pin assignment

hi:

In order to draw a PCB which contains BGA chip (FPGA)conveniently,I want to assigned pin manually in the quartusII,so I can check the correctness of my assignment thougth quartusII compilation.

after compilation,there is no error about assignment ,but there is a critical warning,that is :"timing requirments for slow model timing analysis were not met ".

I want to know if or not the problem of timing waring need to overlook ?

and there is another questions:

Besides pin assignment maunally,is there any better way to assign pins,expecialy for BGA packaging?