One explanation I was given is that the vinegar reacts with the chloride in salt and produces a very weak hydrochloric acid. I tried it but it took forever to see any effect on the copper. Much easier to go and get a gallon of muriatic acid for $10. I only use about an ounce at a time along with 3 oz of peroxide and get boards etched in about 5 minutes.
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RE: [Homebrew_PCBs] Etching with vinegar, peroxide and salt
2016-06-19 by duwaynes@...