[SI-LIST] FW: HSPICE W element field solver model


Hi folks-

In my limited experience looking at measurements of a few selected FR4
samples, I conclude that the dielectric constant and dissipation
factor are pretty constant from DC up to 10 GHz. For the few samples
we've looked at, the values are 4.0 for dielectric constant and
0.014 - 0.02 (depending on sample) for dissipation factor, constant up
to 10 GHz.

In my presentation to the Rocky Mountain EMC Society, in late May, I
showed that if you do not account for the vias in the transmission
line sample under test, you might interpret the response as a
frequency dependent dielectric constant and dissipation factor.

A number of papers and copies of slide presentations we've given on
this topic are posted in the application notes section of our web site
(www.gigatest.com). We show the test structures, the measured data and
the comparison to simulated response assuming a constant dielectric
constant and dissipation factor. We also show what would have happened
if you did not include the vias. If you want more info on this topic,
we are doing a class on related techniques, in late July.

If anyone has measured results from FR4 that shows frequency dependent
effects from 100 MHz to 10 GHz, I'd be interested in seeing the data.

Of course, always keep in mind that not all FR4's are the same. This
is why every end user of an FR4 laminate for high speed applications
where the dissipation factor is important, should make sure they have
measured their laminate at least once to verify it will meet their
performance spec.

Even though the dissipation factor is constant with frequency, the
attenuation due to dielectric loss is frequency dependent and
increases linearly with frequency. Higher frequency components in the
signal will be attenuated more than low frequency components. This
will give rise to rise time degradation and collapse of the eye
diagram.

comments are always welcome.

--eric

**************************************
Eric Bogatin
CTO, Giga Test Labs
v: 913-393-1305
f: 913-393-1306
e: eric@xxxxxxxxxxxx
corporate office:
408-524-2700
134 S. Wolfe Rd Sunnyvale, CA 94086
web: www.gigatest.com <http://www.gigatest.com>
**************************************


From: "Alex Horvath" <alexh@xxxxxxxxxxxxxxxx>
Subject: [SI-LIST] Re: HSPICE W element field solver model
Date: Fri, 8 Jun 2001 10:31:09 -0700


Chris,
I found your statements below very interesting because we have a
consultant
working for us that's telling us 3 gig on a FR-4 backplane (20") is no
big
deal. I told him I had some concerns based on the chip manufacturers
data
which recommended GETEK or similar. Do any simulators take losses into
account?

Are there any publications or papers that discuss in more detail the
DK and
loss tan you mentioned below? This is the first time I have worked at
frequencies where this is a concern.

Thanks,  Alex H
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Chris Mesibov
Sent: Friday, June 08, 2001 4:58 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: HSPICE W element field solver model


Most PCB fabricators and their lamenate suppliers don't characterize
FR4
above
1.5 GHz (i.e. for DK and loss tan).  Therefore specifying controlled
impedance
lines intended for this bandwidth should be rejected by any fab house
worth
their salt.
The problem is that the studies of FR4 at frequencies up to 10Ghz show
dramatic
changes in loss tan and DK over freq and temp.  What this would result
in
for
digital signals is group delay and rise time degradation.  Group delay
is
when
the fourier components of the waveform propagate down the transmission
line
at
different rates.  The rise time degrades because as the frequency
increases,
so
does the loss tangent.  This has the effect of attenuating the
harmonics of
the
waveform, thus slowing the rise time.

Hope this sheds some light.

Chris

Alex March wrote:

>   Dear SI experts,
>
>   I would like to ask about your experiences with the
> W element field solver model in HSPICE. I am trying to
> make some simulations in the Gigahertz range with FR4
> material and I am not sure about what value I should
> use for the conductivity of FR4.
>
> Thank you,
>
> Alex







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