2L FPC with 50u” hard gold plating on gold finger area.

Why choose hard gold plating for this design? Because gold finger has to plug and pull, apply hard gold plating on gold finger area can enhance friction resistance without reducing conductivity.

What’s the difference between Hard gold plating and Soft gold plating?

Hard gold plating is often used for frequent plug such as DRAM module only card slot, can be in the plug and pull condition for a long time, so its characteristic is smooth and hard surface, its composition contains nickel gold and more than 3% cobalt luster nickel, cobalt can increase the hardness of gold, hard gold plating is not suitable for gold or aluminum wire, the gold surface looks bright.  

Electroplating soft gold is mainly applied to WIRE BONDING, such as BGA, CSP and other boards. The main components are 99.999% pure gold (thickness 20UINCH) and matte nickel (thickness 150UINCH). The addition of nickel matte makes the surface of gold look dull.