Does Xilinx recommend substrate materials for PCB design for high-speed interfaces?
Xilinx does not recommend specific material for PCB substrate material when designing with Xilinx devices.
It is the customer's responsibility to make the correct choice for their application. The PCB Design User Guide for the architecture used (for example, for UltraScale this is (UG583) UltraScale Architecture PCB Design User Guide) should be consulted before making any such decisions.
Customers should also carry out board simulation using IBIS-AMI before tape-out of their board design. Results from such simulation can give a good indication of whether the board design is adequate to transmit the required high-speed interface signals.