Regarding the issue of a microblaster damaging the PWB, it might depend on
the system used and the media in the system.  I did my evaluation of the CCR
system (with their recommended media, which is a plastic, I believe) with a
direct spray on an uncoated board (solder mask).  The solder mask wasn't
even scratched.

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879


        -----Original Message-----
        From:   Gregg Klawson [SMTP:[log in to unmask]]
        Sent:   Thursday, June 05, 2003 8:07 AM
        To:     [log in to unmask]
        Subject:        Re: [TN] Urethane Coating Spot Removal...

        Hi Steve,

        We use Uresolve Plus Gel from Dynaloy for spot urethane c/c removal
(we use Conap CE-1155).  It's a gel so it doesn't run all over the board and
works fairly quickly depending on your coating thickness.   We sometimes
set-up an "assembly line" and spot strip many boards at a time:  apply the
gel, wait, wipe off, rinse, clean, inspect.

        You have to be careful with microblasting.  The operator can easily
blast through the coating and into the PWB butter coat or solder mask if
they are not careful.  It can be tedious work if you have a large area to do
and lots of assemblies.

        I think the soldering iron burn through method is OK for small
components and small jobs.  However there's always a concern with thermally
overstressing the PWB with burn-though c/c removal of through-hole
components.  If you are working with surface mount parts you also need to
get all the c/c off the pads so you can solder the new part in place, which
can be a challenge.

        We've even evaluated a laser removal method but that was not
successful due to the normal variations you see in coating thickness across
a board.  The laser wasn't "smart" enough to sense the coating thickness and
adjust it's power accordingly.

        -- Gregg


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