Dell Inspiron 13z (N311z, Mid 2011) - Manual (Page 64)

64 Processor Heat Sink
5 Remove the heat-sink assembly from the system board.
Replacing the Heat-Sink Assembly
NOTE: The original thermal pad can be reused if the original processor and
heat sink are reinstalled together. If either the processor or heat sink is replaced,
use the thermal pad provided in the kit to ensure that thermal conductivity is
achieved.
NOTE: This procedure assumes that you have already removed the heat-sink
assembly and are ready to replace it.
1 Follow the instructions in "Before You Begin" on page 9.
2 Align the three captive screws on the heat-sink assembly with the screw
holes on the system board and tighten the screws in sequential order as
indicated on the processor heat sink.
1 heat-sink assembly 2 captive screws (3)
3 system board
1
2
3