[SI-LIST] Re: PCB signal speed over temperature
- From: art_porter@xxxxxxxxxxx
- To: wil.choon.song@xxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 22 Jul 2003 07:17:05 -0600
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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