0R resistor implemented as PCB trace

We have several times needed to implement a 2-pad component as a PCB trace. Use cases include:

  • We need to separate the analog and digital grounds of a circuit that uses a microcontroller, and connect them together at just one point of our choice;
  • We use fine PCB traces to implement a strain gauge;
  • We want to implement a small inductor as a spiral of copper trace.

In all cases, we need the two ends of the component that is implemented as a PCB trace to be on different nets. Otherwise things can go badly wrong very quickly. We could achieve this by inserting a 0R resistor in series with the PCB trace concerned. But this is not optimal, and sometimes there is insufficient space for an additional component.

One option would be to create a mall 2-pad footprint in KiCad such that the 2 pads are shorted by a trace within the footprint, as long as Kicad treats the 2 pads as being on separate nets. Is this possible?

There are eeschema symbols “net tie” in “Device” library
These have corresponding footprints library “NetTie”

Yes, it’s possible. You can check out the net ties as apurvdate mentioned. They are made by adding a non-pad copper polygon between two pads. There are no tracks in footprints, you have to create a graphic polygon and change its layer in the properties. It’s not possible to draw directly to a copper layer, therefore you need to change the layer later.

Be careful with DRC, it may behave differently with these non-pad copper areas.

Thanks, both of you. We used NetTie and it solved the problem.

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