In the past, we used EMI shields with a separate cover.  The walls of the
shield are soldered to the board and after cleaning, the cover is snapped in
place.  After testing, the cover could be tack soldered if required.  This
worked very well.  I don't know if your customer would be interested in
this, but if so, I could try to dig up some information for you.

Jim Marsico
Senior Engineer
Production Engineering
AIL/Electronics Systems Group
An EDO Company
[log in to unmask] <mailto:[log in to unmask]>

        -----Original Message-----
        From:   Steve Abrahamson [SMTP:[log in to unmask]]
        Sent:   Wednesday, May 02, 2001 7:01 PM
        To:     [log in to unmask]
        Subject:        [TN] Unusual Cleaning Operation- Help!

        Howdy,

        I have got a major mess on my hands.  We may soon be running a
double sided
        SMT product that needs to be fully cleaned due to a conformal
coating
        process.
        Both sides of the assembly have two 2" x 1" x .3" RF Shields that
are
        soldered to the PCA.  There are SMT components under the shield, and
the
        shields have two .040" holes on top- the rest of the shield is
sealed.
        Just in case we cannot clean 100% of the residue out of these
shields, the
        customer requires a no-clean chemistry solder paste.  (They claim no
clean
        residue has caused problems with past due to issues with the battery
        pack...I am not much of an electrical guy, and cannot refute them).
        They are pushing us towards a vapor degrease cleaning method, since
they
        had used the process sucessfully during the design phase with good
luck.

        Question 1: If we did use a non aqueous solvent for cleaning,
especially
        one that has evaporative characteristics (any HCFC replacement),
could we
        avoid the "bake out" process?

        Question 2: Would a cold soak process with somthing like Bioact be a
viable
        alternative- and be performed without a bake out?

        Question 3: Would ultrasonics be valuable (if we had alternating
frequency
        such as with the Smartsonic system), or could more damage be done.

        Steve Abrahamson
        208-898-2695
        [log in to unmask]


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Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
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