[SI-LIST] Re: I have a question related package parasitic extraction
- From: realbalm <realbalm@xxxxxxxxx>
- To: mkhusid@xxxxxxxxxx, cnepsc@xxxxxxxxxxx
- Date: Tue, 9 Dec 2003 16:34:13 -0800 (PST)
Dear Michael Khusid,
I understand and agree with your opinion.
But, you seem to have forgotten mentioning RESISTANCE.
According to my simulated results, the errors except RESISTANCE, that is
capacitance and inductance, are negligible. By the way, RESISTANCE was not.
Comparing with the model #3, the resistance sum of model #1 and model #2 had a
difference with about 16%.
From the viewpoint of resistance, I have simplified that model #3 have series
connected two different resistances. Therefore, I think the resistance sum of
model #1 and model #2 should be equal to that of model #3.
Is this wrong?
-------------------------------------------------------------------------------------------------------------------------------
model #1. only one bonding wire (very long length with uniform cross-section)
model #2. only one lead (very very short length with uniform
cross-section which is different from bonding wire)
model #3. the structure composed of model #1 and model #2
-------------------------------------------------------------------------------------------------------------------------------
Michael Khusid <mkhusid@xxxxxxxxxx> wrote:
Neeraj,
Ansoft Spicelink has two modules. The 2D module, which Jayaprakash
refers
to, is the one that solves for per-unit parameters calculates loop
inductances.
The 3D modules, which KD refers to, is typically used for 3D problems
like
wirebonds. The latter module does indeed solve for partial inductances.
KD,
If you have very long trace with uniform cross-section, then indeed
capacitance/inductance/resistance are linear with length. That's how
original telegrapher equations were derived.
If there is a discontinuity between two signals, e.g. a trace and
wirebond,
than mutual interaction (inductance and capacitance) will produce
non-additive results. That is, the properly done addition also needs to
include mutual interaction.
> As for L, there should be and there is difference. Small difference
also
> expected for C.
Neeraj, you are ignoring the effect of mutual capacitance which is
non-zero
in this case.
Best regards,
Michael
----------------------------------------------------------------
Michael Khusid
Ansoft Corporation
SI/HF Application Engineer
25 Burlington Mall Road, 5th floor
Burlington, MA 01803-4100
Tel 781-229-8900 Ext. 134
Fax 781-229-8624
---------------------http://www.ansoft.com ---------------------
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx =
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Neeraj Pendse
> Sent: Tuesday, December 09, 2003 1:56 PM
> To: edpc108@xxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: I have a question related package parasitic
> extraction
>
> Jayprakash:
>
> The definition of inductance that the transmission line equations use
is
> different from that used by Ansoft SPICELINK. The former is Loop
> inductance, which scales with length but the later is Partial
inductance
> which does not because of self coupling.
>
> KD:
>
> I can think of two reasons for this difference:
> #1: source and sink assignments in the two models, especially the
> contact of the lead with the wire in the "separate" models
> #2: Skin effect: Did you solve AT the freq of interest or did you
solve
> at the default 100 MHz and "reduced" to the freq you want? In the
later
> case, one has to be careful because the "reduction" result is
generated
> by simple formula and is not valid for all frequencies in my opinion.
>
> As for L, there should be and there is difference. Small difference
also
> expected for C.
>
> Also, there will be some difference due to the fact that the mesh on
> each object in the three cases will be different because of the
> differences in geometry. I think this error in a simple case can be
> reduced by tightening the convergence criterion to let's say 0.2% or
so.
> Hope that helps.
>
> - Neeraj.
>
> Jayaprakash wrote:
> > Hello Patrick,
> >
> > Then the same argument should hold good even for
> > Transmission line model described using telegrapher's
> > equation?
> >
> > By telegrapher's equation, Transmission line has
> > uniform RLGC per unit length. The output voltage is
> > given by
> >
> > Vo =3D exp(-gamma*Line_length)*vin (for a perfectly
> > matched system)
> >
> > Is this description of Transmission line not really
> > scalable? (Going by the explanation given below, I
> > expect over projection of loss for longer lines than
> > actually it is)
> >
> >
> > Thanks and regards,
> > Jayaprakash.
> >
> >
> > --- Patrick Zilaro
wrote: >
> > KD,
> >
> >>There is nothing wrong with the commercial solver.
> >>Even if you were to
> >>simulate a planar structure such as a trace, you
> >>would see that the "parts"
> >>do not add up to the "whole". For example, if you
> >>simulated a 5mm trace and
> >>a 10mm trace using the exact same stack-up, etc. you
> >>would find the
> >>following:
> >>
> >>1) capacitance -> 2*5mm trace should be pretty equal
> >>to 10mm trace
> >>2) (ac) resistance -> 2*5mm trace should be less
> >>than the 10mm trace
> >>3) inductance -> 2*5mm trace should be even more
> >>less than the 10mm trace
> >>
> >>This is because each segment of the structure
> >>interacts with the rest of the
> >>segments. So be careful, when you break up a
> >>problem, especially since you
> >>are introducing error on the optimistic side (where
> >>you usually would prefer
> >>to be on the pessimistic side).
> >>
> >>Regards,
> >>
> >>Patrick
> >>
> >>-----Original Message-----
> >>From: si-list-bounce@xxxxxxxxxxxxx
> >>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of KD
> >>KIM
> >>Sent: Monday, December 08, 2003 3:59 PM
> >>To: si-list@xxxxxxxxxxxxx
> >>Subject: [SI-LIST] I have a question related package
> >>parasitic
> >>extraction.
> >>
> >>
> >>Dear all,
> >>I have a question and be happy to write to you.
> >>
> >>I have simulation the structure composed of only one
> >>bonding wire and one
> >>lead,
> >>using FEM commercial solver, Ansoft Spicelink like
> >>below for extraction
> >>parasitic values,
> >>R, L, and C.
> >>
> >>I have simulated for below three cases.
> >>
> >>1. the structure contained only one bonding wire
> >>2. the structure contained only one lead
> >>3. the structure composed of one wire and one lead
> >>
> >>I think the value for case 3 equal to the values
> >>case 1 added case 2.
> >>But the result was not. The difference was about 16%
> >>for the Resistance.
> >>Of course, other parasitic values also have some
> >>differences considerably.
> >>Is this difference resulted from the defect of the
> >>FEM commercial solver?
> >>I want to know that what do you think about it?
> >>Please reply to my e-mail.
> >
> >
> >
> > =3D=3D=3D=3D=3D
> > Balachandran Jayaprakash
> > Celestijnenlaan,
> > 3/61, 3001, Heverlee,
> > Leuven, Belgium.
> > Mobile: +32-472-630120
> >
> > =
________________________________________________________________________
> > BT Yahoo! Broadband - Save =A380 when you order online today. Hurry! =
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