Gert, I agree, but...During our early years I did a score of channel
experiments looking at peak-peak DJ of a 10G channel in Keysight ADS with
zero, med, and very high surface roughness and saw increase of jitter but not
as significant as compared to return loss and resonance in the system. If
your system has only -5dB of return loss SDD11 at 1 to 2X Nyquist or huge
resonance nulls due to nasty vias, for example, I would work on improving
return loss and your overall signal integrity before thinking about
ultra-smooth copper.
Gert, let's catch up at DesignCon, good American beer is on WRT.
- Al
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf Of
Havermann, Gert
Sent: Wednesday, December 18, 2019 2:31 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] AW: Surface roughness of copper
Hi Maruthi,
Almost everything exceeding 10G serial (as in 10GBASE-KR or 40GBASE_KR4) needs
roughness control. This is mainly because the loss budget of higher Bitrates is
very restricted and Epoxy is already quite lossy.
If you are making very lossy designs for 10GBASE-KR, then it is worth looking
into roughness as well.
The harmonics are not relevant for function, only for measurement. Given the
loss of Epoxy at higher harmonics and the low amplitude of the harmonics
(compared with the basic wave), the PCB is a great low pass filter and only the
basic frequency sine wave will be seen at the receiver (that’s the regular
shape of an eye-diagram at the receiver).
Mit freundlichen Grüßen / Kind regards.
Gert Havermann
Signal Integrity Engineer
Dept.: Corporate Technology Services
HARTING Stiftung & Co. KG
Marienwerderstraße 3
D-32339 Espelkamp
Phone +49 (0)5772 47 857
Fax +49 (0)5772 47 90857
mailto:gert.havermann@xxxxxxxxxxx
http://www.HARTING.com
----------------------------------------
HARTING Stiftung & Co. KG | Postfach 11 33, 32325 Espelkamp | www.HARTING.com
Persönlich haftende Gesellschafterin:
HARTING Führungsstiftung | Amtsgericht München | HRA 108479 | München
Vorstand: Dipl.-Kfm. Philip F. W. Harting (Vorsitzender), Dipl.-Kffr. Maresa W.
M. Harting-Hertz, Dipl.-Kfm. Dr.-Ing. E. h. Dietmar Harting, Dipl.-Hdl. Margrit
Harting, Dipl.-Ing. (FH) Dipl.-Wirtsch.-Ing. (FH) Andreas Conrad, Dr. iur.
Michael Pütz Sitz der Gesellschaft: Espelkamp | Amtsgericht Bad Oeynhausen |
HRA 9021 | UST-ld Nr. DE812136745
-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> Im Auftrag von
MARUTHI PRASANNA C
Gesendet: Mittwoch, 18. Dezember 2019 11:10
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Surface roughness of copper
Hi everyone
What's the minimum bitrate after which I should start worrying about the
surface roughness parameters of the copper used in PCB ?
Does the amount of signal energy in the first harmonics , second harmonics have
any impact on this ?
I appreciate answers on this , thanks in advance .
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