Liquid epoxy resin composition and semiconductor device

A liquid epoxy resin underfill composition comprising

• (A) a liquid epoxy resin, said liquid epoxy resin being liquid at 25° C.,
• (B) an aromatic amine curing agent, wherein the total amount of the aromatic amine curing agent is such that the ratio of the epoxy equivalent of the liquid epoxy resin to the amine equivalent of the aromatic amine curing agent is in the range from 0.7:1 to 1.2:1,
• (C) from 0.5 to 20 parts by weight per 100 parts by weight of components (A) and (B) combined of microcapsules containing a phenolic hydroxy-bearing benzoic acid derivative having the general formula (2):
• wherein R4, R5 and R6 are each independently selected from the group consisting of hydrogen, hydroxyl, C1-C10 alkoxy, and substituted or unsubstituted monovalent C1-C12 hydrocarbon groups which may be separated by at least one atom selected from oxygen, nitrogen, sulfur and silicon,
• said microcapsules employing as their shell material a member selected from the group consisting of:
• polymers composed of (meth)acrylic monomers, polymers composed of monofunctional monomers, and polymers composed of polyfunctional monomers;
• said (meth)acrylic monomers selected from the group consisting of C1-C8 alkyl esters of acrylic acid, C1-C8 alkyl esters of methacrylic acid, C1-C8 alkyl esters of itaconic acid, C1-C8 alkyl esters of crotonic acid, and substituted derivatives thereof wherein the alkyl group is substituted with an allyl group;
• said monofunctional monomers selected from the group consisting of styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, and vinyl acetate;
• and said polyfunctional monomers selected from the group consisting of ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, divinylbenzene, bisphenol A di(meth)acrylate, and methylenebis(meth)acrylamide,
• said phenolic hydroxyl-bearing benzoic acid derivative being enclosed within the polymer shell,
• wherein said microcapsules (C) have an average particle size of 0.5 to 10 μm, and
• wherein an amount of the phenolic hydroxy-bearing benzoic acid derivative leached out from said microcapsules with cresol at 30° C. for 15 minutes is at least 70% by weight of the total content of the phenolic hydroxy-bearing benzoic acid derivative in said microcapsules, and
• (D) 50 to 400 parts by weight per 100 parts by weight of epoxy resin (A) and aromatic amine curing agent (B) combined of an inorganic filler having an average particle size at most about one-tenth as large and a maximum particle size at most one-half as large as the size of a flip chip gap between a substrate and semiconductor chip in a flip chip semiconductor device.