Abstract: Disclosed is an epoxy resin composition comprising: (A) a polymerized compound including, as structural components, phosphaphenanthrene and at least one constituent selected from a structural unit of a phenolic novolak polymer and a structural unit of a phenolic novolak polymer in which a hydrogen atom of a phenolic hydroxyl group is substituted by phosphaphenanthrene; (B) an epoxy resin having two or more epoxy groups in a molecule; and (C) a curing agent that cures the epoxy resin.

Abstract: The invention relates to a prepreg, obtained by impregnating a base material with an epoxy resin composition containing an epoxy resin (A), a curing agent (B), an accelerator (C), a phenoxy resin (D), and an inorganic filler (E) and semi-hardening the impregnated material, wherein the inorganic filler (E) has an average particle diameter of 3 ?m or less. When a circuit with a narrow wire distance is formed on a surface of a insulator substrate composed of such a prepreg by using a method of forming the circuit by plating process, an amount of the plating remaining on the insulator substrate surface at the circuit contour periphery can be reduced. As a result, it leads to stabilization of inter-circuit insulation resistance and increase in a yield during production of printed wiring boards.

Abstract: The present invention provides an improved epoxy resin composition enabling better dimensional stability of a laminate by decreasing the coefficient of thermal expansion in its thickness direction of a laminate manufactured using an epoxy resin composition as a material, and by retaining a high level of adhesion in the cured product thereof, enabling better drilling workability of the laminate and suppression of crack development therein during the drilling process, and enabling to decrease impregnation of the plating solution into the laminate associated with those cracks. This epoxy resin composition includes: (A) an epoxy resin; (B) a curing agent composed of phenolic novolac resin curing agent or amine curing agent, (C) an inorganic filler composed of aluminum hydroxide with or without spherical silica; and (D) an elastic component made of minute particles having a core-shell structure with its shell constituted by a resin which is compatible with said epoxy resin (A).

Abstract: The invention relates to a prepreg, obtained by impregnating a base material with an epoxy resin composition containing an epoxy resin(A), a curing agent (B), an accelerator (C), a phenoxy resin (D), and an inorganic filler (E) and semi-hardening the impregnated material, wherein the inorganic filler (E) has an average particle diameter of 3 ?m or less. When a circuit with a narrow wire distance is formed on a surface of a insulator substrate composed of such a prepreg by using a method of forming the circuit by plating process, an amount of the plating remaining on the insulator substrate surface at the circuit contour periphery can be reduced. As a result, it leads to stabilization of inter-circuit insulation resistance and increase in a yield during production of printed wiring boards.