We haven't had a problem with paste on the back of the stencil.  You may
want to investigate your stencil printer to see why it isn't performing
properly.  We have an ultrasonic stencil cleaner that seems to clean solder
off stencils very easily with a 2 minute cycle.

Kathie Lambert
Process Engineer
Northrop Grumman
Baltimore, MD

        -----Original Message-----
        From:   Martin, Jesse [SMTP:[log in to unmask]]
        Sent:   Monday, August 16, 1999 3:08 PM
        To:     [log in to unmask]
        Subject:        [TN] Solder paste stencils

        Has anyone had a problem with solder paste stencils that have a
build up of solder paste on the bottom (PCB) side of the stencil that won't
come off in the stencil cleaner? I think what happens is the vacuum/paper
wiper leaves some on the bottom after each wipe and the more it wipes the
harder it is to get off. I can pop it off with an Xacto knife or the like
but is very time consuming. Only other thing that works is using a
Scotchbrite pad but that leaves a lot of scratches (which probably causes
faster build up). Have also tried stainless steel cleaner with no luck. We
use an old Austin American batch aqueous cleaner with saponifier at 120
degrees F. Any and all ideas welcome.

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