Since polymer layer 10 has a maximum acceptable temperature for softening/melting, which in the case of FEP, is about 270-300??? C., it is preferable to use alloys or metal systems (i.e. containing one or more of tin, silver, indium, tin or bismuth) with melting temperatures less than 300??? C., or which can be vacuum deposited, i.e. via sputtering, vapor deposition or ion implantation at less tha