Laminated fin heat sink for electronic devices

Abstract

A heat sink may transfer heat from electronic devices. A heat conductive base may have integrally attached thereto a plurality of parallel fins. The fins may be made up of two sheets of material. One sheet may be a metal having significant structural integrity and the other sheet of material may be a pyrolytic graphite material having excellent heat transfer characteristics. The two layers may be integrally bonded together.

Description

BACKGROUND

[0001] This invention relates to removing heat from heat producing electronic devices such as microprocessors.

[0002] In operation, electronic devices, including microprocessors, tend to generate heat. Their performance may be adversely affected by their temperature. Thus, it is advantageous to remove heat from the integrated circuits as effectively as possible.

[0003] To this end, heat sinks are commonly attached to integrated circuit packaging. These heat sinks may include fins and integrated heat spreaders which transfer heat from the integrated circuit packaging to the heat sink.

[0004] Existing heat sinks tend to be heavy, contributing to weight of the overall electronic device. In some electronic devices, including mobile devices, overall weight is an important factor.

[0005] Thus, there is a need for ways to improve the heat transfer from electronic devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a partial, front elevational view of one embodiment of the present invention in the course of manufacture;

[0007] FIG. 2 is a partial, front elevational view of the embodiment of FIG. 1 after further processing; and

[0008] FIG. 3 is a perspective view of one embodiment of the present invention.

DETAILED DESCRIPTION

[0009] Referring to FIG. 1, a heat sink base 12 may be formed of copper or other heat conducting material. The base 12 may have a number of closely spaced fin receiving apertures 16. In one embodiment, the fin receiving apertures 16 may have a downwardly expanding, dovetail shape.

[0010] A heat sink fin 14b may include a metallic layer 18 and a graphite or non-metallic layer 16. The non-metallic layer 16 provides good heat transfer characteristics at relatively lower weight compared to metals. In other words, the layer 16 is lighter than the layer 18 per unit of volume. The layers 16 and 18 may be bonded together along the line 20.

[0011] In the illustrated embodiment, the layers 16 and 18 are of equal thickness. One of the layers 16 or 18 may be thicker in some embodiments.

[0012] In order to join the fin 14b to the base 12, crimping forces, indicated by the arrows A and B, may be applied in one embodiment. In other words, the heat sink fin 14b may be inserted into the slot 16. Thereafter, the two opposed sides of the base 12 are compressed together causing the edges 17 to cut into and engage the material of the fin 14b. To this end, it may be advantageous, in some embodiments, that the material of the base 12 is harder than the material used for the layer 16 or 18.

[0013] Referring to FIG. 2, the completed structure may include a fin 14a engaged in a dovetail arrangement in the base 12. Indentations 19 may be formed in the fin 14a caused by the base material 12 crimping process.

[0014] The fins 14 may be made of a high conductivity metal and a pyrolytic graphite material in some embodiments. The two material sheets may be compressed together and held in place with a high thermal conductivity adhesive along the bond line 20 to form a laminated fin 14. The laminated fin 14 may then be permanently attached to the heat sink base 12, for example, using the crimping process illustrated in FIGS. 1 and 2. The laminated fin 14 is used in place of the traditional solid metal fin, achieving improved thermal performance and reduction in weight in some embodiments.

[0015] The metal layer 18 provides structural integrity to the laminated fin 14. An isotropic metal layer 18 may also act as a medium to transfer heat to the surrounding air via forced convection, as one example. In one embodiment, the layer 18 may be aluminum.

[0016] The layer 16, which may be graphite, may spread the heat in a more efficient manner than metal since layer 16 may have a thermal conductivity value on the order of three times that of solid metals. Since graphite material is non-isotropic, thermal conductivity in one direction is significantly lower than in the other two directions of heat transfer. As a result, heat may be transferred effectively in the direction of the fin height and length, but not so in the direction of fin thickness. However, this is insignificant since the heat can still easily be transferred through the relatively thin fin thickness.

