FR3121779A3 - Heat sink element for an active heat sink system. - Google Patents

Abstract

Heat sink element for an active heat sink system. The invention relates to a heat sink element (50) intended for cooling an electronic device, comprising a substrate (10) and a cover (30) at least partially covering the substrate (10), the substrate comprising an underside (11) flat, a flat upper face (12) parallel to the lower face (11), and four side faces joining the upper and lower faces (11,12), including a front face (13) and a rear face (14 ), parallel and facing each other, the substrate (10) comprising a plurality of through holes (15), called first holes, extending longitudinally from the front face to the rear face (13 ,14), parallel to the upper face (12) and a plurality of non-through orifices (16), called second orifices, extending from the upper face (12) and perpendicular to the first orifices (15), and wherein each second port (16) passes through a plurality of first ports (15), each of the first ports having a first end (15a) on the front face (13) intended for the inlet of the heat transfer fluid and a second end (15b) on the rear face (14) intended for the evacuation of the heat transfer fluid, each of the second orifices having a single end (16a) closed off by the cover (30) covering the upper face (12). Figure for abstract: Fig. 2

Description

Heat sink element for an active heat sink system.

The present application relates to a heat sink element used to transfer heat away from a heat source such as, for example, an electronic device in operation. The invention also relates to an active heat dissipation system comprising such a heat dissipating element.

It is known that an electronic device, such as a microprocessor of an aircraft computer, generates a large amount of heat during its operation. The heat must be efficiently evacuated so that the electronic device retains its full functional capacities and is not, in the long run, damaged.

Passive heat sink systems, such as those comprising a thermally conductive substrate plate attached to the electronic device to be cooled and a set of plates or fins extending from the substrate plate to dissipate heat by convection into the ambient air, are not efficient enough to cool high power electronic devices.

To overcome the lack of efficiency of passive heat dissipation systems, active heat dissipation systems using forced circulation of coolant in a closed loop circuit are used. Such a system 1, shown in , comprises connected two by two by conduits 6a, a pump 3, a fluid cooling element 4 (example: a radiator exposed to fresh air blown by a fan), a heat sink element 5 which interfaces directly with the electronic device 2 to be cooled. A heat transfer fluid circulates in the system under the action of the pump 3 and stores in the heat dissipating element 5, part of the heat produced during the operation of the electronic device 2, and loses, in the cooling element of the fluid 4, stored heat.

An architecture of a heat sink element 5 is presented in the article "A Honeycomb Microchannel Cooling System for Microelectronics Cooling" Xiaobing Luoa et al, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, China Department of Mechanical and Power Engineering, Nanchang Institute of Technology, Nanchang, 03 March 2011.

The heat dissipating element presented in this paper comprises a hollow parallelepiped-shaped metal substrate with one face heat-sealed to the electronic device to be cooled and which forms the lower face of the dissipating element. The substrate comprises a chamber, intended to receive the circulating heat transfer liquid, which is hermetically closed by a cover which forms the upper face of the dissipating element. A stack of metal plates, each arranged parallel to the underside, is arranged in the chamber. Each of the plates includes recesses forming honeycomb patterns and the recesses are aligned from plate to plate. The superposition of plates thus allows the formation of a plurality of channels whose walls are the contours of the aligned recesses of the different plates. The heat from the electrical device will, by natural convection, rise in the channels from the lower face to the upper face. The liquid present in the channels, constantly renewed under the action of the pump, stores part of the heat of the electronic device. The micro-channels, due to their particular shape, provide a maximized exchange surface with the fluid in the volume considered to promote heat dissipation by forced convection.

Such a heat-dissipating element is efficient, but its manufacture is tricky, because it is not easy to quickly and inexpensively produce a multitude of honeycomb patterns on a plate. There is a need to find a heat dissipating element intended for an active heat dissipation system which is simpler to manufacture while having equivalent efficiency in terms of heat dissipation.

