01 March 2005
rough, indirect measure of EMI shielding. In addition,
repeatedly compressed and depressed.
a contact resistance of 2.5 milliohms is specified
across joints for grounding and lightning strike
h. Conformability: Accommodate joint unevenness.
7-5. EFFECTS OF CORROSION.
b. Corrosion resistance of gasket material:
Properties should not change with service (e.g.
7-5.1. GENERAL. Corrosion can degrade the electrical
corrosion which produces an insulting layer of material).
and mechanical properties of a joint. The exposure of
EMI gaskets to various environmental conditions can
c. C o m p a t i b i l i t y with the mating surface:
significantly reduce its shielding effectiveness and
Electrochemical compatibility to prevent galvanic
service life. Under field service conditions, military
d. Good adhesive qualities: Required for electrical
contact and environmental scaling.
Fillers Used in EMI
e. Chemical resistance to solvents: Properties
should not change with exposure to operational
chemicals (e.g. fuel, paint stripper, hydraulic fluid).
f. Resilience: Resistance to compression required
for electrical contact and environmental scaling. Long
term pressure should not cause permanent deformation
(compression set). Normal deflection for solid
rectangular elastomer seals range from 5 to 15%.