I understand that prior to polyimide, vacuum metallized Teflon film was used for flex PCB's.  Seems to me this would be an excellent RF board material in place of  PTFE panel material (at 2 mil thickness a 50ohm trace would be 6 mil wide).  Has it disappeared totally and if so, why?
   
   
Phil Hersey
[log in to unmask]
(702) 884-5388x128