The present invention aims to remedy all or part of this need. To this end, the subject of the invention is a heat sink element comprising a substrate and a cover covering at least part of the substrate, the substrate comprising a flat lower face intended to be affixed against a face of an electronic device to be cooled. , a flat upper face parallel to the lower face, and four flat lateral faces joining the upper and lower faces, including a front face and a rear face, parallel and facing each other, characterized in that the substrate comprises a plurality of through holes, called first holes, all parallel to each other and extending longitudinally from the front face to the rear face, parallel to the upper face and a plurality of non-through holes, called second holes, extending from the top face and perpendicular to the first apertures, and wherein each second aperture passes through a plurality of first apertures, each of the first apertures having a first end on the front face intended for the entry of the heat transfer fluid into the substrate and a second end on the rear face intended for the evacuation of the heat transfer fluid from the substrate, each of the second orifices having a single end, arranged on the face upper, closed by the cover covering the upper face.

The invention also relates to an active heat dissipation system by forced circulation of heat transfer liquid comprising such a heat dissipating element.

The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being made in relation to the attached figures, among which:

the is a schematic view of an active heat dissipation system by forced circulation of coolant liquid which comprises a heat dissipating element;

the is a sectional view of a heat sink element according to the invention;

the is a perspective view of the substrate of the heat sink element shown in , according to one embodiment of the invention.

In relation to the , a heat dissipating element 50 according to the invention for an active heat dissipating system 1 as described above, takes the form of a parallelepipedal element and comprises a machined substrate 10, a cover 30 which covers at least part of the substrate 10, and covers 41-42 to allow the hydraulic connection of the heat sink element 50 with conduits 6a for the circulation of the heat transfer fluid.

The substrate 10 is made, for example, of a composite material or of metal (eg copper), or of graphite. The cover 30 is made, for example, of metal, or of composite material, or of graphite or else of silicone. The covers 41-42 are, for example, made of a flexible material such as silicone.

The substrate 10 comprises a flat lower face 11, an upper face 12 parallel to the lower face 11, and four flat side faces joining the upper faces 12 and lower faces 11. Among the side faces, there is a front face 13 and a face rear 14, parallel and facing each other, and perpendicular to the other faces of the substrate.

The lower face 11 is intended to be affixed against a face of the electronic device to be cooled 2 and fixed to the latter by means, for example, of a thermally conductive glue.

The substrate 10 comprises a plurality of orifices 15,16 which form channels for the flow of the heat transfer fluid in the substrate, including:

- a plurality of through orifices 15, called first orifices, all parallel to each other and extending longitudinally from the front face 13 to the rear face 14, parallel to the upper 12 and lower 11 faces. Each of the first orifices thus has an end 15a on the front face 13 and an end 15b on the rear face 14. The ends 15a, 15b of the first orifices are provided for the inlet/outlet of heat transfer fluid inside the substrate 10.

- a plurality of blind orifices 16, called second orifices, pierced on the upper face 12, all parallel to each other and extending longitudinally, from the upper face 12, between the upper face 12 and the lower face 11, perpendicular to the upper face 12 and therefore to the first bores 15. Each of the second orifices thus has a single end 16a arranged on the upper face 12.

These first and second orifices 15, 16 are obtained by machining (drilling) the substrate 10. The substrate 10 is machined such that each second orifice 16 passes through several first orifices 15 in the height of the substrate 10 defined as being the smallest distance between the upper 12 and lower 11 faces.

The cover 30, installed on the substrate 10 after the machining of the latter, covers the upper face 12 to close the second orifices 16. The cover 30 is fixed to the substrate, in a sealed manner, by a welding or gluing process according to the material from which it is made.

In the embodiment illustrated in , the first and second orifices 15,16 are dimensioned and drilled according to a diagram making it possible to obtain an optimal ratio between a high number of orifices 15,16 made and a good mechanical strength of the substrate 10. Thus, the first and second orifices 15,16 all have the same diameter and, according to the drilling diagram, the first orifices 15 are distributed in the substrate 10 according to a first repeating pattern and the second orifices 16 are distributed in the substrate 10 according to a second repeating pattern.

More specifically, identically for the front face and the rear face 13,14, the first orifices 15 are arranged in columns 17a-b over the width of the front/rear face 13,14, where each column 17a-b is extends over the height (defined as the smallest dimension between the lower face and the upper face) of the front/rear face 13,14. Columns 17a-b are separated from each other by a constant distance. In each column 17a-b, the orifices 15 are separated from each other by a first constant pitch between each orifice, and identical for all the columns 17a-b. The first repeating pattern consists of two columns 17a-b, with a first and a second column, and where the centers of the first orifices 15 of the first column 17a are offset, according to the height of the front/rear face 13,14, from the center of the first orifices 15 of the second column 17b, by a distance equal to half the diameter of a first orifice 15.

