Conductor Surface Roughness

A discussion over on the SI-LIST on conductor surface roughness triggered Lee Ritchey to write a nice summary of the state of things when signals are fast enough that you are concerned about losses at high frequencies. You can read it in full here, but in short this is the essence:

• I specify copper roughness on all of my fabrication drawings where I am concerned about losses at high frequencies.
• To do that, I must also specify the laminate suppliers (each laminate supplier has its own way of specifying copper roughness).
• To make sure the fabricator does not undo all of this, I must also specify the surface treatment that is used.
• In addition, skew is an issue, so the type of glass weave is important as well.
• Of course, this means that you can’t shop your designs all over the place and choose suppliers on price alone.

If you want to learn more about how to go about doing this in the real world, Lee teaches a great one-day course on this subject. We call it “Lee Ritchey: Stackup Design“.

We also conductor surface roughness and lots of other PCB stackup subjects in the 3-day SI course we run worldwide on-site and as open classes.

See you out there.