Mechanically compliant thermal spreader with an embedded cooling loop for containing and circulating electrically-conductive liquid

• US 20100065256A1
• Filed: 09/12/2008
• Published: 03/18/2010
• Est. Priority Date: 09/12/2008
• Status: Active Grant

• Current Assignee: Rockwell Collins, Inc. (Rtx Corporation)
• Original Assignee: Rockwell Collins, Inc. (Rtx Corporation)
• Inventors: Strzelczyk, Anthony J., Lower, Nathan P., Wilcoxon, Ross K., Dlouhy, David W., Wooldridge, James R.
• Granted Patent: US 8,616,266 B2
• Time in Patent Office: Days
• US Class Current: 165/104.310
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing
• CPC Class Codes: F28D 15/00 Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies F28D17/00, F28D19/00, F28D20/00 take precedence
• CPC Class Codes: F28F 21/065 the heat-exchange apparatus employing plate-like or laminated conduits
• CPC Class Codes: F28F 21/089 Coatings, claddings or bonding layers made from metals or metal alloys F28F19/06 takes precedence
• CPC Class Codes: F28F 2250/08 Fluid driving means, e.g. pumps, fans
• CPC Class Codes: F28F 2255/02 Flexible elements
• CPC Class Codes: F28F 3/06 the means being attachable to the element
• CPC Class Codes: G06F 1/20 Cooling means
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/73253 Bump and layer connectors
• CPC Class Codes: H01L 23/473 by flowing liquids H01L23/4332, H01L23/4338 take precedence
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H05K 7/20254 Cold plates transferring heat from heat source to coolant
• CPC Class Codes: Y10T 29/49353 Heat pipe device making

Abstract

The present invention is a thermal spreader for providing a high effective thermal conductivity between a heat source and a heat sink. The thermal spreader may include a mechanically flexible substrate. The mechanically flexible substrate may be at least partially constructed of organic materials. The mechanically flexible substrate may form an internal channel which is configured for containing an electrically-conductive liquid. The thermal spreader may further include a pump. The pump may be configured for being connected to the substrate and for circulating the electrically-conductive liquid within the internal channel. The thermal spreader may further include one or more thermally-conductive, rigid metal inserts. Each insert may be configured for being in thermal contact with the electrically-conductive liquid and the substrate and for promoting heat transfer between the thermal spreader and the electrically-conductive liquid.

Claims

1. A thermal spreader, comprising:

a mechanically flexible substrate, the mechanically flexible substrate forming an internal channel, the internal channel being configured for containing an electrically-conductive liquid, the internal channel being further configured to allow for closed-loop flow of the electrically-conductive liquid within the internal channel; and

a pump, the pump configured for being connected to the mechanically flexible substrate, the pump being further configured for circulating the electrically-conductive liquid within the internal channel,

wherein the thermal spreader is configured for being connected to a heat source and a heat sink, the thermal spreader being further configured for directing thermal energy from the heat source to the heat sink via the electrically-conductive liquid.

2. A thermal spreader as claimed in claim 1, further comprising:

an insert, the insert configured for being integrated with the mechanically flexible substrate, the insert being further configured for promoting thermal energy transfer to the electrically-conductive liquid and for promoting thermal energy transfer from the electrically-conductive liquid.

3. A thermal spreader as claimed in claim 2, wherein the insert includes a first surface and a second surface, the second surface being located generally opposite the first surface, the first surface configured for being oriented toward the internal channel, the second surface configured for being oriented away from the internal channel, the first surface including an extension portion for promoting thermal energy transfer between the insert and the electrically-conductive liquid and for providing structural support for the mechanically flexible substrate.

4. A thermal spreader as claimed in claim 3, wherein the insert is a rigid insert and is constructed of metal.

5. A thermal spreader as claimed in claim 4, wherein at least one of:

the first surface of the insert; and

an electrically-conductive liquid contact portion of the mechanically flexible substrate is coated with a layer of alkali silicate glass.

6. A thermal spreader as claimed in claim 5, wherein a thickness value of the layer of alkali silicate glass is a value included in a range of thickness values from 0.1 microns through 10.0 microns.

7. A thermal spreader as claimed in claim 1, wherein the mechanically flexible substrate is at least partially constructed of organic materials.

