Epoxy resin composition for encapsulation of semiconductor devices

Claim 1

An epoxy resin-based composition which comprises: (A) 100 parts by weight of a thermally curable epoxy resin; (B) from 100 to 600 parts by weight of an inorganic filler selected from the group consisting of finely pulverized quartz, powders of fused quartz glass, synthetic silica powder, talc, mica flakes, silicon nitride, boron nitride, alumina or mixtures thereof; (C) from 1 to 50 parts by weight of a combination composed of (C-1) from 2% to 75% by weight of an organopolysiloxane represented by the average unit formula R.sup.1.sub.u R.sup.2.sub.v SiO.sub.(4-u-v)/2 in which R 1 is a hydrogen atom or a monovalent group selected from the class consisting of monovalent hydrocarbon groups, alkoxy groups, hydroxy group and polyoxyalkylene groups of the formula --(--R 3 --O--) m R 4 , R 3 being an alkylene group selected from the class consisting of ethylene, propylene and butylene groups, R 4 being a hydrogen atom or a monovalent hydrocarbon group having 1 to 8 carbon atoms and m being a positive integer of 2 to 4, R 2 is a substituted monovalent hydrocarbon group having, in the substituent thereon, a functional group selected from the class consisting of epoxy, amino, hydroxy, carboxyl, mercapto, carbamoyl and carbamoylamino groups, the subscript u is a positive number and the subscript v is a positive number with the proviso that u+v is in the range from 1.90 to 2,10 inclusive, and (C-2) from 98% to 25% by weight of a copolymer composed of the segments of a polymeric aromatic moiety free of silicon atoms and segments of an organopolysiloxane moiety; and (D) a sufficient amount of a suitable curing agent in a proportion by weight to the epoxy resin from about 1:5 to about 2:1.