Folks:
I have heard the figure, 30 grams of component mass per square inch
of pad area.
Joe H.
> -----Original Message-----
> From: sahmad [SMTP:[log in to unmask]]
> Sent: Wednesday, July 08, 1998 4:29 PM
> To: [log in to unmask]
> Subject: Re: [TN] ASSY: BGA sanity check
>
> 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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