8. A thermal spreader as claimed in claim 1, wherein the electrically conductive liquid includes at least one of a liquid metal and a liquid metal alloy.

9. A thermal spreader as claimed in claim 8, wherein the liquid metal alloy includes at least two of Gallium, Indium, Tin, Zinc, Lead, and Bismuth.

10. A thermal spreader as claimed in claim 1, wherein the pump is at least one of a piezoelectric positive displacement pump, an inductive pump, and a solid state magnetic pump.

11. A thermal spreader as claimed in claim 3, wherein the extension portion of the first surface of the metal insert is at least one of:

a fin, a pin, and a plate.

12. A thermal spreader as claimed in claim 1, wherein the electrically-conductive liquid includes a metal having a melting temperature of less than 50 degrees Celsius.

13. A thermal spreader as claimed in claim 2, wherein the insert is at least partially constructed of at least one of:

a graphite foam, a graphite alloy foam, a copper alloy foam, an array of carbon nanotubes, and a thermally conductive filament.

14. A thermal spreader as claimed in claim 9, wherein the mechanically flexible substrate is at least partially constructed of organic-inorganic composite materials including at least one of:

glass, ceramics, carbon, metal reinforcements, thin metallic sheets, molded plastic materials, standard circuit board materials, flexible circuit board materials, and rigid-flex circuit cards.

15. A thermal spreader as claimed in claim 1, wherein the heat source is an electronic component connected to a circuit board and the heat sink is a chassis in which the circuit board is mounted.

16. A thermal spreader, comprising:

a mechanically flexible substrate, the mechanically flexible substrate forming an internal channel, the internal channel being configured for containing an electrically-conductive liquid, the internal channel being further configured to allow for closed-loop flow of the electrically-conductive liquid within the internal channel, the mechanically flexible substrate including a surface configured for contacting the electrically-conductive liquid, said surface of the mechanically flexible substrate being coated with alkali silicate glass, at least a portion of the mechanically flexible substrate being constructed of an organic material;

a pump, the pump configured for being connected to the mechanically flexible substrate, the pump being further configured for circulating the electrically-conductive liquid within the internal channel; and

a rigid metal insert, the rigid metal insert configured for being integrated with the mechanically flexible substrate, the rigid metal insert being further configured for promoting thermal energy transfer to the electrically-conductive liquid and for promoting thermal energy transfer from the electrically-conductive liquid, said rigid metal insert including a surface configured for contacting the electrically-conductive liquid, said surface of the rigid metal insert being coated with alkali silicate glass,

wherein the thermal spreader is configured for being connected to a heat source and a heat sink, the thermal spreader being further configured for directing thermal energy from the heat source to the heat sink via the electrically-conductive liquid.

17. A method for providing a thermal spreader, said method comprising:

fabricating a mechanically flexible substrate, said mechanically flexible substrate forming an internal channel configured for containing and allowing closed-loop flow of electrically-conductive liquid, at least a portion of the mechanically flexible substrate being constructed of an organic material;

integrating a pump with the mechanically flexible substrate, said pump configured for circulating the electrically-conductive liquid within the internal channel; and

fabricating a plurality of rigid metal inserts, each rigid metal insert configured for being integrated with the mechanically flexible substrate for promoting the transfer of thermal energy both to and from the electrically conductive liquid,

wherein the thermal spreader is configured for being connected to a heat source and a heat sink, the thermal spreader being further configured for directing thermal energy from the heat source to the heat sink via the electrically-conductive liquid.

18. A method as claimed in claim 17, further comprising:

forming a plurality of extension portions on a surface of each rigid metal insert included in the plurality of rigid metal inserts, said extension portions configured for promoting thermal energy transfer between the rigid metal insert and the electrically-conductive liquid; and

connecting the plurality of rigid metal inserts to the mechanically flexible substrate.

19. A method as claimed in claim 18, further comprising:

coating a metal portion of an electrically-conductive liquid contact surface of the mechanically flexible substrate with a layer of alkali silicate glass; and

coating an electrically-conductive liquid contact surface of each rigid metal insert with a layer of alkali silicate glass.

20. A method as claimed in claim 19, further comprising:

integrating a plurality of passivation metal-coated electrodes with the mechanically flexible substrate, said electrodes configured for generating an electrical current flow through the electrically-conductive liquid via an applied voltage to said electrodes.