Across the width of the upper face 12, the second orifices 16 are arranged in lines 18a-b separated from each other by a constant distance, and each line lines 18a-b extends over the length (defined as the smallest distance between the front face and the rear face) of the upper face 12. Each line 18a-b comprises a plurality of second orifices 16 with a second pitch (the second pitch is greater than the first pitch, of the order of ten times greater) between each second orifice 16 of the same line 18a-b and identical for all lines 18a-b. The second repeating pattern consists of two lines 18a-b, with a first and a second line, and where the centers of the second orifices 16 of the first line 18a are offset, along the length of the upper face 12, from the center of the second orifices 16 of the second line 18b, a distance equal to half the diameter of an orifice 16a.

From the hydraulic point of view, for the substrate 10 covered with its cover 30, the first orifices 15 form first fluid channels C1, called horizontal channels open at their two ends 15a-b, while the second orifices 16 form second C2 channels, called vertical channels, closed at their ends 16a.

The first channels C1 are connected to a first conduit 6a at the level of the front face 13 and to a second conduit 6a at the level of the rear face 14 of the substrate 10. For this purpose, each of the rear face 14 and of the face 13 front is closed by a cover 41-42 which is fitted in a sealed manner (for example by means of gaskets, not shown) on the substrate 10 provided with its cover 30. The cover 41-42 has the shape of a dome or bell of so as to define a chamber 41a-42a with the front/rear face and into which all the first channels C1 open. The cover 41-42 comprises a fluid passage 41b-42b, into which is fitted, in a sealed manner, a connector (not shown) for the connection of a conduit 6a in order to allow a fluid to pass from the conduit 6a to the room 41a-42a or vice versa.

The action of the pump 3 makes it possible to bring the heat transfer fluid supplied by the first conduit 6a into the chamber 41a formed between the front face 13 and its cover 41 then to cause the fluid to penetrate into the substrate 10 via the ends 15a of the first orifices 15 arranged on the front face 13.

Inside the substrate 10 covered by its cover 30, the action of the pump 3 creates a majority circulation of the heat transfer fluid in the horizontal channels C1 in a main direction going from the front face 13 towards the rear face 14 of the substrate to the introduction and extraction of the heat transfer fluid into/out of the heat dissipation element 50, and on the other hand a minority circulation of the fluid in the vertical channels C2 connected to the main channels C1, in a secondary direction, perpendicular to the main direction.

After circulation inside the substrate 10 covered by its cover 30, the heat transfer fluid leaves the substrate 10 through the ends 15b of the first orifices 15 arranged on the rear face 14, accumulates in the chamber 42a defined between the face back 14 and its cover 42, then is then evacuated through the second conduit 6a.

When the heat dissipation element 50 is arranged on a hot electronic device 2, the secondary direction goes, due to thermal convection, from the lower face 11 towards the upper face 12 of the substrate.

The speed of movement of the heat transfer fluid in the vertical channels C2 is lower than the speed of movement of the fluid in the horizontal channels C1 since the direction of flow in the vertical channels C2 is perpendicular to the main direction. These features make it possible to create a recirculation of the heat transfer fluid between the horizontal C1 and vertical C2 channels which will have the effect of "pumping" the heat produced by the electronic device 2 and of evacuating it by mixing between the heated fluid and the fluid cooler constantly renewed under the action of the pump 3.

In detail, the fluid present in the vertical channels C2 and at the level of the lower face 11 will store heat produced by the operation of the electronic device 2. The forced convection moves the hot fluid in the vertical direction, towards the upper face 12. At each intersection of a vertical channel C2 with a horizontal channel C1 along the displacement of the hot fluid in the vertical direction, a part of the hot fluid, mixes with the colder fluid moving in the horizontal channel C1 according to the direction main, and part of the heat is thus evacuated out of the substrate in the main direction.

In addition to its effectiveness in reducing the temperature of an electronic device, the heat dissipation element 50 according to the invention is constructed simply, in particular by drilling the substrate. In the event that a heat dissipation element 50 of great length is necessary, and in order to facilitate its manufacture as well as its implementation on the electronic device, the substrate 10 can be constructed in modules welded to each other and then covered by a hood 30.

