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 ------------------------------------------------------------------ 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 archives are viewable at: =3D20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=3D20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =3D20 ------------------------------------------------------------------ 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 archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 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 archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 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 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