[SI-LIST] Re: Board via characteristics (fwd)
- From: Chris Cheng <chris.cheng@xxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 9 May 2002 14:06:18 -0700
I believe the need for 2.5D or 3D is to extract
out the so call residue parasitic. The basic
concept is calculating the ideal inductance
(which to me is not quite correct) of a
continuous trace vs. the same length of
trace but going through a via in the middle.
This is supposed to take care of the via
inductance and any flinging effect at the
turn.
IMO, if you simply need a single value of
inductance for a via, you are better off
saving your money and just use the rule of
thumb of 1nh per mm. The result between that
and 2D or 2.5D will be reasonably close.
When you truly start to worry via inductance,
you really need to have a complete picture of
the current loop between the signal, reference
plane and the return via for both. Something
I've been preaching for a long time.
-----Original Message-----
From: Ray Anderson [mailto:Raymond.Anderson@xxxxxxx]
Sent: Thursday, May 09, 2002 1:50 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Board via characteristics (fwd)
A number of vendors market a beast known as
a 2.5D field solver. This is a 2D solver
with the capability thrown in to "model"
'selected' 3D structures such as vias and
coaxial structures.
Typically the modeling for these 3D structures
isn't done by way of field solving, but by
way of embedded closed form equations/approximations.
So when you perform the model synthesis with
a 2.5D 'solver', you actually do a solution
to a fields problem for the 2D structures, but
when you run it on a via, you actually just
do an equation based approximation. Most 2.5D
solvers that I've seen that implement the modeling
of vias output a lumped 'pi' model (C-L-C) of
the via discontinuity.
If any vendors of 2.5D solvers would like to
through in their 2 cents worth on the topic
I'd like to hear/read their comments.
Ray Anderson
Sun Microsystems Inc.
>
>
>I have heard this claim before but not bothered to check it out. Why?
From
>a conceptual or theoretical perspective it seemed inappropriate. Don't
most
>2D Field Solvers assume they are given the 2D cross-section of a structure
>which is long with respect to the analysis frequency? How do you take an
>appropriate 2D cross-section of a via? Seems to me a via is very much a 3D
>structure. But I've been wrong before. :-)
>
>Aubrey Sparkman
>Signal Integrity
>Aubrey_Sparkman@xxxxxxxx
>(512) 723-3592
>
>
>> -----Original Message-----
>> From: David Hoover [mailto:dhoovy@xxxxxxxxxxxxx]
>> Sent: Thursday, May 09, 2002 2:50 PM
>> To: si-list@xxxxxxxxxxxxx
>> Subject: [SI-LIST] Board via characteristics (fwd)
>>
>>
>>
>>
>> Gang,
>>
>> I was asked if I could forward this
>> question to the list for input. I'm a
>> fabricator that builds high speed PCBs
>> out of many different composites. I'm
>> also very curious about modeling vias
>> because I co-chair the IPC committee
>> on Controlled Impedance Circuit Boards and
>> High Speed Logic Design and during the last couple of
>> Conference Meetings this topic has
>> came up. I run a 2D Field Solver which I
>> believe can model for vias. Just never have
>> done it.
>>
>> Any and all response would be greatly
>> appreciated.
>>
>> David Hoover
>> Field Application Engineer
>> Data Circuit Systems, Inc.
>> (408) 280-0422 X233
>> http://www.datacircuits.com
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
