>I have been doing it last 6 years or so on 1.27 mm pitched BGAs
>on two signal layers (top and bottom), planes as necessary (actually
>6 in all cases so far), 3 lines between BGA pads, pitched 10 mils
>(say, 5 mils trace and 5 mils gap, these may vary to 4-6 or 6-4).
>Pad to gap is 5 or even 4 mil, drilling is 0.3mm or 0.2mm (I leave
>this choice to the PCB house). I drill each BGA pad so I can have
>access to all signals since my borads are typically expected
>to begin to work and sell from revision 1; I have posted some
>info before on how to avoid problems with the drilled BGA pads.

I saw you'r doing radioactive measurement equipment. How do you handle the
fpga sensitivity to radiation ..?