As Flexible PCB supplier china knows that, generally, PCB board etching processes can be divided into two types: Wet etching and Dry etching.

Wet Etching:

Wet etching is usually done with an acid solution to dissolves the unwanted copper based on chemical reactions. Successful Chemical Etching lies in the selection of an appropriate chemical solution and etch material. There are two kinds of chemicals for us to choose.

Acidic Chemicals: Ferric Chloride (FeCl3) / Cupric Chloride (CuCl2).
Acid etching is a very efficient process that involves removing copper from any inner layer of the FR-4 circuit board. Acid etching is used for these types of plates because of how precise etching can be. The acid in the PCB etching fluid does not react with the photoresist, which means that the metal does not have as much undercut. The only disadvantage of this type of copper etching pcb is that the acid etching process takes longer to complete than alkaline etching and other methods.

Alkaline Chemicals: chloride copper (CuCl2 Castle, 2H2O) + hydrochloride (HCl) + hydrogen peroxide (H2O2) + water (H2O).
Basic etching can be applied to the outermost layer of a circuit board. Since alkaline etching can be done faster than acid etching, you don’t need to worry about any residual copper uniformity being damaged. Due to the composition of the alkaline solution, it is considered more active than the acidic solution, which means that careful monitoring is required to ensure the accuracy of the etching process.

These two types of etching processes have proven to be effective because large volumes of etching can be performed at lower operating costs. Acid and alkaline etching can also be used with many different metals.

Dry Etching:

Dry etching processes typically use plasma to activate chemical reactions between the substrate and surface atoms of the laminate, which can dissolve unwanted copper. Dry etching is not limited to plasma etching, laser etching PCBs can also be used for the process.

Plasma Etching:
Plasma etching is one of the main applications of plasma treatment. The process is designed to help reduce liquid waste disposal in the manufacturing process and enable selectivity that is difficult to obtain with wet chemistry. During plasma etching, a highly energetic and reactive substance produced by a selected process gas (e.g. O2 or fluorine-containing gas) bombards the sample surface and reacts with the sample surface, with the result that the surface material is broken down into volatile and/or smaller molecules that are then removed by the vacuum system. Part or the entire top layer of the surface can be etched. Therefore, plasma etching is a dry and clean process that does not require any chemicals. Most importantly, plasma etching enables controlled and precise etching on very small scales. It is also particularly popular because it reduces the possibility of via contamination or solvent absorption. Nonetheless, the plasma etching is costly. The chemical properties of the process gas determine how its plasma reacts with the surface of the material, and thus the effectiveness of plasma etching.