Two gold-colored surfaces, different specifications
ENIG means electroless nickel immersion gold. Electrolytic hard gold uses a different deposition process and is commonly specified for contact wear. Both can appear gold, but appearance does not establish equivalent thickness, composition or service behavior. Match the coating system to the function of the surface.
| Question | Electrolytic hard gold | ENIG |
|---|---|---|
| Typical design purpose | Selected wear-contact areas. | Solderable PCB surfaces and other qualified uses. |
| Process distinction | Electrolytic gold deposition with electrical access. | Electroless nickel followed by immersion gold. |
| What to specify | Deposit, underplate, thickness, region and acceptance. | Complete ENIG requirements and applicable acceptance basis. |
| Repeated mating | Assess the qualified contact system. | Do not substitute for a hard-gold wear specification without qualification. |
| Mixed-finish board | Selective area requires process review. | Can be specified elsewhere when the combined process is agreed. |
Use selective finishes when functions differ
A PCB may have edge contacts intended for mating and component pads intended for assembly. Clearly map both areas, including the transition and any masking requirements. Review the combined process rather than treating two independent finish notes as a complete manufacturing instruction.
Do not buy a substitute based on the word gold
If a quote proposes a finish alternative, compare the actual deposit, thickness, underplate and qualification requirements. Ask which acceptance criteria change and what evidence supports the substitution. A cost reduction that changes contact behavior should be treated as an engineering change, not a cosmetic alternative.
Keep standards tied to the correct process
A standard addressing one coating system does not automatically certify another. Identify the specific standard and revision required by the drawing, then confirm its applicability to the selected finish. This website does not claim certification or blanket compliance for a build that has not been reviewed.
Continue the specification
Read the selective hard gold guide, convert units with the thickness tool, and define the inspection evidence required for your project.
Have a drawing to review? Send your gold finger PCB requirements with the connector part number, quantities and any open questions. Files are optional.