You
are ready to spend over $200 plus a 2-year contract for the latest smartphone with
a much higher hardware standard. But should you? The newest ads claim
that the quad-core processors will ensure a much faster user experience. But
the truth is smartphones are not designed to operate at full capacity without
overheating.
An interesting test on Google Nexus 4
smartphone published by Anandtech showed one of the important issues that the
smartphone companies face. They tested the device in a freezer and in a room at
standard temperature. The performances in video gaming are benchmarked, which
almost doubles in the freezer. According to their test, the smartphone operates
at a reduced frequency when it is hot, which is then like driving a Lamborghini
along with the jammed traffic. It has been rumored that the major smartphone
companies are looking into the potential application of “liquid cooling” techniques
to help avoid this issue.
Actually,
the heating problem is well acknowledged by the industry. It is a barrier that
hinders the performance boost of all “computers”, including smartphones. One fact
is that the heat flux generated by today's microprocessors is loosely
comparable to that on the Sun's surface. But the chip temperature has to be
kept below 100 ⁰C. The situation for smartphones is more challenging. No one
wants to hold even a 50 ⁰C cellphone in hand.
The problem with
smartphones, unlike normal computers, is that they don’t have fans inside. “A
simple model can show the maximum heat dissipation rate is around 3 Watts, even
at ideal conditions,” according to Rui Mao who has studied heat managing
materials in electronic devices for more than 5 years. The power of a typical cutting
edge microprocessor for smartphones at its full load is roughly the same or
even larger. This means that the claims about smartphone performance are vastly
overstated.
What
makes the situation worse is that the heat is not evenly distributed in the
smartphone. Leyden Energy imaged the temperature at the back of a smartphone
loaded with demanding apps. The region where the microprocessor locates reaches
a peak temperature twice as high as that at the edges. The traditional approach
of using graphite and foil radiator to transfer the heat to the outer casing
seems to be out-paced by the processors, according to several comments on the liquid-cooled phones. The liquid-cooling technology uses heat pipes to
help spread the heat from the processor. It is already widely implemented in
ultrabooks and NEC has launched the world’s first smartphone (Medias X06E which is only available in Japan)
with ultra-thin heat pipes. It is rumored that other major player in the market
like Apple, Samsung and HTC are also not far from adopting this technology.
A
heat pipe used in electronic devices normally consists of a sealed pipe made of
copper and filled with working fluid. The fluid evaporates at the hot end and
condensate at the cool end in each heat transfer cycle. Although this is a
mature technology in computers and even tablets, there are still practical
challenges to fit the thickness within 1 millimeter for smartphones. The
present yield for 0.6 millimeter heat pipes is only 30%, but DigiTimes is still
optimistic for more products to hit the market in 2014.
While
waiting for the companies to deliver us new phones armed with this liquid cooling
technology, we shall bear in mind that no single technique makes a smartphone
stand out. Facilitating heat dissipation is one thing; reducing heat generation
is another, plus the ever increasing demand on performance. The smartphone is a
complex system. Perhaps, looking behind the advertisement could help you make a
wiser choice.
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