There really isn't a spec, it's more of a derived number from the type of
connectors and backplane tolerances selected by the designer. Most mating
connectors when plugged in have an electrical travel mating length. This is
the distance the connectors slide from the point of first contact to when
they are properly seated. This distance on some connectors is as small as
.030" and on others as large as .150". A properly designed backplane would
contain sufficient rigidity in the material to prevent excessive bowing
during vibration or card insertion. If a stress and dimensional analysis
shows the backplane will bow beyond the electrical travel length, then
corrective measures must be undertaken to stiffen the assembly. This may
include, but not be limited to metal stiffeners on the backplane or side /
top rails on the card cage to add strength.


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Denis Caissie
Litton Electronic Systems Packaging
603-424-4273

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