I have received prototype PBGA (256 pins) devices from Motorola (actual part number = KXPC850ZT50). These parts seemed very warped on the edges. When I put the part on a plain surface, it rocks quite a bit when I press lightly on a corner. I have had intermittent problems with the pins on the corners. How can I mesure if the level of warpage is acceptable ? What measures can I take to minimize the effect of this warpage.