FEDEVEL
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IgorStojanovic , 09-27-2018, 03:50 AM

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 , 09-28-2018, 02:47 AM

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 , 09-28-2018, 02:53 AM

Yes, it makes sense. Thank you.

robertferanec , 10-01-2018, 12:43 AM

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

IgorStojanovic , 10-01-2018, 10:29 AM

That is very useful. Thank you Robert.

Paul van Avesaath , 10-02-2018, 03:03 AM

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)