Published in Military Embedded Systems
Written by Ivan Straznicky
For critical and intelligent deployed embedded modules, air-flow-through (AFT) cooling describes an approach that brings the coolant much closer to heat-generating electronics than standard conduction-cooled approaches. As a result, compared to conduction cooling, AFT increases the amount of power that can be cooled and decreases device temperatures.
With air-flow-through (AFT) cooling of deployed electronics, air is contained within the closed duct of the module’s heat exchanger, which is separated from the module’s electronics. The interface between the module and chassis requires an air seal to prevent air escape or contaminant ingress. AFT modules are typically thicker than similar conduction modules due to the AFT heat exchanger, which means that mezzanine cards need connectors to the host card with taller mated heights. This arrangement also provides superior cooling to the mezzanine card, because the primary side of the mezzanine is adjacent to the heat exchanger.
In recent years, interest in AFT has gained renewed momentum in the VITA Standards Organization (VSO) and elsewhere. The following AFT standards and/or Working Groups are currently active in the VSO:
- VITA 48.5 Standard (Mechanical Standard for Electronic Plug-in units Using Air Flow Through Cooling) and VITA 48.5 Revision Working Group (Mechanical Standard for VPX REDI Air Flow Through Cooling, Multi-Pitch)
- VITA 48.8 Standard (Mechanical Standard for VPX REDI Air Flow Through Cooling, 1.0” to 1.5” Pitches)
- VITA 48.9 Working Group (Mechanical Standard for Electronic VPX Plug-in Modules Using Air Flow Through Cooling – Retractable Seals)
- The VITA AFT standards provide excellent approaches for thermal management. In addition to the inherent advantages that AFT delivers, system designers also benefit from the VSO’s adherence to open standards, collaboration, rigor, and professionalism in developing the standards.