The standard establishes the requirements for the deposition of ENEPIG surface finishes on PCBs. It sets the strict performance metrics, testing frequencies, and thickness requirements that board fabricators must meet to ensure the finish remains solderable and wire-bondable over a prolonged shelf life. The ENEPIG Plating Structure
Meets Category 3 solderability requirements, ensuring a shelf life of at least 12 months under proper storage. ipc4556 pdf