Although it was known in the Android community from other high-end smartphones already released this 2015 year that the Qualcomm Snapdragon 810 suffered of overheating in their first die revision (you can take a look to my previous article) it seems that Sony decided go ahead with it in their latest high-end Xperia Z5 family.
Although not mentioned, it is most than probably that Sony is using the die revision 2.x of it, which suffers lower over heating but anyhow noticeable by the user if you use the SoC at maximum throttle (as gaming).
However, it looks like Sony decided to introduce some extra thermal dissipation techniques coming from higher size consumer electronics equipment or computers; more complex but also efficient to spread the heat along the phone, instead of a single heat sink point above the SoC.
In next pictures you can see how Sony added a couple of thermal copper heap pipes connected to a bigger heat sink and even thermal paste on top of the SoC, which makes more complex (and expensive) the inners and assembly of the Z5 phones family, but less noticeable to the user when the SoC warms up:
And for the Z5 Premium:
Of course, these kind of techniques are not very usual in high integrated smartphones due the higher manufacturing costs, labor time and lower reliability at long term. I assume that Sony Mobile R&D team had to make some trade-off’s this year to be able to release a newer Z family member with higher specs (currently 810 v2.1 is the highest, while the 820 is ready to be released) able to compete with the strong competition coming from China (as the OnePlus, Huawei, Meizu, Mi, Lenovo/Motorola), Korea (Samsung/LG) and for sure, Apple with their iPhones.