stackup calculations and ApsimRLGC - si-list / [SI-LIST] FW: Impedance

[SI-LIST] FW: Impedance / stackup calculations and ApsimRLGC

From: "Kevin Buchanan" <buck@xxxxxxx>
To: "Si-List" <si-list@xxxxxxxxxxxxx>
Date: Fri, 22 Nov 2002 14:11:14 -0500

Hi All,

   Can any one elaborate on the below text. As can
be seen this was originally sent to the Mentor exp_pcb_sig forum.

   We depend on the fab houses normally to provide stackup info
and this does raise questions. Also, what tools are being used
to develop stackups.

Thanks,
Buck...

-----Original Message-----
From: Paul Gingras [mailto:paul@xxxxxxx]
Sent: Friday, November 22, 2002 1:42 PM
To: Kevin Buchanan
Subject: FW: Impedance / stackup calculations and ApsimRLGC




-----Original Message-----
From: owner-exp_pcb_sig@xxxxxxxxxxxx
[mailto:owner-exp_pcb_sig@xxxxxxxxxxxx]On Behalf Of Ian Coggins
Sent: Friday, November 22, 2002 12:15 PM
To: exp_pcb_sig@xxxxxxxxxxxx
Subject: Impedance / stackup calculations and ApsimRLGC


Hi,

Without trying to start a flame war, I have a fab house using
'ApsimRLGC' from Applied Simulation Technology to calculate their board
stackups and impedances.  However, we just discovered something rather
alarming.

We use Hyperlynx ourselves, and have had many other fab houses confirm
our figures using other sources so pretty much rely on hyperlynx. I've
also been advised that the IPC calculators are incorrect (from the words
of Rick Hartley no less)

Now, we find a major discrepiancy between what ApsimRLGC is calculating
compared to Hyperlynx. It would seem that when calculating differential
pair impedance, ApsimRLGC is listing the edge coupled seperation as
being center to center, but is actually using it as an edge-edge
measurement.

[ Taking the center-center seperation reported by ApsimRLGC and using it
as the edge-edge seperation gives roughly the same impedance ].

However, the different figures are enough to cause 10-15% error (in our
case) BEFORE manufacturing tolerances are applied. This is a major issue
for us.

I'm wondering if anyone else here has

A) any feedback on hyperlynx calculations using a tdr or similar to
verify the calculations
B) any feedback on the apsimRLGC calculations - 



Regards
Ian Coggins


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[SI-LIST] FW: Impedance / stackup calculations and ApsimRLGC

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