Happy, I wouldn't call the charts 'messed up'... They have de-rating factors built into them and they were based upon Phenolic material in the beginning and have been used for many, many years... Mike Jouppi is helping to make more accurate thermal modeling available to Designers and engineers who need more accurate charts to work from... but these charts work, and work well... because they have a lot of margin built into them... personally I don't like designing without some safety margin... it's like insurance. If you are designing against the cutting edge then Mike has a program that will let you calculate the thermal performance of a given trace based upon all of the variables... http://www.thermalman.com/3.shtml Best regards, Bill Brooks - KG6VVP PCB Design Engineer , C.I.D.+, C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 e-mail:[log in to unmask] http://www.dtwc.com http://pcbwizards.com -----Original Message----- From: Happy Holden [mailto:[log in to unmask]] Sent: Wednesday, April 06, 2005 11:30 AM To: [log in to unmask] Subject: Re: [DC] PCB TECHNOLOGY (2 oz copper) If the need for thicker copper is to carry more current, be aware that the "IPC - 2221 Generic Standards on Printed Board Design Figure 6-4" on page 38 is incorrect. Fortunately, it is approx. 4X off the real numbers, which means you can run four (4) times the current through a trace (or plane) for the same temperature rise. The new IPC Standard that is being worked on is IPC- 2152. This will have very accurate charts to help you size traces and planes. The Chairman of this group, Michael Jouppi, has a web site just for PCB conductor sizing and thermal issues at www. thermalman.com. It contains the complete sordid history as to how these design curves got so messed up, but also good charts and data on what the proper sizing should be. So if the 2 oz or 3 oz innerlayers are for carrying more current, they may not be required. Happy Holden Westwood Associates Kitty Hines <[log in to unmask]> Sent by: DesignerCouncil <[log in to unmask]> 04/06/2005 01:54 PM Please respond to "(Designers Council Forum)" <[log in to unmask]>; Please respond to Kitty Hines <[log in to unmask]> To [log in to unmask] cc Subject Re: [DC] PCB TECHNOLOGY (2 oz copper) Jack, Thanks for your input. This going to be a 16-layer board, (2) layers to be 3oz, 6 layers to be 2oz., the rest will be 1oz. copper. The board is .187 thick, so it is possible. I'm just trying to find out if there are any issues I need to consider. Trace/space widths should be just fine, so I guess I'm gonna go with it and see what happens! Thanks Again, Kitty Hello all, One of our PCB suppliers came out with a PCB design that have 2 ounces of copper on all layers. Until now we have worked with PCB that have 2 ounces of copper only on the exterior layers, and only one ounce of copper on the interior layers. We do not have experience working with PCBs with 2 ounces of copper on all the layers. Would you mind helping us to gain more knowledge regarding these PCBs? Are there any risks associated with this design: thermal events, concerns, things that we should be aware of? Thanks in advance, .......................................................... Kind regards Erika E. Sanchez PCB Designer Siemens VDO Internet: http://www.siemensvdo.com ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------------