Ken,
        Use a SIR pattern such as IPC A-24. Measure a known length of RMA wire
solder and solder each comb with the same length of solder. Clean per your
standard procedure.
        Repeat with no clean wire solder without cleaning.
        Subject the pattern to SIR testing per IPC or Bellcore.
        Coat a second set of assemblies and test.
If the result is equal or better, I would use it in the commercial world.

P.S. why don't you dip it after the wires are soldered to the panel, but
prior to placement in the housing (if possible). This can eliminate masking
and you can clean it in-line.

Also, I have seen solder in place sockets that can arrive masked and
recieve open wires.

Aric

Aric Parr
-------------
Original Text
From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 3/10/98 4:10 PM:
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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