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When it comes to obtaining high-quality images, many different factors come into play. Typically, most of these factors come down to your imaging equipment and cleanroom; however, there are factors involved in the etching process that can affect the quality of your image. Here are five steps to ensure your etching process is optimized for the best image quality.
1. Be wary of undercut.
When you are etching to obtain your circuitry patterns on a PCB, beware of undercut. Due to your solution’s etch factor—the ratio of sideways etch to downward etch—your image will need to compensate any change and variation that can arise. Naturally, when you create a line with a photoresist to make a feature, the outcome of that feature will be smaller because of the sideways etching. PCB designs typically account for this, but if you are working with thicker copper layers for your PCBs, you will have to be cautious and ensure that the sideways etch does not impact the features you desire.
2. Monitor your etchant quality.
Maintaining consistency of your etch chemistry is the key to ensuring your etcher gives a quality image. As you etch panels, your etchant will decline in quality because it loses reaction potential (from the depletion of reactants), and with that, you will pick up contaminants. To prevent this from affecting your etching process, you will need to implement process controls to maintain the properties of your etchant. Depending on the etching solution you utilize, the factors you need to control will vary. If you are unsure how to monitor or maintain your etch process, it is best to seek experienced help and consult your etch equipment manufacturer.
3. Clean your nozzles regularly.
As I mentioned, etching panels will introduce contaminants into your etching bath. With this, your nozzles can become clogged with debris. Frequently cleaning your nozzles is an easy measure you can take to prevent debris from affecting etch quality. Doing this will ensure that your panels receive a consistent spray pattern throughout the etch chamber.
To read this entire article, which appeared in the October 2022 issue of PCB007 Magazine, click here.