Dear Ian When I calculate the current of a .035 mil .002 via I do not get 10 amps, ether by the curcumfrience or the 1/2 method. Think of a via as a cardboard tube if you fold it together it is 1/2 the curcumfriance wide and twice as thick. The reason for the fold method is the via is like two resistors in paralell ( sorry i cant spell this early in the morring), using the standard current chart I roughly calculate a .035 via at .0175 * 3.14 = about .055 wide and .004 thick the current capacity is only 4 to 5 amps at 35 degrees, and 12 in paralell would only give you 48 to 60 amps . I have worked with heavy copper an big current boards all my life and from time proven tests I do not like to push a via with current, two problems, first the via is never sold even copper, they are full of thin spots and low density copper. second if you heat a via up to much it fails, the heat causes the barrel to expand and push up on the top pad, and it will crack. I wrote a book on power and printed circuits,that may help you if you are interseted you can e-mail me at [log in to unmask] --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------