D630 - Processor Thermal Cooling Assembly - how tight should it be?

I have removed the thermal assembly from my D630.

Cleaned it

Replaced the processor.

Now I am ready to reassemble.  (It has the Intel graphics chip FWIW).

The thermal assembly is spring loaded... how tight should I tighten the screws?  Should I tighten the screws until they bottom out, just engage.... how tight is too tight? What happens if I overtighten?

THANKS!