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March 1998

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Subject:
From:
Kenny Bloomquist <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 10 Mar 1998 13:06:03 -0800
Content-Type:
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I have a question regarding soldering assemblies after they have been
confromal coated.  This is for a DOD customer and we do all soldering with
RMA flux.  Here is the scenario:

We solder all the components into a PWB in our wave solder machine using RMA
flux.  We mask all the wire entry holes that are to be soldered later.  The
boards get tested, cleaned; cleanliness tested and conformally coated with
polyurethane, except for the holes that will be soldered later.

They then go into the next higher assembly in which a large number of wires
are attached.  Due to the size and shape of the assembly at this point it is
difficult to clean in any sort of a batch system.  We currently bench clean
with IPA (ProClean), rinse with IPA, dry and brush conformal coat over the
connections.

Finally my question is, what would you see as a problem with soldering these
wires using no clean/low residue flux and brush confromal coating over the
connections?  How would you qualify this process since conventional
cleanliness testing is out of the question due to size and condition of all
the other material attached to this assembly now, (wires, sheet metal,
thermal compound, etc).

This would obviously be a considerable saving due to the tremendous amount
of cleaning we currently do.

All comments and suggestions are greatly appreciated.

KennyB

Ken Bloomquist
Sr. Principal Process Eng.
PRIMEX Aerospace Company
[log in to unmask]
(425) 881-8990 ext. 6645

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