Silicone adhesive for semiconductor element

Abstract

A silicone adhesive for a semiconductor element that is suitable as a die bonding material for fixing a light emitting diode chip to a substrate. The adhesive includes (a) an addition reaction-curable silicone resin composition having a viscosity at 25° C. of not more than 100 Pa·s, and yielding a cured product upon heating at 150° C. for 3 hours that has a type D hardness prescribed in JIS K6253 of at least 30, (b) a white pigment powder having an average particle size of less than 1 μm, and (c) a white or colorless and transparent powder having an average particle size of at least 1 μm but less than 10 μm. The adhesive exhibits high levels of concealment, effectively reflects light emitted from the LED chip, and also exhibits favorable chip positioning properties, superior adhesive strength, and excellent durability.

1 . A silicone adhesive for a semiconductor element, comprising components (a), (b) and (c) shown below:
 (a) an addition reaction-curable silicone resin composition, having a viscosity at 25° C. of not more than 100 Pa·s, and yielding a cured product upon heating at 150° C. for 3 hours that has a type D hardness prescribed in JIS K6253 of at least 30,   (b) a white pigment powder having an average particle size of less than 1 μm, and   (c) a white or colorless and transparent powder having an average particle size of at least 1 μm but less than 10 μm, wherein   a combination of components (b) and (c) is used in an amount of 12 to 600 parts by mass per 100 parts by mass of component (a).   
   
   
       2 . The silicone adhesive according to  claim 1 , wherein the white pigment of component (b) comprises at least one material selected from the group consisting of titanium oxide, zinc oxide, white lead, zinc sulfide, calcium carbonate and kaolin. 
   
   
       3 . The silicone adhesive according to  claim 1 , wherein component (b) is composed of titanium oxide. 
   
   
       4 . The silicone adhesive according to  claim 1 , wherein component (c) is composed of alumina. 
   
   
       5 . The silicone adhesive according to  claim 3 , wherein component (c) is an alumina powder composed of alumina particles with a shape of flake. 
   
   
       6 . The silicone adhesive according to  claim 1 , wherein component (a) comprises components (A), (B), (C) and (D) described below:
 (A) an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms within each molecule, and having a viscosity at 25° C. of not more than 1,000 mPa·s,   (B) a polyorganosiloxane represented by an average composition formula (1) shown below:
   (R 1 R 2   2 SiO 1/2 ) m (R 1 R 2 SiO 2/2 ) n (R 2   2 SiO 2/2 ) p (R 1 SiO 3/2 ) q (SiR 2 (OR 3 )SiO 2/2 ) r (SiO 4/2 ) s   (1) 
   
     wherein R 1  represents an alkenyl group or a monovalent hydrocarbon group other than an alkenyl group; R 2  represents a monovalent hydrocarbon group that does not contain an alkenyl group, provided that at least 80% of R 2  groups are methyl groups; R 3  represents a hydrogen atom or an alkyl group; m, n, p, q, r and s are numbers that satisfy m≧0, n≧0, p≧0, q≧0, r≧0 and s>0 respectively, provided that m+n>0, q+r+s>0, and m+n+p+q+r=1,
 which at 25° C. is either a liquid having a viscosity of at least 1,000 Pa·s or a solid, in an amount that provides 60 to 90 parts by mass of component (B) per 100 parts by mass of a combination of component (A) and component (B), 
 (C) an organohydrogenpolysiloxane represented by an average composition formula (2) shown below:
   R 4   a H b SiO (4−a−b)/2   (2) 
 
 
     wherein R 4  represents a monovalent hydrocarbon group other than an alkenyl group, and at least 50% of R 4  groups are methyl groups; and a and b are positive numbers that satisfy 0.7≦a≦2.1, 0.001≦b≦1.0 and 0.8≦a+b≦3.0,
 having at least two SiH bonds within each molecule, and having a viscosity at 25° C. of not more than 1,000 mPa·s, in an amount that yields a total number of SiH bonds that is 0.5 to 5.0 times a total number of alkenyl groups within a combination of component (A) and component (B), and 
 (D) an effective amount of a platinum group metal-based catalyst. 
 
   
   
       7 . A silicone adhesive according to  claim 6 , wherein the organopolysiloxane of component (A) is a linear organopolysiloxane having at least two alkenyl groups bonded to silicon atoms within each molecule, in which a main chain is composed of repeating diorganosiloxane units, and both molecular chain terminals are blocked with triorganosiloxy groups. 
   
