Conduction cooling solutions for rugged computers, optimal for harsh environments.

 This post covers the use of conduction cooling techniques in stackable and modular systems. Under which conditions such systems are most commonly used? Is it possible to create customized systems, yet compliant to industry standards? How conduction cooling is applied in stackable and modular systems?

Read more in the research by senior design engineer at Fastwel, Alexey Sorokin, first presented at the Embedded World 2015 exhibition.

 The conduction cooling solutions are gaining popularity when in need of high performance boards in systems operating in harsh environments (-40C to +85C). Often such systems are designed for mission-critical applications and should therefore be resistant to harsh environment conditions: electromagnetic influence, shocks/vibrations, damp heat, salt mist, etc.

Dump Heat  Picture3   Electromagnetic compatibility   Electromagnetic compatibility   Extended temperature range   Shocks, vibrations   Picture2

The conduction cooling solutions improve systems reliability, yet they should remain flexible while complying with multiple standards. Let’s analyze the two most commonly used conduction-cooling solutions: Compact PCI — Serial – a modular system, based on PICMG standard and a Stackable PC System, based on a Stack-PC standard.

Compact PCI-Serial solution works with Conduction Cooling Assembly (CCA) technology, which consists of CCA FRAME and CCA Enclosure. CCA Enclosure defines: card retainer channel width, backplane position, board Pitch 5HP. The design of such systems is usually customized, based on clients’ requirements.
Enclosure surface works as a system heat spreader while CCA Frame surface works as a module heat spreader. (See below)

CPCI2

Each CPCI module has one or few hot components that should fit CCA Frame. The main idea is to dissipate power along the frame to its edges. The main obstacle to provide good cooling solution is chips tolerances: each chip has its surface roughness and flatness. Fastwel modules have adjustable heat spreader part with heat pipes inside for high performance modules.
Stackable approach is another way for conduction cooling application. Modules in such systems are located next to each other, there are no backplanes, and board pitch is 15.24 mm. The most popular form-factors are StackPC and PC/104.
If for PC/104 format, there are no clear guidelines on how to build a stack and how to dissipate power from modules in the middle of the stack. In case of StackPC, there is a common approach to building a stack, which is a considerable advantage of this form-factor.

Stack

As you can see in the picture, the standard heat plates are used (with the same plate shape and fixing method). This makes Stack PC easy to install – just screw wedge locks, easy access to I/O connectors, easy maintenance. Heat plates dissipate the heat along the enclosure. There is a possibility of adding regular modules without heat plates to conduction cooled stack.

Summary: The conduction cooled solutions allow the use of high performance modules in harsh environment  (operation temperature up to +70 ºС). For this reason, these solutions are commonly used for mission critical applications. The two solutions, described in the topic are Compact PCI – serial and Stackable PC systems. Compact PCI is a standard modular system, providing high results; however, there are risks of not optimal heat dissipation in cases when the fit is not perfect. Fastwel addresses this problem with adjustable heat spreader parts. Stack PC is a more flexible and yet standardized solution: the heat plates have the same shape; they are easy to mount and to adjust.

Which systems do you usually use? Please, share your opinions below.

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