Gold plating has many applications, but is primarily used in electrical components for its low contact resistance, ability to prevent corrosion in various environments, and excellent solderability properties. Gold plating is ordered using a combination of purity (Type) and hardness (Grade/Code) classifications as defined by industry specifications, as well as the thickness (Class) desired. The appearance of the finished product may range from matte to bright, depending on the type of deposit, if an underplate is needed, and the overall type and finish of the supplied material.
MIL-DTL-45204“Gold Plating, Electrodeposited
99.7% gold minimum; hardness grade A, B, or C
For general-purpose, high-reliability electrical contacts, solderability, and wire wrap connections.
99.0% gold minimum; hardness grade B, C, or D
A general-purpose, wear-resistant gold, It will not withstand high-temperature applications because the hardening agents in the gold coating will oxidize.
99.9% gold minimum; hardness grade A only
For semiconductor components, nuclear engineering, thermo-compression bonding, and high-temperature application.
A: 90 knoop, maximum
B: 91 - 129 knoop
C: 130 - 200 knoop
D: 201 knoop, minimum