[SI-LIST] Re: Signal Integrity issues at -40 degrees C
- From: "LATOURRETTE,JEFF" <jeff.latourrette@xxxxxxxxxxxxx>
- To: <weirsi@xxxxxxxxxx>, <jhill@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 19 May 2006 10:48:00 -0700
John:
On FR-4 (& similar) materials, the change in height (coefficient of
thermal expansion in Z direction) should dominate your trace impedance
changes over temperature. Some of these materials are optimized for
less change, but in general, it's a concern if your design is very
impedance sensitive (like filters, matching networks, resonant networks,
etc).
It's pretty straightforward to run impedance calculations for your
traces at your temperature extremes to see if there is any concern. A
lot of designs are fairly tolerant of impedance changes & often these
over temp impedance changes are on the order of the tolerances offered
by PCB fab houses.
I don't have any info on dielectric constant over temperature (I've
actually found it hard to locate), but I would expect this variation to
be much more of a 2nd order effect. You can experiment with it and see
how much variation matters.
Regards.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of steve weir
Sent: Friday, May 19, 2006 7:42 AM
To: jhill@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Signal Integrity issues at -40 degrees C
John, there may be some change in the loss at low temperature due to=20
crystallization of water. I would expect tanloss to increase, but do=20
not have hard data. I don't think the fast corner at low temp is the=20
killer. I think the slow corner at high temp will have the worse=20
timing margins. I would check with Isola, Nelco etc on the specifics=20
of the dielectric.
Regards,
Steve
At 07:06 AM 5/19/2006, Hill, John wrote:
>Hello,
>We are starting a new design with 5 DDR2 memory busses and three
>microprocessors. The design must work from -40 to +85 degrees C. I am
>concerned that at low temperatures the edge rates will increase and I
>don't know what will happen to the characteristic impedance of the
>traces. I expect to have more issues with Signal Integrity issues at
-40
>than at 25 degrees C. Is this correct?
>
>BTW, does anyone know the temperature coefficient of the Dielectric
>Constant of various FR4 materials?
>
>Best regards,
>
>John
>
>
>---------------------------------------
>The information in this email and attachments hereto may contain=20
>legally privileged, proprietary or confidential information that is=20
>intended for a particular recipient. If you are not the intended=20
>recipient(s), or the employee or agent responsible for delivery of=20
>this message to the intended recipient(s), you are hereby notified=20
>that any disclosure, copying, distribution, retention or use of the=20
>contents of this e-mail information is prohibited and may be=20
>unlawful. When addressed to Takata customers or vendors, any=20
>information contained in this e-mail is subject to the terms and=20
>conditions in the governing contract, if applicable. If you have=20
>received this communication in error, please immediately notify us=20
>by return e-mail, permanently delete any electronic copies of this=20
>communication and destroy any paper copies.
>---------------------------------------
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at: =20
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
=20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
