The basic knowledge of printed circuit board (PCB)

Printed circuit board (PCB) almost appear in every electronic device. If there is electronic components in some kind of device, they also be mounted on various sizes of PCB. Except fixing these varieties of small sparts, the main function of PCB is to provide electrical connection for sorts of PCB parts to each other. As the electronic equipments become more complicate and require more spares, the circuits and spares on PCB also become more and more intensive. Standard PCB look like this. Bare board (without any top spares) is also often to be called Printed Wiring Board (PWB). 

The baseboard itself is made of insulate and inflexible materials. The tiny circuit material on the surface which can be seen called the copper foil. Oringinally copper foil is covering the entire board, but some parts of them were etched during manufacturing process, the left parts become tiny circuits like mash lines. These circuits are called conductor pattern or PCB layout, and used to provide electrical connection for PCB components.

For fixing the parts on the PCB, we weld their pins on the wiring directly. For a basic PCB (single-panel), all components were concentrated on the one side, and wirings were concentrated on the other side. As such, we need punch holes on the board, for pins to get through to the other side of the board, so pins of components were welded on the other side of the board. Because of it, the front side and back side of PCB are called Component Side and Solder Side.

If there is a certain part on PCB need to be removed or put back after the production is completed, socket will be used when the component mounting. Because the socket is soldered directly on the board, the parts can be any disassembly. See below is ZIF (Zero Insertion Force, zero-pluggable power type) socket, which allows parts (here refers to the CPU) can be easily inserted into the socket, also can be removed. Fixed pole near socket can be fixed after you inserted into the socket.

If you interconcet two PCBs, generally we will use the edge conncetor of known as "Goldfinger". Goldfinger contains many bare copper pads, in fact these copper pads are also one part of PCB routing. Normally, when connection we will put the gold finger from one PCB inserted into the appropriate slot from another piece of PCB (commonly called expansion slots). In the computer, such as graphics cards, sound cards, or other similar interface cards, are connected to the motherboard by the gold finger. 

Green or brown on the PCB is solder mask color. This layer is an insulating protective layer can protect the copper, the parts can be prevented from being welded to the incorrect place. Besides, a silk screen layer will be printed on the solder resist layer. Usually there will be printed some text and symbols (mostly white) to mark out the position of the parts on the board. The silk screen is also called legend.