All,
a word of caution regarding RTF: this is not defining the roughness of the
copper foil at all, it is just a flipped-over foil, with the drum side (from
the electro-deposition on the drum) is facing the laminate instead of the
outside.
There are RTF foils with a roughness of the matte side that are similar to
standard roughness and some that are having a roughness Rz of ~5um (similar to
VLP).
Granted, HVLP (or all the other supplier specific names) is not telling you
much either, as it is not an IPC-4562 defined roughness.
Bottom line, my recommendation would be to not assume something, but check with
the supplier what you really get and document your needs in the data package
(e.g. fab drawing or similar).
Best regards,
alex
----------------------------------------------------------------------------------------------------------------------------------------
Alexander Ippich
Technical Director, Signal Integrity & Advanced Technology
Product Manager RF/Microwave
OEM Marketing Europe
Tel.: +49 170 / 63 68 571
e-mail: alexander.ippich@xxxxxxxxxxxxxxx
web: www.isola-group.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of lsimonovich@xxxxxxxxxxxxxxxxxxxxx
Sent: Thursday, December 19, 2019 09:38 PM
To: leeritchey@xxxxxxxxxxxxx; maruthi934@xxxxxxxxx; shlepnev@xxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Surface roughness of copper
When you look up roughness parameters for RTF/VLP they are very close
anyway. In fact some laminate suppliers do not offer VLP in lieu of RTF.
There is however a significant Rz difference between RTF/VLP and HVLP.
Conservatively about 1/2 depending on who's RTF foil is chosen by your
laminate supplier.
It is true modern serdes with Tx FIR and Rx DFE are capable of tolerating
the loss. But sometimes there also requirements to meet IEEE Chip-module and
OIF CEI VSR insertion loss budgets which have max channel loss of 10 dB at
Nyquist. In these channels there is an expectation of only simple CTLE
equalization for the plug-in modules.
It's not unusual to have 8-10 inches of PCB routing from a switch chip to a
faceplate SFP module for example, so even a 0.3 dB/in difference at Nyquist,
meeting the loss budget is often a challenge.
Bert Simonovich
Signal/Power Integrity Practitioner | Backplane Specialist | Founder
Email:Lsimonovich @lamsimenterprises.com
LAMSIM Enterprises Inc.
Web Site:
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Blog:
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf
Of Lee Ritchey
Sent: 19-Dec-19 2:10 PM
To: maruthi934@xxxxxxxxx; shlepnev@xxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Surface roughness of copper
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://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.simberian.com%2FAppNotes.php&data=02%7C01%7Calexander.ippich%40isola-group.com%7C672380ca7ddb40fe693e08d784c39a9d%7C5af4d76f3b0c4d7e8999ae030864a301%7C0%7C0%7C637123848411678818&sdata=4WWDLzALDW42Z0ibm3PmXwKmiYfMaJrIGLNuSZTe5YY%3D&reserved=0
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://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.simberian.com%2FWebinars.php&data=02%7C01%7Calexander.ippich%40isola-group.com%7C672380ca7ddb40fe693e08d784c39a9d%7C5af4d76f3b0c4d7e8999ae030864a301%7C0%7C0%7C637123848411678818&sdata=oSo0KpPJVKRNRGuPPCrBI9qpxLytP4em9Xp3%2FObGpDI%3D&reserved=0
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
https://nam03.safelinks.protection.outlook.com/?url=www.simberian.com&data=02%7C01%7Calexander.ippich%40isola-group.com%7C672380ca7ddb40fe693e08d784c39a9d%7C5af4d76f3b0c4d7e8999ae030864a301%7C0%7C0%7C637123848411678818&sdata=MIqI%2F%2FVIuSEwFm10E%2FKBpsKzSDvh5QQBtEvHqMpSAzQ%3D&reserved=0
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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