Very ggod question for naive Dan I use a ratio thst has some validity though results vary with process management and requirements as well as the process itself. If I specify one mil of copper plating in a typical hole wall, whatever that is now, I expect to verify about 1.2 mils on the board surface. So, if I start with .5 oz. Cu folil on the board outer layers, I will see about 1.9 mils total for traces, as an example, on the surface. There's some math in there somewhere and Rudy probably will provide the real answer. Earl --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------