ENGINEERING ANSWER
Copper surface profile can increase conductor loss and influence electrical behavior at high frequency. A material Df value does not capture that contribution. Foil grade and the chosen roughness model belong in the simulation record.
What to decide before release
Compare laminate constructions with the same geometry and meaningful copper information. Ask the fabricator which roughness data applies to the dielectric-facing surface after processing. Validate the model with representative transmission lines.
Checks to put in your design brief
- Record foil identity
- Use supported roughness parameters
- Compare measured insertion loss
Important distinction
Avoid attributing all measured excess loss to dielectric constant or loss tangent when the copper model is unknown.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.