We have not seen a difference. From a materials perspective a single ply opening offer less CTE mismatch and stress which should yield less of a contribution to warpage. Certainly the "square" weave plies offer the best stress management. The real factors in warp are resin content differential above of below the centerline with copper differences a second. I would think the glass styles are getting into the PPM ranges for contributions to bow. Jeffrey Bush Director, Quality Assurance and Technical Support VERMONT CIRCUITS INCORPORATED 76 Technology Drive - POB 1890 Brattleboro, Vermont 05302 Voice - 802.257.4571 ext 21 Fax - 802.257.0011 <http://www.vtcircuits.com/> -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerald Gagnon Sent: Wednesday, June 14, 2006 9:54 PM To: [log in to unmask] Subject: [TN] Warpage in single ply vs multi-ply multilayer stackups Hi All, I should probably know the answer to this, but thought I'd pose the question and get alternative theories and points of view. Is anyone finding a difference in the level of PWB warpage between multilayer constructions made of multi-plies versus single-ply? Assume in both cases that the supplier, processing, and materials are identical. Best Regards, Gerry _________________________________________________________________ Don't just search. Find. Check out the new MSN Search! http://search.msn.click-url.com/go/onm00200636ave/direct/01/ --------------------------------------------------- Technet Mail List provided as a 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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 847-615-7100 ext.2815 -----------------------------------------------------