Electronic device for optimised cooling of electronic components

Abstract

The invention relates to an electronic device, including: - a printed circuit board (2); - an electronic component (3) assembled on the printed circuit board (2); - a cooling device (4) assembled to the printed circuit board (2), the cooling device (4) comprising a cooling face (40) facing the electronic component (3); - a mounting system comprising: o a positioning device (5) assembled to the cooling device (4), the positioning device being configured to adjust the distance between an upper face (30) of the electronic component (3) and the cooling face (40) of the cooling device (4); and o a locking device (6) assembled to the printed circuit board (2) and to the cooling device (4), the locking device (6) being configured to immobilise the cooling device (4) on the printed circuit board (2).

Description

DESCRIPTION Electronic device allowing optimized cooling of electronic components

[0001] The invention relates to the field of on-board electronics. It relates more specifically to that of on-board electronic devices comprising an electronic card.

[0002] Embedded electronic devices are used in various fields and for various applications (aeronautics, automotive, medical equipment, etc.). These electronic devices must meet certain constraints, including reduced size and increasingly high power. The increase in power at constant volume makes it difficult to cool the electronic components of embedded electronic devices.

[0003] In addition, embedded electronic devices must be able to withstand the constraints of their operating environment. These environmental constraints are related to temperature, random and sinusoidal vibrations, and shocks, and vary in particular depending on the area of use. Environmental constraints can be classified into three types: very mild, intermediate, and severe or very severe. The VITA 20, VITA 48.x, VITA48.8, VITA 46, IEEE 1 101.x, IEEE1386.x, VITA47 standards define these environmental constraints.

[0004] In very mild environments, cooling devices for electronic components of the electronic device may be mounted on a printed circuit board of the electronic device using flexible mountings (spring mounting type).

[0005] This type of flexible mounting is not suitable for harsh or very harsh environments where temperatures can vary between -40°C and +85°C, random vibrations can reach 2000Hz, sinusoidal vibrations can reach 5g, and shocks can reach 40g. It is necessary that the cooling devices are mounted to the desired electronic components. cool using rigid assemblies capable of withstanding these environmental constraints.

[0006] Figure 1 shows an example of a rigid mounting of the prior art. This figure shows in a cross-sectional view an electronic device comprising a printed circuit board (PCB), an electronic component mounted on the printed circuit, and a cooling device configured to cool the electronic component. The electronic device further comprises screws allowing rigid mounting of the cooling device on the electronic component. The screws pass through the printed circuit and are inserted into housings formed in the cooling device. An internal face of the cooling device, called the cooling face, is located opposite the electronic component to be cooled. Due to this mounting, a large space is present between the cooling face and the electronic component. This space is generally filled by a thermal blanket.

[0007] This prior art solution is not satisfactory from a thermal point of view. Indeed, a temperature loss of a few degrees Celsius is observed at the level of the thermal blanket. The cooling of the electronic component is therefore not effective.

[0008] The invention aims to provide an electronic device whose assembly makes it possible to withstand any type of environment and in particular severe or very severe environments, and in which the cooling of the electronic components is effective.

[0009] The invention proposes for this purpose an electronic device comprising: - a printed circuit; - an electronic component assembled on the printed circuit; - a cooling device assembled to the printed circuit, the cooling device comprising a cooling face facing the electronic component; - a mounting system comprising: o a positioning device assembled to the cooling device, the positioning device being configured to adjusting the distance between an upper face of the electronic component and the cooling face of the cooling device; o a device for locking the position of the cooling device and the positioning device; and o a device for fixing the printed circuit and the cooling device, the fixing device being independent of the locking device.

[0010] Thanks to the mounting system, and in particular to the positioning device, the invention makes it possible to improve the thermal contact between the cooling device and the electronic component to be cooled. This makes it possible to efficiently cool electronic components with a high power density.

[0011] The mounting system is advantageously rigid. The invention is therefore of particular interest for use under severe or even very severe environmental constraints, but can be used in all types of environments.

