CPUs such as this shouldn't be using a thermal pad, they just aren't conductive enough, it will be okay if the CPU isn't using much power, but if something ramps it up it is likely to get hotter than it should and could start thermal throttling much sooner.
Thermal paste is only intended to fill the almost microscopic pits and gaps when two metal surfaces touch, you should really only need the smallest amount, and the interface between CPU and heatsink should be a good amount of metal to metal contact for the best conductivity. So when they ship these things with a huge amount of thermal grease trying to bridge any sort of gap, is just poor, and they basically don't care. It will probably work for a bit, but thermal cycling will mean the paste will end pulling apart or drying out leaving a gap. Adding extra copper shims helps but adds more 'resistance' to the heat transfer. If you are going to add a shim, it is better to add between the copper slug and the case/heatsink, this way it can be screwed down well for the best contact, and the metal slug is then directly on the CPU which helps to quickly get the heat away from the CPU die.
As we are finding, these things are just being flooded out of China, if they work its more luck than anything, if they fail in a year or two no one is going to go to the trouble of sending it back and any legal consumer rights we might have are impossible to enforce against these Chinese companies.
Cavet emptor
