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April 2006

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Tue, 18 Apr 2006 09:18:19 -0500
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text/plain
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text/plain (49 lines)
It is typically done using a fixture made of Durostone. This prevents
the selective solder process, whether wave-soldering or selective
fountain/jet soldering, from filling other holes or pads where solder is
not desired. Some examples of these types of fixtures can be seen at
www.dmipallet.com. These people make these fixtures and are the best in
the world at it. Believe me, I know, I've tried them all. 
Another method would be to use a temporary solder maskant that is
available in peelable or soluble form (peelable, low ammonia is best).
Both will contaminate your wash process, the peelable less so depending
on how diligent the operator is at removing it prior to wash. Even when
peeled some residue will remain on the pwb.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Tuesday, April 18, 2006 8:46 AM
To: [log in to unmask]
Subject: [TN] Selective Soldering

While inspecting a board produced by mass manufacturing techniques, I
noticed the backside had been selectively soldered.  The areas where
through hole components are located appear to have been gasketed off (as
detected by observing the no-clean flux residue) by either the fluxing
or wave-like processing.  Any ideas as to how that was done?  Its clear
that the board wasn't wave soldered as there are open PTH's in the areas
not soldered.  A multi-nozzle solder fountain?

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