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per_electric 27th October 2009 05:19 PM

PCB track width?

I'm in the middle of designing a PCB for an audio power amplifier. However I don't know how to estimate how wide the tracks have to be for the more high-current parts, like output, ground connections, power rails etc. Also, I'm not very familiar with calculating the maximum currents that can be expected in these lines.

Any input much appreciated!!


peranders 27th October 2009 07:10 PM

For 10 A you'll need approx. 5 mm traces at 70 um and signal traces 0.5 mm.

PCB Trace Width Calculator

Trace width is very dependent if the trace is at the edge of the board, if the pcb is mounted horizontally or vertical etc.

Mooly 27th October 2009 07:24 PM

Remember also that when it comes to grounds you MUST consider what is actually going to be flowing in the conductors too. You HAVE to design so that all signal grounds are uncontaminated. Increasing the print size 10 fold will not eliminate this kind of issue.

As a classic example of that only today I was looking at an old Rotel amp and the 1 inch or so square copper print that connects the two smoothing caps together has a clearly visible ripple component across it of the order of several millivolts.

You must treat each conductor as a resistance... if it helps put nominal values in of say 1 ohm and ask yourself "would that cause a volt drop that would influence the signal ? " the answer must be NO :)

peranders 27th October 2009 07:34 PM

Ground is very critical in good analog pcb's so it can be a good idea to let us review your work, free of charge :nod:

per_electric 27th October 2009 07:58 PM

That would be very kind of you!!:)

So, as I understand it, the best thing you could do is separate all the signal grounds from all the other grounds, and then run two individual cabels to the star ground?

Steerpike 27th October 2009 11:37 PM

Tinning the track manually, with a good thickness of solder, can up its current rating significantly.

Speedskater 28th October 2009 12:12 AM

Tinning a solid wire continuously to the track helps even more.

h_a 6th November 2009 12:50 PM

Tin is by a factor of 10 a worse conductor than copper, any solder ontop of a trace maybe looks good but won't lower resistance much.

Anyway, with 70mum boards currents as high as 15A are not a big deal anyway.

Have fun, Hannes

wwenze 6th November 2009 01:00 PM

Would the tinning result is sonic changes like tinned copper vs untinned copper wires?

peranders 6th November 2009 01:29 PM

This is a typical question with two answers:

Yes :nod:

No :no:

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