ENVIRONMENTAL PROTECTIONS FOR THE TACTICAL EDGE
Rugged Packaging and Cooling Technologies
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Cooling Architectures
AIR COOLING
(ANSI/VITA 48.1) — Conventional
Air cooling may be subdivided into CFM and air management
approaches. A CFM, or "cubic feet per minute" approach, is
the "traditional" approach to cooling (ANSI/VITA 48.1) and is
in widespread use within many commercial, development
and other applications that are deployed within relatively
benign environments. This approach relies upon fans to
push cooling air across the OpenVPX modules to remove
their generated heat. Although the lowest cost, this type of
cooling is the least efficient of the VITA cooling architectures
as the air tends to take the path of least resistance, often
not adequately cooling the hottest module regions.
CONDUCTION COOLING
(ANSI/VITA 48.2) — Rugged
To maximize heat dissipation and increase processing
density, modern conduction-cooled architectures feature
efficient heat spreaders, advanced thermally conductive
materials and enhanced thermal interfaces. However,
processing solutions powered by many contemporary
processors produce more heat than venerable, rugged and
reliable conduction-cooled solutions can handle. These
applications are being designed/upgraded with more effective
air-management, liquid and hybrid cooling approaches that
are similarly rugged, but offer greater cooling capability.
LIQUID FLOW-THROUGH
(ANSI/VITA 48.4) — High Performance
Liquid is a more effective coolant than air, delivering
significant thermal performance over even the best air-
cooled management approaches. The cooling liquid, often
the platform's own fuel, is connected via dripless quick-
disconnects and circulated within each module's cooling
jacket. This approach is similar to a car engine cooling
system. The ability to expel so much heat enables full-
throttle, deterministic (no CPU thermal throttling) and reliable
processing. Keeping processing elements well within their
maximum operating temperature increases a module's mean
time between failure (MTBF) by an order of magnitude.
AIR FLOW-BY
(ANSI/VITA 48.7) — Managed
Air Flow-By™ uses an air management approach of cooling
instead of a CFM method. Rather than pointing an unmanaged
air stream across each OpenVPX module, Air Flow-By
uses a plenum (reservoir) of pressured cooling air, which
is directed (managed) across each module. Air Flow-By
modules are sealed units (EMC and environmentally) that fit
snugly within their chassis and without further consideration
would block any airflow altogether. The effectiveness of
Air Flow-By is achieved by introducing module-specific air
passageways across their surfaces directing air to their hot
spots; these channels regulate where the cooling occurs
and how much cooling is applied. In effect, the cooling air
is efficiently applied to where the heat is generated and
has no opportunity to take the path of lesser resistance.
The Air Flow-By architecture cools both sides of each module.
The cooler PCB side of the module (few, if any active devices)
contributes additional cooling to the hot component-side
of the module it abuts, maximizing its effectiveness.
Full Air Flow-By design packages are available from VITA's
website for members under the Fair, Reasonable, and
Non-Discriminatory, zero-cost (FRAND-Z) licensing terms.
Figure 1: 6U OpenVPX Liquid Flow Through (ANSI/VITA 48.4) module
Figure 2: 3U OpenVPX Air Flow-By (ANSI/VITA 48.7) module
Mezzanine card
(Fits within
standard 1-inch
pitch OpenVPX slot)
Primary heatsink
(Component side)
Secondary
heatsink
(PCB side)
Heat
spreader
