0R resistor implemented as PCB trace

Layout
1

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?

2

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

3

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.

4

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

5

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