Thermally Conductive Interface

• US 20070113399A1
• Filed: 11/07/2006
• Published: 05/24/2007
• Est. Priority Date: 05/24/2005
• Status: Active Grant

• Current Assignee: American Standard Circuits, Inc.
• Original Assignee: American Standard Circuits, Inc.
• Inventors: Patel, Bhavik, Sites, Gary, Kumar, Sundaram
• Granted Patent: US 7,540,081 B2
• Time in Patent Office: Days
• US Class Current: 29/831
• CPC Class Codes: H05K 2201/0162 Silicon containing polymer, e.g. silicone
• CPC Class Codes: H05K 2201/0209 Inorganic, non-metallic particles
• CPC Class Codes: H05K 2203/0191 Using tape or non-metallic foil in a process, e.g. during filling of a hole with conductive paste
• CPC Class Codes: H05K 2203/068 Features of the lamination press or of the lamination process, e.g. using special separator sheets
• CPC Class Codes: H05K 3/0061 onto a metallic substrate, e.g. a heat sink heat sinks for electric apparatus H05K7/20
• CPC Class Codes: H05K 3/386 by the use of an organic polymeric bonding layer, e.g. adhesive
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 428/14 Layer or component removable to expose adhesive
• CPC Class Codes: Y10T 428/24926 including ceramic, glass, porcelain or quartz layer
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

A thermally conductive material is provided as a mixture of a silicone, a ceramic powder, and a curing catalyst. The material may be pre-formed into a pad and each side of the film protected with removable release layers. Each side of the film may also include a coating of an adhesive material that aids in coupling the interface film with a surface. The material may alternatively be produced in a screen-printable paste. As such, a layer of the paste may be screen-printed on a surface as complete sheet form or as a patterned film by using a stencil patterned screen mesh. The interface material is sandwiched between a printed circuit board and a heat sink to form the circuit board assembly. In a multi-step press process, the assembly is cured and a laminate formed. The assembly process may also include a priming function that prepares metal surfaces of the circuit board and heat sink for receiving the interface material.

Claims

1. A method of manufacturing a circuit board assembly having improved heat dissipation functionality comprising:

providing a thermally conductive, electrically non-conducting interface film including;

a first side and a second side wherein the interface includes resilient silicone, a ceramic powder for enhancing thermal conductivity, an organic curing catalyst, a first release layer protecting a first side, and a second release layer protecting a second side;

sandwiching the interface between a metal base layer of a printable circuit board and a planar side of a heat sink to form the assembly;

in a mechanism for applying pressure, applying a first pressure treatment to the assembly at a room temperature to increase surface contact and to remove air pockets;

applying a second pressure treatment to the assembly at a high temperature to cure the interface and create a laminate; and

applying a third pressure treatment to the assembly at a low temperature to controllably return the assembly to room temperature.

2. The method of claim 1, wherein the resilient silicone is a dimethyl silicone.

3. The method of claim 1, wherein the ceramic powder includes a ceramic selected from the group consisting of aluminum oxide;

aluminum nitride; and

boron nitride.

4. The method of claim 1, wherein the interface film further includes:

a first adhesive applied to the first side; and

a second adhesive applied to the second side.

5. The method of claim 1, wherein the second pressure treatment includes application of at pressure of at least 140 psi at a temperature of at least 320 degrees Fahrenheit for at least 20 minutes.

6. The method of claim 1, further comprising:

trimming excess interface material from an edge of the assembly.

7. The method of claim 1, wherein the interface film has a pre-laminate thickness of between 2 and 200 mils.

8. The method of claim 1, wherein the interface film has a pre-laminate thickness of approximately 4 mils.

18. The method of claim 8, wherein the dimethyl silicone is a methyl-poly silicone oxide.

9. A method of manufacturing a circuit board assembly having improved heat dissipation functionality comprising:

screen-printing a thermally conductive, electrically non-conductive interface layer onto a first planar surface of one of a printable circuit board and a heat sink, wherein the interface layer comprises a mixture of dimethyl silicone, a ceramic powder for enhancing thermal conductivity, and a curing catalyst;

sandwiching the interface layer between a the first planar surface and a second planar surface of the remaining one of the printable circuit board and the heat sink to form the assembly;

applying a first pressure treatment to the assembly at a room temperature to increase surface contact and to remove air pockets;

applying a second pressure treatment to the assembly at a high temperature to cure the interface and create a laminate; and

applying a third pressure treatment to the assembly at a low temperature to controllably return the assembly to room temperature.

10. The method of claim 9, wherein the second pressure treatment includes application of at pressure of at lease 140 psi at a temperature of at least 320 degrees Fahrenheit for at least 20 minutes.

11. The method of claim 9, wherein the third pressure treatment includes application of at pressure of approximately 40 for at approximately 10 minutes.

12. The method of claim 9, wherein the second pressure treatment includes application of at pressure of approximately 150 psi at a temperature of at approximately 330 degrees Fahrenheit for at approximately 20 minutes.

13. The method of claim 9, prior to screen-printing the interface layer, cleaning, surface roughening and applying a primer to the planar surface of the printable circuit board.

14. The method of claim 9, by which film is applied in a continuous form or as a stencil patterned format, further comprising:

repeating the screen-printing function a predetermined number of times to achieve a desired interface thickness.

15. The method of claim 9, wherein the organic curing catalyst is a peroxide.

16. The method of claim 9, wherein the ceramic powder includes a ceramic selected from the group consisting of aluminum oxide;

aluminum nitride; and

boron nitride.

17. The method of claim 9, further comprising:

trimming excess interface material from an edge of the assembly.

19-20. -20. (canceled)