[SI-LIST] Re: Temperature effects on backplanes?
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: David.Bond@xxxxxxx
- Date: Fri, 18 May 2012 10:00:49 -0400
water has a non-linear Er and TanD, especially near freezing when phase is
changing.
BTW, your packages have even worse variation with temperature. Most
organic substrate materials have extremely high water absorption.
For more information, you can read our paper from DesignCon 2012
Temperature and Moisture Dependence of PCB and Package Traces and the
Impact on Signal Performance, Miller, Jason, et. al., DesignCon 2012
--
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC
On Fri, May 18, 2012 at 9:13 AM, Bond, David <David.Bond@xxxxxxx> 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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