In PCB high-frequency circuit boards, a lead-tin corrosion-resistant layer is pre-plated on the copper foil portion that needs to be retained. The remaining copper foil is then etched away using a chemical process, known as etching. Today, the editor from the high-frequency board manufacturer will explain the types of etching for PCB high-frequency circuit boards and the commonly used etchants.
Types of Etching for PCB High-Frequency Circuit Boards
1. Pattern Plating Method: During etching, the board has two layers of copper. Only one layer of copper is completely etched away, while the remaining layer forms the final required circuit.
Full-Board Copper Plating Process: The entire surface of the high-frequency circuit board is plated with copper. The parts outside the photoresist only have a tin or lead-tin corrosion-resistant layer. Compared to pattern plating, its major drawback is that copper plating is needed twice all over the board, and they must be etched away during the etching process.
There is another method, which involves using a photosensitive film as a corrosion-resistant layer instead of a metal plating layer. This method is similar to the inner layer etching process.
2. Types of Etchants for PCB High-Frequency Circuit Boards
Ammonia-based etchants are commonly used chemical solutions that do not react chemically with tin or lead-tin. In addition, there are ammonia water/ammonium sulfate etchants, which allow copper to be separated out by electrolysis after use; these are generally used in non-chlorine etching processes. Some people also use sulfuric acid-hydrogen peroxide as an etchant to corrode the outer layer graphics, although this method hasn't been widely adopted yet.
These are the types of etching for PCB high-frequency circuit boards and the commonly used etchants.
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