Low temperature, fast curing silicone compositions

1. A method of preparing a low temperature-curing rapid seal on a fixture comprising administering to a surface of said fixture a composition comprising:

(a) a reactive silicone having at least two unsaturated functional groups;

(b) a silicone crosslinker having at least two reactive silicon hydride functional groups;

(c) a catalyst system comprising a rhodium-based catalyst; and

(d) a stabilizing effective amount of an inhibitor system comprising a peroxide and an acetylenic compound.

2. The method of claim 1 , wherein said fixture comprises an electronic component.

3. The method of claim 1 , wherein said reactive silicone is represented by the structure:

wherein R 1 , R 2 , R 3 , R 4 and R 5 may be the same or different and are hydrogen, alkyl, alkenyl, aryl, alkoxy, alkenyloxy, aryloxy, (meth)acryl or methacryloxy provided that at least two of R 1 , R 2 , R 3 , R 4 and R 5 have up to 12 carbon atoms (C 10-12 ) and include an unsaturated group; and n is an integer between about 100 and 1,200.

4. The method of claim 1 , wherein the rhodium-based catalyst is selected from the group consisting of tris(tributylsulfide) rhodium trichloride; (acetylacetonato)di-carbonyirhodium; tri(triphenylphosphine) rhodium chloride having the formula (Ph 3 P) 3 RhCl; rhodium acetate dimer having the formula [(CH 3 COO) 2 Rh] 2 ; rhodium acetylacetonate having the formula Rh(acac) 2 in which acac is the acetylacetonato group forming a ring structure with the rhodium atom; RhCl 3 (EtSCH 2 SiMe 3 ) 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; RhCl 3 (n-BuSCH 2 SiMe 3 ) 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; RhCl 3 (PhSCH 2 SiMe 3 ) 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; RhCl 3 [(Me 3 SiCH 2 ) 2 S] 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; rhodium-containing transition metal complex; and combinations thereof wherein the rhodium-containing transition metal complex is selected from metallocenes of the following structures:

where

R 1 and R 2 are selected from H; a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; acetyl; vinyl; allyl; hydroxyl; carboxyl; —(CH 2 ) n —OH, where n is an integer in the range of 1 to about 8; —(CH 2 ) n —COOR 3 , where n is an integer in the range of 1 to about 8 and R 3 is a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; H; Li; or Na; —(CH 2 ) n —OR 4 , wherein n is an integer in the range of 1 to about 8 and R 4 is a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; or —(CH 2 ) n N + (CH 3 ) 3 X − , where n is an integer in the range of 1 to about 8 and X is Cl − , Br − , I − , ClO 4 − or BF 4 − ;

Y 1 and Y 2 , which may be the same or different or may not be present at all, are selected from H, Cl − , Br − , I − , cyano, methoxy, acetyl, hydroxy, nitro, trialkylamines, triaryamines, trialkyiphosphines, triphenylamine, tosyl and the like;

A and A′, which may be the same or different, are C or N;

m and m′, which may be the same or different, are 1 or 2; and

M e is Rh.

5. The method of claim 1 , wherein the acetylenic compound is an alpha acetylenic alcohol selected from the group consisting of octynol, 1-octyn-3-ol, 3-butyn-2-ol, 2-phenyl-3-butynol, 3,5-dimethyl-1-hexyn-3-ol, propargyl alcohol and combinations thereof.

6. The method of claim 1 , wherein the peroxide is selected from the group consisting of cumene hydroperoxide, tertiary butyl hydroperoxide, tertiary butyl perbenzoate, ditertiarybutyl peroxide, dicumyl peroxide and combinations thereof.

