Polymer composite thermal interface material with high thermal conductivity

Patent metadata

Field	Value
Publication number	US-2016137900-A1
Application number	US-201414546394-A
Country	US
Kind code	A1
Filing date	Nov 18, 2014
Priority date	Nov 18, 2014
Publication date	May 19, 2016
Grant date	—

Abstract

The present invention relates generally to thermally conductive adhesives for thermal interfaces in electronic packaging, and more particularly, to a polymer-based composite thermal interface material (“TIM”) with an inter-penetrating network (IPN) polymer matrix consisting of polyurethane and an epoxy that is fully crosslinked. The IPN polymer matrix is designed to improve overall thermal conductivity by the altering the dispersion/distribution of thermally conductive fillers, the filler/polymer interfaces, and/or phonon scattering behaviors in the composite.

First claim

What is claimed is:

1 . A thermal interface material (TIM) comprising:
a polymer based composite comprising an inter-penetrating network (IPN) matrix structure; and a thermally conductive filler dispersed throughout the IPN matrix.

2 . The TIM of claim 1 , wherein the IPN matrix structure has a flexible branch terminated with end —OH or —CF3 moieties.

3 . The TIM of claim 1 , wherein the IPN matrix structure is comprised of two components in a 1:1 ratio that are fully cross-linked.

4 . The TIM of claim 1 , wherein the IPN matrix structure is comprised of a polyurethane and an epoxy.

5 . The TIM of claim 4 , wherein the polyurethane comprises:
approximately 0.8 equivalent to approximately 1 equivalent of poly(caprolactone) glycol; and approximately 2 equivalents of 4,4′-diphenylmethane diisocyanate.

6 . The TIM of claim 4 , wherein the epoxy comprises:
approximately 120 equivalents of methyl methacrylate; approximately 2 equivalents of trimethylolpropane trimethacrylate; and approximately 1 equivalent of benzoyl peroxide.

7 . The TIM of claim 4 , wherein the epoxy comprises:
bisphenol A diglycidyl ether; and approximately 1 wt % (relative to the bisphenol A diglycidyl ether) of 2,4,6-tri(dimethylaminomethyl) phenol.

8 . The TIM of claim 1 , further comprising a cross-linking agent.

9 . The TIM of claim 8 , wherein the cross-linking agent comprises imidazole.

10 . The TIM of claim 1 , wherein the thermally conductive filler particles comprise flakes, powder, hollow spheres, or fibers of BN or AlN.

11 . A method of forming a thermal interface material (TIM) comprising:
forming a polyurethane prepolymer; forming an epoxy prepolymer; mixing the polyurethane prepolymer and the epoxy prepolymer to form a crosslinked inter-penetrating network (IPN); and adding a thermally conductive filler.

12 . The method of claim 11 , wherein the forming the polyurethane prepolymer comprises:
charging a resin kettle with approximately 2 equivalents of 4,4′-Diphenylmethane diisocyanate; adding approximately 0.8 equivalent to approximately 1 equivalent of poly(caprolactone) glycol to the resin kettle under stirring; and maintaining a temperature of approximately 60° C. for approximately 40 min.

13 . The method of claim 11 , wherein the forming the epoxy prepolymer comprises:
charging a resin kettle with approximately 120 equivalents of distilled methyl methacrylate; stirring in approximately 2 equivalents of distilled trimethylolpropane trimethacrylate; and stirring in approximately 1 equivalent of benzoyl peroxide.

14 . The method of claim 11 , wherein the forming the epoxy prepolymer comprises:
charging a resin kettle with approximately 120 equivalents of bisphenol A diglycidyl ether; stirring in approximately 3 wt. % of imidazole relative to the bisphenol A diglycidyl ether; and stirring in approximately 1 wt. % of 2,4,6-tri(dimethylaminomethyl) phenol relative to the bisphenol A diglycidyl ether.

15 . The method of claim 11 , wherein the IPN matrix has a flexible branch terminated with end —OH or —CF3 moieties.

16 . The method of claim 11 , further comprising adding a cross-linking agent to the epoxy prepolymer.

17 . The method of claim 11 , wherein the polyurethane prepolymer and the epoxy prepolymer are mixed in a 1:1 ratio.

18 . The method of claim 11 , wherein the IPN is fully crosslinked.

19 . The method of claim 11 , wherein the adding the thermally conductive filler comprises:
stirring flakes, powder, hollow spheres, or fibers of BN or AN into the IPN matrix.

20 . The method of claim 11 , wherein the polyurethane prepolymer and the epoxy prepolymer are in a 1:1 ratio.

Assignees

• IBM

Inventors

• Lin Wei

Classifications

• H10W40/251

  Organics · CPC title

• C08G18/3206

  aliphatic · CPC title

• C09K5/14 Primary

  Solid materials, e.g. powdery or granular · CPC title

• C08G18/4277

  Caprolactone and/or substituted caprolactone · CPC title

• C08G18/7671

  containing only one alkylene bisphenyl group · CPC title