Hey John, The best reason I could give to stay away from single ply prepregs would be resin starvation. A single ply of 1080 is about 3.5 mils thick before pressing and 2.5 mils after pressing, that only leaves about .5 mils per side to fill copper to substrate voids. Since 1/2 oz copper is .7 mils thick the math doesn't come out to good. I have seen (though didn't like) single ply construction done between planes (no thermals). There could be arguments for single ply lamination but for reliability (reduced delam possibilities) I would always recommend minimum 2 plys. Since 1 ply of 1080 tends to press to about 2.5 mils you could probably still get away with 2 plys of 106 at about 3 mils and have much better reliability. Hope it helps. Good Luck FNK Frank N Kimmey CID+ Sr. PCB Designer Powerwave Technologies EDH 916-941-3159 FAX 916-941-3195 -----Original Message----- From: John Parsons [mailto:[log in to unmask]] Sent: Wednesday, August 20, 2003 10:15 AM To: [log in to unmask] Subject: [TN] FAB: Single vs Double Ply Multi-Layer Construction I believe that in days of old IPC and various other specifications disallowed single ply prepreg constructions. I don't have the spec's handy but I do not believe that this is a current IPC requirement. While some OEM's still carry this specification I am looking for insight into what the concerns, real or imagined were with single ply construction. Potential shorting between ultra thin dielectrics I can understand but I am concerned with this application regarding more conventional builds ie. 1080, 2116 pregs etc., 0.062 boards to 12-14 layers. Regards John Parsons --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------