Printed Circuit Board Etching Process
At present, pattern plating is the typical PCB etching process during the whole printed circuit board (PCB) production. A tin-lead resist layer is pre-plated on the copper foil part that needs to be kept on the outer layer of the board. The remaining copper foil is then chemically etched away, this process is known as etching.
It should be noted that there are two layers of copper on the board during etching. Only one layer of copper in the outer layer must be etched away, and the rest will form the final required circuit. The feature of this type of pattern plating is that the copper plating layer only exists under the lead tin resist layer.
Another method is to plate copper on the entire board. The only part other than the photo-sensitive film is the tin or lead-tin resist layer. This process is called full-plate copper plating process. The biggest drawback of full-plate copper plating compared to pattern plating is that its surface must be plated with copper twice and must be etched away. Therefore, when the wire width is very fine, a series of problems will arise. At the same time, side corrosion can seriously affect the uniformity of the lines.
Currently, tin or lead tin is the most commonly used for resist layer used in the etching process of ammonia etching agents. Ammonia etchant is a commonly used chemical liquid that does not react chemically with tin or lead tin. Ammonia etchant mainly refers to ammonia/chlorinated ammonia etching solution.