Heatsink with periodically patterned baseplate structure

• US 7,848,108 B1
• Filed: 08/06/2009
• Issued: 12/07/2010
• Est. Priority Date: 08/06/2009
• Status: Active Grant

• Current Assignee: Lenovo International Limited (Lenovo Group Ltd.)
• Original Assignee: International Business Machines Corporation
• Inventors: Chikando, Eric N., Maas, John S., Archambeault, Bruce R., Connor, Samuel R.
• Primary Examiner(s): CHERVINSKY, BORIS LEO
• Application Number:
  US12/536,655
• Time in Patent Office: 488 Days
• Field of Search: None
• US Class Current: 361/719
• CPC Class Codes: H01L 23/3677 Wire-like or pin-like cooling fins or heat sinks
• CPC Class Codes: H01L 23/467 by flowing gases, e.g. air H01L23/473 takes precedence
• CPC Class Codes: H01L 23/552 Protection against radiation, e.g. light or electromagnetic waves
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A heatsink including an electromagnetic bandgap structure reduces electromagnetic interference caused by an integrated circuit in an electronic device. One embodiment provides a heatsink having a base with an array of electrically-conductive, thermally-conductive patches spaced apart in two dimensions of a reference plane and having a thickness perpendicular to the reference plane. The patches are interconnected by a plurality of branches. Each branch connects adjacent patches and has a width in the reference plane of less than a width of each adjacent patch. A plurality of thermally conductive cooling fins coupled to a surface of the base and extend normal to the reference plane. The cooling fins may be formed of a thermally-conductive, electrically non-conductive material or may be coupled to the base by a thermally-conductive, electrically non-conductive material. The periodically patterned structure of the base, together with a solid metal layer of a circuit board, form an electromagnetic bandgap structure that reduces certain frequencies of electromagnetic noise caused by the integrated circuit.

Claims

1. A heatsink, comprising:

a base having a periodically patterned structure comprising an array of electrically-conductive, thermally-conductive patches spaced apart in two dimensions of a reference plane and having a thickness perpendicular to the reference plane;

a plurality of branches structurally connecting the patches, each branch connecting adjacent patches and having a width in the reference plane of less than a width of each adjacent patch; and

a plurality of thermally conductive cooling fins coupled to the base and extending normal to the reference plane.

2. The heatsink of claim 1, wherein a cross-section of the periodically-patterned structure is constant in a direction normal to the reference plane.

3. The heatsink of claim 1, further comprising:

a thermally conductive, electrically non-conductive filler filling the spaces between the adjacent patches.

4. The heatsink of claim 1, wherein the patches have an electrical conductivity coefficient of at least 10^7 S/m and a thermal conductivity coefficient of greater than 1 W/m*K.

5. The heatsink of claim 1, further comprising:

a thermally-conductive, electrically non-conductive binder coupling the cooling fins to a surface of the base.

6. The heatsink of claim 1, wherein the cooling fins are thermally-conductive and electrically non-conductive.

7. The heatsink of claim 1, wherein each branch has a surface area of less than about 15 percent of the surface area of either of the adjacent patches in the reference plane.

8. The heatsink of claim 1, wherein the periodically patterned structure and the branches share common first and second opposing surfaces.

9. An apparatus comprising:

a printed circuit board including a continuous, electrically-conductive layer;

a processor physically coupled to the printed circuit board and electrically coupled to the electrically-conductive layer; and

a heatsink coupled to the circuit board in thermal contact with the processor, the heatsink including a base having a periodically patterned structure comprising an array of electrically-conductive, thermally-conductive patches spaced apart in two dimensions of a reference plane that is parallel to the conductive layer and having a thickness perpendicular to the conductive layer, a plurality of branches structurally connecting the patches, each branch spanning an opening between two adjacent patches and having a width in the reference plane of less than a width of each adjacent patch, and a plurality of thermally conductive cooling fins coupled to the base and extending perpendicular to the reference plane.

10. The apparatus of claim 9, wherein the conductive layer of the printed circuit board is a ground plane.

11. The apparatus of claim 10, further comprising:

a plurality of metal posts securing the processor to the circuit board, wherein the metal posts are not grounded to the ground layer.

12. The apparatus of claim 9, further comprising a thermally-conductive, electrically non-conductive binder coupling the cooling fins to the base.

13. The apparatus of claim 9, wherein the periodically-patterned structure has a substantially constant cross-section taken parallel to the reference plane.

14. The apparatus of claim 9, further comprising:

a thermally conductive, electrically non-conductive filler filling the spaces between the adjacent patches.

15. The apparatus of claim 9, wherein the patches have an electrical conductivity coefficient of at least 10^7 S/m and a thermal conductivity coefficient of greater than 1 W/m*K.

16. The apparatus of claim 9, wherein the thermally-conductive, electrically non-conductive binder comprises an epoxy.

17. The apparatus of claim 9, wherein each branch has a surface area of less than about 15 percent of the surface area of either of the adjacent patches.

18. The apparatus of claim 9, wherein the periodically patterned structure and the branches share common first and second opposing planar surfaces.

19. A method of reducing the propagation of electromagnetic noise generated by an integrated circuit, comprising:

identifying a frequency band of the electromagnetic noise generated by the integrated circuit;

selecting a periodic pattern of spaced apart patches interconnected by branches with geometry having stopband within the identified frequency band; and

thermally contacting the integrated circuit with a heatsink having a base that includes an electrically-conductive, thermally-conductive material having the selected periodic pattern.

20. The method of claim 19, wherein the step of selecting a periodic pattern of spaced apart patches interconnected by branches with geometry having stopband within the identified frequency band comprises selecting one or more of the group consisting of a patch width, a patch length, a branch width, a branch length, and a base thickness.