I don't know of any official standard that gives a
specific ruling on connector pins. The generic
immunity standards refer without comment to the
basic standards and the basic standards refer to
points accessible to personnel during normal use
including customer's maintenance. The overview
of immunity tests, standard IEC1000-4-1 reiterates
this saying that the ESD shall be applied to all
normally accessible points on the EUT
The opinion of the Competant body that we use is
that if the user can reasonably reach a connector
and may do so at some time during any operation
that you might reasonably expect him or her to do,
the pins of the connector should be tested if there
is a fair chance that a finger or metal object
approaching the connector would discharge to
the contacts rather than the shell. Thus large
flat connectors with non-recessed contacts or
plastic shelled connectors should have the pins
tested but narrow metal shelled connectors with
the shell earthed and contacts recessed need
only be tested to the shell. A few tests have
shown that female BNC's discharge to the shell
but male BNC's can discharge to the pin. Standard
width D types with female contacts discharge to the
shell and those with male contacts nearly always
do. Wide shell 3 row D types can discharge to the
pins with both sexes.
Do not forget the indirect ESD test. I have found that
for plastic cased equipment with unscreened wires
running away from the connector internally an ESD
test to a coupling plane 100mm from a connector
face can have more effect than a direct discharge
to the pin.
Nick Rouse
