By my calculations you need 580 sq. mil of copper to carry 25 amps continuous with a 30 degree C temperature rise. Being conservative, that means you need an external trace of 480 mils wide in 1 ounce copper, and 250 mils wide in 2 ounce copper. I would add a safety factor (1.25-1.5x) to these sizes before using them at that high of current though. Jeffrey A. McGlaughlin PCB Designer Battelle Memorial Institute Columbus Ohio [log in to unmask] -----Original Message----- From: Anne Ledger [SMTP:[log in to unmask]] Sent: Thursday, 28 October, 1999 16:50 To: [log in to unmask] Subject: [TN] Copper thickness for 25 amps Good Afternoon Technet, Does anyone know how thick a trace is required to carry 25 amps in 1 oz copper? How about 2 oz copper? Let's assume it's .062 thick material. Need help ASAP. Thanks in advance. Anne Ledger EMDS, Inc. [log in to unmask] ############################################################## 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 Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## 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 Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################