[SI-LIST] Re: Routing Parallel vs. Paralell
- From: "Xilei Liu" <xileil@xxxxxxxxxxx>
- To: weirsi@xxxxxxxxxx, pcbjack@xxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Thu, 14 Sep 2006 16:54:08 +0000
Jack,
Wondering whether I should give your MATH question my PHYSICAL answer or
not.
Firstly, I assume that the coupling you mentioned refers to the coupling
between these two traces of different configurations.
Secondly, assuming that you have 1.6mm FR4(er=4.31), double sided, size
30*30mm^2; by APLAC simulation, the coupling factor(Ze-Zo)/(Ze+Zo) for 6mil
traces (1/2oz) routed 6mil broadside is about 0.65; and the coupling factor
for 6mil traces routed 6mil(edge to edge) side by side is about 0.60; 1oz
copper doesn't change the results with 1/2oz copper.
So, it sounds that the statement"traces routed 1 inch in parallel will
couple the same amount as traces routed .2 inches broadside (layer to
layer)" is incredible, unless there is air or other material between "layer
to layer"?
Well, should leave this MATH question to experts. Please give me $3 whenever
possible ;)
Regards,
Celine
>From: steve weir <weirsi@xxxxxxxxxx>
>Reply-To: weirsi@xxxxxxxxxx
>To: pcbjack@xxxxxxxxx,si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Routing Parallel vs. Paralell
>Date: Thu, 14 Sep 2006 07:34:38 -0700
>
>Jack that is what we have field solvers for. You used to be able to
>rent time on Polar 8000 for about $20/hr. Otherwise find someone
>with Polar or Ansoft and run the model.
>
>Steve.
>At 07:29 AM 9/14/2006, Jack Olson wrote:
> >I got a MATH question I don't know how to solve...
> >I want to know the difference between running traces
> >parallel on the same layer (side by side) compared
> >to running them on different layers right on top of
> >each other (broadside).
> >
> >I know won't be a simple answer,
> >so I will provide a simple example:
> >
> >Say I am using 6mil traces with 6mil clearances on
> >layers that are 6mil apart using half ounce copper
> >(which is nearly .6mils) and both layers are internal.
> >
> >What distance can I route side by side and get the
> >same coupling as if I had routed them broadside?
> >
> >So I want a simple thing to remember that says
> >something like, "traces routed 1 inch in parallel will
> >couple the same amount as traces routed .2 inches
> >broadside (layer to layer)
> >
> >Does anyone know how to make my rule-of-thumb?
> >and if I change to 1oz copper, will the rule double?
> >
> >onward thru the fog,
> >Jack
> >
> >
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