VAPOR CHAMBER FOR COOLING AN ELECTRONIC COMPONENT

Abstract

The invention relates to a vapor chamber (10), comprising a sealed casing (12) which comprises two main walls, wherein a first main wall is an evaporator wall (14) and a second main wall is a condenser wall (16), wherein the two main walls are connected by side connections (18, 20) to form a sealed volume (21) inside the two main walls and the side connections (18, 20), wherein a plurality of pillars (22) is provided in the sealed volume (21) such, that the pillars (22) connect the evaporator wall (14) and the condenser wall (16), wherein the pillars (22) have a first contact area (24) to the evaporator wall (14) and a second contact area (26) to the condenser wall (16), and wherein the pillars (22) further comprise an intermediate cross section area (28) being arranged between the first contact area (24) and the second contact area (26), wherein the extension of the intermediate cross section area (28) is smaller compared to the extension of both of the first contact area (24) and the second contact area (26).

Claims

1. A vapor chamber, comprising a sealed casing which comprises two main walls, wherein a first main wall is an evaporator wall and a second main wall is a condenser wall, wherein the two main walls are connected by side connections to form a sealed volume inside the two main walls and the side connections, wherein a plurality of pillars is provided in the sealed volume such, that the pillars connect the evaporator wall and the condenser wall, wherein the pillars have a first contact area to the evaporator wall and a second contact area to the condenser wall, and wherein the pillars comprise an intermediate cross section area being arranged between the first contact area and the second contact area, wherein the extension of the intermediate cross section area is smaller compared to the extension of both of the first contact area and the second contact area.

2. The vapor chamber according to claim 1, wherein the pillars at least in part have an outer surface which is at least in part provided with a curvature proceeding from the evaporator wall to the condenser wall.

3. The vapor chamber according to claim 2, wherein the curvature forms a concave structure.

4. The vapor chamber according to claim 3, wherein the pillars at least in part have an outer contact angle α to at least one of the evaporator wall and to the condenser wall, wherein the outer contact angle is in a range of more than 90° and smaller than 180°.

5. The vapor chamber according to claim 1, wherein the pillars are provided at least in part with a porous structure at their outer surface.

6. The vapor chamber according to claim 1, wherein the pillars are provided at least in part with at least one groove proceeding from the evaporator wall to the condenser wall.

7. The vapor chamber according to claim 1, wherein at least one groove has at least one of a depth and a width in the range of 5 μm to 500 μm.

8. The vapor chamber according to claim 1, wherein the smallest extension of an intermediate cross section area is smaller compared to the extension of both of the first contact area and the second contact area in a ratio of 1-100.

9. (canceled)

10. (canceled)

11. The vapor chamber according to claim 1, wherein the pillars at least in part have an outer contact angle α to at least one of the evaporator wall and to the condenser wall, wherein the outer contact angle is in a range of more than 90° and smaller than 180°.

12. The vapor chamber according to claim 2, wherein the pillars at least in part have an outer contact angle α to at least one of the evaporator wall and to the condenser wall, wherein the outer contact angle is in a range of more than 90° and smaller than 180°.

13. The vapor chamber according to claim 1, wherein a body comprising the two main walls and the pillars connecting the main walls is structurally consistent with formation by additive manufacturing.

14. The vapor chamber according to claim 13, wherein at least the two main walls comprise a porous structure and in that the pillars are provided with a porous structure or a groove at least a part of their outer surface, wherein the porous structure of the two main walls and the porous structure or the groove structure of the pillars are formed in a continuous manner.

15. The vapor chamber according to claim 13, wherein the pillars at least in part have an outer surface which is at least in part provided with a curvature proceeding from the evaporator wall to the condenser wall.

16. The vapor chamber according to claim 15, wherein the curvature forms a concave structure.

17. The vapor chamber according to claim 16, wherein the pillars at least in part have an outer contact angle α to at least one of the evaporator wall and to the condenser wall, wherein the outer contact angle is in a range of more than 90° and smaller than 180°.

18. The vapor chamber according to claim 13, wherein the pillars are provided at least in part with a porous structure at their outer surface.

19. The vapor chamber according to claim 13, wherein the pillars are provided at least in part with at least one groove proceeding from the evaporator wall to the condenser wall.

