Gerry, We have used the graphs and current carrying information in Harper's "Handbook of Wiring, Cabling, and Interconnecting for Electronics", Chapter 8, "Rigid Printed Wiring and Connector Systems", published by McGraw-Hill, as a basis for our design rules in this respect. A point to watch if you are in a high current rating situation is to ensure that your VIAS are appropriately rated, and have not only enough copper in the hole (circumference/plating thickness), but also have sufficient copper VIA CONTACT cross-sectional area around the via circumference, within the plane/tracking. You may need to use multiple vias to achieve this. Also, if your current rating is not continuous, you may be able to down-rate. Within the plane areas, it will be the current carrying paths that really matter - between obstacles, unconnected vias etc. I always start with 1oz Cu and only go to 2oz if there is a (for instance, current carrying) need. We have only used 4oz Cu for thermal planes/thermal conductivity purposes, within a high cold wall temperature environment (80degC), which from what you have implied, may be similar to yours. Hope this helps, Clive ffitch MBUK ______________________________ Reply Separator _________________________________ Subject: DES: Current carrying capacity of innerlayer planes Author: [log in to unmask] at INTERNET Date: 17-05-97 7:49 Hi All I'm looking for a methodology for determining the current carrying capacity of an innerlayer power plane as a function of copper weight. Let's assume the max op temp of the laminate is 105C which allows a 30 degrees temp rise above ambient(?) It's the old "one ounce copper versus two, three, or four ounce copper" plane design question again ...... Data, viewpoints, and experiences would be welcome as well. I do know that for high speed situations, IR drop is the limiting factor. In this case, it's current carrying capability. Thanks in advance Gerry *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************