Jim,
Should the weight of the part on the bottom side of the board not be less
than the retaining force generated by the surface tension of the molten
solder for it not to fall off the board? Did any of the parts you used
violate this criterion?
Thanks.
Syed.
-----Original Message-----
From: Fulton Feng [SMTP:[log in to unmask]]
Sent: Wednesday, July 01, 1998 5:24 PM
To: [log in to unmask]
Subject: Re: [TN] ASSY: BGA sanity check
FYI
> -----Original Message-----
> From: Maguire, James F [SMTP:[log in to unmask]]
> Sent: Wednesday, July 01, 1998 8:31 AM
> To: [log in to unmask]
> Subject: Re: [TN] ASSY: BGA sanity check
>
> Jerry,
>
> We recently did some testing of "double sided reflow" related to
> reliability. In our testing we were wondering if reflowing a 2nd
time
> with the part on the "bottom" of the PWB (so gravity pulls the
part away
> from the PWB surface) would impact reliability (and also, if it
would
> stay in place during reflow).
>
> Our results showed a) it stayed in place and b) no impact on
reliability
> (we've passed >1600 cycles -55/125C thermal shock with 30 min.
dwells at
> temp per side without any electrical intermittents.
>
> Jim
> ================================================
> James F Maguire
> Associate Technical Fellow
> Boeing
> Information, Space & Defense Systems - Phantom Works
> phone (253)657-9063
> fax (253)657-8903
> pager (206)982-3737
> email [log in to unmask]
> =================================================
>
> > ----------
> > From: Jerry Cupples[SMTP:[log in to unmask]]
> > Reply To: TechNet E-Mail Forum.;Jerry Cupples
> > Sent: Tuesday, June 23, 1998 3:15 PM
> > To: [log in to unmask]
> > Subject: [TN] ASSY: BGA sanity check
> >
> > Hello, TechNet....
> >
> > Soldering (inline convection furnace) BGA's on both sides of a
board
> > is
> > beyond my own experience, but it seems to violate a principle
(at
> > least an
> > imaginary one) related to the controlled collapse, or perhaps
liquids
> > under
> > tension.
> >
> > For a board design using 3 commercial BGA packages (PBGA 256,
eutectic
> > balls on 1.27 mm pitch), am I obstinately blocking the path of
> > progress by
> > requesting that this package style be confined to only one
surface of
> > a new
> > board design?
> >
> > If you are doing this today and it is a piece of cake, go ahead
and
> > brag;
> > but I would prefer to hear that caution is well advised, i.e.
tales of
> > misery, shame and corporate disaster resulting from such
mistakes. ;-)
> >
> >
> > cheers,
> >
> >
> >
> >
> > Jerry Cupples
> > Interphase Corporation
> > Dallas, TX USA
> > http://www.iphase.com
> >
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