[SI-LIST] Re: DC Resistance calculation in 2.5D solver
- From: John Lin <johnlinc@xxxxxxxxx>
- To: long.0.yang@xxxxxxxxx
- Date: Thu, 17 May 2012 09:09:30 +0800
Hi all,
at DC, freq=0,the current loop has only copper resistance, The nearest path
shall have least resistance. the large plane or thickness ,the less
resistance.
thanks .,
john Lin
2012-5-17 ¤W¤È8:48 ©ó "Long Yang" <long.0.yang@xxxxxxxxx> ¼g¹D¡G
> Hi,
> For a lot of times I doubted when I heard that current distributes
> uniformly along power/ground plane.
> Current source is most being a point connection, and current channel is
> always larger planes.
> Here is my understandings about why not uniform distribution
> 1) Even at DC, charges move from source to destination following the
> nearest path, and .
> 2) Charges cannot accumulate unlimited only in one path, visually many
> paths. The nearest path, the most density.
> 3) Gauss's law is applicable at DC.
>
> Just share my understanding. Point out anything if wrong or comment
>
> thanks
> Long
>
> On Wed, May 16, 2012 at 5:40 AM, Istvan Novak <istvan.novak@xxxxxxxxxxx
> >wrote:
>
> > Hi,
> >
> > I wont comment on the specific tools, but will give you some generic
> ideas.
> >
> > We many times dont realize that DC resistance calculations can be almost
> > as tricky as the high-frequency computations. We usually assume
> > (wrongly) that at DC the current density is uniform in the conductor
> > cross section, but except of a few hypothetical cases, it is not. This
> > is why, even at DC, the correct answer needs careful volume meshing, to
> > make sure that the different current density values are captured
> > properly throughout the conductor volume, including the end connections
> > leading to the observation points. Most tools have knobs for you to
> > turn on some of the key parameters (you may be surprised to see that
> > once you start turning those knobs, you get different answers from the
> > same tool to the same DUT).
> >
> > So when you compare results from different tools, you may want to check:
> > - how the meshing is done and get them as close to be similar/same as
> > possible
> > - how the connection is assumed
> >
> > For this second item, one hint: we can not use point connection, because
> > for zero cross section area the current density and the equivalent
> > resistance would be infinite: we have to use finite connecting cross
> > section area. So first you have to find out how the connections are
> > assumed in the two tools and then make sure that they are as
> > close/similar as possible. If these key elements are the same or close,
> > we can then expect similar results.
> >
> > Regards,
> >
> > Istvan Novak
> > Oracle
> >
> >
> > On 5/16/2012 7:52 AM, Tesla wrote:
> > > Hi, Experts
> > > In 2.5 field solver(eg: Sigrity or SIwave), if i want to get DC
> > resistance of interconnect, i use the two method:
> > >
> > > 1 Use FEM to calcute from DC to Fmax Hz, use the DC s parameter to get
> > the S parameter
> > >
> > > 2 Use IR drop in the analysis to get the DC resistance
> > >
> > > but the two method give two different DC resistance value, Which one i
> > should trust?
> > >
> > > Thanks.
> > >
> > >
> >
> >
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