[SI-LIST] Re: PCB signal speed over temperature

At a previous job, I looked at the temperature effects on propagation of
signals on striplines.  Both dielectric constant AND loss tangent are
temperature-dependent.  This results in slight changes in loss, shifts in
progation delay and dispersion.  A good reference which I found, comparing
material parameters, is at: http://www.datacircuits.com/pages/eng_mat.html .
This does not, unfortunately, include temperature dependence.  Some web
searching will find scattered information which might answer some of your
questions.

Eric Sweetman

----- Original Message ----- 
From: <art_porter@xxxxxxxxxxx>
To: <wil.choon.song@xxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, July 22, 2003 6:17 AM
Subject: [SI-LIST] Re: PCB signal speed over temperature


> We discussed this a bit here. The only thing that you would expect to
change with temperature would be the dielectric constant of the PC substrate
and its thickness (throuhg temp coefficient of dimensions). I haven't found
any specs or discussions on the temp coefficient of dielectric constant or
PC board material, but it seems unlikely that it would vary significantly.
The delays in active circuits vary much more with temperature, and these
changes are well characterized by semiconductor vendors.
>
> One thing that does measurably change the dielectric constant is the
humidity. This effect has in fact been exploited to measure moisture content
by making TDR or VNA measurements. When you take a PC board from a cold, wet
place to a hot, dry place, allow it a few days or weeks to dry out, then you
may see a detectable change in propagation delay. So in that indirect sense,
temperature can affect propagation delay.
>
> Art Porter
>
> -----Original Message-----
> From: Song, Wil Choon [mailto:wil.choon.song@xxxxxxxxx]
> Sent: Monday, July 21, 2003 8:41 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: PCB signal speed over temperature
>
>
> Hi,
>
> Referring to Hermann question, can anyone help us with the temperature
> vs SI concerns? Hope there could be some discussions on this topic :)
>
> Thanks a lot,
> Wil Choon
>
> -----Original Message-----
> From: hermann.ruckerbauer@xxxxxxxxxxxx
> [mailto:hermann.ruckerbauer@xxxxxxxxxxxx]=20
> Sent: Wednesday, June 18, 2003 7:18 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] PCB signal speed over temperature
>
> Hello all,
>
> Maybe somebody can give me a hint or direct me to any ressources about
> this
> topic.
>
> On a PCB there are a lot of mechanical and electrical parameters more or
> less dependent on temperature.=20
> I found a lot of ressouces discussing dependencies of material
> properties.
> What I would be interested in is
> the overall dependency of the signal flight time on temperature. The
> different temp dependencies might have
> different effects on flight time, and might compensate or worsen each
> other.
>
>
> - Does anybody know how much effect a temp change for e. g. 0C to 100C I
> would have to consider for signal flight
> time ?
> - What would be the main contributor to this change ?
> - Or is the effect not even measerable at all ?
>
> Thanks a lot
>
> Hermann
>
>
>
> Infineon Technologies
> Hermann Ruckerbauer
> MP PDT PD DES 5 / MchB / Room 3448
> Balanstrasse 73
> D-81541 Munich
> Germany
> Phone: +49 (89) 234 25041
> Fax.:  +49 (89) 234 9555437
> e-mail: Hermann.Ruckerbauer@xxxxxxxxxxxx
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