I FOUND THIS ITEM OF INTEREST FOR YOU.
HOPE IT CLEARES THINGS UP.
What is on the bottom of your cpu is a thermal 'pad.'
These arn't very good, because when the cpu gets hot the pad melts to cover up any imperfections between the cpu and heatsink so there can be a good heat transfer.
Only problem is, the damn pad acts like superglue as well, so when you want to take your cpu out of the socket/take the hsf off, they both come off together, my cpu got ripped out of the socket due to a thermal pad!!!
I would invest in getting thermal paste.
However AMD will say if the thermal pad is damaged replace it with another AMD reccomended thermal paste/pad otherwise you risk having your warrenty voided.