[SI-LIST] Re: [SI-LIST]: Which tool is the best
- From: MikonCons@xxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 19 Apr 2004 19:48:11 EDT
Hi, Michael Vrbanac:
I'll answer in three parts. In short, Linpar and Multlin are a tremendous
value for the money. I think you can buy the pair for $500.
1. Linpar vesus Apsim is a whatness. PCB vendors DDI and Sanmina-SCI both
use Apsim versions that have a capability to embed correction factors for
predictions versus actual TDR test data on traces. Their version costs ~$25K. I
have
worked closely with both companies and obtained the raw Apsim Zo predictions.
Linpar predictions are right on top of them (typically less than 1%
difference). The cost advantage is obvious.
I just responded separately to Abe Riazi at Serverworks. Here is an excerpt
you may be interested in.
********
Unfortunately, it only allows rectangular shapes for traces in the routine
mode of use. I believe, however, that you can create your own shapes in the
custom user mode. I have found that once you know the etch taper produced by a
particular PCB vendor, a simple averaging of the top and bottom trace widths
get
you within 2% of their own (and corrected) Zo predictions.
In some cases, where precision is very important, I obtain trace width, taper
versus trace thickness, and actual TDR data versus dielectric material,
thickness, etc., from the PCB vendor and make a correlating adjustment equation
that includes a multiplying factor and a dc offset. A typical correction for
the
Linpar predicted value for Zo is of the form
Zo(predicted) *1.0347 +0.46 = Zo(obtained by TDR test).
The correction factors are heavily influenced by individual pressure and
temperature processes used for lamination by the vendor AT EACH DIFFERENT
FACILITY
(even for the "same" stackup and materials). These factors vary slightly with
the layup configuration and target line impedance (e.g., symmetrical
stripline, dual stripline, and microstrip, including different surface plating
thicknesses). Often the dc offset correction is not required to obtain a good
match
over a wide range of targeted Zo values. Cooperating vendors routinely make
these measurements to embed their own corrections for Zo predictions;
therefore,
they freely offer up the (generaly existing) data.
After a correlation is made to a particular facility and process line, the
prediction accuracy to actual cross sections of PCB test coupons (from that
facility) is typically within 1%, which is comparable to the measurement
accuracy
on the cross sections.
FYI, the UNCOMPENSATED software predictions for the Zo of striplines by major
vendors (e.g., Sanmina-SCI, DDI, etc.) when using the trapezoidal trace
shapes typically agree within 1% or better with the original Linpar predictions
(using average trace widths). I have verified this fact wih multiple vendors
and
multiple facilities of these same vendors.
*******
2. Micro-Cap has always been a step ahead of PSPICE on most features by
typically two years. They provided schematic capture (and symbol entry) about
six
years ahead of the integration of OrCAD and PSPICE. I have not personally used
Electronics Workbench, but other consultants that I have conversed with for
over 15 years have indicated that they found it limited in sophistication. I
recommend you try the evaluation version of MC8 to see its power fo yourself.
3. Re: MULTLIN:
I have attached a paper I presented at PowerCon that should answer your
questions best. I made some slide additions and upgrades before I presented it,
but
there ae no differences in the conclusions. Sorry about the file size, but it
covers a lot. (NO FILE attached for SI List)
Good reading and evaluating to you.
Mike
Michael L. Conn
Owner/Principal Consultant
Mikon Consulting
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