[0012] The independence of the locking of the positioning device from the fixing of the cooling device on the printed circuit allows the disassembly of the printed circuit without modifying the adjustment of the positioning of the cooling device. This allows in particular the disassembly of the printed circuit for repair without altering the adjustment of the positioning of the cooling device in relation to the electronic component. Any intervention on components other than the electronic component for which cooling is ensured is facilitated. For this type of intervention, a step of adjusting the position of the cooling device in relation to the electronic component is thus avoided.

[0013] Particularly convenient preferred features of the electronic device according to the invention are presented below.

[0014] The cooling device may include at least one housing configured to receive the positioning device.

[0015] The housing can be a through hole.

[0016] The positioning device may comprise at least one adjustable column configured to be inserted into said at least one corresponding housing.

[0017] The locking device may comprise an adhesive applied between said at least one adjustable column and said at least one corresponding housing.

[0018] The adjustable column may have a thread configured to cooperate with a tapping made in the housing.

[0019] the locking device may comprise welding or brazing of said at least one adjustable column in said at least one corresponding housing.

[0020] The locking device may comprise a crimping of the adjustable column in said at least one corresponding housing.

[0021] The at least one adjustable column may include a cavity configured to at least partially receive the fastening device.

[0022] The fastening device may include a screw having a threaded shank, the threaded shank extending through the printed circuit board. The cavity of the adjustable column includes a thread complementary to the threaded shank of the screw.

[0023] The cooling device may include several housings. Each housing extends near a periphery of the electronic component. The positioning device then includes as many adjustable columns as there are housings.

[0024] The fixing device can be assembled to the PCB and remote cooling device of the positioning device.

[0025] The cooling device may include at least one cavity configured to at least partially receive the attachment device.

[0026] The electronic device further comprises a thermal connection between the upper face of the electronic component and the cooling face of the cooling device.

[0027] Other features and advantages of the invention will become apparent in the description below with reference to the appended drawings, given as non-limiting examples: - Figure 1 is a sectional view of an electronic device of the prior art; - Figure 2 is a perspective view of an electronic device according to one embodiment of the invention; - figure 3 is an exploded view of figure 2; - figures 4, 5 and 6 represent in section several variants of a part of the electronic device of figure 2; - figures 7 to 10 show steps in assembling the electronic device of figure 4; and - Figure 11 is a sectional view of the electronic device according to another embodiment of the invention.

[0028] Figures 2 to 4 represent an electronic device 1 according to one embodiment of the invention.

[0029] The electronic device 1 comprises a printed circuit board 2 (or PCB).

[0030] The printed circuit 2 comprises at least one fixing hole 20. The printed circuit 2 here comprises several fixing holes 20, in particular four fixing holes 20. The fixing holes 20 are for example through holes. In the example shown, the fixing holes 20 extend in a rectangular arrangement. Of course, the number, shape and / or arrangement (or positioning) of the fixing holes may vary. For example, the printed circuit 2 may comprise three fixing holes 20. The fixing holes 20 may then extend in a triangular arrangement.

[0031] The electronic device 1 also comprises at least one electronic component 3. The electronic component 3 is assembled on the printed circuit 2, for example by soldering.

[0032] The electronic device 1 here comprises several electronic components. The electronic components are assembled on the printed circuit board 2. The printed circuit board 2 serves as a mechanical support for the electronic components and allows them to be electrically connected.

[0033] The invention is particularly concerned with electronic components that generate a lot of heat. The electronic component 3 that heats up, here called hot electronic component 3, is for example a processor (or CPU from the English central processing unit).

[0034] The electronic component 3 is assembled on a surface of the printed circuit 2 extending between the fixing holes 20. The fixing holes 20 thus extend around the electronic component 3. More precisely, each fixing hole 20 extends near a corner of the electronic component 3.

[0035] The electronic device 1 also comprises a cooling device 4 or heat sink. The cooling device 4 is configured to cool the hot electronic component 3. The cooling device 4 is configured to absorb the heat from the electronic component 3 and dissipate it into the ambient air, thus maintaining an optimal operating temperature. As an alternative to the ambient air, the cooling device can drain the heat by any other means: by natural and / or forced convection, by conduction, for example by means of a hydraulic circuit and / or by radiation.

[0036] The cooling device 4 comprises a cooling face 40 (visible in FIG. 4) facing the electronic component 3. The cooling face 40 is facing an upper face 30 of the electronic component 3.

