Remove The Upper Case - Lenovo IdeaPad S540 Series Hardware Maintenance Manual

Figure 22. Remove the system board
Go to
https://support.lenovo.com/partslookup
part:
System board

Remove the upper case

Make sure the following FRU (CRU) has been removed.
"Remove the lower case" on page 28
Step 1. Disconnect the battery pack cable and remove four screws.
Attention: Do not pull the cable. Use your fingernail to disconnect the cable.
to look up the Lenovo part number of the following replacement
.
Chapter 4 Removing a FRU or CRU
41