Page 18 - 2021 Connectivity Components: Everything but the Connectors eBook

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» A pin and socket with selective gold plating
Gold plating
Due to the high cost of gold, contact plating is typically deposited in thin layers of 5 μin to 100 μin (0.13 μm to 2.54 μm). The thicker the gold-plated layer, the more durable and resistant to temperature and corrosion the contact becomes. Gold plating thicknesses depend on application performance requirements and industry standard requirements. For instance, applications with minimal wear considerations, such as fixed contacts, typically require 4 to 20 μin (0.10– 0.51 μm) of gold plating. Applications with modest wear considerations, such as male pins and female sockets with moderate mating cycles, typically require 30 to 50 μin (0.76 to 1.27 μm) of gold plating, and applications with high wear considerations, such as mil-specs or high mating cycles, typically require a minimum of 50 μin (1.27 μm) of gold plating. Heavy gold plating of 50 μin or more meets MIL-G-45204 plating specifications for corrosion resistance from mud, dirt, moisture, salt spray, and other contaminants. Thicker gold plating also increases the number of mating cycles.
Plating methods
There are many methods for metal plating contacts, but they all fall under one of two overarching process categories: electroplating or electroless plating. Electroplating processes require an electric current, while electroless plating processes use a chemical reaction as a catalyst for plating.
Electroplating via immersion bath is more suitable to large-volume projects and offers improved surface uniformity, protection from surface abrasion, and the ability to build the thickness of the metal substrate. Electroplating is ideal for creating adhesion for components that need to be thermocompression bonded, as surfaces can be enhanced through electroplating.
Electroless plating is a chemical plating technique that creates metal coatings on various materials by autocatalytic chemical reduction of metal cations in a liquid bath. An advantage of electroless plating is that it creates an even layer of metal regardless of the geometry of the surface. Electroplating can cause uneven layers depending on the shape of the surface.