Shean,
you mean 1 mm? not 1 mil...
                        jk

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Shean Dalton
Sent: Friday, October 08, 2004 12:53 PM
To: [log in to unmask]
Subject: Re: [TN] Soldering .8mm BGAs


Hello Al,

Yes, I strongly suspect you can use an inline with DI water to clean
underneath a < 1 mil stand-off.  Most current technologies, which were
sometimes successful a stand-of height of 2-3 mils or greater, are not
successful at lower standoff heights.  Many of these systems were
developed when 10 mil standoffs were the norm.  Realizing the
limitations of current technologies, we undertook theoretical and
empirical analysis to determine how to direct DI water, and, air in a
manner that caused penetration and flow underneath a 1 mil standoff
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"urn:schemas-microsoft-com:office:office" />



Theoretical analysis was undertaken with Finite Elemental Analysis model
of such parts-in-process.  The FEA computation model included the
process area; from the water and air delivery systems to the area
underneath the 1mil standoff flip chip.  The results demonstrated how-to
(and how-not-to) effectively penetrate, and, cause a continual
flushing/drying action underneath this tight clearance area.  While the
surface tension is high with water, properly applied mechanical energy
is required to overcome the many forces that are encountered at this low
standoff, densely populated geometry.  Application testing with test
coupons and real-world assemblies has confirmed to us that the implied
theory of the computational modeling does hold true in the real world.
Thru this applied technology, new levels of capability have been
achieved in cleaning low standoff devices.  These findings have been
published and are available.  Continued analysis of surface cleaning and
related surface energy's is underway.  The first part of this continued
analysis was recently presented at SMTAI, held in Chicago, USA.

Shean Dalton
Austin American Technology
(512) 335-6400
www.aat-corp.com <http://www.aat-corp.com>

Hello Technetters:
>
> Processing a 16"x20", .125" thick double-side mixed-tech (smt both
sides,
> and pth component side) with at least two .8mm BGAs with .45mm balls:
>
> one is a 84 pin package is a 9 x 15 - 135 - ball matrix with 51
> depopulated balls in the center of the package
> the other is a 8 x 12 - 96 ball - matrix with 8 depopulated balls - 4
at
> either end of the matrix
>
>
> Two quick questions:
>
> Can I clean (in-line) using di water only if I use OA flux? Or, do I
need
> to switch to no-clean for BGAs less than 1mm?
> For rework, flux only? Or can I micro-stencil or dispense?
>
>
> As always, thanks in advance for your replies,
>
>
> Al Kreplick
> Sr. Mfg. Eng.
> Teradyne, Inc.
> 500 Riverpark Drive
> Mail Stop NR500 1-1
> North Reading, MA 01864
> Tel: 978-370-1726
> Pager: 888-561-6485
>
>
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