OSP coating

Organic Surface Protection, OSP for short, is a thin, transparent protective layer on printed circuit boards that is barely visible to the naked eye. In contrast to other well-known substances used to refine surfaces, it is much harder, making aggressive tip styles particularly suitable for contacting them. Since contact with gold causes a chemical reaction, contacting OSP-coated surfaces with conventional test probes is only of limited suitability.

Also see: INGUN E-TYPE® FUSION test probes.