[email protected]d wrote:
> >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 ..?

I don't. For two reasons - one, because the measuring equipment
does not experience any radiation of concern. Often the levels
measured are below the natural background, and the detector
is placed in a lead shield with 10+ cm walls... There are also
high count rate applications, but it is the detector which
sees the counts, not the analyzer (several meters cable).

Second, I only use CPLDs, not FPGAs, in my equipment.... :-) :-).
(I use Coolrunners).

Dimiter

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Dimiter Popoff Transgalactic Instruments

http://www.tgi-sci.com
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