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80 PCB007 MAGAZINE I MAY 2022 Copper has become a valuable metal, and with the growth of EV has come higher cur- rents needed in PCB resulting in increased weight of copper in PCBs. is creates the need for increased copper etching and con- sumption of copper etchants. Alkaline ammonium chloride and acidic cupric chloride remain the most used etchants with various peroxide-sulfurics as micro- etches. Still in use, but in much smaller appli- cations, are ferric chloride, alkaline ammo- nium sulfate, alkaline cupric chloride, and sodium persulfate. 1,2 Any ammonium compounds in rinse water complicate water treatment as they will chelate any metals in the final effluent and make it more expensive to treat. Etchant Regeneration Techniques Karl Dietz wrote on this topic several times in his Tech Talk Series. No less than eight col- umns were devoted to etching chemistry, but Copper Etchant Regeneration only one went into details about chemical regeneration (TT#92). e etching Tech Talk columns were: • TT#92: Etchant Recycling (CircuiTree, May 2003) • TT#112: Ammoniacal Etching (Part A) (CircuiTree, January 2005) • TT#113: Ammoniacal Etching (Part B) (CircuiTree, January 2005) • TT#119: Fine Lines in High Yield (CircuiTree, August 2005) • TT#151: Ferric Chloride Etching of Copper (the PCB Magazine, April 2008) • TT#158: Fine Line Etching Revisited, Part A (the PCB Magazine, November 2008) • TT#159: Fine Line Etching Revisited, Part B (the PCB Magazine, December 2008) • TT#160: Fine Line Etching Revisited, Part C (the PCB Magazine, January 2009) Happy's Tech Talk #8 by Happy Holden, I-CONNECT007

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