Stefan Mileschin

The Phison E21 controller paired with Micron’s 176-layer TLC NAND does result in a good mainstream drive in terms of performance, even surpassing Silicon Power rated speeds, which operates at decent temperatures in normal operation. However, if your projects do imply writing very large sequences of data at once, the drive will heat up to about 80 degrees Celsius while using the stock thin graphene heatspreader. In that case, we will surely recommend a custom heatsink or simply installing the drive on a motherboard with an integrated cooling system.

http://www.madshrimps.be/articles/article/1001386/