Heat spreading circuit assembly

• US 7,889,502 B1
• Filed: 11/04/2005
• Issued: 02/15/2011
• Est. Priority Date: 11/04/2005
• Status: Expired due to Fees

• Current Assignee: NeoGraf Solutions, LLC
• Original Assignee: Graftech International Holdings Inc (Graftech International Limited)
• Inventors: Reis, Bradley E., Cartiglia, James R.
• Primary Examiner(s): Gandhi; Jayprakash N
• Assistant Examiner(s): SMITH, COURTNEY L
• Application Number:
  US11/267,933
• Time in Patent Office: 1,929 Days
• Field of Search: 361/710, 361/719, 361/703, 361/707, 361/717, 165/80.3, 165/185, 165/46, 165/172, 257 13- 14, 257/79, 174/16.3, 428/195.1
• US Class Current: 361/717
• 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
• CPC Class Codes: H05K 1/0203 Cooling of mounted components H05K1/0272 takes precedence
• CPC Class Codes: H05K 1/182 associated with components mounted in the printed circuit board, e.g. insert mounted components [IMC]
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 7/205 Heat-dissipating body thermally connected to heat generating element via thermal paths through printed circuit board [PCB] details of PCBs relating to heat transfer H05K1/0201
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Abstract

A circuit assembly including a substrate which has a dielectric layer, a heat spreader layer located at a first surface of the substrate, a heat generating component located at a second surface of the substrate, and a thermal pathway in thermal connection between the heat spreader layer and the heat generating component.

Claims

1. A circuit assembly comprising a substrate which comprises a dielectric layer, a heat spreader layer which comprises at least one sheet of compressed particles of exfoliated graphite having two major surfaces, wherein the heat spreader layer is located at a first surface of the substrate, wherein the second surface of the substrate has a circuit thereon and an LED having an LED mounting plane mounted on the circuit, and a thermal pathway in thermal connection with both the heat spreader layer and the LED, wherein the thermal pathway has a length such that it extends through the substrate and at least substantially through the heat spreader layer and further wherein the surface area of the major surface of the heat spreader layer which is located at the first surface of the substrate is greater than the surface area of the surface of the substrate at which the heat spreader layer is located such that the heat spreader layer extends perpendicular to the LED mounting plane.

2. The circuit assembly of claim 1, wherein the dielectric layer comprises a material selected from the group consisting of glass fiber impregnated with resin;

polytetrafluoroethylene;

expanded polytetrafluoroethylene;

a polymer;

a ceramic material;

or combinations thereof.

3. The circuit assembly of claim 1, wherein the dielectric layer comprises anodized aluminum, aluminum nitride, aluminum oxide or alumina.

4. The circuit assembly of claim 1, wherein the thermal pathway comprises a thermally conductive material.

5. The circuit assembly of claim 4, wherein the thermal conductivity of the thermal pathway is greater than the through-thickness thermal conductivity of the dielectric layer.

6. The circuit assembly of claim 5, wherein the thermal pathway comprises copper, aluminum, or alloys thereof.

7. The circuit assembly of claim 5, further comprising a dielectric layer on the thermal pathway, wherein the dielectric layer comprises anodized aluminum, aluminum nitride, aluminum oxide or alumina.

8. The circuit assembly of claim 7, wherein the heat spreader layer is bent at an angle of about 90°

.

9. The circuit assembly of claim 1, wherein a thermal interface material is positioned between the heat generating component and the thermal pathway.

10. The circuit assembly of claim 9 wherein the thermal interface material comprises a grease, an epoxy material, solder, a sheet of compressed particles of exfoliated graphite, or combinations thereof.

11. The circuit assembly of claim 1, wherein the heat spreader layer has a black outer surface.

12. The circuit assembly of claim 1, wherein the heat spreader layer is at least partially encapsulated.

13. The circuit assembly of claim 12, wherein the heat spreader layer is at least partially encapsulated in a polymer or anodized aluminum.

14. The circuit assembly of claim 13, wherein the polymer or anodized aluminum which encapsulates the heat spreader layer comprises the dielectric layer.

15. The circuit assembly of claim 1, wherein the LED has a thermally conductive slug or rivet extending therefrom.

16. The circuit assembly of claim 15, wherein the slug or rivet extends into thermal contact with the heat spreader layer.

17. The circuit assembly of claim 1, wherein the thermal pathway comprises a collection bar having a plurality of thermal pathway units extending therefrom.

30. The circuit assembly of claim 1, which comprises a component of an LCD display.

33. The circuit assembly of claim 1, wherein the thermal pathway comprises a thermal via.

36. The circuit assembly of claim 1, wherein the thermal pathway has a length at least equal to the thickness of the substrate and heat spreader layer.

18. A circuit assembly comprising a substrate which comprises a dielectric layer having two surfaces, a heat spreader layer comprising at least one sheet of compressed particles of exfoliated graphite having two major surfaces, wherein the heat spreader layer is positioned adjacent a first surface of the substrate, a circuit located at a second surface of the substrate with an LED having an LED mounting plane mounted on the circuit, and a thermal pathway which extends through the substrate and is in thermal connection with both the heat spreader layer and the LED, wherein the surface area of one of the major surfaces of the heat spreader layer is greater than the surface area of the first surface of the substrate such that the heat spreader layer extends perpendicular to the LED mounting plane and beyond the second surface of the substrate.

19. The circuit assembly of claim 18, wherein there is a gap between the substrate and the heat spreader layer.

20. The circuit assembly of claim 18, wherein the thermal pathway comprises a thermally conductive material.

21. The circuit assembly of claim 20, wherein the thermal conductivity of the thermal pathway is greater than the through-thickness thermal conductivity of the dielectric layer.

22. The circuit assembly of claim 19, wherein the heat spreader layer has a black outer surface.

23. The circuit assembly of claim 19, wherein the heat spreader layer is at least partially encapsulated.

31. The circuit assembly of claim 18, which comprises a component of an LCD display.

34. The circuit assembly of claim 18, wherein the thermal pathway comprises a thermal via.

24. A flex circuit comprising a substrate which comprises a flexible dielectric layer, a heat spreader layer comprising at least one sheet of compressed particles of exfoliated graphite having two major surfaces, wherein the heat spreader layer is located at a first surface of the substrate, a circuit located at a second surface of the substrate with an LED having an LED mounting plane mounted on the circuit, and a thermal pathway in thermal connection with both the heat spreader layer and the LED, wherein the thermal pathway has a length at least equal to the thickness of the substrate and heat spreader layer and further wherein the surface area of one of the major surfaces of the heat spreader layer is greater than the surface area of the surface of the substrate at which the heat spreader layer is located such that the heat spreader layer extends perpendicular to the LED mounting plane.

25. The flex circuit of claim 24, wherein the dielectric layer comprises a polymer.

26. The flex circuit of claim 24, wherein the thermal pathway comprises a thermally conductive material.

27. The flex circuit of claim 26, wherein the thermal pathway comprises copper.

28. The flex circuit of claim 26, wherein the thermal pathway has a length approximately equal to the thickness of the substrate and heat spreader layer.

29. The flex circuit of claim 26, wherein the thermal pathway has a length approximately equal to the thickness of the heat spreader layer.

32. The flex circuit of claim 24, which comprises a component of an LCD display.

35. The flex circuit of claim 24, wherein the thermal pathway comprises a thermal via.