Why do PCB circuit boards need surface treatment

　　The core purpose of surface treatment for PCB circuit boards is to protect copper foil circuits from oxidation and corrosion, improve soldering reliability and conductivity, and enhance the environmental resistance of circuits, ensuring stable operation of circuit boards throughout the entire production, storage, and use cycle. The specific reasons and effects are mainly as follows:

　　The conductive core of PCB to prevent copper foil oxidation is copper foil. Exposed copper is easily oxidized in air, moisture, or acidic or alkaline environments, forming a non-conductive copper oxide layer. The oxide layer can directly lead to poor contact of the circuit, welding failure, and even cause short circuits or open circuits in the circuit. Surface treatment will form a dense protective film on the surface of copper foil, isolating copper from contact with the external environment and avoiding oxidation problems at the root.

　　When assembling circuit boards to improve soldering performance, it is necessary to connect component pins to solder pads through soldering, and good wetting is the key to reliable soldering. Untreated copper surfaces have poor wettability, making it difficult for solder to spread evenly and prone to defects such as virtual soldering and false soldering. The surface treatment layer (such as hot air leveling, chemical nickel plating, etc.) can enhance the bonding force between the solder pad and the solder, allowing the solder to quickly spread and form a firm solder joint, reducing the rate of welding defects.

　　Enhanced environmental and wear resistance: Some PCBs are applied in harsh environments such as high humidity, high salt spray, and high temperature (such as industrial control equipment and automotive electronics). The surface treatment layer can improve the corrosion resistance and wear resistance of the circuit board, extending its service life. At the same time, the processing layer can also enhance the hardness of the PCB surface, avoiding physical damage such as scratches and wear during subsequent processing or use.

　　Optimizing surface treatment processes with different electrical performance can improve the electrical characteristics of PCBs in a targeted manner. For example, electroless nickel gold (ENIG) plating has good conductivity and low contact resistance, making it suitable for connector pads or key contacts that require frequent insertion and removal; Organic solder mask (OSP) can maintain the flatness of the copper surface and is suitable for high-density, fine pitch component packaging processes.

　　To meet the production process requirements, PCB manufacturing requires multiple processes such as cleaning, baking, and film coating. Surface treatment can improve the adhesion of the copper surface and avoid the detachment of dry films, solder mask layers, etc; At the same time, some processing techniques (such as silver deposition and tin deposition) can improve the heat resistance of PCBs, meeting the requirements of high-temperature soldering processes such as reflow soldering and wave soldering.

　　Common PCB surface treatment processes include organic solder mask (OSP), hot air leveling (HASL), electroless nickel gold plating (ENIG), silver deposition, tin deposition, etc. The cost, performance, and applicable scenarios of different processes vary, and should be selected according to the application needs of the PCB.