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5 Things to Know About Thermal Management in Embedded Computing

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Cooling electronic boards can be a huge challenge, especially where powerful systems need to be ready for fanless operation. Dissipating heat using a purely mechanical coupling is expensive and consumes valuable space, not to mention that the boards need to be specially designed for this cooling concept from the start.
How to choose the right cooling method? These questions could help to find the answer.

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5 Things to Know About Thermal Management in Embedded Computing

  1. 1. Textmasterformat bearbeiten ▪ Second Level ▪ Third Level ▪ Fourth Level Fifth Level February 8, 2018 5 Things to Know about Thermal Management for Embedded Computing
  2. 2. 2 Thermal Management for Embedded Computing Cooling electronic boards can be a huge challenge, especially where powerful systems need to be ready for fanless operation. Dissipating heat using a purely mechanical coupling is expensive and consumes valuable space, not to mention that the boards need to be specially designed for this cooling concept from the start. How to choose the right cooling method? These questions could help to find the answer. 1: How much heat can be transferred from my device? 2: What is convection cooling? 3: What is conduction cooling? 4: How to integrate appropriate cooling into 19”-systems? 5: Is conduction cooling for existing boards possible?
  3. 3. How much Heat can be Transferred from my Device? The heat flow that results from a temperature difference is responsible for the transfer of any heat. The bigger the temperature difference and the space available, the bigger the heat flow. Additionally, it depends on the thermal conductivity, a constant that depends on the material, it’s surface, and thickness. Every layer of material of a finite thickness adds to the total thermal resistance depending on its material and surface. For an IC, for instance, this is the package filling, the heat conducting film, and the heat sink. Obviously, the higher the thermal conductivity of the layers involved in the transfer is, the more efficient is the cooling.
  4. 4. What is Convection Cooling? This type of heat transfer is the easiest method to cool board assemblies. It is done by guiding an air flow along the surface to be cooled. While the mechanical set-up is simple, there are some facts that 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 on the other hand they create the need for maintenance during the device's lifecycle. Cooling fans are also components that have a limited lifetime, and their failure may lead to a total loss of some electronic components.
  5. 5. lhhWhat is Conduction Cooling? This technology 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. Suitable measures must be taken to minimize the thermal transfer resistance from the electronic component to be cooled to the enclosure wall. On the one hand, this is ensured by choosing the right materials. Aluminum and copper are proven materials here. 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. The gradient between the inner and outer temperature follows the rules already described: the cooler the outer enclosure surface, and the larger it is, the smaller the total thermal resistance of the arrangement.
  6. 6. How to Integrate Appropriate Cooling into 19”- Systems? While conventional conduction cooling is useful for individual PCBs, 19” racks with multiple boards preclude the cards’ surfaces to connect directly to the enclosure wall. System designers need to find alternative methods to get the heat out of the system, such as building upon the principles of conduction cooling. One implementation of this design is an aluminum board assembly that fits over the critical heat areas, essentially extending the overall conduction-cooling principles. Another way is using the actual component contact surfaces on the PCB to transfer heat through additional copper layers inside the PCB. Of course, both impact the available surface for component placement, and determine the number of copper layers, so these methods need to be undertaken at the onset of PCB design.
  7. 7. Is Conduction Cooling for Existing Boards Possible? If we accommodate for slightly more rack space than required for traditional boards, it can be done. By using the guide rail area as an extension of the conduction-cooling method, the designer can clamp the PCB to an aluminum frame, which totally encloses the card. Even components at the bottom side can be thermally coupled to the frame, resulting in exceptional heat management. Standard 3U cPCI boards can be installed in a special rack system and operate without convection cooling. This way, a card can host more functionality because the cooling infrastructure does not take away precious space. ➢ Learn more about rugged computing at MEN
  8. 8. www.men.de/competencies/rugged-computing/ www.menmicro.com/competencies/rugged-computing/ www.men-france.fr/competencies/rugged-computing/

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