The Difference Between Immersion Gold and Gold Plating

　　PCBs surface treated with immersion gold and gold plating have strong oxidation resistance and conductivity. They’re slightly better than the surface treatment of immersion tin we mentioned earlier. In order to plate a gold layer on the PCB, we can adopt two processes, immersion gold and gold plating. Many people think these two processes are the same, but they are not. There are big differences between them.

　　Immersion gold: Immersion gold is also known as ENIG. It adopts the method of chemical deposition, which is to generate a plating by chemical redox reaction. And it is also a way to reach a thicker layer of chemical nickel gold.

　　Gold plating: Gold plating is flash gold, the principle of electrolysis, generally refers to the "electroplating gold", "electrolytic gold", "electric gold" and so on. There are soft gold and hard gold, and generally hard gold is used for gold fingers. The principle is to dissolve nickel and gold (commonly known as gold salt) in a chemical solution, immerse the PCB in the electroplating cylinder and switch on the current a nickel-gold plating on the copper foil of the PCB.

　　The difference between Immersion gold and Gold plating:

　　1. The crystal structure is different; Generally, the thickness of immersion gold is much thicker than gold plating’s. The immersion gold is golden and the gold plating is slightly white.

　　2. As the crystal structure of immersion gold is different from that of gold plating, the immersion gold is easier to weld than the gold plating without causing bad welding.

　　3. The crystal structure of the immersion gold is denser than gold plating and is not easily oxidized.

　　4. The immersion gold is softer than gold plating, so PCB golden-finger are generally use gold plating, hard gold are more wear-resistance.

　　5. The immersion gold only has nickel gold on the pad, and signal transmission in the skin effect does not affect the signal in the copper layer.

　　6. As the wiring becomes denser, the line width and spacing are less than 0.1mm. Gold plating is easily short out the gold wire. PCBs treated with immersion gold only has nickel gold on the pad, so it will not easily cause a gold wire short circuit.

　　7. The immersion gold treatment’s PCB has only nickel gold on the pad, so the combination of soldering resistance and copper layer on the circuit is stronger. The spacing will not be affected when the project is compensated.

　　8. Generally, PCBs with higher requirements will be adopted immersion gold. PCBs surface treated with immersion gold typically do not result in “black pads” after assembly, so the actual use of the immersion gold process has reached 90%.

　　The above is the difference between immersion gold and gold plating