I'm really lost since I've never encountered anything like this...: Just applying thermal paste and the cooler seems to damage the CPU without it being ever turned on before.
Processor: Ryzen 7 1700
Cooler: Mugen 5
Thermal Paste: Arctic MX-2
Steps to reproduce:
Apply (a little) too much thermal paste
Gently screw the cooler on top
Pull it off again
Observe the result, notice the effect only is on the sides of the heat spreader, not on top!
The amount of thermal paste applied correlates with the erosion(?) on the CPU. I actually had a similar problem before but didn't notice it til the PC suddenly died. I shipped the CPU back and got it instantly RMA'd. Now I usually am someone who wants to find the error here, so I did every step that I usually do and after every step more than before observed the CPU again. And I noticed the same effect that I could see with the "broken" CPU was with this one -- without ever turning it on. Just applying thermal paste and (some) pressure results in this erosion. I honestly don't know what to say. Is this expected and no "problem" and the old CPU just died for some other reason? Did anyone ever encounter this symptom too?