Introduction to PCB Gold Plating Process!
Electroplating with gold is a surface treatment method in PCB manufacturing, scientifically known as electroless nickel-gold plating. It's one of the earliest surface treatment techniques for PCBs. The process involves first depositing a layer of nickel on the solder pads of the PCB, followed by another layer of gold on top of the nickel. It is mainly divided into two types: hard gold plating and soft gold plating. Now, let's delve into some detailed information about the electroless nickel-gold plating process!
Electroless nickel-gold plating and electroless nickel plating belong to the same category of nickel-gold surface treatment techniques. However, while electroless nickel plating employs the principle of chemical deposition to generate the coating, electroless nickel-gold plating utilizes the principle of electrolysis. The process involves initially depositing a layer of nickel, around 3μm to 8μm in thickness, on the copper surface of the PCB solder pads through electrodeposition. Subsequently, a thin layer of gold, approximately 0.01μm to 0.05μm thick, is plated on top of the nickel layer. The nickel layer serves to prevent diffusion between the gold layer and the copper surface, while the gold layer acts as a protective barrier against oxidation or corrosion.
Electroless nickel-gold plating is mainly categorized into hard gold plating and soft gold plating, each suitable for different applications. Hard gold plating, being an alloy, boasts characteristics such as wear resistance and a smooth, bright surface. It is primarily used in products with frequent insertions and removals, notably in applications like edge connectors. On the other hand, soft gold plating, being pure gold, exhibits a slightly darker surface luster and is primarily utilized for wire bonding in chip packaging, particularly in applications like COB wire bonding pads.
Electroless nickel-gold plating can mitigate the impact of external environmental factors on PCBs, thereby extending their storage lifespan. Furthermore, PCBs treated with electroless nickel-gold plating exhibit excellent wear resistance and corrosion resistance. Despite these advantages, electroless nickel-gold plating also presents some noteworthy drawbacks, such as high internal stress and poor solderability.