Heat stable aryl polysiloxane compositions

1. A cured aryl polysiloxane composition comprising:

A. an alkylene bridged aryl polysiloxane comprising:

at least two silicon-bridging alkylene moieties; and

from at least 30 mole percent to no more than 99.9 mole percent silicon bonded aryl groups, based on total moles of silicon bonded organic groups of the alkylene bridged aryl polysiloxane;

and

B. a hydrosilation catalyst,

wherein

the hydrosilation catalyst is a metal or metal compound comprising a Group VIII element selected from platinum, rhodium, palladium, and combinations thereof; and

the hydrosilation catalyst, and any derivatives thereof, is present in a combined amount of at least 0.005 ppm to less than 0.6 ppm, expressed as a Group VIII element equivalent value, based on the weight of the cured aryl polysiloxane composition; and

wherein the cured aryl polysiloxane composition does not discolor during 14 days of heat aging at 200° C. in air, as indicated by a CIE b value, determined using CIE 1976 L*a*b* D 65 (illumination angle)/10(observation angle) color test method, of no more than 2.0 measured through a 0.6 millimeter thick specimen of the cured aryl polysiloxane composition after the heat aging.

2. The cured aryl polysiloxane composition of claim 1 ,

wherein:

the alkylene bridged aryl polysiloxane is represented by the average compositional formula I,

(R 1 n SiO (4-n)/2 ) a (O (4-p-r)/2 R 2 p SiZ r SiR 3 q O (4-q-r)/2 ) b   (I)

wherein:

for each (R 1 n SiO (4-n)/2 ) unit:

subscript n equals independently 0, 1, 2, or 3;

for each (O (4-p-r)/2 R 2 p SiZ r SiR 3 q O (4-q-r)/2 ) unit:

subscript p equals 0, 1, 2, or 3;

subscript q equals 0, 1, 2 or 3;

p+q=0 to [8−(2r+1)];

subscript r=1, 2, or 3;

Z is selected from —CHR 4 CHR 5 —X s , arylene, substituted arylene, and combinations thereof, wherein at least two Z groups are selected from CHR 4 CHR 5 —X s —, wherein:

—CHR 4 CHR 5 —X s — is the silicon-bridging alkylene moiety;

X is independently selected from methylene, phenyl, substituted phenyl, and combinations thereof;

subscript s=0 or 1; and

R 4 and R 5 are independently selected from hydrogen atom and alkyl;

R 1 , R 2 , and R 3 are selected from alkenyl, hydrogen atom, aryl, alkyl, hydroxy, alkoxy, aryloxy, other hydrocarbon radical, and combinations thereof;

subscripts a and b are selected to conform with the mole fraction of the (R 1 n SiO (4-n)/2 ) unit and the (O (4-p-r)/2 R 2 p SiZ r SiR 3 q O (4-q-r)/2 ) unit, respectively;

0<a<1; 0<b<1; and

a+b=1.

3. The cured aryl polysiloxane composition of claim 2 , wherein at least 70 mole percent to 100 mole percent of R 1 , R 2 , and R 3 combined are selected from vinyl, hydrogen atom, methyl, phenyl, naphthyl, phenoxyphenyl and combinations thereof.

4. A method of making the cured aryl polysiloxane composition of claim 1 , comprising the steps of:

A. providing:

i) an aryl alkenyl polysiloxane comprising:

at least two silicon bonded alkenyl groups; and

from at least 30 mole percent to no more than 99.9 mole percent silicon bonded aryl groups, based on total moles of silicon bonded organic groups of the aryl alkenyl polysiloxane;

ii) a hydrido silicon compound comprising:

at least two silicon bonded hydrogen atoms; and

from 0 mole percent to no more than 99.9 mole percent of the silicon bonded aryl groups, based on total moles of silicon bonded organic groups of the hydrido siloxane compound; and

iii) a hydrosilation catalyst;

B. combining the aryl alkenyl polysiloxane, the hydrido silicon compound, and the hydrosilation catalyst to produce a curable aryl siloxane composition;

C. curing the curable aryl siloxane composition to form the cured aryl polysiloxane composition; and

D. optionally, purifying the cured aryl polysiloxane composition by a technique comprising steps selected from: removing at least a portion of the hydrosilation catalyst; deactivating at least a portion of the hydrosilation catalyst; and combinations thereof,

wherein:

the hydrosilation catalyst is a metal or metal compound comprising a Group VIII element selected from platinum, rhodium, palladium, and combinations thereof;

the hydrosilation catalyst is present in an amount of at least 0.005 ppm to less than 0.6 ppm, expressed as a Group VIII element equivalent value, based on the weight of the curable aryl siloxane composition; and

the cured aryl polysiloxane composition does not discolor during 14 days of heat aging at 200° C. in air, as indicated by a CIE b value, determined using CIE 1976 L*a*b* D 65 (illumination angle)/10(observation angle) color test method, of no more than 2.0 measured through a 0.6 millimeter thick specimen of the cured aryl polysiloxane composition after the heat aging.

