The overall functionality of a PCB board depends upon the conductivity of copper tracks. These tracks tend to oxidize when exposed to the atmosphere, and creates problems when soldering during component placement. OSP or Organic Solderability Preservative does two things in PCB supplier china: temporarily protect exposed copper from being oxidized and improves solderability before component fixation (assembly).

OSP creates a very thin (100-4000 Angstroms) organic coating on the PCB board, which is a water-based chemical compound of ‘Azole family’ such as benzotriazoles, imidazoles, and benzimidazoles. This compound gets absorbed by the exposed copper and generates a protected film to prevent oxidization.

Advantages of OSP in PCB supplier china:
Low cost
Environment-friendly
Re-workable, but can’t take more than 2-5 rounds of reflow soldering before degradation
It is lead-free and can handle SMT components easily
It provides a coplanar surface, well suited for tight-pitch pads (BGA, QFP).

Disadvantages of OSP in PCB supplier china:

Not Good for PTH (Plated Through Holes)
Short Shelf Life, less than 6 month
Inspection is difficult as it is transparent and colorless
requires careful handling, as it’s susceptible to mechanical damage
OSP Surface Finish Process:

The OSP finishing process is composed of three major steps, including pre-cleaning and making the PCB board ready for smooth OSP coating application:

Clean: Organic contaminants such as oil, fingerprints, oxidation film etc. are removed to get a clean PCB board.
Topography Enhancement: To improve the bonding forces between exposed copper and OSP film, micro-etching is performed to minimize the oxidation generated on copper.
Deionization Rinse: Before final OSP application, the OSP solution is populated by ions so that it can be eliminated easily during soldering.