# Is current important for calculating spacing between traces?

Current is needed for calculating the trace width. Voltage is important for the spacing between conductors. Is the current in any way important for the calculation of the trace spacing?

• maybe for for heat dissipation Oct 15, 2022 at 1:17

A trace with a high AC current could magnetically couple an unwanted signal into a nearby trace. The higher the AC current the higher the magnetic field, the higher chance of an induced signal getting into the other trace. Somewhat like the primary and secondary windings in a transformer. So in that sense you would want to keep a high current (AC) trace further away from other traces.

• It's also good to route power traces such that the supply trace is adjacent to or directly above or below the other, as a pair. This will keep the magnetic field between the traces and away from other traces and components. Oct 15, 2022 at 4:38
• This shows up in switching regulator designs, sometimes.
– TLW
Oct 15, 2022 at 17:45

It practically all comes down at how far your return plane is and if the carrying conductor or the neighbor is a signaltrace, switching node, antenna or comparable. You want to minimize the spread of E-fields and H-fields; especially for a microstrip, with a signal. (Air/no dielectric above)

In case of a 2-layer pcb: almost 1.5mm. (!) In a 4-layer board it’s very close in case of a layer 1/2 or 3/4 arrangement (less than 0.2 mm) If the fields spread out further downwards to the return plane, they also do to the sides: crosstalk.

Assuming you are talking about PCB traces.

No, the voltage on the trace is not required for trace width.

The trace width, thickness and temperature rise are parameters for calculating current capacity.

Update: Current is not necessary for calculating the spacing between traces.

For completeness spacing will affect crosstalk and impedance both common mode and differential.

Kicad has a very good calculator to assist in selecting an appropriate trace width

• and what about Is current important for calculating spacing between traces? To upvoters here: read the answer and the question and compare these at least formally before clicking 'this answer is useful' Oct 15, 2022 at 2:55
• @V.V.T:Is that better?? Oct 15, 2022 at 3:07