (10) present in the exchange part (14).

5. Electronic device according to any one of claims 1 to 4 wherein said at least one section reduction means is formed on the closing wall (6) and includes additional pins (32) projecting from the face of the closing wall (6) facing the cooling channel (8) in the exchange portion (14).

6. Electronic device according to the preceding claim, wherein the additional pins (32) each extend between the pins (10) present in the exchange portion (14).

7. Electronic device according to claims 3 or 4 combined with claims 6 or 7, wherein said additional pins (32) extend from the deformation (30) of the closing wall (6), both the additional pins and the means for reducing the deformation formation section.

8. Electronic device according to any one of claims 1 to 7 in which at least one section reduction means comprises at least one rib (34) extending from said outer face (12) between two pins (10).

9. Electronic device according to the preceding claim in which the rib (34) has a height less than the height of the pins (10), the height being measured in a direction perpendicular to said outer face (12).

10. Electronic device according to any one of claims 8 or 9, wherein at least one group of ribs (34) is configured to form parallel lines of ribs (34) forming a fluid circulation conduit along the outer face (12).