Is it obvious by your question you've laminated epoxy resin systems with heavy copper
weights? It must be as you know this is doable with some effort and very resin rich prepreg
at about 70%. The same is true for polyimide but, as you also know, is much less forgiving
in the press.

Using an old press cycle, I hardly remember, the process was manageable. I don't have my
notes anymore but the cycle was something like a "kiss" at near ambient for 15 minutes then
up to 190 then trying to hold a 3 or 4 degree/second rate of rise to 270 then straight up to
400 for final cure after 4 hours in the press (recommended over post baking). Again, you
probably have the latest recommended press cycles or are able to get them from your favorite
material supplier.

The trick was to get "juicey" enough prepreg to "swamp" the 10 oz copper and to manage the
thermal effects the heavy copper weight produced. This, coupled with the right thermal lag
material was a balancing act.

Anyway, it can be done. It can't be done nearly as easily as when using epoxy resin systems.
Often I found voids along the copper edges and some delamination after thermal stress. I
think the success percentage was somewhere in the 40% range for me. Others probably are more
fortunate.

There are alternatives as using 2 five ounce planes internally. Another is to use the old
Buss Systems trick of "embossing" a stainless steel plate with the exact circuit image
representing the heavy copper circuitry. Then, use resin rich prepreg to fill and wrap up
the copper plane.

Don't know if any of this helps. It just reminded me of what I forgot.

Earl Moon

################################################################
TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################