Meaning
Durable coating consisting of gold alloyed with a small percentage of cobalt or nickel to increase the hardness and wear resistance of the surface. This hard gold plating typically features a thickness between 0.75 and 1.25 micrometers to withstand hundreds of mating cycles. It provides the necessary mechanical strength for edge connectors and battery terminals in mobile devices.
Wear Resistance
Alloying elements disrupt the grain structure of the gold to prevent it from galling or smearing during use. While pure gold is soft and easily displaced hard gold plating maintains its structural integrity under the high pressure of a contact spring. This hardness is measured on the Knoop scale to ensure the coating meets the specification for the intended application.
Electrical Stability
Low contact resistance remains constant even after the interface experiences significant mechanical stress. Because hard gold plating resists the formation of insulating oxides it ensures a clean signal path for high speed data or power delivery. Connectors in mission critical modules rely on this stability to prevent data errors or voltage drops.
Deposition Control
Manufacturers monitor the chemistry of the plating bath to maintain the correct ratio of gold to hardener. If the cobalt content becomes too high the hard gold plating may become brittle and prone to cracking under thermal stress. Precise control over the current density during the electrolytic process ensures a uniform thickness across the entire contact area.
This consistency is required to meet the stringent specifications of military and aerospace connectivity standards.