   
       8 . The silicone adhesive according to  claim 6 , wherein an amount of alkenyl groups is within a range from 0.01 to 1 mol/100 g relative to a solid fraction of component (B). 
   
   
       9 . The silicone adhesive according to  claim 6 , wherein an amount of component (B) is within a range from 70 to 80 parts by mass relative to 100 parts by mass of a combination of component (A) and component (B). 
   
   
       10 . The silicone adhesive according to  claim 1 , wherein component (a) comprises components (P), (Q) and (R) described below:
 (P) an organopolysiloxane represented by an average composition formula (3) shown below:
   R x (C 6 H 5 ) y SiO (4−x−y)/2   (3) 
   
     wherein R represents identical or different, unsubstituted or substituted monovalent hydrocarbon groups or alkoxy groups, or a hydroxyl group, provided that 0.1 to 80 mol % of all R groups are alkenyl groups; and x and y are positive numbers that satisfy 1≦x+y<2 and 0.20≦y/(x+y)≦0.95,
 which at 25° C. is either a liquid having a viscosity of at least 100 mPa·s, or a solid, 
 (Q) an organohydrogenpolysiloxane represented by an average composition formula (4) shown below:
   R″ c H d SiO (4−c−d)/2   (4) 
 
 
     wherein R′ represents identical or different, substituted or unsubstituted monovalent hydrocarbon groups other than aliphatic unsaturated hydrocarbon groups; and c and d are positive numbers that satisfy 0.7≦c≦2.1, 0.002≦d≦1.0 and 0.8≦c+d≦2.6,
 having at least two Si—H bonds within each molecule, and having a viscosity at 25° C. of not more than 1,000 mPa·s, wherein at least 5 mol % of a total number of R′ groups and silicon atom-bonded H atoms within the composition formula (4) are phenyl groups, and 
 (R) an effective amount of a platinum group metal-based catalyst. 
 
   
   
       11 . The silicone adhesive according to  claim 10 , wherein in the formula (3) that represents component (P), 0.5 to 50 mol % of all R groups are alkenyl groups. 
   
   
       12 . The silicone adhesive according to  claim 10 , wherein component (Q) has at least three Si—H bonds within each molecule. 
   
   
       13 . The silicone adhesive according to  claim 10 , wherein in the formula (4) that represents component (Q), 10 to 50 mol % of all silicon atom-bonded R′ groups and hydrogen atoms are phenyl groups. 
   
   
       14 . The silicone adhesive according to  claim 10 , wherein component (Q) is composed of an organohydrogenpolysiloxane mixture containing an organohydrogenpolysiloxane in which at least 15 mol % of all silicon atom-bonded R″ groups and hydrogen atoms are phenyl groups, and an organohydrogenpolysiloxane in which less than 15 mol % of all silicon atom-bonded R″ groups and hydrogen atoms are phenyl groups, in a weight ratio of 1:9 to 9:1. 
   
   
       15 . The silicone adhesive according to  claim 10 , wherein component (Q) is composed of an organohydrogenpolysiloxane mixture containing an organohydrogenpolysiloxane in which 15 to 70 mol % of all silicon atom-bonded R″ groups and hydrogen atoms are phenyl groups, and an organohydrogenpolysiloxane in which 0 to 14 mol % of all silicon atom-bonded R″ groups and hydrogen atoms are phenyl groups, in a weight ratio of 1:9 to 9:1. 
   
   
       16 . A light emitting device comprising a substrate, a light emitting element and a cured resin layer interposed between the substrate and the light emitting element, wherein said cured resin layer comprises a cured product of a silicone adhesive comprising components (a), (b) and (c) shown below:
 (a) an addition reaction-curable silicone resin composition, having a viscosity at 25° C. of not more than 100 Pa·s, and yielding a cured product upon heating at 150° C. for 3 hours that has a type D hardness prescribed in JIS K6253 of at least 30,   (b) a white pigment powder having an average particle size of less than 1 μm, and   (c) a white or colorless and transparent powder having an average particle size of at least 1 μm but less than 10 μm, wherein   a combination of components (b) and (c) is used in an amount of 12 to 600 parts by mass per 100 parts by mass of component (a).   
   
   
       17 . The light emitting device according to  claim 16 , wherein the substrate is a gold-plated substrate.