OSP is the abbreviation of Organic Solderability Preservatives. Simply put, OSP is a chemical method to grow an organic film on a clean bare copper surface.This film has anti-oxidation, thermal shock resistance, humidity resistance.It is used to protect the copper surface of the circuit board from being oxidized or sulfurized in the normal environment; but in the subsequent soldering high temperature, this protective film must be easily removed by the flux quickly.The exposed clean copper surface is immediately combined with the molten solder in a very short time to become a strong solder joint.
1、Process flow: degreasing → water washing → micro-etching → water washing → pickling → pure water washing → OSP → pure water washing → drying
2.Principle: An organic film is formed on the copper surface of the circuit board, which firmly protects the surface of fresh copper and can prevent oxidation and pollution at high temperatures. OSP film thickness is generally controlled at 0.2-0.5 microns.
3.Features: good flat surface, no IMC is formed between the OSP film and the copper of the circuit board pad, allowing direct soldering between the solder and the circuit board copper (good wettability), low temperature processing technology, low cost (can be lower than HASL ), Less energy use during processing, etc. It can be used on both low-tech circuit boards and high-density chip package substrates.