[SI-LIST] Re: Surface roughness of copper
- From: Chuck Corley <corley@xxxxxxxxx>
- To: Lyndell.Asbenson@xxxxxxxxxxx
- Date: Sun, 22 Dec 2019 09:38:50 -0800
Nicely said. Still, I'll take a good measurement over a simulation any day.
That's why we make such elegant measuring equipment.
I am amazed at your statement?
Measurements and simulations go together. You need both. When
simulating, measurements are needed to verify the simulation results.
In the Network/Spectrum Analyzer world we call it "calibration". Your
Spectrum/Network Analyzer measurements don't have good quality unless
you calibrate the instrument to a known measurement standard.
I should have said this in my earlier post: I double-check my board
simulation work and parameters by verifying them against actual
measurements. When I'm doing board design I do simulations and then
compare them to an actual board that's the same or close in materials
and stackup to what I want to do, and then use measurements from that
board to tune/adjust the parameters ("calibrate") until I match up with
the measurement results. Then I have both "checked" and "calibrated" my
simulations.
I suspect Lee's comment might be directed to when people do simulations
and don't check or calibrate their simulations against real board
measurements. If that's what he means than he's right. Often people
can accidently come up with simulation results that don't match reality.
For example they may have entered a parameter wrong for the frequency
or the board material characteristics without knowing it, and simulate
incorrect results.
Chuck
Chuck Corley, National Instruments
On 2019-12-21 17:09, Lyndell Asbenson wrote:
Lee,
I am amazed at your statement?
-Lyndell Lee Asbenson
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Lee Ritchey
Sent: Friday, December 20, 2019 11:34 AM
To: corley@xxxxxxxxx
Cc: maruthi934@xxxxxxxxx; shlepnev@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx;
si-list-bounce@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Surface roughness of copper
Chuck,
Nicely said. Still, I'll take a good measurement over a simulation any day.
That's why we make such elegant measuring equipment.
Lee Ritchey
Speeding Edge
P.O. Box 817
Bodega Bay, CA
94923
408-781-0253
I took the energy needed to be mad
And wrote some blues
Count Basie
Worry is like a rocking chair,
It keeps you busy, but doesn't get you anywhere.
Ross Ritchey
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf
Of Chuck Corley
Sent: Friday, December 20, 2019 9:45 AM
To: leeritchey@xxxxxxxxxxxxx
Cc: maruthi934@xxxxxxxxx; shlepnev@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx;
si-list-bounce@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Surface roughness of copper
Hi Maruthi,
What's the minimum bitrate after which I should start worrying about
the surface roughness parameters of the copper used in PCB ?
You were probably hoping for a one-word answer. But instead you might
have heard back many more words than you had wished for.
Here's what I suggest as the best answers to your question in order of
quality:
1. Best quality results: Use a simulator and enter the values as part
of your simulations. This will also allow you to learn how big an
effect this has by modifying your simulation to include or remove the
roughness effects on different runs.
2. Use Lee's list of measurements below as a rough guideline of the
losses you could expect. Not quite as good as actually simulating it
(no offence Lee ;-) but still a good estimate of how much loss you can
expect at the frequencies Lee documented.
3. Lowest quality answer: 10 Gbit/sec. This is probably the simple
one-word answer you were hoping for. This is about the speed where I
start to worry about it. But it also depends on the trace length and
other factors, so this is not an absolute answer. This is more of a
"somewhere around 10 Gbit/sec, but it depends" kind of answer. Not
nearly as high quality of an answer as #1 or #2.
Chuck
Chuck Corley, National Instruments
On 2019-12-19 11:09, Lee Ritchey wrote:
Here is some measured data that you can use to decide whether smooth
copper
is worth the cost.
In 2013 we build a test PCB with a set of trace layers built from Reverse
treat copper ( what you get if you don't specify a finish) and VLP copper.
The paper was 5-TP5 Titled High Speed Losses in various materials
The test traces were 8" long (20 cm) and 4.5 mils (.11 mm) wide.
At 5 GHz (10 Gb/S) the loss was 0.2 db.
At 14 GHz (28 Gb/S) the loss was 2 db.
When you need to specify smooth copper depends on how good your serdes
are,
how long the path is and how good the laminate is. Some newer serdes
toleratet38 db loss at 28 Gb/S. Takes a pretty long path to need smooth
copper with such serces.
Lee Ritchey
Speeding Edge
P.O. Box 817
Bodega Bay, CA
94923
408-781-0253
I took the energy needed to be mad
And wrote some blues
Count Basie
Worry is like a rocking chair,
It keeps you busy, but doesn't get you anywhere.
Ross Ritchey
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On
Behalf
Of MARUTHI PRASANNA C
Sent: Thursday, December 19, 2019 8:18 AM
To: shlepnev@xxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Surface roughness of copper
Thank you Yuryl , I'll go through them .
On Wed, Dec 18, 2019, 8:45 PM Yuriy Shlepnev <shlepnev@xxxxxxxxxxxxx>
wrote:
Hi Maruthi,
The best way to figure it out is with a numerical experiment.
To start with, pick up a realistic roughness model that correlates
with the measurements - a number of such models for different type of
copper treatments is available in our app notes at
https://www.simberian.com/AppNotes.php Build a model of your link and ;
see the impact by turning the roughness on and off.
The impact of different signal degradation factors, including
roughness, for different data rates was a subject of the recent SIJ
webinar - see #9 at https://www.simberian.com/Webinars.php
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
www.simberian.com [1] [1 [1]]
Simbeor - Accurate, Productive and Cost-Effective Electromagnetic
Signal Integrity Software to Design Predictable Interconnects!
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of MARUTHI PRASANNA C
Sent: Wednesday, December 18, 2019 2:10 AM
To: si-list@xxxxxxxxxxxxx
Subject: [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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