Hi Jason,
The anisotropy of layered PCB dielectrics shows up on the measurements for
differential strip lines as difference in phase or group delay of the odd
and even modes. So, you can use any data or publications that allow or
compare odd and even modes to see the effect of the layering. The outcome
will depend on a particular material - for instance in #2014_01 at
https://www.simberian.com/AppNotes.php some materials showed anisotropy and
some (Nelco) did not. If difference between odd and even modes is
negligible, no reason to simulate it. Otherwise, either layered dielectric
model (physical, preferred) or averaged anisotropic dielectric model
(permittivity tensor) can be used, to take it into account. See more in
2016_01 (Material world tutorial) at
https://www.simberian.com/TechnicalPresentations.php
Considering the vias, periodic capacitive loading of the via barrels can
slow down the wave quite a bit (barrel to planes). If you measure delay
through it and compute "effective" dielectric constant, it may come out
higher than the Dk of the dielectric it is filled with. Sharp
discontinuities on the surface of vias and on the edges of the planes also
increase the capacitance and the effective dielectric constant (slows down
wave). Some of those effects can be simulated, but some may require an
anisotropic dielectric models.
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
www.simberian.com
Simbeor - Accurate, Productive and Cost-Effective Electromagnetic Signal
Integrity Software to Design Predictable Interconnects!
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Jason Ellison
Sent: Friday, December 13, 2019 10:19 AM
To: si-list
Subject: [SI-LIST] PCB Isotropy
Hello SI Community!
Does anyone know of a PCB laminate permittivity isotropy study?
Specifically, I'd like to know if the permittivity is different when the
signal is propagating through the board vias (Z-direction) vs along traces
within the board (X-Y direction).
Cheers,
Jason
Employed by and affiliated with Amphenol AICC (https://www.amphenol-icc.com/
)
------------------------------------------------------------------
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 forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
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 forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
