[SI-LIST] Re: DC Resistance calculation in 2.5D solver
- From: Long Yang <long.0.yang@xxxxxxxxx>
- To: istvan.novak@xxxxxxxxxxx
- Date: Wed, 16 May 2012 17:47:43 -0700
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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