This might not work for your application but I know someone who sends
the bare board out to Berquist for them to do a heatsink attach to the
PWB prior to module assembly.  For this application, they initially used
to bond to both soldermask and solder surfaces but then decided to cover
the entire region with soldermask after they had problems with one
particular board supplier.  Contact Berquist for the type of epoxy used
and prep method, if any.


Paul Terranova
Analytical and Environmental Test Services Lab
Worldwide Module Components Group

 Digital Equipment Corp
 200 Forest Street
 Mail Stop: MRO3-1/D2
 Marlboro,  MA  01752-3085

'    Phone: (508)467-3109
* Fax: (508)467-6796
* Email: [log in to unmask]

        -----Original Message-----
        From:   D'Angelo, Ken [SMTP:[log in to unmask]]
        Sent:   Thursday, February 26, 1998 9:58 AM
        To:     [log in to unmask]
        Subject:        [TN] Laminate surface abrasion

        As a normal part of building bonded PWB / heatsink assemblies,
it's
        necessary to abrade the bondside of the PWB in preparation of
attaching the
        heatsink.  We're presently abrading the PWB surfaces with
Scotch-brite pads
        using a manual method.  This method works great for the
prototypes and
        engineering models, but any suggestions for streamlining the
process for
        hundreds of parts?

        Just some added info - PWB surfaces can be multifunctional or
polyimide
        laminate as well as cured no flow prepreg surfaces.  In some
cases,
        plated-through holes are present and the need to thoroughly
clean the
        barrels prior to heatsink bonding is critical.

        I've heard about the use of plasma (?) etch or a standard PWB
scrubber
        equipped with Scotch-brite wheels as method of surface
preparation.  Not
        sure of the pros and cons of alternative methods.

        Any thoughts, please advise and thanks in advance.

        Ken D'Angelo
        Tyco Printed Circuit Group- VAS
        15 Tyco Drive
        Stafford Springs, CT 06076

        T:  (860) 684-8000, ext. 4332
        F:  (860) 684-0714

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