The function of metal coating on USB connector socket：
1. The plated USB socket is not easy to be oxidized and vulcanized.
2. It can improve its mechanical properties and enhance its wear resistance to a certain extent.
3. Optimize the electrical performance of USB socket, establish and maintain the impedance of USB socket.
4. The precious metal coating is relatively simple to contact the metal that produces the interface, which maintains the stability of the contact interface impedance.
5. Generally, the surface of the metal coating will be covered with an oxide film to prevent the oxide film from cracking when the USB socket is mated, and to ensure that the contact interface is not oxidized.
The electroplating of USB socket terminals also has the functions of beauty, protection and prolonging the life of products, and the surface of products is coated with corrosion-resistant materials.Mechanical or engineering properties also include improving the lubricity and strength of products, including improving the conductivity of products, improving the reflectivity of light, reducing contact impedance, improving the weldability of products and so on.

The influence of terminal material selection is as follows:
1. Conductivity: small material resistance.
2. Extensibility: help USB socket terminal molding.
3. Hardness: reduce the wear and tear of USB socket terminal metal.
4. Yield strength: it can have large displacement within the elastic range.
5. Stress relaxation: when the USB socket terminal is stressed for a long time or used at high temperature, the load resistance can still be maintained.