Polymer composite thermal interface material with high thermal conductivity

Patent metadata

Field	Value
Publication number	US-10047264-B2
Application number	US-201414546394-A
Country	US
Kind code	B2
Filing date	Nov 18, 2014
Priority date	Nov 18, 2014
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

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, the IPN matrix structure being comprised of a polyurethane and an epoxy in a 1:1 weight ratio, and the IPN matrix structure being fully cross-linked, wherein the IPN matrix structure has a branch terminated with end —CF 3 moieties;
a thermally conductive filler dispersed throughout the IPN matrix structure, the thermally conductive filler including BN in the amount of approximately 20% to approximately 40% by weight; and wherein the polyurethane comprises: approximately 0.8 weight equivalent to approximately 1 weight equivalent of poly(caprolactone) glycol; and approximately 2 weight equivalents of 4,4′-diphenylmenthane diisocyanate.

2. The TIM of claim 1 , 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.

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

4. The TIM of claim 3 , wherein the cross-linking agent comprises imidazole.

5. 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,
wherein the polyurethane prepolymer and the epoxy prepolymer are mixed in a 1:1 weight ratio,
wherein the IPN is fully crosslinked, wherein the IPN has a branch terminated with end —CF 3 moieties,
wherein the thermally conductive filler includes BN in the amount of approximately 20% to approximately 40% by weight, and wherein the forming the polyurethane prepolymer comprises: charging a resin kettle with approximately 2 weight equivalents of 4,4′-Diphenylmethane diisocyanate; adding approximately 0.8 weight equivalent to approximately 1 weight equivalent of poly(carprolactone) glycol to the resin kettle under stirring; and maintaining a temperature of approximately 60.degree. C. for approximately 40 min.

6. The method of claim 5 , wherein the forming the epoxy prepolymer comprises:
charging the 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.

7. The method of claim 5 , further comprising adding a cross-linking agent to the epoxy prepolymer.

8. The TIM of claim 1 , wherein the BN is in the amount of approximately 30% by weight.

9. A thermal interface material (TIM) comprising:
a polymer based composite comprising an inter-penetrating network (IPN) matrix structure, the IPN matrix structure being comprised of a polyurethane and an epoxy, and the IPN matrix structure being fully cross-linked, wherein the IPN matrix structure has a branch terminated with end —CF 3 moieties;
a thermally conductive filler dispersed throughout the IPN matrix structure, the thermally conductive filler including BN in the amount of approximately 20% to approximately 40% by weight; and wherein the polyurethane comprises: approximately 0.8 weight equivalent to approximately 1 weight equivalent of poly(caprolactone) glycol; and approximately 2 weight equivalents of 4,4′-diphenylmethane diisocyanate.

10. The TIM of claim 9 , wherein the BN is in the amount of approximately 30% by weight.

11. The TIM of claim 9 , 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.

Assignees

• IBM

Inventors

• Lin Wei

Classifications

• H10W40/251

  Organics · CPC title

• C09K5/14 Primary

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

• C08G18/3206

  aliphatic · CPC title

• C08G18/6644

  having at least three hydroxy groups · CPC title

• C08G18/7671

  containing only one alkylene bisphenyl group · CPC title