Mike,
        We do this two different ways. First, I need to say that we breakout
the surface pads to 12 mil vias (tented with soldermask) underneath the
BGA's. On double sided CCA's, we place the capacitors directly under and
around the the BGA footprint, targetting the caps to the power pins. On
single sided CCA's, we place the caps around the BGA. Most of our CCA's are
too dense to allow the .150 rework zone around the BGA's. We do supply local
fiducials and metallic "crop marks" for placement.

Michael Hiteshew
Lockheed Martin NE&SS-Baltimore
[log in to unmask]
(410) 682-1259


> ----------
> From:         Kuczynski, Michael @
> SPACENAV[SMTP:[log in to unmask]]
> Sent:         Friday, October 27, 2000 8:38 AM
> To:   'DesignCouncil'; 'PCB_SIG'; 'TechNet'
> Subject:      BGA/caps placement
>
> I'd like some opinions on capacitor placement for BGAs.
>
> Where are you placing the filter caps; top or bottom (we're using 0508 and
> 0603)
> If on the top, how far away are you placing them. (we're using a .150
> keepout for rework) and are they helping
> What problems do the rework guys have with the caps on the bottom
>
> Any insights/thoughts on this subject would be appreciated
> There seems little, middle ground on this issue for engineering and mfg.
>
> Michael Kuczynski    Librarian/Sr. Designer
> L3 Communications    1-201-393-2122 (Ph)
> Space & Navigation   1-201-393-6681 (Fax)
> 699 Rt. 46 E         Mail Stop PL1/J8
> Teterboro,NJ 07680
> [log in to unmask]
>

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