Patent ID: 8362115

Claim:
An epoxy resin composition comprising epoxy resin, phenolic resin, cure accelerator and inorganic filler, said epoxy resin comprising: (1) 20-50% of Formula I; (2) 10-40% of Formula II; and (3) 0-30% of Formula III and/or 0-40% of Formula IV, wherein Formula III and Formula IV are not 0% simultaneously; wherein, R 1 and R 2 are independently hydrogen or C 1 -C 6 alkyl; n is an integer from 0 to 50 in Formula I; the ratio of the number of phenolic hydroxyls in said phenolic resin to the number of epoxy groups in the epoxy resin mixture is 0.8-1.3; all of said percentages are percentages relative to the total mass of the epoxy resin mixture characterized in that said inorganic filler is a composite inorganic filler, wherein, said composite inorganic filler is silicon dioxide; the particle size distribution of said composite inorganic filler is as follows: 18-24% is less than 3 μm, 20-30% is more than or equal to 3 μm and less than 12 μm, 45-57% is more than or equal to 12 μm and less than 48 μm, 5-17% is more than or equal to 48 μm and less than 75 μm, wherein the percentage is a percentage by which the total mass of the composite inorganic filler is occupied, and wherein said composite inorganic filler has a median particle diameter of 14-20 μm, and an average particle diameter of 18-24 μm.