Wherever electrical power is generated, there is also power dissipation, which heats up the components. This heat needs to be transferred away to prevent overheating. For semiconductors there is a maximum junction temperature, above which the semiconductor ceases to work. The right method to dissipate excess heat heavily depends on the mechanical and environmental conditions, as well as the field of application. Conduction Cooling is a way of transporting the heat without needing fans, and also providing a metal frame makes the solution even more rugged!

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June 28, 2018
5 Things to Know about Conduction Cooling (CCA)

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Power Dissipation for Harsh Environments
Wherever electrical power is generated, there is also power dissipation, which
heats up the components. This heat needs to be transferred away to prevent
overheating. For semiconductors there is a maximum junction temperature,
above which the semiconductor ceases to work. The right method to dissipate
excess heat heavily depends on the mechanical and environmental conditions, as
well as the field of application.
Conduction Cooling is a way of transporting the heat without needing fans, and
also providing a metal frame makes the solution even more rugged!
1: What is the difference between conduction and convection cooling?
2: Which are the advantages of convection vs. conduction cooling?
3: Are there conduction cooled COTS components available?
4: Are there any other arguments for conduction cooling beside having no fans?
5: Which temperature range can be achieved with conduction cooling?

3. What is the Difference between
Conduction and Convection Cooling?
▪ Convection cooling is the easiest method to cool board assemblies. It is done by
guiding an air flow along the surface to be cooled. Forced air convection cooling uses
fans to blow and direct air towards the electronic components with or without heat
sinks
▪ Conduction cooling optimizes the thermal contact to conduct the heat from the
source to the outer wall of the enclosure. This makes the enclosure itself a heat
radiator

4. Which are the Advantages of
Convection vs. Conduction Cooling?
Forced air convection cooling:
▪ is the most effective cooling method and can be realized cheap and easy. While the
mechanical set-up is simple, some factors may turn out to be serious drawbacks,
depending on the application. With flowing air, impurities and liquids can find their way
into the device, and can do damage. Complex filtering equipment can reduce this risk,
but then maintenance is necessary during the device's lifecycle. Cooling fans also have a
limited lifetime, and their failure may lead to a total loss of some electronic
components.
Conduction-cooled designs:
▪ provide greater flexibility than convection, particularly for extreme conditions. However,
conduction cooling requires careful implementation. Suitable measures must be taken
to maximize the thermal transfer between the electronic component being cooled and
the enclosure wall. On the one hand, this is ensured by choosing the right materials. On
the other hand, the boards inside the enclosure need to be placed in the right way, and
the heat-conducting cooling blocks need to have such masses that optimum heat
transport is guaranteed.

5. lhhAre there Conduction Cooled COTS
Components Available?
Yes, of course.
The IEEE 1101.2-1992 standards describes the
specifications for Eurocard-based circuit card
assemblies – so all VMEbus and CompactPCI
cards. For all cPCI and cPCI Serial cards, MEN also
offers conduction cooling frames up to a complete
conduction cooled COTS system. There are also
some VITA standards for PMC boards and other
plug-in modules defined. In addition to that, MEN
is driving a new standard combining PICMG and
VITA technologies for robust COM modules:
Rugged COM Express (RCE) or VITA 59. This
standard defines a slightly adopted PCB board to
realize a massive conduction cooling frame.

6. Are there Any Other Arguments for
Conduction Cooling Beside Having no Fans?
To make a computer really rugged it needs a robust housing to withstand
extreme climatic conditions. With the massive metal block which is needed for
conduction cooling also other advantages come along to protect the electronics
inside. This includes protection from dust, chemicals or humidity within a sealed
enclosure and resistance against high shock and vibration effects by having the
metal block firmly screwed to the carrier card or system enclosure.
Rugged COM Express modules are
even 100% EMC-proven thanks to
the aluminum cover on top and all
four sides, as well as the bottom
cover of the carrier board.

7. Which Temperature Range can be
Achieved with Conduction Cooling?
Depending on the power dissipation and used components, the typical
temperature range of MEN products with conduction cooling is -40 to +85°C. This
is perfectly suited also for railway applications, which require temperature ranges
from -40 to +70°C for the device and for 10 minutes up to +85°C according to EN
50155. With the robust COM module family Rugged COM Express, an additional
5°C can be dissipated on average, depending on the processor.
At MEN, all products can be tested and qualified in our in-house test laboratory to
work in the extended temperature range.
➢ Get a competencies overview on our
website
➢ Video: COM Express and a RCE module
have a chat

8. www.menmicro.com/competencies/rugged-computing/