1. Not sure what's meant except that the hole wall copper is thinner than the external copper. 2. .001" would be electroplated (total) copper as electroless is typically less than .0001" thick 3. Tin-lead and gold are negligible conductors relative to copper, due to the product of their cross-sectional area (esp. for Au) and their conductance (esp. for Sn-Pb) being so much lower Timothy Reeves QA Manager/Process Engineer ECD Circuit Board Division 13626 S. Freeman Road Mulino, OR 97042 (800) 228-8198 Fax (503) 829-5482 -----Original Message----- From: Lum Wee Mei [mailto:[log in to unmask]] Sent: Thursday, August 10, 2000 10:59 PM Subject: Via current current capacity I came across this paragraph in Printed Circuit Handbook by Clyde Coombs, Jr stating : "Consider a 0.04" diameter hole plated to a 2oz internal poew plane with 0.001" minimum copper in the hole. The copper hole wall is equivalent to 0.04 x 0.001 x pi = 125 x 10exp -6 sq. in. "The copper plating of the hole wall is the smallest conductor in the path and for purposes of calculation in current-carrying capacity, consider it an internal conductor of a multilayer." My questions are : 1. Why consider the copper plating of the hole wall as internal layer and not external? 2. Is the copper plating here which is 0.001" refers to only the electroless copper thickness or inclusive of copper plating? 3. Why is the tin-lead plating or gold plating never be considered when calculating current-carrying capacity for component hole or via? Hope to learn more from your experts out there. Regards. ############################################################## 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 ##############################################################