Abstract: A microelectronic device containing one or more dies bonded to a substrate 0.5-8 mil thick thermoplastic adhesive film is disclosed. The adhesive's main constituent is a thermoplastic organic high polymer containing the elements of carbon and hydrogen, and one or more of the elements oxygen, nitrogen, sulfur, halogen in its repeating unit. The polymer's Vicat softening temperature is 30.degree.280.degree. C., preferably 70.degree.-230.degree. C. The adhesive may also contain up to 45 volume percent of a thermally conductive inorganic filler of 0.5-20 micrometer particle size. The attachment process simply consists of heating and pressing the film, sandwiched between the adherent surfaces, above the melting temperature and cooling to ambient.