Start with the contact application
Hard-gold plating is used for electrical contact surfaces where the selected deposit and underlayer must withstand the intended mating conditions. An edge connector is a common example. Its performance also depends on geometry, contact force, counterpart material, environment and the required number of mating operations.
Distinguish this requirement from a solderable ENIG finish. Both may contain gold, but their process and intended interfaces differ. Do not approve a substitution based on appearance or the assumption that any gold-colored pad has the same wear behavior.
Specify the complete plated region
Provide drawings that identify the contact pattern, required finish boundaries, plating system and any relevant thickness or hardness requirement. The underlying layer and substrate preparation matter alongside the gold deposit. Agree on the applicable acceptance specification and how measurements will demonstrate it.
There is no universal maximum useful gold thickness for every PCB. A thicker deposit changes cost and processing but does not correct an unsuitable contact geometry or mating system. Confirm the available process and justified requirement with the fabricator and connector specification rather than using an arbitrary thickness table.
Review selective plating with fabrication
- Identify the areas that need contact plating and those that need solderability.
- Confirm how the selected plating process reaches the required features.
- Coordinate beveling, board thickness and edge tolerances.
- Review mask boundaries, keepouts and adjacent copper.
- Agree on thickness, adhesion and visual inspection evidence.
Selective processing can require manufacturing provisions that differ from an all-over finish. Review the proposed artwork and sequence before release. Avoid leaving temporary plating connections or process assumptions unresolved in the final functional design.
Validate the mating interface
Inspect finished dimensions against the connector drawing and confirm fit before production release. Where wear or environmental performance is important, establish an appropriate qualification plan for the complete contact pair. A thickness measurement alone does not demonstrate every required mating condition.
Retain the approved contact finish, geometry and supplier process assumptions with the revision. When a connector or plating specification changes, evaluate the effect on the entire interface. Procurement should request the agreed evidence and confirm the selective-plating scope rather than order a generic premium-gold upgrade.