[SI-LIST] Re: Self Inductance and TDR measurements
- From: "Zabinski, Patrick J." <zabinski.patrick@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 31 Aug 2001 14:23:11 -0500
> a) Pat has confirmed the method I was using to calculate the self
> capacitance. However for inductance I have just been using
> L11 as the self
> inductance. Is this correct?
>
Yes. The inductance matrix produced by most EM cross section
simulation tools is just that; inductance, and you can read the
values directly (both on- and off-diagonal).
> b) However I am still puzzled over which # to use to compare with TDR
> measurements.
> The TDR measurements we do use a fixture from ALTAIR
> microwave which has a
> Cu sheet on which the package balls sit and grounds all other
> pins in the
> package except for the pin of interest.
>
Capacitance is easier (at least for me) to visualize, because in
TEM mode, parallel plate capacitance can be directly calculated
based on the two elements you're trying to calculate the
capacitance between.
For inductance, it gets a bit more difficult, in that inductance is
for the "entire loop". For example, inductance of a wire
is incomplete if you do not include the return inductance.
It is sometimes difficult (impossible?) to directly compare
the inductance produced by a simulation tool to something
you measure in the lab.
In the situation you describe (if I'm reading in between the
lines correctly), you are trying to measure the inductance of
a single trace with all other traces grounded. The problem
is (typically in most BGA designs) that the grounded traces
have mutual coupling to the line of interest, so their presence
effects your measurement.
Also in your case, it might be that the referenced ground plane
in the simulation is not necessarily the return path
in your measurement, which will throw things off.
In addition, if the trace you're measuring exits the BGA
at an appreciable distance from the ground-plane ball(s),
the separation can increase the effective inductance.
In short, I've have pretty good success in correlating
capacitance, but inductance is a real bugger of a parameter
to correlate without taking a few (sometimes many) extra
steps to make sure you are truly correlating the same
parameter.
> I have not got a good answer yet as to which number in the simulation
> matrix I should compare the TDR meas. to.
>
Here are a few to keep you busy:
TITLE Validity of Mutual Inductor Model for Electromagnetic Coupling
Between V
ias in Integrated-Circuit Packages and Printed Circuit Boards
AUTHOR Jin Zhao and Jiayuan Fang
SOURCE 1998 ECTC Conference, Seattle, WA
DATE May 25-28, 1998
PAGES na
TITLE Capacitance, Inductance, and Crosstalk Analysis
AUTHOR Charles S. Walker
SOURCE Artech House, Boston
ISBN 0-89006-392-3
DATE 1990
TITLE Extraction of Coupled SPICE Models for Packages and Interconnects
AUTHOR Scott Diamond and Bo Janko
SOURCE Proceedings of IEEE International Test Conference
DATE October 1993
PAGES Paper 20.1
TITLE Guideline for Measurement of Electronic Package Inductance and
Capacitan
ce Model Parameters
AUTHOR na
SOURCE EIA Standard JEP123
DATE October 1995
PAGES 1-20
TITLE Loop Areas - Close 'Em Tight
AUTHOR D. Brooks
SOURCE Printed Circuit Design Magazine
DATE January 1999
TITLE Measuring Package and Interconnect Model Parameters Using
Distributed Im
pedance
AUTHOR Bo Janko (Tektronix) and Peter Decher (Analogy)
SOURCE na
DATE na
PAGES 1-6
TITLE Return Path Inductance in Measurements of Package Inductance
Matrixes
AUTHOR Brian Young
SOURCE IEEE Trans CPMT, Part B, Vol 20, No 1
DATE February 1997
PAGES 50-55
TITLE TDR Tools in Modeling Interconnects and Packages
AUTHOR na
SOURCE Tektronix Appication Note
DATE 1993
PAGES 1-11
TITLE The Inductance Matrix of a Multiconductor Transmission Line in
Multiple
Magnetic Media
AUTHOR Joseph R. Mautz, et. al.
SOURCE IEEE Trans on MTT
VOLUME 36
NUMBER 8
DATE August, 1988
PAGES 1293-1295
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