[0037] The cooling device 4 here comprises cooling fins 41. The cooling fins 41 extend vertically. The cooling fins 41 facilitate convection cooling. Of course, the cooling device 4 may have a different structure. In an exemplary embodiment not shown, the cooling device 4 may be a conduction cooling device.

[0038] The cooling device 4 comprises at least one housing 42. The cooling device 4 here comprises the same number of housings 42 as the number of fixing holes 20 of the printed circuit 2. The cooling device 4 here comprises several housings 42, in particular four housings 42. The housings 42 extend in a rectangular arrangement. The housings 42 thus extend around the electronic component 3. More precisely, each housing 42 extends close to a corner of the electronic component 3.

[0039] In the embodiment of Figures 2 to 8, the housings 42 are located opposite the fixing holes 20 once the cooling device 4 is assembled to the printed circuit 2. Of course, the number, shape and / or arrangement (or positioning) of the housings may vary. For example, the device cooling 4 may comprise three housings 42. The housings 42 may then extend in a triangular arrangement.

[0040] The housings 42 may be holes, typically through or blind holes. The housings 42 have, for example, a cylindrical shape.

[0041] The electronic device 1 further comprises a mounting system. The mounting system comprises a positioning device 5 and a fixing device 6. The mounting system is rigid. In particular, the positioning device 5 and the fixing device 6 are rigid.

[0042] The positioning device 5 is assembled to the cooling device 4.

[0043] The positioning device 5 is configured to position the cooling device 4 relative to the electronic component 3. The positioning device 5 is configured to adjust the distance between the upper face 30 of the electronic component 3 and the cooling face 40 of the cooling device 4. The positioning device 5 makes it possible to reduce as much as possible the space between the upper face 30 of the electronic component 3 and the cooling face 40 of the cooling device 4. The positioning device 5 makes it possible to bring the cooling device 4 into contact with the electronic component 3 to be cooled.

[0044] The positioning device 5 comprises adjustable columns 51. The positioning device 5 comprises the same number of adjustable columns 51 as the number of housings 42 of the cooling device 4. The positioning device 5 here comprises four adjustable columns 51. Each adjustable column 51 has a shape complementary or similar to the shape of the housings 42. Each adjustable column 51 has, for example, a cylindrical shape. More generally, the shapes of the columns 51 and the housings 42 are complementary so as to ensure the guidance of the columns 51 in their respective housings. The sections of the columns and the housings may in particular be square, triangular, etc. Each adjustable column 51 extends at least partly into one of the housings 42. The adjustable column 51 extending into the housing 42 may protrude partly from the housing 42 as seen in FIG. 4.

[0045] In the variant shown in Figure 4, each adjustable column 51 has on an external surface a thread 510 cooperating with a tapping of the corresponding housing 42. Thanks to this screw-nut system (threading and tapping), it is possible to adjust the height position of the cooling device 4 relative to the electronic component 3. In other words, the threading system makes it possible to adjust the distance between the upper face 30 of the electronic component 3 and the cooling face 40 of the cooling device 4.

[0046] Figures 5 and 6 show variants where the adjustable columns 51 and the housings 42 are smooth.

[0047] The adjustable columns 51 make it possible to conform to the deformation of the printed circuit 2. Indeed, since the printed circuit 2 is not always perfectly flat, the height adjustment using the adjustable columns 51 makes it possible to compensate for these flatness defects of the printed circuit 2. This also avoids stressing the printed circuit since the positioning device 5 of the invention allows an adjustment in accordance with the geometry of the printed circuit 2. For example, the adjustable columns 51 can be inserted at different heights in the housings 42 in order to adapt to the geometry of the printed circuit 2.

[0048] A locking device 52 is used to immobilize each adjustable column 51 in the associated housing 42. The locking device 52 notably prevents the threads of Figure 4 from loosening under the effect of vibrations or shocks.

[0049] The locking device 52 is for example an adhesive applied to the thread 510 of the adjustable column 51 prior to its insertion into the housing 42. The locking device 52 may be a thread locker, preferably a strong thread locker so that the assembly of the adjustable columns 51 in the housings 42 can withstand severe or even very severe environmental constraints.

