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As many of you probably already know, PCB etching seems like a simple task on the surface—the selective removal of material using an etching agent. However, quite a few things can go wrong during this process, such as over-etching, copper areas that detach from the board, issues with etching solution, and even accidental removal of critical components. Considered by many to be somewhat of an art form, PCB manufacturers work hard to create a better etching process (remember acid traps?). Adhering to best practice and continuous improvement is a must to help avoid issues with your finished board. In this column, we share our design tips for a better etching process.
Etching Process Overview
Once all of the layers are laminated together, the through-holes are drilled, the copper is plated (both electroless and electroplated), and the outer layer images are applied, it is time to physically create all of the traces and pads for a circuit board via the etching process.
Etching defines the distinctive routes of a PCB. It is also the process that tests the quality of a design by answering the design questions that will determine its functionality. Did you leave enough space? Are your traces wide enough?
PCB manufacture etching is a reductive process, not an additive process. The board starts with a consistent layer of copper throughout, and the etching process removes all unwanted copper. Now, if you think that sounds wasteful, don’t worry; the copper removed during etching is easily captured and recycled.
Remember that we start the PCB process with a fully copper-clad panel. After coating it in a light-sensitive polymer, we project high-intensity UV through an image of the PCB design that you carefully composed. A photoresist layer covers the areas where we want to remove the copper. It is a photo negative of the traces you want to keep.
To read this entire column, which appeared in the March 2020 issue of Design007 Magazine, click here.