OSP is the abbreviation for Organic Solderability Preservatives, also known as copper protector. Simply put, OSP is a chemical method that grows a layer of organic film on a clean bare copper surface. This film has oxidation resistance, heat resistance, impact resistance, and moisture resistance, used to protect the copper surface of circuit boards from oxidation or vulcanization in normal environments; But in the subsequent welding high temperature, this protective film must be easily removed by the flux quickly, so that the exposed clean copper surface can immediately combine with the molten solder to form a solid solder joint in a very short time.

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

　　2. Principle: A layer of organic film is formed on the copper surface of the circuit board, firmly protecting the fresh copper surface and preventing oxidation and pollution even at high temperatures. The thickness of OSP film is generally controlled between 0.2-0.5 microns.

　　3. Features: Good flatness, no IMC formation between OSP film and copper on circuit board solder pads, allowing direct welding of solder and circuit board copper during welding (good wettability), low-temperature processing technology, low cost (can be lower than HASL), low energy consumption during processing, and so on. It can be used on both low tech circuit boards and high-density chip packaging substrates.

　　4. OSP material types: Rosin, Active Resin, and Azole.

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