Etchant Recovery System

Cupric chloride and ammoniacla etchants are used to remove unwanted copper form printed circuit boards. They are used in a continuous"bleed and feed" mode, which leads to the formation of a hazardous copper containing waste. This waste material must be hauled form the site for disposal. In addition, cupric hcloride etchant requires the use of hazardous oxidants such as chlorine gas or sodium chlorate for its regeneration. We propose to replace this method with an electrolytic device, whifch will recover and automatically remove non-hazardous copper metal at the cathods, and regenerate the spent etchant at the anode. It is essential to immediately remove the metallic copper from the system so it cannot re-dissovle in the etchant. The system will eliminate the handling of hazardous oxidants, eliminate the creation of a hazardous waste, and create a closed loop system using existing etching equipment. The proposed system will also be considerably less costly per ounce of copper etched. The proposed system will not require membranes, sice it doe not require the separation of anolyte and catholyte. We have already developed and electrolytic device for the regeneration of ferric chloride etchant, which is widely used in the photochemical machhining industry. The use of the existing device with the etchants used in the printed circuit industry results in the evolutio of chlorine gas. The present deviceed will automatically recover copper metal from the spent cupric chloride etchant and remove it from the sysstem. In Phase I or the proposed study, we will develop a new design for the existing device. This new design will re-direct the chlorine gas formed at the anode into the spent etchant, thus preventing its evolluton. This represents the in-situ generation of the oxidant already in use to re-oxidize the spent cupric chloride etchant. We proposse to accomplish this new design by building a laboratory -sized version of the existing device which cna be easily modified and was designed for experimentation. Several concepts are suggested for this news design, however there is no certainty that this can be done to capture and react all of th chlorine gas formed at the anode. We also propse chemical studies to facilitate the redesign, The proposed study should be equallly applicable to ammoniacla etchan if successfu. In Phase 2, a commercially usable larger machine, based upon the redesign developed in Phase 1 would be constructed and tested.