Have you ever noticed that your phone battery dies more quickly when you have a poor signal?
It does.
Maybe you left your phone running while outside of cellular coverage range, like on a boat or plane, and you noticed it got extremely hot and the battery died in short order.
That’s the way cellular radios work. They kick into high gear when coverage is poor, and then they drain the battery and generate a ton of heat.
This is why Apple (NASDAQ: AAPL) tells its iPhone users to use cellular radios less:
“When you use your device to access data, a Wi-Fi connection uses less power than a cellular network — so keep Wi-Fi on at all times.” —Apple, “Maximizing Performance”
GPS in your smartphone is a pretty serious offender in heating up your phone, too. It utilizes its own radio as well as the cellular data connection and leaves the screen on. These three things greatly increase the temperature of your device.
This is problematic for two reasons. Firstly, there is a positive feedback loop between power and temperature.
Take a look at this chart from Broadcom (NASDAQ: BRCM). It shows how an increase in power consumption drives up the temperature, which then cuts back on available power once the threshold is crossed.
Secondly, heat actually does long-term damage to the battery scale and ultimately shortens its life.
In the past, I’ve made the case that battery life and energy management are the central problems with technology today. If these can be improved, technology will make its way into the smallest reaches of our daily lives.
The management of temperature is closely linked to the management of energy, and it is an area with lots of innovation in the mobile realm. It may end up being the area of physical engineering that is most disruptive in the next 10 years.
How Your Phone Does It Today
Since the inside of our mobile devices are so tiny compared to the battery compartment, there isn’t a lot of room for heat sinks. Some devices include vents in the phone chassis for an outflow of hot air, but most devices use three different things for thermal management: heat shielding, heat dissipation, and thermal conduction.
The iPhone, for example, uses heat-dissipating stickers on its logic board and a large metal heat shield that conducts heat away from the processor and batteries.
The problem with techniques like these is that they’re somewhat expensive and relatively inefficient. This is why the iPhone — and really all mobile devices — still get hot during use.
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Innovations
Heat dissipation is done with “spreaders.” These are either solid or semi-solid materials that suck up and dissipate heat.
For two years, Panasonic has made an impressive 10-micron thick Pyrolytic Graphite Sheet (PGS) heat sink for cell phones. It looks like a tiny square of silver paper that weighs nearly nothing, but it offers thermal conductivity twice as high as copper and three times as high as aluminum. It’s rated at approximately 400 degrees Fahrenheit and is actually pretty amazing.
Fujitsu Laboratories recently debuted a new system that provides thermal management for mobile devices. This works more like traditional PC-style liquid cooling systems.
The innovation is that the pipe is less than a millimeter thick, and Fujitsu says it’s capable of moving approximately five times more heat than thermal spreading materials. The pipe is constructed from copper sheets, and the heat passes through the liquid via capillary action and then is passed to a diffusion plate.
Fujitsu’s liquid cooling system for smartphones will be commercialized in 2018, but it seems an unlikely candidate at present, since liquid cooling is not a common practice in mobile device design.
Still, as mobile devices gain power and lose size, energy consumption and thermal pollution is greatly increasing.
Heat could prove to be one of the biggest problems as we move into the generation of wearable and implantable tech.
Good Investing,
Tim Conneally
For the last seven years, Tim Conneally has covered the world of mobile and wireless technology, enterprise software, network hardware, and next generation consumer technology. Tim has previously written for long-running software news outlet Betanews and for financial media powerhouse Forbes.
