PCB gold immersion, also known as electroless gold plating, is a surface finishing process used in printed circuit board (PCB) manufacturing. This process involves depositing a thin layer of gold onto the surface of the PCB to enhance its electrical conductivity, solderability, and corrosion resistance.

　　The gold immersion process typically begins with a cleaning step to remove any contaminants from the PCB surface. This is followed by an activation step, where a catalyst is applied to the surface to promote the adhesion of the gold layer. Next, the PCB is immersed in a gold plating solution, which contains a reducing agent and a gold salt. The reducing agent causes the gold ions in the solution to be reduced and deposited onto the PCB surface, forming a thin layer of gold.

　　One of the main advantages of gold immersion is its ability to provide a uniform and smooth gold layer on the PCB surface. This is important for ensuring good electrical contact and solderability. Gold immersion also offers excellent corrosion resistance, which can help to extend the lifespan of the PCB. Additionally, the gold layer can enhance the aesthetics of the PCB, making it more visually appealing.

　　However, gold immersion also has some limitations. It is a relatively expensive process compared to other surface finishing methods, such as tin plating or nickel plating. Additionally, the gold layer is relatively thin and can be easily scratched or damaged during handling and assembly. Therefore, care must be taken to protect the gold layer during the manufacturing process.

　　PCB gold immersion is a valuable surface finishing process that can enhance the performance and reliability of printed circuit boards. However, it should be carefully considered in terms of cost and durability requirements before being selected for a particular application.