The green part is called solder resist. These components are resin and pigment, and the green part is green pigment, but with the development of modern science and technology, many other colors have been extended. It is no different from decorative paint. Before soldering is printed on the circuit board, solder resist is pasted and flowed. After printing on the circuit board, the resin will harden due to heating and eventually "cure". The purpose of resistance welding is to prevent the circuit board from moisture, oxidation and dust. The only place not covered by solder resist is usually called pad, which is used for solder paste.
Generally speaking, we choose green because it does not irritate our eyes. It is not easy for production and maintenance personnel to stare at PCB for a long time. In design, the commonly used colors are yellow, black and red. All colors are paints sprayed on the surface after they are made.
Another reason is that the commonly used color is green, so the factory has the most spare green paint, so the cost of oil is relatively low. This is also because different wiring is easier to distinguish from white when repairing PCB, while black and white are relatively difficult to see. In order to distinguish its product grades, each factory uses two colors to distinguish between high-end series and low-end series. For example, ASUS, a computer motherboard company, has a low-end yellow board and a high-end blackboard. Yingtai's backboard is high-end and the green board is low-end.
1. There are signs on the circuit board: the beginning of R is a resistor, the beginning of L is an inductor (usually the coil is wound around the iron core ring, and some shells are closed), and the beginning of C is a capacitor (a tall cylindrical capacitor with cross-indentation on it and a flat chip capacitor), the other two legs are diodes, three legs are triodes, and many legs are integrated circuits.
2. SCR UR; The control circuit has a rectifier VC with power supply; Inverter uf; Converter UC; Inverter ui; Motor m; Asynchronous motor ma; Synchronous motor ms; Dc motor MD; Wound rotor induction motor MW; Squirrel cage motor MC; Electric valve ym; Electromagnetic valve YV, etc.
