HI I have plated heavy copper boards for years ( up to 20 oz of copper) I have not had problem with plating only one oz when the outer layers are 3-10 oz , there is no issue with thermal expansion , other then one study showed a vastly improved resistance to via cracking if there is 3 oz or greater of copper in the hole. seems the expansion forces of FR4 is not as strong as 3-4 oz of copper in the holes. I have a book on heavy copper and survivability studied of heavy copper in the hole. its available at megadawn.com. --------------------------------------------------- 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------