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26 PCB007 MAGAZINE I AUGUST 2024 alkaline etch process when you're not etching a lot of copper. So, this month, I'm picking up where I le off in June. I had mentioned that an oxidation/reduction potential (ORP) monitor could be useful with alkaline etchant, but I ran out of column space. e ORP of an alkaline etch solution is the ratio of Cu +2 ions to Cu +1 ions, just as it is with cupric chloride etchant. However, the ratio of +2 ions to +1 ions is close to 1:1 in an alkaline etch bath, so the working ORP in a healthy bath is closer to 0 mv instead of the upper 500 mv for a cupric bath. You can expect a new alkaline In my June column, I discussed how much control was needed for high-density circuits rather than what was thought necessary. I con- centrated on cupric chloride and alkaline etch issues and equipment, since the etching step in the circuit board manufacturing process is one of the most critical areas where small changes in etchant parameters can have a large effect on the final product. e intention was to con- tinue in the July issue with less critical process steps, such as developing and stripping. How- ever, I got distracted by a specific control issue for alkaline etch, specifically controlling your Chemical and Equipment Control of High-density Circuits, Part 2 The Chemical Connection Feature Column by Don Ball, CHEMCUT