Porosity

The porosity of the gold plating has a certain relationship with the thickness of the plating.

Below 15uin, the porosity increases rapidly, above 50uin, the porosity is very low, and the actual rate of decrease is negligible. This is why the thickness of the precious metal for electroplating is usually in the range of 15~50uin.

There is also a relationship between porosity and substrate defects such as inclusions, laminations, stamping marks, improper stamping cleaning, improper lubrication, etc.

Wearing

Abrasion of the plated surfaces of the terminals also exposes the substrate. The wear or life of a plated surface depends on two properties of the surface treatment: coefficient of friction and hardness. The hardness increases, the friction coefficient decreases, and the life of the surface treatment increases. Electroplating gold is usually hard gold, containing hardening activators, of which Co (cobalt) is the most common hardener, which improves the wear resistance of gold. The choice of palladium-nickel plating can greatly improve the wear resistance and life of precious metal plating. Generally, 20~30uin palladium-nickel alloy is covered with 3uin gold plating layer, which has both good electrical conductivity and high wear resistance. In addition, nickel underlayers are often used to further improve lifetime.

Nickel bottom layer

The nickel underlayer is the primary consideration for precious metal plating and provides several important functions to ensure the integrity of the terminal contact interface. With a positive oxide surface, nickel provides an effective barrier to the substrate and pinholes, thereby reducing the potential for pinhole corrosion; And provides a hard support layer under the precious metal plating layer, thereby improving the life of the plating layer.

What thickness is appropriate? The thicker the nickel bottom layer, the lower the wear, but considering the cost and the roughness of the control surface, the thickness of 50~100uin is generally selected.