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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