PCB track resistance.

[ken_k]

Hi
I just made a post on another forum (diyAudio Tubes/Valves) and thought it may be worth re posting here. I fully realize most people on this forum are way beyond this, there may be some that are new to this concept.

For those interested in mental estimations of track resistances go to and read this page first.

https://www.edn.com/counting-squares-a-method-to-quickly-estimate-pwb-trace-resistance/#:~:text=copper%20has%20a%20resistance%20of%200.5%20m%CE%A9%20per%20square%2C%20and,x%200.5%20m%CE%A9%20%3D%203.0%20m%CE%A9


 

So if a track is on 1 oz copper and the trace is 1 unit wide and 10 units long it will have a resistance of 0.5 milliohms x 10 so 5 milliohms.
If the track is passing 4 amps it will dissipate (power= current squared x resistance) power = 0.08 watts, the voltage drop will be V=IR so Vdrop = 20mV

Ken K

[HAL]

Hi Ken

Always good to know.  Particularly if there are current measuring devices on the PCB.

Best Regards
Hal

[shantanu@india]

Good info Ken.
Ground planes are quite common in most PCB's. It's quite difficult to assess ground loop currents if they exist. I remember trying to funnel all sectional grounds to a single ground terminating on the ground pin of the 7805 in boards I used to design myself about 25 years back!!