Integrated circuit package having heat sink bonded with resinous adhesive

An integrated circuit package produced by bonding a rear surface of an insulating substrate enclosed in the package to a heat sink such as a cooling fin by a resinous adhesive, which may include one or more fillers, having a Young's modulus of 500 kg/cm2 or less when formed into a film, has high reliability at the bonding portion and withstands without damages even if subjected to thermal shocks.