In general, the more complex the functionality of the electronic product, the longer the loop distance, the more layers PCB will require.The board is made of insulated and non-bendable material. In order to fix the parts on the PCB, we place their pins directly on the wiring. If there are certain parts need to be removed or installed after the production, then the part will be installed when the socket. As the socket is directly soldered to the board, the parts can be arbitrarily disassembled.
If you want to link two PCBs, we generally use "golden finger" edge connector. Gold finger contains a lot of bare copper mat, these copper mat is actually part of the PCB wiring. Usually,we will connect the gold finger from one PCB into the appropriate slot (commonly known as the expansion slot Slot) on another piece of PCB. In computer, such as graphics cards, sound cards or other similar interface cards, are through golden finger to connect with the motherboard.