Aaeon SBC-555 Manual page 22

To install the CPU, follow the instructions that came with it. If no
documentation was provided, the general procedures for installing
a CPU are outlined below:
1. Lubricate the pins on the CPU with lubricant for PGA devices.
This makes the CPU slide in much easier and greatly reduces
the chance of damaging the pins and other components.
2. Carefully align the CPU so that it is parallel to the socket.
Make sure that the notch on the corner of the CPU matches
the notch on the inside of the socket.
3. Gently push the CPU into the socket. There will probably be a
small gap between the CPU and the socket even when it is
fully seated. DO NOT USE EXCESSIVE FORCE!
When you install a new CPU, you may have to adjust other
settings on the board, such as CPU type, CPU clock, and PCI
speed, to accommodate it. Make sure that the settings are correct
for your CPU. Improper settings may damage the CPU.