Definition

Organic Solderability Preservative (OSP) is a thin (0.2-0.5 µm) water-based organic coating applied to bare copper to prevent oxidation. OSP is the most cost-effective surface finish, provides excellent coplanarity, and is RoHS compliant. However, it has limited shelf life (6-12 months), is not suitable for multiple reflow cycles, and provides no protection for exposed copper in the final assembly. OSP is invisible, making inspection more difficult.