Printed circuit board (PCB) design basic knowledge
Printed circuit board (PCB) design basic knowledge
PCB (Printed circuit board, PCB) will appear in almost every kind of electronic equipment. If in a sample devices are electronic parts, then they are inserted in the size of the PCB. In addition to fixed all sorts of small parts outside, the PCB's main function is to provide the above parts of mutual electrical connection. Along with the electronic equipment is becoming more and more complicated, need more and more parts, PCB above line and parts also more and more intensive the. Standard PCB looks like this. Bare Board (above no parts) are often called Printed circuit Board Printed Wiring Board (PWB).
The base plate is board itself by insulating heat insulation, and unyielding material made into. On the surface can see fine line material is copper foil, originally copper foil is covering the entire board, and in the manufacturing process of central by etching disposed, stay part of the network becomes the small line. The line is called the conductor (conductor pattern) or say wiring, and used to provide PCB of spare parts in the circuit connection.
In order to fixed in PCB parts above, we will pick up their feet directly welded on the wiring. In the most basic PCB (single panel), parts were focused on one side, the conductor is concentrated on the other side. Thus we need to make holes in the board, so pin to get through the board to the other side, so parts of the pin is welding on the other side of the. Because of this, the PCB's pros and cons were called parts surface (Component Side) and welding surface (Solder Side).
If PCB above some parts, need to be in production is completed can also take off or put back, so this part will use the install Socket (Socket). Due to the socket is directly welded to the board, parts can be arbitrary dismantling. See below is ZIF (Zero Insertion Force, Zero dial the plug Force type) socket, it can let the parts (here refers to the CPU) can easily plug into the socket, also can tear open come down. Socket by fixed link, can be in you into the parts after the fixed.
If two pieces of PCB interconnections, generally we can use commonly known as the "golden finger" edge joint (edge connector). Gold finger contains many bare copper pad, the copper pad in fact is also a part of the PCB wiring. Usually connection, we will one piece of PCB of gold finger into another slice of PCB appropriate Slot (generally called expansion Slot Slot). In the computer, such as graphics card, sound card, or other similar interface card, it is through the gold fingers and main board connection.
PCB, green or brown, is resistance welding paint (solder mask) color. This layer is insulated protective layer, can protect the copper wire, also can prevent parts are welded to the wrong place. In the soldermask on another will be printed on a layer of silk screen printing surface (silk screen). Usually it will be printed on words and symbols (mostly white), in order to identify the parts in the position of the board. Silk screen printing surface also known as icon surface (legend).
What is the Single panel (Single - Sided Boards)
We have just mentioned, in the most basic PCB, part focused on one side, on the other side of the wire is focused on. Because the conductor appeared only in one side, so we can say this kind of PCB is called a Single panel (Single - sided). Because single panel in the design line there are many strict limit (because only one side, wiring and must not cross between around alone path), so only early circuit to use this kind of board.
What is the Double panel (Double - Sided Boards)
This kind of circuit board of the two sides have wiring. But you have to use both sides of the conductor, both sides must be in between there is proper circuit connection to just go. The "bridge" between the circuit is called the guide hole (via). Guide hole is in the PCB, full of or coated with metal holes, it can be connected with the two sides of the conductor. Because the area of the double side than single panel big times, but also because wiring can each alternative (round to the other side), it is more suitable to use in more complicated than single panel of the circuit.
What is the sandwich plate (Multi - Layer Boards)
In order to increase the area of the wiring can, sandwich plate use more single or double wiring board. Sandwich plate use several piece of double panel, and in each layer board room into a layer after layer stuck fast (bonding). Board layer represents a few layer independent wiring layer, usually layer is even, and contains the most lateral two layer. Most of the main board are four to eight layer structure, but technology can do nearly 100 layers of PCB board. Large super computer mostly used quite layers of main board, but because this kind of computer can be used to replace many ordinary computer cluster, super sandwich plate has been gradually will not be used. Because each layer of the PCB are closely combined, generally not too easy to see the actual number, but if you look carefully the motherboard, perhaps can see.
We have just mentioned guide hole (via), if used in double panel, then is to play in the whole board. But in sandwich plate in the middle, if you want to connect some of the line, then guide hole may waste some other layers of line space. Buried hole (Buried vias) and Blind hole (Blind vias) technology can avoid this problem, because they only through several layers. Blind hole is a few layer internal PCB and surface PCB connection, not through the whole board. Buried hole is connected only internal PCB, so light is from the surface be to look not to come out.
In the multilayer PCB, the whole layer are directly connected with power supply wire. So we will each layer classification for Signal layer (Signal), power layer