Hi Jimmy, I would like to help analyze the copper thickness issue with you but first I would need to know more about the specifics of the design... Here are a few questions that come to mind... What was the width of the trace(s)? How long were the traces? Did you pass the traces from one side of the board to another or an internal plane using multiple vias? Were the traces external or internal to the board structure? Were they under a solder mask? What was the board material type and stack up? What was the temperature ambient that the board was being spec'd to survive in? Were there planes in the board? Are there other heat producing devices pumping heat into the board near the traces? What is nature of the heat conduction path to the ambient air? Thermal rise of the high amperage traces and voltage drop across them needs to be looked at as a system issue... there are many factors that can affect the results... Mike Jouppi's Thermal Man's website is a terrific source for more accurate calculations, but that doesn't mean that you should not build some 'extra headroom' in your designs to cover for worst case situations... In fact the IPC charts that were developed for the Military back in MIL-STD-275 were designed with that headroom in them... de-rated by at least 50%, so they made designs more robust... and thus more survivable under extreme conditions. Send me some more specifics and we can think about the failure issues and come up with a solution... I have design boards for 2500 Watt switcher power supplies and RF power amplifiers so I may be able to lend a little insight into the problem if I can get a little more info to fill in the gaps. Best regards, Bill Brooks - KG6VVP PCB Design Engineer, C.I.D.+, C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 Datron World Communications, Inc. _______________________________________ San Diego Chapter of the IPC Designers Council Communications Officer, Web Manager http://dcchapters.ipc.org/SanDiego/ http://pcbwizards.com -----Original Message----- From: Jimmy Blier - Paradox [mailto:[log in to unmask]] Sent: Wednesday, April 19, 2006 11:44 AM To: [log in to unmask] Subject: [DC] The capacity of electric plating to carry current Hi everyone, I'm facing a dilemma regarding the capacity of electric plating to carry high currents. We made a PCB that had to handle a current of 30 amps. We made some calculations and figured that we needed 3 once copper thickness to achieve the requirements. The PCB manufacture didn't have in stock the required thickness, so they proposed to use a PCB 2 once thick and simply electro plate the missing once. Since we were short in time we agreed to the proposal. The results we got are completely off the track according to what we expected. What could be responsible for this? Does electric plating has the same current capacity or does it differ from the plain old copper on the PCB? Or could this be the result of a calculation error from our part? If so can anyone tell me were I can find more accurate charts and data to establish what need for this high current design? Cheers, -- Jimmy Blier Senior PCB designer Paradox Security Systems Ltd. 780 Industrial Blvd. St-Eustache, Quebec, Canada J7R 5V3 Phone : 450.491.7444 Fax : 450.491.3454 <mailto:[log in to unmask]> <http://www.paradox.ca/> ---------------------------------------------------------------------------- ----- DesignerCouncil 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 DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 847-615-7100 ext.2815 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- DesignerCouncil 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 DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 847-615-7100 ext.2815 ---------------------------------------------------------------------------------