20. The vapor chamber according to claim 13, wherein at least one groove has at least one of a depth and a width in the range of 5 μm to 500 μm.

21. The vapor chamber according to claim 13, wherein the smallest extension of an intermediate cross section area is smaller compared to the extension of both of the first contact area and the second contact area in a ratio of 1-100.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0056] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0057] In the drawings:

[0058] FIG. 1 shows a sectional side view of a vapor chamber according to an embodiment of the invention;

[0059] FIG. 2 shows a pillar for a vapor chamber according to FIG. 1;

[0060] FIG. 3 shows the effect of a vapor chamber according to the invention on the stress distribution; and

[0061] FIG. 4 shows various perpendicular cross-sections of a pillar for a vapor chamber according to FIGS. 1 and 2.

DESCRIPTION OF EMBODIMENTS

[0062] FIG. 1 shows a vapor chamber 10 which is particularly suited for cooling an electronic device, such as a power semiconductor module, not shown as such.

[0063] The vapor chamber 10 comprises casing 12 which is sealed to the outside so that a working fluid which is included in the casing 12 is not able to leave the casing 12 either in liquid or in gaseous form. The casing 12 comprises two main walls. The two main walls comprise an evaporator wall 14 and a condenser wall 16. The evaporator wall 14 is configured for coming in contact with a device to be cooled, such as with a baseplate of a power semiconductor module. The condenser wall 16 is configured for being in an environment having a comparably cooler temperature. For example, the condenser wall 16 is provided at its outside with air fins.

[0064] The two main walls, i.e. the evaporator wall 14 and the condenser wall 16, are connected by side connections 18, 20 to form a sealed volume 21 inside the two main walls and the side connections 18, 20. Further, a wick structure 17 is provided at the inner surface of the evaporator wall 14 and the condenser wall 16 and/or side connections 18, 20.

[0065] FIG. 1 further shows that a plurality of pillars 22 is provided in the sealed volume 21 such, that the pillars 22 connect the evaporator wall 14 and the condenser wall 16. The pillars 22 have a first contact area 24 to the evaporator wall 14 and a second contact area 26 to the condenser wall 16. It is further provided that the pillars 22 are formed such, that they comprise an intermediate cross section area 28 being arranged between the first contact area 24 and the second contact area 26. It is provided that the extension of the intermediate cross section area 28 is smaller compared to the extension of both of the first contact area 24 and the second contact area 26.

[0066] The pillar 22 is shown in more detail in FIG. 2. As already mentioned with regard to FIG. 1, it is shown that the pillar 22 is formed such, that it comprises the intermediate cross section area 28 being arranged between the first contact area 24 and the second contact area 26, wherein it is provided that the extension of the intermediate cross section area 28 is smaller compared to the extension of both of the first contact area 24 and the second contact area 26. In more detail, it may be provided that the smallest extension of an intermediate cross section area 28 is smaller compared to the extension of both of the first contact area 24 and the second contact area 26 in a ratio of 1 to 100.

[0067] This is realized in that the pillar 22 has an outer surface 30 which is at least in part provided with a curvature proceeding from the evaporator wall 14 to the condenser wall 16. In more detail, it is provided that the curvature forms a concave structure. It is thus allowed that the pillar 22 has an outer contact angle α to the evaporator wall 14 and the condenser wall 16, wherein the outer contact angle α is in a range of more than 90° and smaller than 180°. In detail the contact angle α to the condenser wall 16 is shown. The contact angle α to the condenser wall 16 may further be the same or different compared to the contact angle α to the evaporator wall 14.

[0068] It may further be provided that the outer surface of the pillar 22 is provided with a porous structure at the outer surface 30 and/or that the pillar 22 is provided with at least one, preferably a plurality of grooves, proceeding from the evaporator wall 14 to the condenser wall 16. This allows that no abrupt change of direction of the liquid on both main walls is present, so that it is prevented that the capillary pump effect of the wick structure is reduced.

