Lenovo ThinkCentre M90n-1 Hardware Maintenance Manual page 78

Avoid contact with the hot computer. During operation, the computer becomes hot enough to burn the skin.
Before you touch the computer, turn off the computer, disconnect power, and wait approximately 30 minutes
for the computer to cool.
Replacement procedure
1. Remove the bottom cover. See "Bottom cover" on page 67.
2. Peel off the thermal pad and the absorber from the wireless WAN card.
3. Remove the wireless WAN card.
72
M90n-1 Hardware Maintenance Manual