PCB assembly involves chemical reactions. In the PCB fabrication process, etching is the first important chemical step used to form circuit patterns. Chemicals in the etching solution, such as iron(III) chloride (FeCl₃) solution, gradually dissolve the unwanted parts of the copper foil to form the desired circuit pattern.
In addition, there are chemical steps such as copper plating and tin immersion during the production process. Copper plating usually uses chemical copper plating to deposit a solid copper layer on the PCB surface to enhance conductive properties and provide good welding performance and corrosion resistance. Immersion tin is to immerse the pad into an immersion tin solution. By applying an electric current, the tin ions are reduced from the solution and deposited on the surface of the pad to form a thin tin layer. This layer of tin can provide protection and enhance the corrosion resistance of the pad, while also providing good conditions for subsequent soldering connections.