If you are evaluating ENIG finishes, the official standard outlines several non-negotiable parameters. Here is a summary of what the IPC-4556 PDF contains:
Usually 1–2 µin (0.03–0.05 µm). This ultra-thin top layer protects the palladium and ensures low contact resistance while facilitating superior wire bonding. Key Benefits for Manufacturers ipc4556 pdf
It is widely known as the "universal finish" because it supports soldering, aluminum wire bonding, gold wire bonding, and contact applications on a single board. Key Technical Specifications (2015 Amendment) If you are evaluating ENIG finishes, the official