ADLINK cExpress-BT2 - Manual (Page 71)

cExpress-BT2 Page 71
Step 3: Assemble the heatsink onto the COM Express module.
Use the four M2.5, L=6mm screws provided to fasten the heatsink to the module.
Step 4: Place the COM Express module and heatsink assembly onto the connectors on the carrier board as shown.
Then press down on the module until it is firmly seated on the carrier board.
Step 5: Use the five M2.5, L=16mm screws provided to secure the COM Express module to the carrier board from the solder side.