Controlled impedance traces specification for manufacturer

[IgorStojanovic]

Hello to everyone,

I am confused about how to specify to the manufacturer which traces should be controlled impedance. The way how I did the previous controlled impedance designs is to rely to the manufacturer stack up and apply the proper geometry to the specific traces. I also put stack up table in a separate layer - manufacturing notes (learned from Robert). However, some manufacturers (cheap one) insist on doing it on its own. I suppose they doing it by modifying the gerber file and adopting the correct trace geometry. But, how it actually works? How can I tell them, I need that and that trace to be controlled impedance? Does it work like that I described?

Thank you in advance.

[mairomaster]

You can set the impedance controlled tracks to a specific width and describe this in the manufacturer notes. Then the manufacturer will know that those are the desired tracks that need to be modified.

[IgorStojanovic]

Yes, it makes sense. Thank you.

[robertferanec]

We always add screenshots with highlighted nets. It looks something like this (this is file called DIFF100-L3):

[IgorStojanovic]

That is very useful. Thank you Robert.

[Paul van Avesaath]

I Use mechanical layers and use text with reference info, because sometimes i make cutouts in the internal ref planes to change the impedance.. (the world of 75Ohms video sucks in that way)