The size of the pads will be dependant on the process. For 0.35u devices TSMC we use 80x80 pads.
These are made from an 80x80 metal3/4 plate (esd under) with vias around the perifery. The design rules you have will tell you what the requirements are for creating a pad. Passivation is also required again tech dependant this would normally be 70x70 inside the metal3/4