Allowable Die Size in PBGA 456 Package

Hi We are doing 2M gate design and IO PADS are 419 including VDD and VSS PAD. We are palning to PBGA456 Package. In that 36 pins are Thermal. So totally 455 and one NC pins. But we are not clear what is the allowable (Minimum and Maximum) Die size for PBGA456 package. If any body knows please tell me. Thank You Yousuf