Why Etchant Regeneration?
In the process of making PWBs using the “subtractive” process, the circuit pattern is created by chemically etching copper from the unprotected (non-circuit) areas of the copper-coated panel, leaving circuit traces protected with photoresist. Etching can be accomplished with acids or bases, depending on the etch rate and the line width required. The ammoniacal etchants, either ammonium chloride or ammonium sulfate, are most commonly used. Cupric chloride is also used, even though it often requires chlorine gas, a significant health and environmental concern. Approximately 60% of the copper on the board is removed in the typical etching process. As the copper content of the etchant increases, the etchant cannot effectively remove the copper from the board, and it is considered spent. The copper-saturated, spent etchant is stored in drums or a tank, and is ultimately shipped off-site for reclamation. Even in situations where the copper is recovered and the etchant is regenerated by the w
