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Principle and introduction of OSP surface treatment process of PCB board

April 25, 2022

Principle: An organic film is formed on the copper surface of the circuit board, which firmly protects the surface of fresh copper and prevents oxidation and pollution even at high temperatures. The thickness of OSP film is generally controlled at 0.2-0.5 microns.


1. Process flow: degreasing → washing → micro-etching → washing → pickling → pure water washing → OSP → pure water washing → drying.


2. OSP material types: rosin (Rosin), active resin (Active Resin) and azole (Azole). The OSP material used in Shenzhen Link Circuit is the azole OSP that is currently widely used.


What is the surface treatment process of PCB board OSP?


3. Features: good flat surface, no IMC is formed between the OSP film and the copper of the circuit board pad, allowing direct soldering of the solder and the circuit board copper during soldering (good wettability), low-temperature processing technology, low cost (low cost) (In HASL), less energy use during processing, etc. It can be used on low-tech circuit boards and high-density chip packaging substrates. The deficiencies of PCB proofing U-Customer board are: ①The appearance inspection is difficult, and it is not suitable for multiple reflow soldering (generally three times); ②OSP film surface is easy to scratch; ③High storage environment requirements; ④Short storage time.


4. Storage method and time: 6 months in vacuum packaging (temperature 15-35℃, humidity RH≤60%).


5. SMT site requirements: ①OSP circuit boards must be stored in low temperature and low humidity (temperature 15-35℃, humidity RH≤60%) and avoid exposure to acid-filled environments. OSP packaging must be assembled within 48 hours after unpacking ; ② It is recommended to use it within 48 hours after single-sided parts, and it is recommended to store in a low-temperature cabinet instead of vacuum packaging; ③It is recommended to complete the DIP within 24 hours after the completion of SMT on both sides.