What is the PCB copper sinking process? The process of chemical copper?

What is the PCB copper sinking process? The process of chemical copper?

PCB copper deposition process, also known as electroless copper plating or electroless nickel immersion gold (ENIG), is two common processes used in PCB factory production. One is the technique of forming a thin and uniform copper layer on a printed circuit board (PCB). This process is crucial for manufacturing multi-layer PCBs as it allows for the deposition of metal on non-conductive surfaces, thereby creating electrical connections.

The copper sinking process usually involves the following steps:

Cleaning: Firstly, the surface of the PCB needs to be thoroughly cleaned to remove any grease, dust, or other pollutants to ensure good adhesion of the coating.

Micro etching: Use chemical solution to perform micro etching treatment on the surface of PCB to improve its roughness and facilitate the adhesion of copper layer.

Activation: Immerse the PCB in a solution containing a catalyst, usually palladium salt, to form a thin activation layer on the surface of the insulating substrate. This activation layer facilitates the deposition of copper ions.

Copper sinking: Next, the PCB is immersed in a copper sinking solution. The solution contains copper ions and reducing agents. Copper ions are deposited on the surface of the PCB under the action of a catalyst, forming a continuous layer of metallic copper film.

Post treatment: After copper deposition, it may be necessary to rinse and dry the PCB to remove residual chemicals and ensure that the copper layer is uniform and defect free.

The copper sinking process does not require an external power source because it is carried out spontaneously through chemical reactions. Due to its ability to uniformly deposit an extremely thin copper layer on the entire surface, this method is highly suitable for PCB designs without holes or difficult to electroplate.

The deposited copper layer is usually thin, and in order to improve conductivity and durability, it is often covered by subsequent copper plating processes to thicken the copper layer. In some applications, other metals such as nickel or gold may also be plated on the deposited copper layer to provide additional protection and improve welding performance.