[0050] The locking device 52 may alternatively be solder, welding, crimping or an adhesive substance poured into the housings 42 after insertion of the adjustable columns 51 into the housings 42.

[0051] In the variant shown in Figure 5 the shapes of the adjustable columns 51 and the housings 42 are configured to perform brazing or welding or to receive an adhering substance. For this purpose, the adjustable columns 51 protrude from their respective housing 42 and each housing 42 may include a counterbore 421 making it easier to carry out welding or brazing or making it easier to put the adhesive substance in place.

[0052] In the variant shown in Figure 6, the shapes of the adjustable columns 51 and the housings 42 are configured to crimping the adjustable columns 51 each in its housing 42. Each adjustable column 51 comprises, for example, at its end opposite that in contact with the printed circuit 2, a bore 513 allowing a crimping tool to be inserted therein, expanding the outer surface of the adjustable column 51 so that it is mounted tightly in its housing 42. Alternatively, it is possible to provide one or more bores in the cooling device 4 around each housing 42 in order to deform the inner surface of the housing 42 to tighten it and ensure, as previously, tightening of the corresponding adjustable column.

[0053] Even when the adjustable columns 51 are smooth, as shown in Figures 5 and 6, the locking device 52 makes it possible to maintain the adjustment of the positioning of the adjustable columns 51 relative to the cooling device 4.

[0054] In the example shown, each adjustable column 51 comprises a cavity 511. The cavity 511 is configured to receive at least a portion of the fixing device 6. The cavity 511 opens onto one end 512 of the adjustable column 51. The cavity 511 has a substantially cylindrical shape. The cavity 511 comprises a thread (not shown in the figures).

[0055] The fixing device 6 is assembled to the printed circuit 2 and to the cooling device 4.

[0056] The fixing device 6 is configured to immobilize the cooling device 4 on the printed circuit 2. In other words, the fixing device 6 locks the cooling device 4 in its position on the printed circuit 2.

[0057] The fixing device 6 comprises at least one screw 60. The fixing device 6 here comprises several screws 60, in particular four screws 60. The fixing device 6 comprises the same number of screws 60 as the number of fixing holes 20 of the printed circuit 2.

[0058] Each screw 60 comprises a rod 600 and a head 601. The rod 600 of each screw 60 passes through one of the fixing holes 20 of the printed circuit 2. In the exemplary embodiment of FIGS. 2 to 8, the rod 600 of each screw 60 opens into one of the cavities 511 of the corresponding adjustable column 51. Once the screw 60 is assembled to the printed circuit 2 and to the cooling device 4, the head 601 is located against a lower face of the printed circuit 2.

[0059] The rod 600 of each screw 60 is for example threaded. The thread of the threaded rod 600 is complementary to the tapping of the cavity 51 1 of each adjustable column 51.

[0060] A fastening means is used to immobilize each screw 60 in the corresponding cavity 51 1. The fastening means prevents the threads from loosening due to vibrations or shocks. The fastening means is for example an adhesive applied to the shank 600 of the screw 60 prior to its insertion into the cavity 51 1. The fastening means may be thread lock, preferably weak thread lock so as to allow easy disassembly of the screw 60 in the event of the need to intervene on the electronic device 1.

[0061] The weak thread lock allows the screws 60 to be dismantled using conventional tools, in particular a screwdriver, in order to work on the printed circuit. Dismantling the screws 60 does not alter the locking of the position of the positioning device 5. When using adhesives, in particular thread locks, both for locking the position of the positioning device 5 and as a means of fixing the screws 60, it is advantageous to provide, for locking the position of the positioning device 5, an adhesive having a greater retaining force than for the adhesive used as a means of fixing the screws 60 in order to limit the risk of unlocking the position of the positioning device 5 when dismantling the screws 60. For example, it is advantageous to use a strong thread lock for locking the position of the positioning device 5 and a weak thread lock as a means of fixing the screws 60.In other words, the torque required to loosen the screws 60 is advantageously lower than the loosening torque of the adjustable columns 51 in their threading. It is understood that in the variants where the locking of the position of the positioning device 5 is ensured by brazing, welding or crimping, the locking ensures maintenance of the. adjustable columns on the cooling device 4 firmer than that ensured by the means of fixing the screws 60.

