The implementation constraints must accurately reflect the requirements of the final application. Physical constraints such as I/O location and I/O standard are dictated by the board design, including the board trace delays, as well as the design internal requirements derived from the overall system requirements. Before you proceed to implementation, Xilinx highly recommends that you validate the correctness and accuracy of all your constraints. An improper constraint will likely contribute to degradation of the implementation QoR and can lower the confidence level in the timing signoff quality.
In many cases, the same constraints can be used during synthesis and implementation. However, because the design objects can disappear or have their name changed during synthesis, you must verify that all synthesis constraints still apply properly with the implementation netlist. If this is not the case, you must create an additional XDC file containing the constraints that are valid for implementation only.