FreeLists / si-list / [SI-LIST] Re: Finding the impedance of a PCB trace

[Ralf Bruening <ralf.bruening@xxxxxxxx>]

Hello Graham,

just my comments on this as well - I guess you are experiencing
the difference between equations (which sometimes are rather
good, sometimes for some configurations they are rather bad) and
real 2 or 3D field solvers where the difference are mainly in the
different mathematicsal appraoch behind and even as well in how
the area of interest is meshed - nevertheless the variation of
more then 20 % between maximum and minimum is surprising.

regards

       Ralf

BTW: Zukens Hot-Stage fieldsolvers with its 2 kernels (user can
choose between BEM and FEM) gives:

    Boundary Element:   47,60
    FEM  (assuming trapez in rectangular shape): 47,85



Friday, April 29, 2005, 11:28:30 PM, you wrote:

GD> This is, of course, related to my search for a good 6-layer stackup.

GD> What is the impedance of a PCB trace (microstrip) with the following
GD> parameters:
GD> Width ......................... 6.00 mil
GD> Height above return plane ..... 3.20 mil
GD> Thickness ..................... 1.35 mil (1 ounce copper)
GD> Dielectric rel. permittivity .. 4.2

GD> These are the answers I get from various tools:

GD> 41... ohms (http://www.icd.com.au/)
GD> 41.69 ohms (http://www.emclab.umr.edu/pcbtlc/microstrip.html)
GD> 41.69 ohms (TraceSim version 1.0.0)
GD> 41.69 ohms (http://www.technick.net/public/code/cp_dpage.php?
GD> aiocp_dp=util_pcb_imp_calculator)
GD> 41.7 .ohms
GD> (http://www.sunmantechnology.com/resources/cal_cat00.shtml)
GD> 46.14 ohms (ZTOOL Impedance Calculator V1.2)
GD> 47.31 ohms
GD> (http://www.rogers-corp.com/mwu/mwi_java/mwij_vp.html)
GD> 50.89 ohms (http://www.csgnetwork.com/boardrunimpcalc.html)
GD> 51.27 ohms (TxLine version 1.1)

GD> Does anyone have an idea as to why these calculators give results
GD> that vary by 20% and which are more reliable?

GD> Graham.




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_____________________________________________
 
Ralf Bruening 
Product Manager High Speed Design/Partner & Solution Business
Zuken EMC Technology Center
Vattmannstr.3 
33100 Paderborn  
Germany

 
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