oops - mistagged again... ----- Forwarded by LAWRENCE LILE/COL/ENGNR/TMASTER/SALTON on 03/07/2003 04:22 PM ----- LAWRENCE LILE 03/07/2003 04:21 PM To: pic microcontroller discussion list cc: dparks@UVIC.CA Subject: Re: [ELEC]: PCB for High Current (help) A standard trick that us manufatrurers use is to solder a thick bare copper wire to the board. Get the circular mils of copper up to equal a similar bare wire and you'll be safe. Look up wire current carrying capacity in an NEC handbook or on a wire mfr's site. If this is a one-off or a short production run that won't be a problem. Yes you can carry plenty of current through a throughhole pin with a leg in it, I wouldn't worry about it if the pin itself can handle the current. You can also go to 2 oz copper, for greater current carrying ability. I handle 15 amps and 120V all the time on PCB traces in commercial products, so as long as you stay within the safe temperature rise area you should be OK. Each PCB material has a different maximum temperature rating, either rated in absolute temperature or temperature rise above ambient. I don't have this info handy, but memory says FR4 is rated about 130C absolute. If you keep your temperature rise under 80C (55 rise above ambient) you will be plenty safe. -- Lawrence Lile Donovan Parks Sent by: pic microcontroller discussion list 03/07/2003 02:52 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: [ELEC]: PCB for High Current (help) Hello, I am designing a PCB for a motor controller I have developed for a small underwater vehicle being developed at the University of Victoria (www.engr.uvic.ca/~auv). I have a few concerns about putting up to 20A through a PCB trace though. By searching the web I have been able to find a nice program by John Brown (http://hampcb.com/downloads.html) that calculates the maximum current carrying capacity of a copper trace based on the acceptable temperature raise above ambient, trace width, and copper thickness. This is exactly what I am looking for except I have been unable to determine what an acceptable temperature raise above ambient is. At what temperature will the copper trace start to peal off the board? This program indicates that with a trace width of 300 mils, an allowable temperature raise of 50 degree C, and 1 Oz copper plating I can handle 21A - does this sound reasonable? In the same vein, can I put 20A though a throughhole with a pin (i.e. through the leg of my MOSFET from on side of the board to the other) without taking special precautions? I realize I can't put 20A through a simple via, but am not sure if I can do it with a throughole with a pin in it. Sorry for all the questions and obvious lack of knowledge, but this is only my second PCB and the first that has carried any serious current. Thanks, Donovan -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu