Marty,
        We've had very bad luck with bonding heatsinks with prepreg, most
often resulting in a board that looks like a potato chip.  Several years
ago we switched to Arlon's Thermabond with great success.  We've launched
several satellites with bonded on heatsinks and all are still functional, a
true test of surviving rigorous use.
        Howard Feldmesser
        The Johns Hopkins University Applied Physics Laboratory

At  2:54 PM 10/16/97 -0400, Sheppard, Marty - LYPME wrote:
>We are attempting to attach a nickel-plated copper heatsink to a 10
>layer PWB per a set of manufacturing drawings that only states that "the
>heatsink shall be attached with prepreg".  It does not call out a
>pressure, temperature, cycle time, or a type of prepreg.  We have
>assumed that we would need a "low-flow" type of prepreg.  We have tried
>some sample cards with a low-flow prepreg (PC-GF 108V by Westinghouse
>Fortin) that we have on hand;  we have had good registration of the
>heatsink to card, but the adhesion has not been as good as we would have
>liked, and the heatsink seems to have been pressed "into" the board (you
>can feel the outline of the heatsink on the backside of the card).  We
>ran the press at the lowest possible pressure we can for our press (15
>lbs).
>
>We are looking for suggestions from anyone who has experience with
>laminating heatsinks to PWBs.
>
>Thanks,
>
>Marty W. Sheppard / LYPME
>Manufacturing Engineering Support
>(912)-926-9632 DSN 468-9632 Fax: (912)926-7974
>email:  [log in to unmask]
>
>##############################################################
>TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
>##############################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with following
>text in the body:
>To subscribe:   SUBSCRIBE TECHNET <your full name>
>To unsubscribe:   SIGNOFF TECHNET
>##############################################################
>Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
>information.
>For the technical support contact Dmitriy Sklyar at [log in to unmask] or
>847-509-9700 ext.311
>##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################