Method and apparatus for heat dispersion from the bottom side of integrated circuit packages on printed circuit boards

• US 6,349,033 B1
• Filed: 12/29/1999
• Issued: 02/19/2002
• Est. Priority Date: 12/29/1999
• Status: Expired due to Term

• Current Assignee: Radisys Corporation (Reliance Industries Limited)
• Original Assignee: Radisys Corporation (Reliance Industries Limited)
• Inventors: Dubin, Israel, Erwin, Charles M.
• Primary Examiner(s): THOMPSON, GREGORY D
• Application Number:
  US09/474,721
• Time in Patent Office: 783 Days
• Field of Search: 165/80.2, 165/80.3, 165/185, 174/16.3, 174/252, 257/706-707, 257/712-713, 257/720, 361/699, 361/702, 361/704-708, 361/710, 361/715-721
• US Class Current: 361/704
• CPC Class Codes: H01L 2224/33 of a plurality of layer connectors
• CPC Class Codes: H01L 23/36 Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks H01L23/28, H01L23/40, H01L23/42, H01L23/44, H01L23/46 take precedence; heating H01L23/345
• CPC Class Codes: H01L 23/3677 Wire-like or pin-like cooling fins or heat sinks
• CPC Class Codes: H01L 23/3737 Organic materials with or without a thermoconductive filler

Abstract

The present invention relates to a method and apparatus of heat dispersion from the bottom side of an integrated circuit package mounted on a printed circuit board (“PCB”). In operation, a heat slug is thermally coupled to the underside of an integrated circuit (“IC”) package. In one embodiment, the heat slug comprises a disc made of copper or other thermally conductive material in between two layers of elastomeric, conductive material such as silicone imbedded with aluminum particles. The thermal pad extends through each layer of the PCB, including the ground layer. In this way, the ground layer of the PCB is utilized for heat dispersion.

Claims

1. A thermal disc assembly for providing heat dissipation from an integrated circuit having an underside, comprising:

a first elastomeric, conductive layer having a top and bottom surface, wherein the top surface of said first elastomeric, conductive layer is adapted to be thermally coupled to the underside of the integrated circuit;

a conductive disc having a top and bottom surface, wherein said top surface of said conductive disc is thermally coupled to said bottom surface of said first elastomeric, conductive layer;

a second elastomeric, conductive layer having a top and bottom surface, wherein the top surface of said second elastomeric, conductive layer is thermally coupled to said bottom surface of said conductive disc, and wherein said bottom surface of said second elastomeric, conductive layer is in thermal contact with a printed circuit board.

2. The thermal disc assembly of claim 1, wherein said first and second elastomeric, conductive layers comprise a metal dispersed within an elastomeric medium.

3. The thermal disc assembly of claim 2, wherein said elastomeric medium comprises silicone.

4. The thermal disc assembly of claim 1, wherein said conductive disc is formed in the shape of a cylinder having a diameter.

5. The thermal disc assembly of claim 4, wherein said first and second elastomeric, conductive layers are formed in the shape of cylinders having diameters.

6. The thermal disc assembly of claim 5, wherein said diameters of said conductive disc, said first conductive layer, and said second conductive layers are approximately equal.

7. The thermal disc assembly of claim 1, wherein said conductive disc comprises copper.

8. A printed circuit board having a top surface and bottom surface, said printed circuit board designed for providing heat dissipation from an integrated circuit mounted on said printed circuit board, said integrated circuit having an underside, comprising:

a first elastomeric, conductive layer having a top and bottom surface, wherein the top surface of said first elastomeric, conductive layer is adapted to be thermally coupled to the underside of the integrated circuit;

a conductive disc having a top and bottom surface, wherein said top surface of said conductive disc is thermally coupled to said bottom surface of said first elastomeric, conductive layer;

a second elastomeric, conductive layer having a top and bottom surface, wherein the top surface of said second elastomeric, conductive layer is thermally coupled to said bottom surface of said conductive disc, and wherein said bottom surface of said second elastomeric, conductive layer is in thermal contact with a printed circuit board;

thermal vias extending vertically within said printed circuit board and in thermal contact with said second bottom side of said second elastomeric, conductive layer; and

a ground plane extending horizontally through said printed circuit board and thermally coupled to said thermal vias.

9. The printed circuit board of claim 8, wherein said first and second elastomeric, conductive layers comprise a metal dispersed within an elastomeric medium.

10. The printed circuit board of claim 9, wherein said elastomeric medium comprises silicone.

11. The printed circuit board of claim 8, wherein said conductive disc is formed in the shape of a cylinder having a diameter.

12. The printed circuit board of claim 11, wherein said first and second elastomeric, conductive layers are formed in the shape of cylinders having diameters.

13. The printed circuit board of claim 12, wherein said diameters of said conductive disc, said first conductive layer, and said second conductive layers are approximately equal.

14. The printed circuit board of claim 8, wherein said conductive disc comprises copper.

15. The printed circuit board of claim 8, wherein said thermal vias comprise copper.

16. The printed circuit board of claim 8, wherein said thermal vias comprise thermally conductive elastomers having a liquid form, said thermally conductive elastomer being injected into said printed circuit board while said thermally conductive elastomer is in said liquid form.

17. A method of dissipating heat from an integrated circuit having a bottom surface, said integrated circuit being mounted on a printed circuit board having a top surface, comprising:

positioning a conductive disc in thermal contact with said bottom surface of said integrated circuit and said top surface of said printed circuit board, said conductive disc having a top side and a bottom side; and

disposing thermal vias within said printed circuit board board for channeling heat away from said integrated circuit into said printed circuit board, wherein said thermal vias are in thermal contact with said top surface of said printed circuit board; and

placing said top side of said conductive disc in thermal contact with a first layer of thermally elastomeric, conductive material.

18. The method of claim 17, wherein said bottom side of said conductive disc is placed in thermal contact with a second layer of elastomeric, thermally conductive material.

19. The method of claim 18, wherein said first layer of elastomeric, thermally conductive material has a top side and a bottom side, and wherein said top side of said first layer of elastomeric, thermally conductive material is placed in thermal contact with said bottom side of said integrated circuit.

20. The method of claim 19, wherein said second layer of elastomeric, thermally conductive material has a top side and a bottom side, and wherein said bottom side of said second elastomeric, thermally conductive material is placed in thermal contact with said top side of said printed circuit board.

21. The method of claim 17, wherein said thermal vias are created by drilling cavities in said printed circuit board and injecting a liquid, thermally conductive elastomer into said cavities in said printed circuit board.