The green solder mask PCB circuit board is one of the most common printed circuit boards. The "green solder mask" here refers to the green ink covering that can be seen on the surface of the circuit board. In the industry, it is commonly called a solder resist. The FR4 double-sided green solder mask PCB circuit board means that the base material of the circuit board is made of FR4 material. The green solder mask is actually a protective layer, which is coated on the circuits that don't need to be welded and the base material of the printed circuit board. Besides playing a role in protecting the formed circuit patterns for a long time, it can also prevent the physical disconnection of conductor circuits, avoid short circuits caused by bridging during welding, reduce copper pollution in the solder bath, and prevent the deterioration of insulation and corrosion caused by external environmental factors such as dust and moisture.