Polyimides Doped with Silver-II: Surface Conductive Films

Abstract

Polyimides are used for a wide range of applications in areas such as integrated electronic circuits and aerospace devices that require excellent dielectric properties, high temperature stability and chemical inertness (1). On the other hand, some applications require low electrical resistivity and high reflectivity which are characteristics that are more typical of metals. In the attempt to synthesize materials with unique combinations of properties, metal-containing polymeric composite material (2,3) have been suggested as candidates. Insulating polymers possessing desirable technological properties may be rendered conductive by mixing with conductive particles such as carbon black, metal powders, flakes or fibers and metal coated particles, but in many cases high loading levels have been necessary which spoil the polymer’s properties. The approach of Taylor and co-workers (4-10) has been to dissolve additives (metal salts and organometallic complexes) into a poly (amide acid) solution. The resulting films of pre-polymer upon thermolysis undergo both imidization and metallization. Appropriate processing and the correct choice of monomers yield reflective and/or conductive films in which the polymer’s properties are basically maintained (11, 12). Enhanced surface reflectivity has been obtained with copper (13), gold (14), and silver (15-18, 11) compounds; while palladium, platinum (19), and tin (20) salts have improved surface electrical conductivity.