[0062] The electronic device 1 further comprises a thermal connection 7. The thermal connection 7 extends between the upper face 30 of the electronic component 3 and the cooling face 40 of the cooling device 4. The thermal connection 7 is made of a material that can fill gaps or holes present on the surface of the electronic components. The thermal connection ensures good heat conduction. The thermal connection 7 is, for example, a layer of thermal grease, a thermal blanket, etc. The thermal connection 7 is, for example, applied to the upper surface 30 of the electronic component 3 prior to mounting the cooling device 4 on the electronic component 3 and the printed circuit 2.

[0063] Thermal grease offers high thermal performance, thus enabling efficient cooling of the electronic component 3. Thermal grease has the particular advantage of having an extremely low thickness (of the order of a few microns), thus reducing thermal resistance.

[0064] In another exemplary embodiment, the electronic device 1 may not include a thermal connection 7. The cooling face 40 of the cooling device is in direct contact with the upper surface 30 of the electronic component 3.

[0065] Figures 5 to 8 show the assembly steps of the electronic device 1 according to the embodiment described above.

[0066] As seen in Figure 7, the adjustable columns 51 are first inserted into the housings 42 of the cooling device 4.

[0067] The printed circuit 2 and the cooling device 4 are then brought opposite each other (figure 8). The cooling device 4 is positioned above the electronic component 3. In particular, in the example shown, the housings 42 are brought opposite the fixing holes 20 of the printed circuit 2.

[0068] The adjustable columns 51 are arranged at the desired height inside the housings 42 (figure 9). This makes it possible to adjust the position of the cooling device 4 relative to the electronic component 3. Indeed, the distance between the cooling face 40 of the cooling device 4 and the upper face 30 of the electronic component 3 is adjusted by means of the adjustable columns 51. This distance is minimized as much as possible so as to bring the cooling face 40 into contact with the upper face 30 of the electronic component or with the thermal connection 7 extending on the upper face 30 of the electronic component 3. In Figure 9, the height adjustment is ensured by screwing the adjustable columns 51 into their respective threads. For the variants shown in Figures 5 and 6 where the adjustable columns 51 and the housings 42 have smooth surfaces, the height adjustment is done simply by placing the adjustable columns 51 in abutment against the printed circuit 2.

[0069] By means of the positioning device 5, the reference surface for mounting the electronic device 1 is the electronic component 3. This makes it possible to bring the cooling device 4 into contact with the electronic component 3, thereby improving the cooling efficiency of the electronic component 3.

[0070] The positioning device 5 is held stationary by the fixing means, as explained above. For example, thread lock is applied to the thread 510 of each adjustable column 51 prior to the insertion of each adjustable column 51 into the housings 42 of the cooling device 4.

[0071] The screws 60 are finally inserted into the fixing holes 20 of the printed circuit 2 (figure 10). The screws 60 are screwed into the cavities 51 1 of the adjustable columns 51 . The cooling device 4 is thus locked and made integral with the printed circuit 2.

[0072] The mounting system of the previously described embodiment has the advantage of being compact. In fact, the mounting system has a structure such that the positioning device 5 and the fixing device 6 are assembled to each other.

[0073] The locking of the position of the cooling device 4 and the positioning device 5 can be carried out before or after the screws 60 are put in place.

[0074] In another embodiment shown in Figure 11, the positioning device 5 and the fixing device 6 are not assembled to each other. The positioning device 5 and the fixing device 6 are at a distance from each other. This embodiment differs from the previous one in that the adjustable columns 51 do not include a cavity. The adjustable columns 51 are thus cylinders solid. The cooling device 4 comprises cavities 43. The cavities 43 of the cooling device 4 allow the reception of the fixing device 6. The fixing holes 20 of the printed circuit 2 are formed to be offset horizontally relative to the housings 42 when the cooling device 4 is assembled to the electronic component 3. In other words, the fixing holes 20 are not opposite the housings 42 when the cooling device 4 is assembled to the electronic component 3. The fixing holes 20 are configured to be opposite the cavities 43 of the cooling device 4 when the cooling device 4 is assembled to the electronic component 3.

