The invention relates to a method of continuously removing and obtaining ethylene diamine tetraacetic acid (EDTA) from the process water of electroless copper plating, and to devices for carrying out this method.
In the production of printed circuit boards is frequently necessary to resort to a chemical reaction for the deposition of copper. The most important components of these so-called electroless copper plating baths, apart from copper sulphate and sodium hydroxide are a reducing agent, preferably formaldehyde, and ethylene diamine tetraacetic acid (EDTA) as a complexing agent. As the effectiveness of the reducing agent is usually highly increased with high pH-values, the concentrations for EDTA have to be very high to prevent the precipitation of copper hydroxide. In this process, the EDTA is not chemically modified and therefore not used up during the process. For economic and environmental reasons the EDTA has therefore to be removed and recovered from the process water.
|Publication status||Published - 2 Nov 1990|