We've done it (do it) with much success at .8 and 1mm. With
limited/qualified success at .5mm.  Typically we've pre-assembled to bottom
of BGA and then placed as one unit on the motherboard.  Phil Bavaro is a
great resource for this application.

dw



> > Folks,
> >
> > We have a requirement to design a daughterboard that will be soldered
>to
> > the motherboard in place of BGA devices. This means that BGA balls are
> > required (on the secondary side) of the daughterboard so it can be
> > soldered to the existing BGA pattern(s) on the motherboard, as if it
> > were just another BGA. I've not heard of this being done before so I'm
> > hoping others may be able to provide some insight in regards to
> > feasability and process.
> >
> > Thanks Much!
> >
> > Rick
> >
> >
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