Will trends in open-systems standards usher-in increasing use of liquid cooling in embedded computing?

Jan. 26, 2023
The SOSA standard doesn't aim at creating new design guidelines, but instead seeks to incorporate as many existing industry standards as possible.

CHANDLER, Ariz. – Electronics cooling and thermal management for high-performance electronics in aerospace and defense applications is as big and as daunting an issue as it's been for years. Not even new generations of open-systems standards like the Sensor Open System Architecture (SOSA) are expected to provide much relief.

Next-generation RF and microwave components, multicore general-purpose central-processing units (CPUs), general-purpose graphics-processing units (GPGPUs), and field-programmable gate arrays (FPGAs) will run hotter than ever before, and will up the ante for electronics systems designers who must deal with the extra heat.

Still, despite SOSA's apparent inability to provide thermal-management relief for current and future generations of embedded computing, don't expect innovations in electronics cooling to slow at all; in fact, the galloping pace of electronic components development is likely to spur new innovations as enabling technologies move forward.

First off, SOSA probably isn't the place to look for encouraging new developments in electronics thermal management. SOSA is many things to many people; it's intended to reduce development and integration costs for military electronics capabilities and reduce time to field. Yet the new standard doesn't aim at creating new design guidelines, but instead seeks to incorporate as many accepted industry standards as possible.

Related: Thermal management for high-performance embedded computing

SOSA, for example, has adopted the OpenVPX standard of the VITA Open Standards, Open Markets trade association in Oklahoma City. SOSA has begun adopting the U.S. Army's Vehicle Integration for C4ISR/EW Interoperability (VICTORY) standard, industry experts say, and is expected to adopt additional standards in the future. SOSA adopts standards; it doesn't develop them. That's the job of organizations like VITA, and that's where systems designers should look for innovations in electronics thermal management.

"SOSA is not an innovator of future cooling systems," points out Bill Pilaud, director of systems architecture at embedded computing systems specialist LCR Embedded Systems in Norristown, Pa. "VITA will be the one to innovate in modular cooling." Pilaud made his comments in a presentation in January at the Embedded Tech trends conference in Chandler, Ariz.

VITA -- an organization of experts from the embedded computing industry who share common goals -- is where many embedded computing open-systems standards are hammered-out. SOSA has adopted many VITA standards concerning computer boards, backplanes, and high-speed interconnects, and can be expected to adopt thermal-management standards from VITA as they come out. VITA standards also are reviewed and adopted by the American National Standards Institute (ANSI) in Washington.

VITA thermal-management standards are encapsulated in VITA 48, and industry thermal-management best practices guidelines are part of VITA 50. These standards essentially lay out design approaches for air-, conduction-, and liquid cooling, which involve various levels of complexity, reliability, and cost.

Related: Is thermal management up to the high-performance computing challenge?

ANSI/VITA 48.1, for example, describes mechanical requirements for air-cooled 3U and 6U boards. ANSI/VITA 48.2 describes ways to cool conduction-cooled 3U and 6U boards. ANSI/VITA 48.5 defines air flow-through cooling that uses a compact core heat exchanger inside the central heat sink of the unit. ANSI/VITA 48.7 defines air flow-by cooling that convectively cools boards without exposing electronic components to the cooling air. ANSI/VITA 48.8 describes air-flow-through that uses a finned heat exchanger frame inside the enclosure to top-cool primary circuit board and mezzanine board components.

Liquid cooling approaches are defined in ANSI/VITA 48.4 concerns liquid flow-through cooling that uses liquid that flows through an integral heat sink of the board to carry away excess heat efficiently. It is the liquid-cooling approach that scares away many designers because of is reputed high costs and questionable reliability. The future should see more liquid cooling by necessity -- primarily for the most high-performing and hot-running boards.

For these high-performance systems, "my intuition says it all will be liquid cooling; imaging the cooling requirements of a 650-Watt single-board computer," says LCR's Pilaud. Other experts agree. "There will be more open-ness to going to liquid cooling, where in the past it used to be only a last resort," says Justin Moll, vice president, sales at marketing at embedded computing enclosure and backplane specialist Pixus Technologies in Waterloo, Ontario.

About the Author

John Keller | Editor-in-Chief

John Keller is the Editor-in-Chief, Military & Aerospace Electronics Magazine--provides extensive coverage and analysis of enabling electronics and optoelectronic technologies in military, space and commercial aviation applications. John has been a member of the Military & Aerospace Electronics staff since 1989 and chief editor since 1995.

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