What is PCB immersion gold process?
The immersion gold process is a surface treatment method for PCB assembly, also known as chemical nickel-gold, electroless nickel-gold, or immersion nickel-gold. The immersion gold process deposits a layer of metal plating on the bare copper surface of the PCB through a chemical reaction. This plating serves to prevent oxidation and increase the lifespan of the PCB. Let us learn more about the immersion gold process.
There are many types of surface treatment methods for PCBs, such as immersion silver, gold plating, and OSP. Each method has its own advantages, disadvantages, and principles. The principle of the immersion gold process is to chemically plate nickel on the bare copper surface of the PCB and then use a displacement reaction to plate a layer of gold on the surface of the nickel. In simple terms, the immersion gold process involves chemically plating nickel on the bare copper surface of the PCB and then using a chemical reaction to plate gold. The immersion gold process not only meets the requirements of complex PCB assembly but also produces a smooth and solderable plating.
PCBs processed by the immersion gold process have a brighter color, better gloss, and excellent solderability. In addition, immersion gold-plated PCBs have excellent oxidation resistance, electrical conductivity, and longer lifespan.
The immersion gold process has a complex process flow, including several main steps:
- Drilling: eliminates the reactivity of palladium elements in the through-holes to prevent nickel plating during the process.v - Degreasing: removes oxide and oil pollution on the copper surface of the PCB.
- Micro-etching: uses micro-etching solution to remove oxide and residue on the copper surface and roughen the surface to increase the adhesion of the chemical nickel layer.v - Pre-dip: maintains the acidity of the activation tank to keep the copper surface of the PCB clean at all times.
- Activation: generates a layer of palladium replacement on the copper surface of the PCB to activate the copper surface for chemical nickel plating.
- Nickel plating: catalytically reduces nickel ions to deposit elemental nickel on the copper surface of the PCB.
- Gold plating: forms a layer of metal thin film on the surface of the deposited nickel through a chemical displacement reaction.