Most of the mistakes are by the design engineers and not the pcb designers.
The mistakes are:

*       Mixing of I/O devices with clocks, processors and similar noisy
digital devices
*       Inadequate power/ground isolation of noisy digital devices
*       Inadequate I/O filtering
*       Failure to shunt ESD and EFT on I/O lines to chassis ground (not
digital ground)
*       High impedance ground traces (too narrow and/or too long)
*       Connecting I/O shields to the pcb and not to the chassis
*       Inadequate physical isolation of power line filters from noisy
circuits and traces

Richard Woods

        ----------
        From:  rehel...@mmm.com [SMTP:rehel...@mmm.com]
        Sent:  Friday, January 21, 2000 7:48 AM
        To:  emc-p...@majordomo.ieee.org
        Subject:  EMC Circuit Board Design




        Dear List-Members,

        I am requesting information/opinions/etc. on the following:

        When circuit boards are designed, what are the common mistakes that
the
        circuit board designers make regarding EMC (multi-layer boards in
        particular)?

        You can respond to me directly but I would prefer a response to the
list as
        I believe that the question is of interest to many on this
list-server. In
        either event I will compile the responses and resend the compilation
later.

        Thanks for your time,

        Bob Heller
        3M Company



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