Organic Solderability Preservative
Organic Solderability Preservative, or OSP, or preflux is a method for coating of printed circuit boards. It uses a water-based organic compound that selectively bonds to copper and protects the copper until soldering. The OSP uses simple technology with low cost, and that makes it more and more popular among PCB industry. Actually, OSP has a history about 35 years which is longer than SMT. OSP has a variety of advantages, for example, it can be used in a low temperature, its cost is lower than use HASL, less energy is needed during processing, etc. Rosin, active resin and azole are three kinds of materials for OSP, among them azole is the most widely used one.