F ew components are subjected
to extreme conditions in the
way that connectors are. From
commercial aircraft or military
vehicle to medical ventilators,
connectors need to be able
to endure extreme variation in
conditions.
Whether it’s the rapid
temperature fluctuations and
changes in humidity, to persistent
vibration, impacts and signal
interference, connectors must be
able to operate reliably to ensure
their users can get the ‘job done’.
“The industry-standard D38999
is a military-specification connector
that was originally designed in
the 1970s and is now on its thirdgeneration
design,” explains Ammar
Lokhandwalla, customer application
engineer at connector specialist PEIGenesis.
“Like other connectors of its
kind, it’s made up of a few basic
components: a hard outer shell, a
neoprene rubber insert with holes
to house the pins, or contacts, and
sometimes a backshell on the outer
housing that provides additional
shielding and durability.”
When it comes to selecting
a connector, engineers need to
consider a wide variety of properties
depending on their application. One
of the primary considerations is the
choice of materials, for both the
electrical terminations and shell
housing. For example, although
copper offers better electrical and
thermal conductivity, aluminium
is cheaper and easier to form and
plate.
“While copper may be chosen for
high-voltage industrial applications
where heat dissipation and
conductivity are vital, aluminium
may better serve aerospace and
military applications where weight
and corrosion-resistance are more
important,” explains Lokhandwalla.
Ingress protection is another
consideration and connectors that
are designed for industrial food and
“Some military applications
How to
deliver
a reliable
connector
design
use olive-drab green, a colour that
was historically achieved with a
toxic cadmium coating,” explains
Lokhandwalla. “In recent years, this
has been replaced with a black zinc
nickel plating that meets RoHS and
REACH regulations. If engineered
correctly, this black plating can
deliver the same performance as
cadmium coatings and withstand
over 500 hours of salt-spray.”
Not all connector contacts can
be solder-terminated, according
to Lokhandwalla, “Under certain
extreme conditions, the operating
temperature of the application can
exceed the melting point of the
solder, causing connection failure.
For applications where this is a risk,
engineers may prefer to specify a
crimped connector.”
Lokhandwalla makes the point
that when it comes to crimping,
contacts are joined to the wire
by mechanically squeezing them
together to ensure that they
remain in contact no matter the
temperature. Instead of a soldered
connection where the wire is fed
through an eyelet or hook and
What makes for a good connector
design, especially one that looks to
mitigate electromagnetic interference?
New Electronics talks to PEI-Genesis
beverage manufacturing must be
sealed against water jets to allow
equipment and machinery to be
washed down between shifts.
“This protection extends to
marine applications, such as those
in the oil and gas sector where
equipment may need to be fully
submersible for prolonged periods
of time. In these applications,
it may be necessary to select a
polycarbonate connector, with
the right o-rings and grommets to
provide a moisture seal,” suggests
Lokhandwalla.
While aluminium is the preferred
choice of connector material for
many construction, rail, industrial
and military applications, it may still
need to undergo plating to improve
its corrosion-resistance, to provide
further electromagnetic shielding,
and to meet camouflage and colour
needs.
“EMI is a serious
concern for
engineers in
almost every
application,
but especially
situations where
signal integrity is
vital.”
Jakub Kosinski
22 9 February 2021 www.newelectronics.co.uk
/www.newelectronics.co.uk