Hi Cameron,
Besides all the design issues, you must also find suppliers who can produce
your boards to design specifications and that have very little variation in
their process.  Controlled impedance boards will require your board
suppliers to have very controlled processes.  We have found that there can
be large variation in conductor widths, space widths, conductor heights, and
via resistance's from board suppliers.  These variations can occur within a
board, from board-to-board, and from lot-to-lot.  Unfortunately you may need
to take these variations in to count when designing your controlled
impedance boards.

We offer a testing and analysis service that provides process capability
data on PCB manufacturing capabilities.  If you need help in understanding
you board suppliers capabilities please feel free to contact me.

Tim Estes
Conductor Analysis Technologies, Inc.


-----Original Message-----
        From:   [log in to unmask] [SMTP:[log in to unmask]]
        Sent:   Thursday, August 20, 1998 10:35 AM
        To:     [log in to unmask]
        Subject:        [TN] More Controlled Impedance

Thanks to those who responded to my previous question about trying to find
some information about how to design a board with controlled impedance.
Unfortuneatly, I still haven't been able to find any information on the
topic.
I now have an engineer who wants me to design his board with some controlled
impedance. Can anyone tell me what questions I should ask him, and give me
some design considerations that I should pay attention to.
Thanks,
Cameron

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