OSP differs from other surface treatment processes in that it functions as a barrier layer between copper and air; in short, OSP is a chemically grown organic film on a clean bare copper surface. This film has anti-oxidation, thermal shock resistance, and humidity resistance to protect the copper surface from rusting (oxidation or sulfurization) in the normal environment. At the same time, it must be easily assisted in the subsequent welding high temperature. The flux is quickly removed for soldering. An osp pcb is an organic solderability preservative board.
The general process is: degreasing-> micro-etching-> pickling-> pure water cleaning-> organic coating-> cleaning. The process control is relatively easy compared to other methods.
Currently, about 25% -40% of PCBs use organic coating processes, and this proportion has been rising. The organic coating process can be used on low-tech PCBs as well as on high-tech PCBs, such as single-sided TV PCBs and high-density chip packaging boards. For BGA, there are more organic coating applications. If the PCB does not have surface connection functional requirements or storage period limitations, organic coating will be the most ideal surface treatment process.