SILICONE ADHESIVE COMPOSITION AND METHOD FOR PREPARING THE SAME

Abstract

A thermal interface material composition including a blend of a polymer matrix and a thermally conductive filler having particles having a maximum particle diameter no greater than about 25 microns, wherein the polymer matrix includes an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and a hydrosilyation catalyst comprising a transition metal, wherein the transition metal is present in an amount of from about 10 to about 20 ppm by weight based on the weight of the non-filler components and the molar ratio of the silicon-bonded hydrogen atoms to the silicon-bonded alkenyl groups ranges from about 1 to about 2. A method is also provided.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a DMA comparison graph of G′G″ crossover temperatures for Comparative Example 2 vs. Example 1 formulations.

FIG. 2 is a graph of a DMA cure time comparison at 150° C.

FIG. 3 is a graph of a DMA cure time comparison at 80° C.

FIG. 4 is a graph showing adhesion strength as a function of cure temperature.

Claims

1. A thermal interface composition comprises a blend of a polymer matrix and a thermally conductive filler comprising particles having a maximum particle diameter of no greater than about 25 microns, said polymer matrix comprising an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst comprising a transition metal, wherein said transition metal catalyst is present in an amount of from about 10 to about 20 ppm based on the weight of the non-filler component and the molar ratio of the silicon-bonded hydrogen atoms to the silicon-bonded alkenyl groups ranges from about 1 to about 2.

2. The composition of claim 1 wherein the organopolysiloxane is linear.

3. The composition of claim 1 wherein the alkenyl groups are vinyl groups.

4. The composition of claim 3 wherein the alkenyl groups are at the ends of the molecular chain.

5. The composition of claim 1 wherein the organopolysiloxane is a dimethyl polysiloxane blocked with dimethyl vinyl siloxane groups at both ends of the molecule.

6. The composition of claim 1 wherein the organohydrogenpolysiloxane comprises methyl groups.

7. The composition of claim 1 wherein the hydrogen atoms are positioned along the backbone of the molecular chain and at the ends of the molecular chain.

8. The composition of claim 1 wherein the organohydrogenpolysiloxane is a copolymer of methylhydrogen siloxane and dimethyl siloxane blocked with dimethylhydrogen siloxane groups at both ends of the molecular chain.

9. The composition of claim 1 wherein the molar ratio of hydrogen atoms bonded to silicone atoms in the organohydrogenpolysiloxane per alkenyl group in the organopolysiloxane is from about 1.3 to about 1.6.

10. The composition of claim 9 wherein the molar ratio of hydrogen atoms bonded to silicone atoms in the organohydrogenpolysiloxane per alkenyl group in the organopolysiloxane is from about 1.4 to about 1.5.

11. The composition of claim 1 wherein the transition metal is present in an amount of from about 12 to about 19 ppm based on the total weight of the non-filler components of the composition.

12. The composition of claim 11 wherein the transition metal is present in an amount of from about 14 to about 17 ppm based on the total weight of the non-filler components of the composition.

13. The composition of claim 1 further comprising an adhesion promoter.

14. The composition of claim 1 further comprising a catalyst inhibitor.

15. The composition of claim 1 wherein the thermally conductive filler is selected from the group consisting of: boron nitride, boron carbide, titanium carbide, silicon carbide, aluminum nitride, aluminum oxide, magnesium oxide, beryllium oxide, chromium oxide, zinc oxide, titanium dioxide and iron oxide.

16. The composition of claim 1 wherein the thermally conductive filler has a maximum particle diameter of less than 25 microns.

17. The composition of claim 1 wherein the thermally conductive filler has an average particle diameter from about 0.01 microns to about 15 microns.

18. A method for making a thermal interface composition comprising blending a polymer matrix and a filler comprising particles having a maximum particle diameter of no greater than about 25 microns, said polymer matrix comprising an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst comprising a transition metal, wherein said transition metal is present in an amount of from about 10 to about 20 ppm based on the weight of the non-filler components and the molar ratio of the silicon-bonded hydrogen atoms to the silicon-bonded alkenyl groups ranges from about 1 to about 2.

19. The method of claim 18 wherein the alkenyl groups are vinyl groups.

20. The method of claim 18 wherein the organopolysiloxane is a dimethyl polysiloxane blocked with dimethyl vinyl siloxane groups at both ends of the molecule.

21. The method of claim 18 wherein the organohydrogenpolysiloxane comprises methyl groups.

22. The method of claim 18 wherein the organohydrogenpolysiloxane is a copolymer of methylhydrogen siloxane and dimethyl siloxane blocked with dimethylhydrogen siloxane groups at both ends of the molecular chain.

23. The method of claim 18 wherein the molar ratio of hydrogen atoms bonded to silicone atoms in the organohydrogenpolysiloxane per alkenyl group in the organopolysiloxane is from about 1.3 to about 1.6.

24. The method of claim 23 wherein the molar ratio of hydrogen atoms bonded to silicone atoms in the organohydrogenpolysiloxane per alkenyl group in the organopolysiloxane is from about 1.4 to about 1.5.

25. The method of claim 18 wherein the transition metal is present in an amount of from about 12 to about 19 ppm based on the total weight of the non-filler components of the composition.

26. The method of claim 25 wherein the transition metal is present in an amount of from about 14 to about 17 ppm based on the total weight of the non-filler components of the composition.

27. The method of claim 18 further comprising an adhesion promoter.

28. The method of claim 18 further comprising a catalyst inhibitor.

29. The method of claim 18 wherein the thermally conductive filler is selected from the group consisting of: boron nitride, boron carbide, titanium carbide, silicon carbide, aluminum nitride, aluminum oxide, magnesium oxide, beryllium oxide, chromium oxide, zinc oxide, titanium dioxide and iron oxide.

30. A one-part heat cure composition comprising a blend of a polymer matrix and a thermally conductive filler comprising particles having a maximum particle diameter of no greater than about 25 microns, said polymer matrix comprising an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst comprising a transition metal, wherein said transition metal is present in an amount of from about 10 to about 20 ppm by weight based on the weight of the non-filler components and the molar ratio of the silicon-bonded hydrogen atoms to the silicon-bonded alkenyl groups ranges from about 1 to about 2.

31. A method for making a two-part thermal interface composition comprises mixing part A and part B in a 1:1 ratio by weight to form the composition, wherein said composition comprises a polymer matrix and a thermally conductive filler comprising particles having a maximum particle diameter of no greater than about 25 microns, said polymer matrix comprising an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and a hydrosilylation catalyst comprising a transition metal, wherein said transition metal is present in an amount of from about 10 to about 20 ppm based on the weight of the non-filler components and the molar ratio of the silicon-bonded hydrogen atoms to the silicon-bonded alkenyl groups ranges from about 1 to about 2.