5. A method of making an encapsulated semiconductor device, comprising the steps of:

A. providing:

i) an aryl alkenyl polysiloxane comprising:

at least two silicon bonded alkenyl groups; and

from at least 30 mole percent to no more than 99.9 mole percent silicon bonded aryl groups, based on total moles of silicon bonded organic groups of the aryl alkenyl polysiloxane;

ii) a hydrido silicon compound comprising:

at least two silicon bonded hydrogen atoms; and

from 0 mole percent to no more than 99.9 mole percent of the silicon bonded aryl groups, based on total moles of silicon bonded organic groups of the hydrido siloxane compound; and

iii) a hydrosilation catalyst;

B. combining the aryl alkenyl polysiloxane, the hydrido silicon compound, and the hydrosilation catalyst to produce a curable aryl siloxane composition;

C. curing the curable aryl siloxane composition to form a cured aryl polysiloxane composition comprising:

i. an alkylene bridged aryl polysiloxane comprising: at least two silicon-bridging alkylene moieties; and from at least 30 mole percent to no more than 99.9 mole percent silicon bonded aryl groups, based on total moles of silicon bonded organic groups of the alkylene bridged aryl polysiloxane; and

ii. the hydrosilation catalyst,

wherein

D. optionally, purifying the cured aryl polysiloxane composition by a technique comprising steps selected from: removing at least a portion of the hydrosilation catalyst; deactivating at least a portion of the hydrosilation catalyst; and combinations thereof,

wherein:

the hydrosilation catalyst is a metal or metal compound comprising a Group VIII element selected from platinum, rhodium, palladium, and combinations thereof;

the hydrosilation catalyst is present in the curable aryl siloxane composition and the cured aryl polysiloxane composition in an amount of at least 0.005 ppm to less than 0.6 ppm, expressed as a Group VIII element equivalent value, based on the weight of the curable aryl siloxane composition and the curable aryl polysiloxane composition, respectively; and

the cured aryl polysiloxane composition does not discolor during 14 days of heat aging at 200° C. in air, as indicated by a CIE b value, determined using CIE 1976 L*a*b* D 65 (illumination angle)/10(observation angle) color test method, of no more than 2.0 measured through a 0.6 millimeter thick specimen of the cured aryl polysiloxane composition after the heat aging;

E. providing a semiconductor device comprising semiconductor elements; and

F. forming a coating on at least one surface of at least one of the semiconductor elements by a technique comprising steps selected from:

applying the curable aryl siloxane composition to the surface before or during the step of curing;

applying the cured aryl polysiloxane composition to the surface; and combinations thereof.

6. The method of claim 4 , wherein the aryl alkenyl polysiloxane is represented by the average compositional formula II,

(R 6 3 SiO 1/2 ) c (R 7 2 SiO 2/2 ) d (R 8 SiO 3/2 ) e (SiO 4/2 ) f   (II)

wherein:

R 6 3 SiO 1/2 , R 7 2 SiO 2/2 , R 8 SiO 3/2 , and SiO 4/2 are, respectively, an M-unit, a D-unit, a T-unit, and a Q-unit, all of which are primary siloxane units;

subscripts c, d, e, and f are selected to conform with the mole fraction of R 6 3 SiO 1/2 , R 7 2 SiO 2/2 , R 8 SiO 3/2 , and SiO 4/2 , respectively;

0.001≦c≦1; 0≦d≦0.999; 0≦e≦0.50; 0≦f≦0.10;

c+d+e+f=1;

the silicon bonded alkenyl group is present in the aryl alkenyl polysiloxane in an amount of at least 0.1 mole percent to no more than 60 mole percent, based on total moles of the silicon bonded organic groups of the aryl alkenyl polysiloxane;

the silicon bonded aryl group is present in the aryl alkenyl polysiloxane in an amount of at least 10 mole percent to no more than 99.9 mole percent, based on total moles of the silicon bonded organic groups of the aryl alkenyl polysiloxane; and

R 6 -R 8 are selected from alkenyl, hydrogen atom, aryl, alkyl, hydroxy, alkoxy, aryloxy, other hydrocarbon radical, and combinations thereof.

7. The method of claim 4 , wherein the hydrido silicon compound comprises a hydrido silicon compound selected from:

i) a hydrido silicon compound having the average compositional formula III,

(R 9 3 SiO 1/2 ) g (R 10 2 SiO 2/2 ) h (R 11 SiO 3/2 ) j (SiO 4/2 ) k   (III),

wherein:

R 9 3 SiO 1/2 , R 10 2 SiO 2/2 , R 11 SiO 3/2 , and SiO 4/2 are, respectively, an M-unit, a D-unit, a T-unit, and a Q-unit, all of which are primary siloxane units;

subscripts g, h, j, and k are selected to conform with the mole fraction of R 9 3 SiO 1/2 , R 10 2 SiO 2/2 , R 11 SiO 3/2 , and SiO 4/2 , respectively;

0.001≦g≦1; 0≦h≦0.999; 0≦j≦0.50; 0≦k≦0.10;

g+h+j+k=1;

the silicon bonded hydrogen atom is present in the hydrido silicon compound in an amount of at least 0.1 mole percent to no more than 60 mole percent, based on total moles of the silicon bonded organic groups of the hydrido siloxane compound;

the silicon bonded aryl group is present in the hydrido silicon compound in an amount of at least 10 mole percent to no more than 99.9 mole percent, based on total moles of the silicon bonded organic groups of the hydrido siloxane compound; and

R 9 -R 11 are selected from alkenyl, hydrogen atom, aryl, alkyl, hydroxy, alkoxy, aryloxy, other hydrocarbon radical, and combinations thereof; and

ii) a hydrido silicon compound having the formula IV:

R 12 m SiH (4-m)   (IV)

wherein:

m=1, or 2; and

R 12 is selected from alkenyl, aryl, alkyl, hydroxy, alkoxy, aryloxy, other hydrocarbon radical, and combinations thereof;

and

combinations thereof.

8. An encapsulated semiconductor device, comprising semiconductor elements, wherein one or more of the semiconductor elements is coated with the cured aryl polysiloxane composition of claim 1 .