Larry,

Plenty of folks out there are running BGAs on both sides.  There is more
than adequate solder joint surface area to hold the BGA components on during
the inverted reflow.
Unless you are dealing with blind/buried vias, or perhaps micro vias in the
pad, it is difficult to mirror BGAs in the same location on each side of the
board.  I have seen this on test boards without vias, but not in production

Steve A (you don't by chance work with Bob Stathapolus?)

> -----Original Message-----
> From: Larry Koens [SMTP:[log in to unmask]]
> Sent: Wednesday,October 17,2001 10:33 AM
> To:   [log in to unmask]
> Subject:      [TN] double sided BGAs
>
> Dear TechNet,
> My company has been  asked to bid on assembling a board that would have
> two BGAs on the topside and two more BGAs mirrored on the bottomside.
> That is, they will be directly across from each other on both sides. I
> never done them on both sides. So far, everything that I have done has
> been on one side only. Has anyone done them on both sides before?
>
>   I am figuring xray will be a problem as after the second side is
> placed, because the pads/balls will mirror each other on both sides.
> Would I be able to tell the difference between the two BGA connections?
> Suggestions?
>
> Will I need to epoxy the first side BGAs so they would not drop off
> during my second reflow? Wouldn't I need to epoxy them after first
> reflow so that the balls could collapse?
>
> Thanks,
> Larry Koens
> SMT Manufacturing Engineer
> E.I. Microcircuits
> Mankato, MN
>
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