ENGINEERING ANSWER
Etching changes the realized width and sidewall shape of a conductor. The effect on impedance depends on its size relative to substrate height and copper thickness, making narrow traces particularly sensitive.
What to decide before release
Provide finished-line requirements and impedance targets, then allow the fabricator to propose artwork compensation. Evaluate plausible dimensional corners with a field solver and avoid using unnecessary decimal precision in the drawing.
Checks to put in your design brief
- Agree finished width and tolerance
- Check minimum gaps
- Review impedance at dimensional corners
Important distinction
Do not assume the drawn CAD width equals the finished conductor width after plating and etching.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.