We use no clean also and we started out just having the operators hand wash
mis-prints.  But obviously some paste was left in the holes and this was a
problem.  We were using IPA for that.  We have since changed the procedure
to have them wash them in the stencil cleaner.  It is an Austin American
X30C and we use Zestron solvent in it.  I tested several solvents and found
that the Zestron works great.  It dissolves the flux and washes the paste
off boards and stencils very quickly.  If you do not have a good stencil
cleaner to do this you may want to get a little bin to wash them in.  At my
previous company we did not have an automatic stencil cleaner.  We first
had an ultrasonic table top cleaner with IPA in it and it worked OK, but it
got pulled due to the fact that ultrasonic generates heat and IPA has such
a low flash point.  Then we got a small plastic container with a lid and we
submerged the board and brushed it with a brush, then blew the boards off
with compressed air.  That worked pretty well.  Of course these were bare
boards.  We did the same thing for misglued boards with parts on the top
side and it worked well.  This is not a great method, but without access to
an automatic unit, you have to do something.

Good Luck.

Brad Kendall
Hella Electronics Corp.






Wade Oberle <[log in to unmask]> on 01/14/99 10:07:42 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to Wade Oberle <[log in to unmask]>

To:   [log in to unmask]
cc:    (bcc: Brad Kendall/Hella North America Inc.)
Subject:  [TN] Cleaning of mis-printed boards




Dear TechNetters,
        I have a fairly simple problem that I am looking for advice on.
We use no-clean solder paste.  How do some of you clean mis-printed
boards with no-clean paste?  How do you insure you get all of the paste
out of the vias?  If it is a double side reflow board and the first side
is already populated, how do you clean mis-prints on side two and insure
that paste from vias underneath large QFPs is completely removed?  If
you use certain chemicals and/or ultrasonic agitation, are there
specific SMT components that are damaged by the use of these techniques?

Thanks in advance for your replys.

Wade Oberle
Sr. Mfg. Engineer
Manutronics, Inc.
[log in to unmask]

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