01 March 2005
e. Apply a bead of sealant to the surface to which
the EMI gasket will be bonded, one of the two mating
metal surfaces that will be permanently assembled to
the edge of a lap joint, or the gap of a butt joint
(whatever situation applies), using a sealant gun or a
squeezable sealant tube. Using a straight edged wood
b. Clean all surfaces that will contact the sealant
or plastic tool, smooth the sealant bead to form a
with a lint free cloth (Volume V, Chapter 2) moistened
continuous film over the entire contact surface for the
with Isopropyl Alcohol, TT-I-735 (Volume V, Chapter 2),
EMI gasket or the mating metal surface of a permanent
and then wipe the areas dry with a clean cloth of the
assembly as applicable, or smooth the bead at the lap
joint edge to an even, continuous fillet or smooth the
the cleaned areas with bare hands as this will
bead in the butt joint gap to fill the gap entirely and be
recontaminate the surfaces and prevent adhesion of
flush with the surface, as applicable.
f. Press the EMI gasket into the sealant or assemble
the sealant coated surface to the sealant free mating
surface of a permanent assemble, as applicable, while
All sealant and primer application operations
the sealant is wet or within the manufacturer's specified
and component assembly operations after the
sealant application shall be performed within
the temperature range of 60°F to 95°F so that
the sealant will adhere properly.
Sealants and primers are flammable and toxic.
g. Clean up any excess sealant with a lint free cloth
Skin and eye protection are required. Avoid all
sources of ignition. Good general ventilation is
sealant is still wet.
c. If required by the sealant manufacturer, obtain
h. A l l o w the sealant to cure for the time
recommended by the manufacturer, but not less than
Apply it to the surfaces that will contact the sealant per
24 hours, before placing the equipment in service.
the manufacturer's instructions; allow it to cure for at
least 1/2 but not more than 4 hours before applying the
7-7. EMI PACKAGING REQUIREMENTS. Unless
sealant. If more than 4 hours elapse after the primer
otherwise specified, items that are sensitive to EMI
application, repeat steps a, b, and c before applying
should be packaged in accordance with MIL-E-17555
for electromagnetic protection. Marking shall be
accordance with MIL-STD-129.
a multi-component sealant, mix the components
together per the manufacturer's instructions.
To case clean up of excess sealant, Masking
Tape, SAE-AMS-T-21595, Type I (Volume V,
each side of the area to which sealant will be
applied. Install the tape before the sealant is
applied, and remove it as soon as possible
after the sealant is smoothed out.