For what it's worth... here was my reply...
Hi Marty,
I think this would be critical especially if the circuit board is large.
Resistance is only a DC phenomenon, with AC it's impedance. I'm thinking
that if the board has controlled impedance and long runs with fairly small
traces the resistance might throw off the impedance reading. They are
probably looking for a constant to subtract from the impedance. Did that
make any sense?
Feel free to contact me. We design circuit boards as well as build some of
the latest designs and I may be able to tap into our collective experience
here.
Joseph Spicuzza
Quality Assurance Manager
Advanced Interconnect Products Division
Compunetics, Inc.
PH: 412 858-6166
FX: 412 373-8060
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-----Original Message-----
From: Martyn Gaudion [mailto:[log in to unmask]]
Sent: Friday, April 12, 2002 6:25 AM
To: [log in to unmask]
Subject: DC Track resistance - can you help me?
Dear Joseph,
You may be able to help me, as I would
like to know why - in addition to specifying
impedance - an increasing number of PCB designers
and PCB fabricators are also specifying DC resistance
of PCB tracks?
I have had an increasing number of clients ask
me about series resistance being specified on
PCB tracks, but no one seems to know why..
If you are able to help with some of the reasons
why, I would very much appreciate hearing from you.
Kind regards
Martyn Gaudion
www.polarinstruments.com
P.S. If you know a colleage or customer who may be
able to add more information, it would be much appreciated if you
could put me in touch..
Remove me:
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Don Vischulis
Sent: Friday, April 12, 2002 11:49 AM
To: [log in to unmask]
Subject: [TN] Interesting question
Techies:
I received the following email today, and it aroused my curiosity. What
reasons exist for specifying dc track resistance when minimum resistance is
governed by a combination of copper weight and design width, and track
length? Is this a case of over zealous specification or is there a purpose
behind adding another test requirement to a product with extensive
specifications?
Don Vischulis
Original message:
You may be able to help me, as I would
like to know why - in addition to specifying
impedance - an increasing number of PCB designers
and PCB fabricators are also specifying DC resistance
of PCB tracks?
I have had an increasing number of clients ask
me about series resistance being specified on
PCB tracks, but no one seems to know why..
If you are able to help with some of the reasons
why, I would very much appreciate hearing from you.
Kind regards
Martyn Gaudion
www.polarinstruments.com
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