[0069] According to FIG. 3, the positive effect of the present invention is visualized. In detail, an evaporator wall 14 is shown for means of an example. The consequence of the feature according to which the pillars 22 further comprise an intermediate cross section area 28 being arranged between the first contact area 24 and the second contact area 26, wherein the extension of the intermediate cross section area 28 is smaller compared to the extension of both of the first contact area 24 and the second contact area 26 is shown. This allows for significant reduction of spot stresses as indicated in FIG. 3 by stress points 32, wherein FIG. 3a shows stress points by using conventional pillars and FIG. 3b shows stress points 32 by using pillars 22 as described above. In FIG. 3a by using black-filled stress points 32, a high local mechanical spot stress should be indicated whereas according to FIG. 3b and by using white-filled stress points 32, a low and thus reduced mechanical spot stress should be indicated.

[0070] As demonstrated by numerical mechanical simulation, pillars 22 according to the present invention decrease the local stress in the flat surfaces of a vapor chamber 10 by 30%-40%. Reduced stresses lead to extended lifetime and reliability of the vapor chamber 10.

[0071] FIG. 4 shows examples of cross section shapes for pillars 22 that can be embedded in the vapor chamber 10. In more detail, on the left-hand side, a side view of a pillar 22 is shown, in which different cross section planes A to E are defined. On the right-hand side, the geometry of these distinct cross section planes is shown, wherein each horizontal line refers to one common pillar 22.

[0072] Generally, it can be seen that the geometry of the pillars 22 can be selected according to the desired needs and no specific form or symmetry is mandatory. With regard to the following shapes, these may also called cross-sectional shape or geometry.

[0073] According to the first line, the pillar 22 comprises a round shape at the whole length of the pillar 22, i.e. from the evaporator wall 14 to the condenser wall 16.

[0074] According to the second line, the pillar 22 comprises at one end a rectangular shape and on the other end a starlike shape, wherein the end having a rectangular shape may be both the evaporator end or the condenser end.

[0075] According to the third line, the pillar 22 comprises at both ends a shape having the form of a cross, wherein, however, the orientation differs such, that the cross is turned around an angle of 45° along the axis of the pillar 22. At the center part, the form has a shape of a hexagon, which, however, could also be a round shape, for example.

[0076] According to the fourth line, the pillar 22 comprises an arbitrary shape in which every cross sectional plane A to E has a different shape. This row shows that the form of the pillar 22 may be chosen according to the desired needs.

[0077] A vapor chamber 10 as described thus provides an innovative geometry of inner supporting pillars 22. The improved structure allows a higher inner working pressure and a higher mounting pressure since the stress on the flat plates, i.e. the evaporator wall 14 and the condenser wall 16 is reduced by 30-40% as compared to the traditional vapor chambers 10 with cylindric or parallelepiped pillars. Thus, with commonly used fluids, the maximum working temperature can be increased as compared to the state-of-the-art vapor chambers and the use of high-pressure fluids with very good thermal properties as ammonia or even low-pressure refrigerant like R1234zd is also possible. The concave curvature of the pillars 22 with vapor chambers' flat plates, i.e. the evaporator wall 14 and the condenser wall 16 reduce the pressure drop of the liquid flow from the evaporator wall 14 to the condenser wall 16. Furthermore, the vapor space is increased. This improves the thermal performance. As an example, vapor chambers 10 with innovative shapes of the pillars 22 can be cost-effectively produced by additive manufacturing

[0078] Generally, vapor chambers 10 are emerging as the alternative solutions to water cooling for high heat flux densities in power electronic. In order to function as an air heat sink, metallic full bodied lamellas are bonded to condenser side of the vapor chamber 10 increasing the heat transfer area. The heat exchange from the lamellas to the air is the limiting factor of vapor chamber based heat sink coolers because standard type of air fins, such as full bodied lamellas, do not provide high heat transfer coefficient (turbulence) for the air side and also are subjected to the physical limitation due to the fin efficiency. To cope with very high heat losses, three dimensional vapor chamber 10 can be used. In this case, an evaporator and at least one condenser are provided in a T-like arrangement to increase the fin efficiency and the heat transfer to the surrounding area.

[0079] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.

REFERENCE SIGNS LIST

[0080] 10 vapor chamber [0081] 12 casing [0082] 14 evaporator wall [0083] 16 condenser wall [0084] 17 wick structure [0085] 18 side connection [0086] 20 side connection [0087] 21 volume [0088] 22 pillar [0089] 24 first contact area [0090] 26 second contact area [0091] 28 intermediate cross section area [0092] 30 outer surface [0093] 32 stress point