Aerospace & Defense Technology - October 2022 - 30

RF & Microwave Technology
Coextrusion of conductive and nonconductive elastomers, to minimize corrosion of the gasket. (Courtesy Laird R&F Products)
3. Creating a corrosion-resistant window
seal: We needed to create a conductive
seal for a window on a ship.
However, conductive gaskets often
consist of metal fillers, which corrode
in seawater environments. So, making
our seal corrosion-resistant was
our top priority. Leveraging our
knowledge of galvanic compatibility
and experience with comolding, we
created a gasket with a conductive
layer and a nonconductive, absorbing
layer. Essentially, we made the
inside of the window seal conductive
and the outside nonconductive and
corrosion resistant. This nonconductive
layer protected the conductive
portion of the seal from corrosion.
Conductive fluorosilicone extruded D profile. Passivated conductive filler used to minimize corrosion.
(Courtesy Laird R&F Products)
tion was that our signal-attenuating
solution had to also fill a gap. And
since this gap was on an airframe structure,
it expanded and compressed with
movement and temperature changes.
So, rigid conductive surfaces wouldn't
work. Instead, we comolded a ground
plane to the absorber, creating a rubber
(and, by nature, flexible) material that
filled the gap as it expanded and
closed, eliminated edge scatter, and
effectively absorbed signal.
2. Suppressing signal noise from parallel
circuits: When an engineer
needs to suppress high frequency
noise on a circuit board, an absorber
30
is usually the solution. However, in
this instance, we had to suppress
noise from parallel circuit traces. And
with parallel circuit traces, an absorber
can impede signal integrity. The
solution we devised here was to
comold a low dielectric material to
the absorber, putting this dielectric
layer between the absorber and the
circuit traces. With this comolded
solution, the differential mode of the
signal is unaffected while the common
mode is suppressed. The result
in this case was improved signal
integrity and the suppression of signal
interference.
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4. Conductive gaskets that can solve
multiple problems: Electrically conducive
elastomers are an excellent way
to provide shielding and environmental
protection. In some cases, one or
more of the shielded surfaces move
during the operation of the part, for
example, sliding doors or opening and
closing of doors. It also may be on the
external surface of the application and
need to attenuate currents running
along the surface of the vehicle. And
of course, the abrasion of moving surfaces
needs to be resolved.
Some of the unique solutions involve
comolding absorber and conductive elastomer;
embedding conductive fabric into
nonconductive elastomers and unique
geometries using FEA analysis to allow
the closing action to minimize stress and
strain into the part. Wherever abrasion is
Aerospace & Defense Technology, October 2022

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Aerospace & Defense Technology - October 2022

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