PCB board surface is usually painted

Do friends have noticed that the surface of the PCB board is painted on the surface of the board in daily life, why should the board be painted? Let's talk about the reasons.

    First of all, both sides of the PCB are copper layers. In the production of PCBs, the copper layer is manufactured by addition or subtraction, and finally a smooth and unprotected surface is obtained. Although the chemical properties of copper are not as active as aluminum, iron, magnesium, etc., in the presence of water, pure copper and oxygen are easily oxidized; because of the presence of oxygen and water vapor in the air, the surface of pure copper is in contact with air. The oxidation reaction will occur soon. Since the thickness of the copper layer in the PCB is very thin, the oxidized copper will become a poor conductor of electricity, which will greatly impair the electrical performance of the entire PCB.

    In order to prevent copper oxidation, and to separate the soldered and non-welded parts of the PCB during soldering, and to protect the surface of the PCB, engineers invented a special coating. This coating can be easily applied to the surface of the PCB to form a protective layer with a certain thickness and to block copper and air contact. This layer of coating is called a solder mask and the material used is a solder resist.