[0075] In the embodiment of Figure 11, the fixing device 6 also comprises screws 60, in particular screws 60 each comprising a head 600 and a rod 601. The rod 601 of each of the screws 60 is here threaded. The cavities 43 of the cooling device 4 each comprise a thread complementary to the thread of the screws 60.

[0076] Alternatively to the screws 60 and the corresponding threads, the fixing device 6 may comprise other fixing means, advantageously removable and allowing a stop in translation along the axis of the screws 60. It is for example possible to provide means for clipping the printed circuit 2 onto the cooling device 4.

[0077] Alternatively, the fixing device 6 may comprise headless screws, or be formed by stops assembled to the printed circuit 2 and allowing the cooling device 4 to be locked onto the printed circuit 2.

[0078] The electronic device according to the invention allows rigid mounting of the cooling device on the hot electronic component, coming into contact with the hot electronic component so as to create an efficient thermal connection.

[0079] The description of the present invention is made for an electronic device comprising an electronic component (in particular a hot electronic component), a cooling device configured to cool said electronic component, and a mounting system configured to allow the positioning and locking of the cooling device on the electronic component. Of course, the electronic device may comprise several electronic components to be cooled (i.e. several hot electronic components). In this case, the electronic device may comprise a cooling device associated with each electronic component to be cooled, and a mounting system associated with each pair formed by the cooling device and the associated electronic component.

Claims

CLAIMS 1. Electronic device comprising: - a printed circuit (2); - an electronic component (3) assembled on the printed circuit (2); - a cooling device (4) assembled to the printed circuit (2), the cooling device (4) comprising a cooling face (40) facing the electronic component (3); - a mounting system comprising: o a positioning device (5) assembled to the cooling device (4), the positioning device being configured to adjust a distance between an upper face (30) of the electronic component (3) and the cooling face (40) of the cooling device (4); o a locking device (52) for the position of the cooling device (4) and the positioning device (5); and o a fixing device (6) for the printed circuit (2) and the cooling device (4), the fixing device (6) being independent of the locking device.

2. Electronic device according to claim 1, wherein the cooling device (4) comprises at least one housing (42) configured to receive the positioning device (5).

3. An electronic device according to claim 2, wherein the housing (42) is a through hole.

4. Electronic device according to claim 2 or claim 3, wherein the positioning device (5) comprises at least one adjustable column (51) configured to be inserted into said at least one corresponding housing (42).

5. Electronic device according to claim 4, wherein the locking device (52) comprises an adhesive applied between said at least one adjustable column (51) and said at least one corresponding housing (42).

6. Electronic device according to one of claims 4 or 5, in which the adjustable column (51) has a thread (510) configured to cooperate with a tapping made in the housing (42).

7. Electronic device according to claim 4, wherein the locking device (52) comprises welding or brazing of said at least one adjustable column (51) in said at least one corresponding housing (42).

8. Electronic device according to claim 4, wherein the locking device (52) comprises a crimping of the adjustable column (51) in said at least one corresponding housing (42).

9. Electronic device according to one of claims 4 to 8, wherein said at least one adjustable column (51) comprises a cavity (511) configured to receive at least in part the fixing device (6).

10. Electronic device according to claim 9, wherein the fixing device (6) comprises a screw (60) having a threaded rod (600), the threaded rod (600) passing through the printed circuit (2), the cavity (51 1 ) of the adjustable column (51 ) comprising a thread complementary to the threaded rod (600) of the screw (60). 1 1. Electronic device according to one of claims 4 to 10, in which the cooling device (4) comprises several housings (42), each housing (42) extending close to a periphery of the electronic component (3), the positioning device (5) comprising as many adjustable columns (51) as housings (42).

12. Electronic device according to one of claims 1 to 8, in which the fixing device (6) is assembled to the printed circuit (2) and to the cooling device (4) at a distance from the positioning device (5).

13. Electronic device according to claim 12, wherein the cooling device (4) comprises at least one cavity (43) configured to receive at least in part the fixing device (6).

14. Electronic device according to one of claims 1 to 13, further comprising a thermal connection (7) between the upper face (30) of the electronic component (3) and the cooling face (40) of the cooling device (4).

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