The old MIL-STD-275E spec page 34 and 36 has charts in it that give you a
guide that is de-rated based on the Military standards.
http://www.dscc.dla.mil/Downloads/MilSpec/Docs/MIL-STD-275/std275.pdf


The IPC has the same charts in IPC2221 page 38.

According to what I have heard, these charts are approximately 50%
de-rated... and based upon phenolic material. There is some impressive work
being done by Thermalman that gives more realistic numbers to a thermal
design. http://www.thermalman.com/


If you want to use a free online calculator there's one developed by Brad
Suppanz at http://www.geocities.com/CapeCanaveral/Lab/9643/TraceWidth.htm


Best Regards,

Bill Brooks
PCB Design Engineer , C.I.D., C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510


-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Tuesday, May 11, 2004 3:15 PM
To: [log in to unmask]
Subject: [TN] Formula

Although I know it's been discussed numerous times, my search in the
archives
is coming up empty. Is there a formula that gives the relation between trace
width-length and the current it is able to carry for a given foil weight?
Thanks.

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