I am trying to design a PCB circuit in altium designer.

My circuit consists of one ATmega8a, one NRF24l01 and three magnetic relays (mini relay 12V MPR-S-112-A.)

I want to set the trace width to 0.5mm (except power circuit.)

Is that correct ?

If it is wrong, what width should I use?


  • 1
    \$\begingroup\$ Saturn PCB has a handy tool for all sorts of (these things) Link \$\endgroup\$
    – Tyler
    Commented Aug 15, 2019 at 11:03

2 Answers 2


0.5mm is 20mil, right? That's fine for most work at lowish frequencies.

  • \$\begingroup\$ I know this is an old post. But 20mil is NOT 0.5mm. It's 0.508mm. Not a big deal for trace width, maybe. But a real big deal for a 100 pin tqfp with 0.5mm pitch. The error across 25 pins accumulates to 0.2mm. I have just been burned by this - The engineer who created the footprint worked in Imperial units, and also used 20mil=0.5mm \$\endgroup\$ Commented Sep 27, 2023 at 11:24
  • \$\begingroup\$ @StephenCasey If you try putting 0.5mm -- or 20mil -- width traces into a 0.5mm pitch footprint, it won't exactly matter... neither one is going to connect to any of the pads! \$\endgroup\$ Commented Sep 27, 2023 at 12:44
  • \$\begingroup\$ He has specifically asked for tracewidth, and not a pad layout. Yes, 20mil = 0.508mm. And no - there's no "100 pin tqfp" in the schematic shown \$\endgroup\$ Commented Oct 24, 2023 at 6:21

you can use these guidelines Guidelines or similar as a reference for a decent layout. On the right hand side of the GUI, you will find track width graphic.


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