Dell Inspiron 16 Plus 7640 Owner's Manual page 67

The following image(s) indicate the location of the heat sink and provides a visual representation of the removal procedure.
Figure 40. Removing the heat sink
Figure 41. Removing the heat sink
Steps
1. Disconnect the front-firing speaker cable from its connector (SPK2) on the system board.
2. Remove the front-firing speaker cable from its routing guides.
NOTE: Ensure that the front-firing speaker cable does not obstruct the section of the heat sink.
3. Peel the tape that secures the display-cable latch to its connector.
4. Lift the latch and disconnect the display-assembly cable from its connector (LCD1) on the system board.
NOTE: Ensure that the display-assembly cable does not obstruct the section of the heat sink.
5. In reverse sequential order (7>6>5>4>3>2>1), loosen the seven captive screws that secure the heat sink to the system
board.
6. Lift the heat sink off the system board.
Removing and installing Field Replaceable Units (FRUs) 67