[SI-LIST] Re: Temperature effects on backplanes?
- From: ALDO W MORALES <awm2@xxxxxxx>
- To: weirsi@xxxxxxxxxx
- Date: Fri, 18 May 2012 10:15:46 -0400 (EDT)
Hi David:
Moisture Absorption depends non-linearly according to Stoke's law and also of
the substrate material. FR4 is worst in comparison with Rogers. It also depends
of the thickness of the substrate, vias and so on.
Please check the paper we wrote for DesignCon 10
Evaluation of Relative Humidity and Temperature Effects of Scattering
Parameters on Transmission Systems
By Ji Li,Mark Minns, Aldo Morales, Sedig S. Agili (Penn State Harrisburg) and
Mike Resso, Agilent
Aldo
_______________________________________________________________________________________________
Aldo Morales, Ph.D. IEEE Senior Member
Associate Chair of the EE/EET programs
Co-Director, Center of Excellence in Signal Integrity
http://www.hbg.psu.edu/csi
Professor of Electrical Engineering
Penn State Harrisburg
777 West Harrisburg Pike
Middletown, PA 17057
U.S.A.
Phone: (717)-948-6379
Fax: (717)-948-6352
----- Original Message -----
From: "steve weir" <weirsi@xxxxxxxxxx>
To: si-list@xxxxxxxxxxxxx
Sent: Friday, May 18, 2012 9:27:26 AM
Subject: [SI-LIST] Re: Temperature effects on backplanes?
I suspect moisture absorption issues changed you tangent loss. What was
the humidity for these tests?
Steve
On 5/18/2012 6:13 AM, Bond, David wrote:
> Overt the last few years, I've been asked to support a mechanism whereby the
> transmitter's and receiver's equalization on a 10Gps link can be re-optimized
> while operating in mission mode. The claim is that temperature swings can
> wreak havoc on the channel characteristics. I've resisted this because I had
> no data to support it.
> Recently, though, I received S-parameter models for two channels on a back
> plane each extracted a 3 widely spaced temperatures: -25C, +25C and +75C. I
> have very few details on the channel, but expect that it is FR4. To my
> surprise, there is a large change in the channel's behavior.
>
> The Return Loss doesn't change much.
>
> The Insertion loss degrades badly above 5G, develops some very deep and
> narrow nulls around 10G.
>
> What's weird is the pulse and step response. The -25C and +25C pulse delays
> vary a small amount: maybe a 25% increase in delay between the two
> temperatures. However, the difference between 25C and 75C is>300%. (!) for
> both the short and long channels. The attenuation and ISI both increase with
> temperature.
>
> Is this an expected characteristic of FR4? Can anyone explain the non-linear
> increase in delay at the high temperature?
>
> Thanks in advance,
> David Bond
>
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