1/7/2024 0 Comments Wet process layoutEtch undercuts Cupric chloride etchingĬupric chloride is the most widely used etchant since it accurately etches off smaller features. At the track edge, there is always some amount of copper removed under the resist, this is known as an undercut. The tracks are protected with either a plated etch resist or a photo-imaged resist. When the solution hits the copper, it attacks the copper and leaves behind the tracks that are protected. Undercuts are the lateral erosion of the etched material below the protective tin/lead layer. Also, the undercuts are minimum in this method. This method is implemented for the inner layers because the acid doesn’t react with the photoresist and doesn’t damage the required part. The acidic method is more precise and cheaper but time-consuming, compared to the alkaline method. This method involves chemical solvents like Ferric chloride (FeCl 3) OR Cupric Chloride (CuCl 2). The acidic method is used to etch off the inner layers in a rigid PCB.
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