7. The method of claim 1 , wherein said catalyst system further comprises a platinum-based catalyst.

8. The method of claim 7 , wherein the platinum-based catalyst is selected from the group consisting of platinum hydrocarbon complex, platinum alcoholate, platinum chloride-olefin complex, platinum-containing transition metal complex and combinations thereof; wherein the platinum-containing transition metal complex is selected from metallocenes of the following structures:

where

R 1 and R 2 are selected from H; a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; acetyl; vinyl; allyl; hydroxyl; carboxyl; —(CH 2 ) n —OH, where n is an integer in the range of 1 to about 8; —(CH 2 ) n —COOR 3 , where n is an integer in the range of 1 to about 8 and R 3 is a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; H; Li; or Na; —(CH 2 ) n —OR 4 , wherein n is an integer in the range of 1 to about 8 and R 4 is a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; or —(CH 2 ) n N + (CH 3 ) 3 X − , where n is an integer in the range of 1 to about 8 and X is Cl − , Br − , I − , ClO 4 − or BF 4 − ;

Y 1 and Y 2 , which may be the same or different or may not be present at all, are selected from H, Cl − , Br − , I − , cyano, methoxy, acetyl, hydroxy, nitro, trialkylamines, triaryamines, trialkyiphosphines, triphenylamine, tosyl and the like;

A and A′, which may be the same or different, are C or N;

m and m′, which may be the same or different, are 1 or 2; and

M e is Pt.

9. An electronic device comprising:

(a) a chip-on-board component;

(b) a heat-curable silicone composition encapsulating at least a portion of said chip-on-board component, said composition comprising:

(a) a reactive silicone having at least two unsaturated functional groups;

(b) a silicone crosslinker having at least two reactive silicon hydride functional groups;

(c) a catalyst system comprising a rhodium-based catalyst; and

(d) a generally sphencally shaped metal oxide flow modifier present in a sufficient amount to provide a flowable composition with a lower coefficient of thermal expansion.

10. The electronic device of claim 9 , wherein wherein said reactive silicone is represented by the structure:

wherein R 1 , R 2 , R 3 , R 4 and R 5 may be the same or different and are hydrogen, alkyl, alkenyl, aryl, alkoxy, alkenyloxy, aryloxy, (meth)acryl or methacryloxy provided that at least two of R 1 , R 2 , R 3 , R 4 and R 5 have up to 12 carbon atoms (C 1-12 ) and include an unsaturated group; and n is an integer between about 100 and 1,200.

11. The electronic device of claim 9 , wherein the rhodium-based catalyst is selected from the group consisting of tris(tributylsulfide) rhodium trichioride; (acetylacetonato)di-carbonyirhodium; tri(triphenylphosphine) rhodium chloride having the formula (Ph 3 P) 3 RhCl; rhodium acetate dimer having the formula [(CH 3 COO) 2 Rh] 2 ; rhodium acetylacetonate having the formula Rh(acac) 2 in which acac is the acetylacetonato group forming a ring structure with the rhodium atom; RhCl 3 (EtSCH 2 SiMe 3 ) 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; RhCl 3 (n-BuSCH 2 SiMe 3 ) 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; RhCl 3 (PhSCH 2 SiMe 3 ) 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; RhCl 3 [(Me 3 SiCH 2 ) 2 S] 3 in which Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively; rhodium-containing transition metal complex; and combinations thereof; wherein the rhodium-containing transition metal complex is selected from metallocenes of the following structures:

where

R 1 and R 2 are selected from H; a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; acetyl; vinyl; allyl; hydroxyl; carboxyl; —(CH 2 ) n —OH, where n is an integer in the range of 1 to about 8; —(CH 2 ) n —COOR 3 , where n is an integer in the range of 1 to about 8 and R 3 is a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; H; Li; or Na; —(CH 2 ) n —OR 4 , wherein n is an integer in the range of 1 to about 8 and R 4 is a straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; or —(CH 2 ) n N + (CH 3 ) 3 X − , where n is an integer in the range of 1 to about 8 and X is Cl − , Br − , I 1 , ClO 4 − or BF 4 − ;

Y 1 and Y 2 , which may be the same or different or may not be present at all, are selected from H, Cl −, Br − , I − , cyano, methoxy, acetyl, hydroxy, nitro, trialkylamines, triaryamines, trialkyiphosphines, triphenylaniine, tosyl and the like;

A and A′, which may be the same or different, are C or N;

m and m′, which may be the same or different, are 1 or 2; and

M e is Rh.

12. The electronic device of claim 9 , wherein the flow modifier has an average size of about 1 to about 10μ.

13. The electronic device of claim 9 , wherein the flow modifier has an average size of less than about 1 μ.