[SI-LIST] AW: Re: PCB signal speed over temperature
- From: mathias.borcke@xxxxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 22 Jul 2003 18:38:51 +0200
There's little data available as far as I've seen. For ordinary FR4 I =
did
not find anything.
Rogers states eg. for their RO4003 that the Er thermal coefficient is
+40ppm/K.
The expansion coefficient is specified as x: 11ppm/K, y: 14ppm/K, z: =
46ppm/K
--> For this material the mechanical expansion is of the same order of
magnitude as the change of Er.
Regards
Mathias
-----Urspr=FCngliche Nachricht-----
Von: art_porter@xxxxxxxxxxx [mailto:art_porter@xxxxxxxxxxx]=20
Gesendet: Dienstag, 22. Juli 2003 15:17
An: wil.choon.song@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Betreff: [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.=20
Art Porter =20
-----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]=3D20
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.=3D20 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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