Also PCBs are made from fiberglass, so if there's silicon around the chips something is terribly wrong because only the chip die itself, nestled inside the IC package, is silicon.
The thermal paste is Arctic Alumina, nonconductive ceramic thermal compound.
Yay, another designer that actually uses something that's not bulk Chinese thermal paste that comes in 1kg packages

Did you use the same compound on the Gekkoscience Compacs? Been wondering for a long time what goop you put on those ASICs.