Patent ID: 8922031

Claim:
A thermosetting encapsulation adhesive sheet for encapsulating a chip device mounted on a substrate through a connection electrode formed on the chip device, the thermosetting encapsulation adhesive sheet encapsulating the chip device such that the thermosetting encapsulation adhesive sheet covers the chip device while keeping a hollow portion defined between the substrate and the chip device, the thermosetting encapsulation adhesive sheet comprising an epoxy resin composition, the epoxy resin composition comprising the following components (A) to (E): (A) an epoxy resin comprising a naphthalenediol epoxy resin and a bisphenol-A epoxy resin in combination or an epoxy resin comprising a bisphenol-A epoxy resin and a trishydroxyphenylmethane epoxy resin in combination; (B) a phenol resin; (C) an acryl resin; (D) silica powder; and (E) a quaternary phosphonium salt compound, wherein the acryl resin (C) is present in the epoxy resin composition in a proportion of 15 to 70% by weight based on the total weight of the organic components of the epoxy resin composition, wherein the silica powder (D) is present in the epoxy resin composition in a proportion to 60to 80% by weight based on the weight of the epoxy resin composition, wherein the quaternary phosphonium salt compound (E) is present in the epoxy resin composition in a proportion of 0.1 to 10% by weight based on the weight of the epoxy resin composition, and wherein the epoxy resin composition has a viscosity of from 5×10 4 to 5×10 6 Pa·s as measured at a temperature of 80° C. to 120° C. before thermosetting thereof.