Heat Sink with Thermally Compliant Beams

• US 20090039499A1
• Filed: 08/06/2007
• Published: 02/12/2009
• Est. Priority Date: 08/06/2007
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Chainer, Timothy J.
• Granted Patent: US 7,749,812 B2
• Time in Patent Office: Days
• US Class Current: 257/706
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 23/3677 Wire-like or pin-like cooling fins or heat sinks
• CPC Class Codes: H01L 23/433 Auxiliary members in containers characterised by their shape, e.g. pistons
• 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 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/10253 Silicon [Si]

Abstract

A heat dissipating structure includes: a heat spreader; and a plurality of compliant beams attached to the heat spreader. The beams are formed of a high-conductive material such that a maximum stress of each beam is less than a fatigue stress of the high-conductive material; said beams are placed at an angle relative to a chip surface such that the beams are able to exert bending compliance in response to x, y, and z forces exerted upon them. The structure also includes a thermal material interface for bonding said structure to the chip surface. Both the heat spreader and the compliant beams can be machined from a copper block. An alternative heat dissipating structure includes compliant beams soldered to the chip surface.

Claims

1. A heat dissipating structure for dissipating heat generated by an electronic chip, the heat-dissipating structure comprising:

a heat spreader; and

a plurality of compliant beams attached to a surface of the heat spreader, the compliant beams being formed from a high-conductive material such that a maximum stress of each compliant beam is less than a fatigue stress of the high-conductive material;

said compliant beams being placed at an angle relative to a chip surface such that the compliant beams are able to exert bending compliance in response to x, y, and z forces exerted upon them.

2. The heat dissipating structure of claim 1 further comprising:

a thermal interface material for bonding said heat dissipating structure to the chip surface.

3. The heat dissipating structure of claim 1 wherein the compliant beams comprise beryllium copper beams.

4. The heat dissipating structure of claim 1 wherein the compliant beams and the heat spreader are machined from a block of high-conductive material to form a single structure.

5. The heat dissipating structure of claim 1 wherein the heat spreader comprises copper.

6. The heat dissipating structure of claim 1 wherein the heat spreader is placed under a bearing weight to exert z forces on the compliant beams to bring them into physical contact with the chip surface.

7. The heat dissipating structure of claim 1 wherein the compliant beams comprise a serpentine shape and wherein a bottom surface of each of the compliant beams remains parallel to the chip surface.

8. The heat dissipating structure of claim 1 wherein the compliant beams comprise a plurality of angles.

9. The heat dissipating structure of claim 2 wherein a gap between the compliant beams and the chip surface is substantially zero.

10. The heat dissipating structure of claim 1 wherein the beams are placed at an angle lying between forty-five degrees and eighty-five degrees relative to the chip surface, and wherein a bottom surface of each compliant beam is parallel to the chip surface.

11. The heat dissipating structure of claim 1 wherein the bending compliance comprises an ability to bend forward, backward, and laterally.

12. The heat dissipating structure of claim 1 further comprising the electronic chip.

13. The heat dissipating structure of claim 2 wherein the thermal interface material comprises solder balls.

14. The heat dissipating structure of claim 1 wherein the compliant beams are soldered to the chip surface such that a bottom surface of each of the compliant beams remains parallel to the chip surface.

15. The heat dissipating structure of claim 1 wherein the compliant beams are designed based upon a distance from a center point of the chip surface.

16. The heat dissipating structure of claim 15 wherein the bending compliance of the compliant beams varies over the heat dissipating structure based upon the distance from the center point, wherein outermost compliant beams comprise a longer vertical beam structure to allow for increased compliance in the x and y directions.

17. A method of producing a heat dissipating structure, the method comprising:

shaping a plurality of compliant beams;

attaching the plurality of compliant beams to a surface of a heat spreader, wherein the compliant beams are formed of a high-conductive material such that a maximum stress of each compliant beam is less than a fatigue stress of the high-conductive material; and

placing the compliant beams at an angle relative to a chip surface such that the compliant beams are able to exert bending compliance in response to x, y, and z forces exerted upon them.

18. The method of claim 17 further comprising:

placing the heat spreader under a bearing weight to exert z forces on the compliant beams to bring them into physical contact with the chip surface.

19. The method of claim 17 wherein the placing element comprises:

placing the compliant beams at an angle lying between forty-five degrees and eighty-five degrees relative to the chip surface; and

wherein a bottom surface of each compliant beam is parallel to the chip surface.

20. The method of claim 17 further comprising:

placing solder balls between the heat dissipating structure and the chip surface for bonding said heat dissipating structure to the chip surface.