In a non-illustrated embodiment of the invention, the heat dissipation element does not include fitted covers on its ends. The hydraulic connection between a conduit 6a and each front/rear face 13,14 is made via a manifold to which the conduit 6a is connected on the one hand, and to which are connected on the other hand, each of the first orifices arranged.

Thus on each front/rear face 13,14 Each first orifice 15 is connected to the feeder by means of a flexible hose, the end of which is held in the first orifice 15 by known means. For example, the end of the flexible hose is threaded and is screwed into a thread made in each first hole 15.

Claims (9)

1) Heat sink element (50) comprising a substrate (10) and a cover (30) at least partially covering the substrate (10), the substrate (10) comprising a flat lower face (11) intended to be affixed against a face of an electronic device (2) to be cooled, a flat upper face (12) parallel to the lower face (11), and four flat side faces joining the upper and lower faces (11,12), including a front face (13) and a rear face (14), parallel and facing each other, characterized in that the substrate (10) comprises a plurality of through orifices (15), called first orifices, all parallel between them and extending longitudinally from the front face to the rear face (13,14), parallel to the upper face (12) and a plurality of non-through orifices (16), called second orifices, extending to from the upper face (12) and perpendicular to the first orifices (15), and where each second orifice (16) crosses a plurality of first orifices (15), each of the first orifices having a first end (15a) on the front face (13) intended for the entry of the heat transfer fluid into the substrate (10) and a second end (15b) on the rear face (14) intended for the evacuation of the heat transfer fluid from the substrate (10), each of the second orifices having a single end (16a), arranged on the upper face (12), closed off by the cover (30) covering the upper face (12). 2) heat sink element (50) according to claim 1, characterized in that the first and second orifices (15,16) all have the same diameter 3) Heat sink element (50) according to claim 1, characterized in that the first orifices (15) are distributed in the substrate (10) following a first repeating pattern. 4) heat sink element according to claim 3, characterized in that the second bores (16) are distributed in the substrate (10) following a second repeating pattern. 5) heat sink element (50) according to any one of claims 1 to 4, characterized in that it comprises, associated with each of the front / rear face (13,14), a cover (41,42) fitted onto the substrate (10) covered with the cover (30) and covering the front/rear face (13/14) with which the cover is associated, the cover (41,42) comprising a passage (41b,42b) for the passage of a heat transfer fluid towards or out of the substrate (10). 6) heat sink element (50) according to claim 5, characterized in that each cover (41,42) is made of silicone. 7) heat sink element (50) according to any one of claims 1 to 6, characterized in that the substrate (10) is made of a material selected from a composite material, a metallic material, graphite. 8) heat sink element (50) according to any one of claims 1 to 7, characterized in that the cover (30) is made of a material taken from a composite material, a metallic material, graphite, silicone. 9) Active heat dissipation system (1) of an electronic device to be cooled (2), the system comprising, connected in pairs by conduits (6a), a pump (3) adapted to move a heat transfer fluid, a heat transfer fluid cooling element (4), a heat dissipating element (50) intended to interface with the electronic device to be cooled (2), the heat dissipating element (50) comprising a substrate (10) and a cover (30) covering at least part of the substrate (10), the substrate (10) comprising a flat lower face (11) intended to be affixed against a face of the electronic device (2) to be cooled, an upper face (12) plane parallel to the lower face (11), and four flat side faces joining the upper and lower faces (11,12), including a front face (13) and a rear face (14), parallel and facing one of the other, characterized in that the substrate (10) comprises a plurality of through orifices (15), called first orifices, all parallel to each other and extending longitudinally from the front face to the rear face (13, 14), parallel to the upper face (12) and a plurality of non-through orifices (16), called second orifices, extending from the upper face (12) and perpendicular to the first orifices (15), and where each second orifice (16) passes through several first orifices (15), each of the first orifices having a first end (15a) on the front face (13) intended for the entry of the heat transfer fluid into the substrate (10) and a second end (15b) on the rear face (14) intended for the evacuation of the heat transfer fluid from the substrate (10), each of the second orifices having a single end (16a), arranged on the upper face (12), closed off by the cover (30) covering the upper face (12).