2.Organic Solderability Preservatives(OSP)
The general process of OSP process is: degreasing -> microcorrosion -> pickling -> pure water cleaning -> OSP coating -> cleaning.The process control is relatively easy to others.
OSP is a process that meets the RoHS directive requirement for PCB surface finish. It has anti-oxidation, thermal shock and moisture resistance, which can protect the copper surface not rust (oxidation or vulcanization, etc.) in normal environment.
Merits: The process is simple, the surface is very smooth, suitable for lead-free soldering and SMT;Easy to rework, easy to operate, suitable for horizontal line operation;Suitable for mixed surface finish (such as OSP+ENIG).Low cost and environmental friendly.
Demerits: Limit of the times of reflow soldering (the OSP coating will be destroyed after multiple welding, basically 2 times is no problem);Not suitable for pressing technology and binding;Nitrogen is needed to protect in SMT.Not suitable for SMT rework.Storage conditions are more strict.
Flash gold is a chemical deposition method,the gold is deposited on the surface by chemical reactions.
Merits: Longer storage time;Suitable for contact switch design and gold wire binding;Suitable for electrical testing.
Demerits: Higher cost;