Electroless nickel immersion gold, or ENIG, places a nickel layer and a thin gold surface over designated copper features. It is a solderable surface-finish option that should be evaluated with the actual package geometry, assembly process and acceptance requirements. Its gold appearance does not make it equivalent to a wear-resistant hard-gold contact finish.
Define the intended connection
Identify whether the surface will be soldered, contacted or used in another joining process. Review compatibility for that application rather than assuming every gold-colored finish is interchangeable. For sensitive RF structures, include the finish in the electrical review where its conductor stack matters.
Specify measurable requirements
State the applicable finish specification and edition, required thickness limits, inspected features and reporting needs. Confirm the measurement method and sampling plan with the supplier. Avoid copying a thickness range without understanding whether it applies to the selected process and purchase requirement.
Review process integrity
The final appearance cannot establish the integrity of every underlying interface. Ask how the supplier controls and verifies the finish process and handles nonconforming results. When investigating a solder-joint failure, consider board finish, component termination, soldering history and mechanical loading together.
Preserve the approved process on repeat orders
Keep the finish requirement with the drawing and assembly qualification record. Review changes to finish type or process through the agreed change-control procedure. A repeat part number should not silently receive a different surface system.
Release checklist
- State finish type and governing specification.
- Confirm measurement and acceptance records.
- Check compatibility with actual assembly operations.
- Keep contact-wear requirements separate.