Hi Tony,

The operators here came up with an ingeniously simple solution.  They turn
the board up side down in a bath of isopropyl alcohol.  They put a couple of
wooden cotton tipped swabs on the bottom of the bath and make sure that the
edges of the boards are resting on the swabs - not places where the solder
paste is located.  Then they just let the board sit for 15 - 30 minutes.
After a while they tap the back of the board and the solder paste literally
falls off.  They remove the board, wipe it down with fresh alcohol, and
reprint the board.  It seems to work as we haven't had a problem with stray
solder balls in places where they shouldn't ought to be.

Kathie Lambert
Process Engineer
Northrop Grumman
Baltimore, MD

        -----Original Message-----
        From:   Tony Conlon [SMTP:[log in to unmask]]
        Sent:   Friday, July 06, 2001 3:44 AM
        To:     [log in to unmask]
        Subject:        [TN] Cleaning of Mis-printed boards ...

        Morning folks,
                                    Here's a brief summary of the situation:
Boards
        exiting the screen printer and found to be mis-printed ... we are
manually
        cleaning at the moment (AlphaMetals Screenwash & Lint-free cloths)
... it
        works but not consistant ... thus auditors etc ... would not be
particulary
        impressed. Due to certain issues we have decided that we cannot
clean
        boards for a particular customer ... they have to be scrapped. Big
problem!

        In the past we have tried the old 'Kerry stencil cleaner' (operates
by
        means of a rotating arm dispensing the cleaner approx 20min cycle)
as a
        board cleaner ... with Vigon SC200 solution: The result ... ok ...
but we
        have gold contact-fingers to contend with and the paste seems to
lodge at
        the fingers edge and the rest ...
        We also tried the newer 'Kerry' machine (Ultra-sonic based) ... not
        successful either I'm afraid.

        We have also tried a Branson Ultrasonic cleaner (with Vigon &
Clean-thru)
        approx 30min cycle ... same story as above.

        Right guys! Any super-duper cleaning equipment/solution spring to
mind? The
        gold contact-fingers are really making life difficult.

        Cheers guys,

        Tony.


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