This is crazy, the CPU is under the RAM chip (step 9). Is this kind of layout frequent? I guess you can't have a high power (and high heat dissipation)...
You can still sink a lot of heat under the chip through the PCB, and you can still put a thermal sink on top. But yeah, these packages need to run pretty cool. This particular CPU runs at 1.8V now.
See: http://en.wikipedia.org/wiki/Package_on_package