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.
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