I have a customer who is asking for 60-90 Ohms (single ended) on
     a card bus PCB that has the same parameters as a 6 lyr PCMCIA at
     .020 thk max. The specified trace requirements also recommend a
     prop delay of 150-190 ps/In (Tpd). Modeling this little jewel leads
     one into PTFE type Er. However, the Tpd drops below recommendations.
     Using FR-4 type materials drops the linewidth down into micro 
     miniature ranges.
        Has anybody else encountered such a requirement?
        Is this a realistic requirement?
     
     Any and all replies will be greatly appreciated.
     
     Dave Hoover (Groovy) 

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