OSP is Organic Solderability Preservatives.
OSP is to grow a layer of organic skin film on the clean bare copper surface by chemical method. The film has oxidation resistance, heat shock resistance and moisture resistance, which is used to protect the copper surface of circuit board from oxidation or vulcanization in normal environment. However, in the subsequent welding high temperature, the protective film must be easy to be The flux is removed rapidly, so that the exposed clean copper surface can be combined with the molten solder in a very short time to form a solid solder joint.
1. Process flow: oil removal → water washing → micro etching → water washing → acid pickling → pure water washing → OSP → pure water washing → drying.
2. Principle: an organic film is formed on the copper surface of the circuit board to firmly protect the fresh copper surface and prevent oxidation and pollution under high temperature. The thickness of OSP film is generally controlled at 0.2-0.5 micron.
3, Features: smooth surface, there is no IMC formation between OSP film and PCB pad copper, allowing direct soldering of solder and PCB during welding (good wettability), low temperature processing technology, low cost (less than HASL), less energy consumption during processing and so on. It can be used on low technology circuit boards as well as on high density chip packaging substrates.
4. OSP material types: rosin, active resin and azole. The OSP material used in deep circuit is the most widely used azole OSP.
5. Insufficient:
① The appearance inspection is difficult, so it is not suitable for multiple reflow welding (generally three times);
② OSP film surface is easy to be scratched
(3) Higher storage environment requirement.
(4) the storage time is short.
6, storage mode and time: vacuum packaging for 6 months (temperature 15-35 degrees, humidity RH < 60%);
7. SMT site requirements:
(1) OSP circuit boards must be stored at low temperature and low humidity (temperature 15-35 degrees C, humidity RH = 60%) and avoid exposure to acid gas flooded environment. OSP packaging will be assembled within 48 hours after unpacking.
② It is recommended to use it within 48 hours after single side loading, and it is suggested to use low temperature cabinet for storage instead of vacuum packaging;
(3) when SMT is completed on both sides, it is recommended that DIP be completed within 24 hours.
