ENGINEERING ANSWER
ENIG, immersion silver and OSP should be compared against the same RF geometry, assembly process and environment. There is no single finish ranking that is correct for all products.
What to decide before release
Build a decision table covering conductor loss, solderability, contact requirements, storage and environmental reliability. Ask suppliers for process-specific details and use representative coupons where electrical differences matter.
Checks to put in your design brief
- Prioritize product requirements
- Control the comparison geometry
- Include handling and assembly constraints
Important distinction
Avoid choosing from appearance or a broad frequency cutoff without evidence for the intended construction.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.