[0017] The layer 16 may be in intimate contact with the base 12 to improve the heat transfer through the laminated fin 14. To this end, the laminate fin 14 may be permanently attached to the base 12.

[0018] In some embodiments of the present invention, graphite material with advantageous heat transfer properties can be used in a fin shape having relatively extended aspect ratios. Normally, graphite material would not be sufficiently tough to be used in such environments. However, the combination of graphite and metal has both advantageous heat transfer properties and sufficient structural integrity.

[0019] Referring to FIG. 3, the heat sink fins 14 may be attached to a base 12 so that a large number of fins are arranged in close proximity. The fins 14 may be rectangular in shape, in one embodiment, with the long axis extending along and into the base 12. An electronic device 20, such as a microprocessor, may be thermally coupled to the base 12. In some embodiments, thermal interface materials may be utilized between the device 20 and the base 12. In addition, an integral heat spreader may be applied between the electronic device 20 and the base 12. In some embodiments, the electronic device 20 may consist of an integrated circuit enclosed within an integrated heat spreader.

[0020] In one embodiment of the present invention, the aspect (height to thickness) ratio of the fins 14 may be higher than 20:1. In one particularly advantageous embodiment, the aspect ratio may be 60:1.

[0021] While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.

Claims

What is claimed is:

1. A method comprising: forming a heat transfer fin of a laminate of a metallic and a non-metallic layer, said metallic layer providing structural integrity to the laminated fin.

2. (canceled)

3. The method of claim 1 including permanently securing said fin to a heat conductive base using crimping.

4. The method of claim 1 including adhesively bonding said metallic and non-metallic layers.

5. The method of claim 1 wherein forming a heat transfer fin includes forming a fin of a laminate of a metallic and a pyrolytic graphite material.

6. The method of claim 1 including forming the fin with an aspect ratio higher than 20:1.

7. The method of claim 5 including forming the fin with an aspect ratio of 60:1.

8. The method of claim 1 including securing heat transfer fin to an integrated circuit.

9. The method of claim 8 including securing said heat transfer fin to a microprocessor.

10. The method of claim 2 including forming the metallic and non-metallic material of equal thicknesses.

11. A heat sink comprising: a heat sink fin including metallic and non-metallic materials, said metallic material providing structural integrity to said fin; and a conductive base, said fin secured to said base.

12. (canceled)

13. The heat sink of claim 11 wherein said fin is crimped to said base.

14. The heat sink of claim 11 wherein said metallic and non-metallic materials are adhesively bonded.

15. The heat sink of claim 11 wherein said non-metallic material is a pyrolytic graphite material.

16. The heat sink of claim 11 wherein the fin aspect ratio is higher than 20:1.

17. The heat sink of claim 16 wherein the fin aspect ratio is 60:1.

18. The heat sink of claim 11 wherein said base is secured to an integrated circuit.

19. The heat sink of claim 18 wherein said integrated circuit is a microprocessor.

20. The heat sink of claim 11, said fin including a first sheet of metallic material and a second sheet of non-metallic material, said sheets being laminated together.

21. The heat sink of claim 20 wherein said first and second sheets are of equal thicknesses.

22. An integrated circuit comprising: an integrated circuit chip; and a heat sink secured to said chip, said heat sink including a heat transfer fin of a laminate of metallic and non-metallic material, said metallic material providing structural integrity to said fin.

23. The circuit of claim 22 wherein said heat sink includes a conductive base, and said fin is crimped to said base.

24. The circuit of claim 22 wherein said metallic and non-metallic materials are adhesively bonded.

25. The circuit of claim 22 wherein said non-metallic material is a pyrolytic graphite material.

26. The circuit of claim 22 wherein the fin aspect ratio is higher than 20:1.

27. The circuit of claim 26 wherein the fin aspect ratio is 60:1.

28. The circuit of claim 22 wherein said heat sink includes a base secured to said integrated circuit chip.

29. The circuit of claim 28 wherein said integrated circuit chip is a microprocessor.

30. The circuit of claim 22 wherein said metallic and non-metallic material are of equal thicknesses.