Silicone resin composition for encapsulating luminescent element and process for producing optical-semiconductor electronic part with the same through potting

A silicone resin composition for encapsulating light-emitting elements comprising:

• (A) a liquid or solid organopolysiloxane having at least two alkenyl groups per molecule represented by Average Compositional Formula (1):
• RnSiO(4−n)/2 (1)
• wherein each R is independently a substituted or unsubstituted monovalent hydrocarbon, alkoxy, or hydroxy group;
• 0.1 to 80 mol % of R which is a substituted or unsubstituted monovalent hydrocarbon comprises alkenyl groups;
• and n is a positive number that satisfies 1≦n<2;
• (B) an organohydrogenpolysiloxane having at least two Si—H bonds per molecule represented by Average Compositional Formula (2):
• R′aHbSiO(4−a−b)/2 (2)
• wherein each R′ is independently a substituted or unsubstituted monovalent hydrocarbon excluding an aliphatic unsaturated hydrocarbon;
• and a and b are each positive numbers that satisfy 0.7≦a≦2.1, 0.001≦b≦1.0, and 0.8≦a+b≦2.6;
• and/or
• an organohydrogensilane represented by Formula (3):
• R′cSiH(4-c) (3)
• wherein each R′ is as defined above, and c is 1 or 2;
• and
• (C) an addition reaction catalyst;
• the composition further comprising (D) 2 to 25 wt % of silica with a mean particle size of 1 to 30 nm based on the total amount of Components (A) and (B);
• the composition having a viscosity (23° C.) of more than 10 Pa·s and less than 70 Pa·s, and having a thixotropic index of 2.0 to 5.5;
• and the composition being used for encapsulation using a potting method.