Maßgebende Aspekte beim Thema Thermal Management

By Alix Paultre

It seems that thermal-management issues are constantly cropping up in consumer electronics, plaguing manufacturers of products from game consoles to tablets to phones. Some issues involve devices that are “merely” unpleasantly hot (which tells me that it won’t be very happy in a hot ambient), but other cases involved catastrophic thermal runaway (a fancy way of saying that the device burst into flames). What is wrong with this picture? Doesn’t anyone remember that proper device design also involves proper thermal management?

Current moving through a circuit cannot do so without some loss, and that loss is expressed as waste heat. Even if an entire device was made up of Impossibilium chips on a Stupendium substrate and was a superconductor at room temperature, the work performed in the semiconductors themselves (not to mention motors, MEMS, or transducers) would generate waste heat that would have to be dissipated. People like Alex Lido have been lecturing us on increasing semiconductor thermal issues and the problems of component density for over a decade now, and heat-exchange technology is actually pretty sophisticated.

Why do so many products have thermal issues?

Market pressure

Everyone wants to have the “it” device, or at least the product that everyone who can’t get the “it” device winds up buying. In the consumer space, that often involves size. Designers are being forced to compromise on thermal management in a race to the tiny. If just a few millimeters of a design included additional thermal management – heat pipes, heat sinks, micro air channels for thermal vias, etc. – were incorporated into a design we would have far fewer stories of people burning or discomforting themselves with their electronics. In some cases, users were accused of using their devices in an “inappropriate ambient”, a fancy way of saying that the device can’t operate well in warm places. We all know that the customer dictates the design, but the industry needs to be more upfront about basic thermal issues and the need to address them properly in a device.

Unknown situations

Interestingly enough, products made for markets other than consumer aren’t impacted as heavily by thermal issues, as markets such as commercial and industrial (not to mention automotive and Mil/Aero) do have guidelines, both formal and informal, on thermal management and other important performance characteristics. This is because there are serious business consequences when your product does not perform and your business depends on it (or in the case of Mil/Aero, often your life). For example, recently here at GlobTek we had an RFID power application where the client was concerned about the power supply’s thermal management in the thinner air of an aircraft cargo hold. Less-dense air has a lowered ability to capture and move heat, challenging cooling systems designed for sea-level air densities and thermal characteristics. GlobTek addressed the customer’s need by ensuring that the cooling system in the power supply was able to function at altitudes as high as 9500 feet (2950 meters). The power supplies were altitude-tested to ensure they met the customer’s requirements.

Sometimes a thing is just broke. Some designs miss something, like the nature of the ambient environment, or storage issues, or ergonomic device issues where unforeseen user situations could block vent holes, cover heat sinks, or add waste heat from peripheral devices. Many of these issues aren’t really a manifestation of poor design, just one that may not have been thought out for all possible operating modalities (although the less charitable would still call that poor design). A device that is intended for consumer use should meet environmental requirements that must take into consideration the fact that people take their stuff everywhere. The current generation growing up only releases the death grip on their smartphones when they need to use the other hand for something important.

Leave a little space

There are new thermal-management methodologies available now, as well as older technologies given new life due to new core technology. Improved heat spreaders, novel use of materials and package designs, and better design and modeling can ensure that any device released into the market can perform in any environment that can support human life. We need to both implement the best thermal management as well as push back on pressures to compromise design to gain marketing points or bragging rights. The fact is that devices are now more and more driven by user ergonomics and software applications than device size limitations anyway, and one should not sacrifice device reliability and user experience in a pursuit of product selling points.

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