Epoxy resin composition, prepreg and multilayer printed-wiring board

摘要

An epoxy resin composition is disclosed, which comprises, as an essential component, a phosphorus compound having an average of not less than 1.8 and less than 3 of phenolic hydroxy groups reactive with an epoxy resin and an average of not less than 0.8 of a phosphorus element in the molecule, an inorganic filler having an average particle diameter of not greater than 30 mu m, a bifunctional epoxy resin having an average of not less than 1.8 and less than 2.6 of epoxy groups in the molecule and a hardener, wherein the bifunctional epoxy resin is contained at an amount of not less than 51 % by mass relative to the whole epoxy resin. Dicyandiamide or a polyfunctional phenol system compound having an average of not less than 3 of phenolic hydroxy groups in the molecule are used as the hardener and a ration (a/c) of equivalent (a) of a phenolic hydroxy group of the phosphorus compound and equivalent (c) of an epoxy group of the bifunctional epoxy resin is not less than 0.3 and less than 0.75. Further, a combination of dicyandiamide and a polyfunctional phenol system compound having an average of not less than 3 of phenolic hydroxy groups in the molecule can be used as the hardener, wherein aluminium hydroxide is used as the inorganic filler, an amount of the inorganic filler to be added is not less than 15 parts by mass and less than 100 parts by mass relative to 100 parts by mass of the resin solids constituent, and the content of a phosphorus element is not less than 0.8 % by mass and less than 3.5 % by mass relative to the whole resin solids constituent.