As military programs continue to place an ever growing reliance on embedded computer systems, developments in rugged computer design must continue to advance to keep pace with this demand. This can be accomplished by understanding how individual elements in rugged designs are critical to ensuring a system can perform in harsh environments.Among the many elements composing rugged system engineering are thermal management and cableless design. Examining these individual ruggedization techniques will provide better understanding into the role they play to ensure the most durable systems possible.
With heat issues often credited as the largest contributor to system failures, designing rugged systems to meet these thermal challenges is critical. The key to successful thermal design is getting heat into contact with ambient air for convection to the external environment as quickly as possible. By implementing a variety of thermal management techniques, heat can be dissipated fast enough to prevent a phenomenon known as thermal runaway. Thermal runaway is an increase in temperature that changes the conditions in such a way that causes exponential temperature increases, ultimately leading to destruction.
Relying on convection cooling inside a system has its limits as heat passes rather slowly (high thermal resistance) to the surface of the chassis where it can be dissipated. However, advancements in conduction cooling have had a tremendous impact on rugged system design. For example, custom-designed clamshell heat sinks can be fitted to encapsulate each printed circuit card assembly, using wedge locks as the contact point with the card stack to dissipate heat more quickly (lower thermal resistance) to the chassis. The clamshells, which essentially work as heat spreaders, and the thermally conductive gap pad significantly reduce thermal issues.
Heat spreaders are also being designed to accommodate a number of thermal options, such as top-mounted heat sinks, fan heat sinks and heat pipes to effectively cool microprocessors. Innovative heat pipe/heat spreader combinations are proving especially effective in the thermal management of stand-alone rugged boxes.
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