Heat = epic fail
Systems must be protected from No. 1 cause of electronic failure - heat, both internal and external
With the continuing push from all rugged systems users for ever smaller and yet more capable devices, thermal management technologies are rising in importance. They always have been an issue for rugged system developers, but with the current emphasis on less costly systems and size, weight and power efficiencies, it’s become one of the most critical items.
It’s not hard to see why, because heat is the No. 1 reason for electronics failures. Rugged systems must be protected from external heat sources because of the environments they need to operate in, but it’s the creation of heat within those systems that has created the need for innovative management techniques.
“You are starting to see some interesting things [in the smaller devices] with regard to thermal packaging and industrial packaging, so you can still maintain a high level of ruggedness without ending up with a 5 pound box,” said David Krebs, director of VDC Research's Mobility & Wireless Practice.
Computer systems now use multiple high-speed cores that pump out a lot of heat. They are hard enough to cool in a regular office environment, let alone in the kind of hostile environment rugged systems have to exist with.
High-end and larger rugged systems use liquid cooling techniques, but that makes everything more expensive and difficult to manage. Smaller systems — which are getting ever smaller — can’t be cooled that way, and the need to close out any ingress panels to guard against dust and moisture more or less does away with using fans to cool things. Also, fans have fairly high failure rates.
“We focus for reliability reason on passively cooled devices,” said Mike Southworth, director of marketing for embedded systems developer Parvus Corp. “These are systems with no moving parts, so you need things such as heat pipes, heat spreaders, special thermal pads and the enclosure itself.”
The key to this kind of cooling is to get the heat into contact with the ambient air in the system enclosure so convection can be used to get it to the outside environment as fast as possible. Using convection alone would be too slow, so other techniques must be used to drive the heat to the surface of the enclosure, from which the heat is then dissipated.
Parvus models the best thermal management designs for each of its systems, using thermal imaging cameras to identify hot spots, measuring the temperatures with thermocouples, and then using computer-aided design software to simulate and model the best ways to manage the heat.
The company recently ruggedized an industrial Ethernet switch from Cisco that provided for very little ingress of dust, moisture and other things, Southworth said, and it had to design an enclosure that was fully sealed so it could be completely dunked in water.
“In that case there needs to be special thermal management to conduct the heat out to metal, so the box itself could be turned into one big heat sink,” he said.
In some systems, particularly smaller handheld devices, the use of ultra-low-power processors such as Intel’s Atom could take care of the need for thermal management. But that poses a problem for many of the applications that users increasingly expect from front-line rugged devices, which can’t run well on these processors. Which means rugged system developers will have to keep coming up with ever smarter ways to handle fast processors - and the heat they produce.