A printed circuit, chip carrier or other substrate for an electronic power circuit can comprise a heat transfer device engineered to dissipate heat generated from the electrical operation of the circuit. The heat transfer characteristic or heat sink capacity of the device results from formation in a polymer film of an array of cylindrical metallic portions in the film that draw heat from the circuit package. We have found that by forming such an array of metallic cylinders wherein each cylinder has a diameter less than about 25 .mu.m, the array defined by a distance on center of about 50-125 .mu.m has a substantial heat transfer characteristic. We have found that when the polymer film has the array of metallic cylinders within the film to a degree that at least about 8%, preferably 10-15% of the surface area of the film is occupied by the metallic cylinder, that the heat transfer characteristics of the film is virtually identical to copper metal. The surprisingly high heat transfer characteristics of the film is surprising and unusual when considering the heat transfer characteristics of the polymeric material surrounding the relatively small proportion of metal. The metallic cylinders are the preferred structure of the metallic portions in the film, however, such cylinders can have some variation of the cylinder structure. Further, any regular array of the cylinders in the film can be used.