Aerospace & Defense Technology - December 2024 - 6

Materials
End Users
For all users, several key factors must
be considered when choosing materials
to be implemented in products for these
applications.
Thermal stability and resistance. Aerospace
and defense environments often
expose materials to high temperatures.
Laminates and films must exhibit excellent
thermal stability to maintain performance
and prevent degradation over
time. They must not only be able to
withstand extreme operational temperatures
and changes in temperature without
degrading; they must also provide
sufficient heat dissipation to prevent
overheating of components.
Electrical performance. Optimal elecFigure
2. Flex circuits offer numerous advantages over traditional rigid circuit boards, including lighter
weight, smaller area, bendability, durability and resistance to environmental extremes. (Image: DuPont
Interconnect Solutions)
inates potential failure points, reduces
weight, and saves space.
Rigid-flex boards are available in two
main forms:
* A separate flex circuit connecting two
rigid boards, acting as a sort of hinge
between them, which enables stacking
of the layers when the flex circuit is
bent; or
* Rigid and flex substrates integrated
together into a single electronic board.
They offer high reliability even when
subjected to shock or extreme vibration.
This makes these boards well suited for
such high-reliability applications as aircraft
instrumentation, communication
systems, missile guidance systems, and
space flight vehicles, to name a few.
Laminates play an important role in
circuit boards' performance. They are
Standard
IPC-4202
IPC-4203
IPC-4204B
Description
Flexible Base Dielectric for Use in Flexible Printed
Boards
Cover and Bonding Material for Flexible Printed
Circuitry
Coverlay, Bondply, Unsupported Sheet Adhesive
Flexible Metal-Clad Dielectrics for Use in Fabrication
of Flexible Printed Circuitry
NASA Outgassing Speciation SP-R-0022
vital for establishing electrical properties
and thermal limitations, providing
mechanical integrity to flex circuits,
and enabling circuits to be fit into the
desired footprint.
Similarly, polyimide films serve several
purposes. Key functions include
serving as:
* Base dielectrics, applied as a manufacturing
guide on flex printed boards;
* Coverlays to protect flexible lines on
flex circuit; or
* Stiffeners for flex and rigid-flex boards,
providing stability without losing
flexibility.
Properly chosen films and laminates
deliver a number of important benefits
for PCB development and fabrication,
including electrical insulation, mechanical
stability, miniaturization, signal
integrity, and ease of manufacturing.
DuPont Product
Kapton®
Pyralux®
Pyralux®
Pyralux®
Pyralux®
Kapton®
Pyralux®
Pyralux®
Pyralux®
Pyralux®
Film
LF
FR
HT
AP
Film
AP
LF
FR
HT
Table 1. Material supplier standards and specs. (Image: DuPont Interconnect Solutions)
6
trical insulation and conductivity are
crucial for the proper functioning of
electronic systems. Materials with superior
dielectric properties, including low
dielectric constant and dissipation factor,
are preferred to minimize signal loss
and prevent electrical failures. High-frequency
compatibility is another essential
parameter for applications involving
high-speed data transmission.
Chemical and mechanical properties.
Laminate and film materials must
endure mechanical stress, vibration,
impact and sudden shocks without compromising
their integrity. This requires
high tensile strength and flexibility,
which are vital to maintaining structural
integrity. Additionally, the materials
must resist exposure to harsh chemicals,
moisture, and UV radiation. These properties
help ensure electronic components'
longevity and reliability.
In addition, domestic suppliers
require fast access to quality materials
and the ability to build boards in U.S.,
rather than having them built overseas
and shipped. U.S.-based polyimide
film providers with established expertise
in laminates and films offer a distinct
advantage. As the only U.S. laminate
supplier that makes and utilizes
its own polyimide films, DuPont has
brought unique Pyralux® laminates
and Kapton® polyimide films to the
aerospace and defense markets for
more than 30 years.
As an example, Pioneer Circuits has a
long history of collaboration with DuPont,
spanning four decades of partnership with
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Aerospace & Defense Technology - December 2024

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