Is this 4oz before plating or after plating? Typically you start with 3oz Cu and plate 1oz, which gives you a little more than 0.001" Cu plating in the holes. Don't forget to allow for etch factor, i.e., a 0.020" trace will be equivalent to 0.017" or so after etching. Forget about 6 or 7 mil traces. You can use 3 oz copper for inner layers, but the same scenario above applies. Check with your current supplier(s) to see if they have any heartburn about this. Thay may want to only see 2 oz Cu at the maximum. Be sure and spell out exactly what you want in your documentation. Have you thought about a 6-layer board, using 2 oz copper on the inner layers, duplicating say, layer 2 and 4, and 3 and 5? This would distribute any resulting heat. and you would get better current-carrying capacity because of the redundant thermal connections (if you use them). Roger M. Stoops, PCB Designer Spectra Precision Inc. Ph: 937.233.8921 5475 Kellenburger Rd. 937.233.4574 ext Dayton, OH 45424-1099 288 USA Fax: 937.233.7511 Member IPC Designer's Council, C.I.D. Darrel Therriault To: [log in to unmask] <darrelt@NCUB cc: E.COM> Subject: [TN] 4 oz Cu Sent by: TechNet <[log in to unmask] ORG> 05/22/00 07:19 PM Please respond to "TechNet E-Mail Forum."; Please respond to Darrel Therriault TechNetters, Design Engineering is requesting we go to 4 oz Cu for a new power module design, 4 layer PWB. Any gotcha's with 4 oz Cu we need to be aware of and is this a fairly standard job for PWB houses?? Any comments, info or recommended PWB suppliers appreciated. Tks......DT ############################################################## TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - 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 1.8c ############################################################## 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################