Re: [SI-LIST] : Linpar 2-D field solver experiences?

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Date: Tue Feb 27 2001 - 12:50:51 PST

Hi, Benoit:

I had used the original DOS-based Linpar since about 1989 with good success,
but only for simple structures because of program limits. I obtained the
Linpar for Windows, version 2.0 just a few months ago and have great praise
for it.

I mainly use the multi-layer section which allows me to stack up planes,
cores, foils, and different pre-pregs with the easy-to-use graphical user
interface. The predictions for microstrip are very accurate, but the
stripline constructions (multi-conductors of different sizes in all
configurations) are also process dependent. The raw Zo predictions are
typically 4% to 7% lower than measured results and therefore need some "fudge
factors." This arises because the pre-preg layers in a stackup have different
glass/resin mixes, a variation in the degree of etch on signal layers, plus
the pressure and temperature used in the cure process alters the effective
dielectric constant.

I have obtained a correlation with Sanmina data that is very accurate (<1 Ohm
error, which is within the measurement accuracy). With their supplied
correction factors (which vary with trace configurations), I consistently get
a more accurate match to measured results using Linpar than they do using a
newly implemented AppSim package that (they say) cost more than $25,000.

I have not yet tried the custom construction portion of the program (been
super busy with multiple clients) and am curious about the process. As time
permits, could you send me a small sample of a structure you have analyzed
with comments as appropriate? That would help me to bridge the knowledge gap
as to how to interface an Excel file with Linpar.

As regards field visualization, there used to be a simple display tool called
QuickField available as a free download off the web. But perhaps you should
try Sonnet Lite, a free 3D planar EM software program at I will be trying it in the next
couple of weeks (as time allows) and will give you commants as available (if
you are interested).

Good Engineering to you,


Michael L. Conn
Owner/Principal Consultant
Mikon Consulting

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