July 2017
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manufacturers; extremes that would quickly
render commercial components non-func-
tional. This commitment to extreme rugged
design demands adherence to the underly-
ing strategy at every stage, from component
selection to manufacturing. It impacts ther-
mal management, without doubt, but it also
influences the way the board is laid out, the
thickness of the PCB substrate and of course
the design of the enclosure.
While some manufacturers may feel testing is
only part of the final production phase, those
with a true focus on rugged design understand
that testing must be an integral part of the
entire product development and manufactur-
ing process. Testing should be applied at the
earliest stages of design, through a wide vari-
ety of protocols and methodologies. ADLINK
has developed its own Extreme Temperature
Testing (ETT) methodology that forms part
of the selection process for individual com-
ponents. In addition, it follows a high-margin
circuit design approach that favors compo-
nents that are proven to function reliably,
even when exposed to extremes in tempera-
ture across wide voltage ranges. This helps
deliver products like the Extreme Rugged
COM Express Type 6 Computer-on-Module,
for example.
As part of this approach, ADLINK employs IT
Equipment (ITE) 180-compliant high-tem-
perature PCB substrates, as recommended
by the American Society of Heating, Refrig-
eration and Air-Conditioning Engineers
(ASHRAE). As part of the testing process, all
components have documented evaluations
for MTBF and full derating calculations. Once
a design has been approved it moves to the
prototyping stage, which involves more vali-
dation and testing using a process intended to
really uncover the potential weaknesses of a
design. Using repeated test cycles, prototypes
are tested to their extremes through combina-
tions of temperature and six-axes vibration
stress tests. Inevitably, this arduous process
reveals the operating limits of a design, pro-
viding valuable data on how to improve the
overall product at the earliest possible point
– and long before it has the chance to fail in
the field.
The same stringent approach to validation is
applied to any thermal management solutions
employed, both active and passive. This may
also involve the use of advanced Computa-
tional Fluid Dynamics modelling software,
which can help test a design under a number
of scenarios during the prototype stage. It
may even involve the use of wind tunnel test-
ing to evaluate the effectiveness of heatsinks.
Highly Accelerated Life Test, or HALT, is an
important part of this test methodology, as
is ETT. It puts components through a series
of tests carried out at extremely high and low
temperatures, but involves more than plac-
ing a motherboard in an oven or chiller. To
be truly useful and conclusive, the process
requires tests to be carried out in a methodical
way, often to a specific customer requirement.
Making testing part of the entire product
development process means ETT is used
at multiple points in the design cycle. This
starts with functional tests that ensure the
board boots up across the entire extended
temperature range. Engineering samples of a
prototype are then subjected to four-corner
testing; testing that a board remains stable
and reliable at the minimum and maximum
temperature and voltage design parameters.
Following this, ADLINK test engineers will
put the board through thermal shock tests
and HALT testing. Only when the design has
passed all these tests can it progress to a pilot
production run, during which engineers will
continue to subject the board to functional
and burn-in tests under ETT conditions, in
order to fully assess yield.
Once in production, the HALT methodology
steps up a gear, by putting increasing levels
of stress on components. This includes more
temperature cycling, applied over shorter
periods of time, along with more aggressive
six-axes vibration testing, both in isolation
and concurrently. Throughout the applica-
tion of HALT, engineers constantly monitor
and measure critical elements of the system
under test, including the processor, interfaces
and memory sub-systems. In the event of a
fault developing it is analyzed until the cause
is identified and a potential design improve-
ment can be evaluated. This process continues
until the stress applied causes the component
to fail; tested to destruction.
All the data gathered during all of seven HALT
stages is used to improve the overall design
process. The seven stages of the ADLINK
HALT process are as follows. 1) Power on
units in continuous functional test loop. 2)
Progressively increase extremes of tempera-
ture. 3) Induce six-axis vibration. 4) Margin
power (±5%). 5) Stress to failure. 6) Evaluate
failure. 7) Implement design improvements.
C
OVER
S
TORY
Figure 2. The MXC-6400 Series delivers an Extreme Rugged compliant solution for intelligent
transportation operations such as passenger information systems and CCTV systems for rail
transport and maritime control centers.
Figure 1. The Extreme Rugged ADLINK COM Express Modules are all MIL-STD-810G and
MIL-STD-202G compliant. The server-class Type 7 modules are a perfect fit for operating at the
IoT edge in extended temperature ranges from -40°C to +85°C.
