6 Fabrication
6.6 Surface finish

The Surface Finish is the most important step in the process between PCB manufacturing and PCB assembly with two main functions, one of which is to preserve the exposed copper circuitry and the other of which is to provide solderable surface when soldering components to the PCB. Surface finish is located at the outermost layer of PCB and above copper, playing a role as a "coat" for copper. There are different type of surface finish, each one has a different purpose (depending on where the PCB has to work and assembly process requirements) and also has a different application method. The most popular are: ENIG (Electroless Niquel Immersion Gold), OSP (Organic Surface Protection), HASL (Hot Air Leveling), Immersion Silver and Immersion Tin.