PCB Track Width/Copper Thickness

Discussion in 'The Projects Forum' started by yakuut, Jan 6, 2011.

  1. yakuut

    Thread Starter New Member

    Sep 21, 2009
    Hi Everyone,
    Just needed some suggestion on PCB design.I am driving a 15V,30A DC motor,now the PCB track size to withstand 30A should be around 21mm. Any suggestion on how to do this.

    Also what does the copper thickness of 2 Oz,4 Oz represent??
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    2oz means 1 square foot of copper that thickness would weigh 2 ounces, same for 4oz.

    To carry 30Amps, the length of the track would need to be known. It would be around 3/4" wide for a 6" track using 4oz copper (max cap 34A). You want to add a bit of leeway so the trace doesn't become a fuse during a surge.

    If the track is longer than 6", the width needs to be greater.
    yakuut likes this.
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    A method sometimes used on PCB's that must carry large currents into themselves and out again.

    A piece of 16 or 14 gauge tinned bare copper is bent and laid down over top of and soldered to the copper trace, or even better, the design brings the large current wires directly to the places where they enter and leave the board.

    Running such large currents through a pcb without 'cheating' is hard to do without it having a large effect on the nearby circuits.

    Basically, such things are not done in the production of electronics products. They are avoided with techniques, tricks, or whatever you want to call it. You should devise a way of bringing the current to where it needs to be without running it through the PCB like all the other twisted, maze-work like, traces you are so used to seeing.
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    I design circuit boards that carry from 15 to 100A all day long. I would NEVER use the solder a bare wire to the trace method for a production product. (but its been done and the assembly people complained constantly about it)

    There are many PCB trace calculators online and all include how much "trace heating" can you tolerate
    In general I don't run anything over 15A on typical 2oz copper laminates.. I usually use 3,4, or 5 oz copper laminate depending on how much room I have for traces.

    I've done 30A with a 1/4" trace width (approx 3" trace length) (1/4" trace on both sides of a 4 oz circuit board) and I've done 100A on a 1/2" trace on 5oz copper laminate too (again the trace on both sides).

    http://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/ start here.. I took the formulas on that page and dropped them into excel and "modified" them slightly based on my own thermal testing of the real products.