전기화학반응에 의한 폐 염화철 에칭액의 재생 및 구리회수 시스템 개발

Abstract

PCB 제조공정 중 에칭 공정에서 발생하는 PCB의 에칭 폐액을 전기화학적 방법을 이용하여 양극에서 이를 재생하고, 음극에서 구리를 석출하기 위한 실험을 하였다. 에칭 공정 중에 사용되는 염화철 에칭액은 계속되는 에칭 공정에 의해 에칭 액 속의 구리농도 상승과 에칭액의 ORP의 저하 때문에 에칭 능력이 떨어지게 된다. 이러한 에칭 폐액은 현재 주로 화학적으로 재생되고 있으나 많은 환경적 문제점을 일으키기 때문에 전기화학적 반응을 이용하여 폐 염화철 에칭액을 재생시키는 방법이 더욱 친환경적인 공정 기술이다. 본 연구에서는 이러한 염화철 에칭 폐액의 전기적 재생장치를 개발하기 위한 기초실험과 관련 제어실험을 수행하였다. 모든 실험 과정을 MATLAB과 DAQ(Data Acquisition: 정보수집) System을 이용하여 자동 제어하였으며 양극액과 음극액이 섞이지 않도록 사이에 음이온에 교환 막을 설치하여 전해조를 구성하였다. 양극액은 염화철 에칭 폐액을 그대로 사용하였고 음극액은 염화철 에칭 폐액을 조건에 맞게 0.5N 염산에 희석하여 사용하였다. 양극액에는 DSA 전극을 삽입하고 음극액에는 카본 전극을 삽입하여 반응을 진행하였다. 음극에서는 환원이 일어나면서 액 속에 있는 Cu 이온들이 전극 판에서 입자상 구리로 석출되고 양극에서는 Cu+이온과 Fe2+이온이 산화하여 각각 Cu2+이온과 Fe3+이온이 생성되도록 하여 다시 에칭 능력을 갖추도록 하였다. 염화철 에칭 폐액에는 구리와 철, 두 가지 금속 이온들이 동시에 함유되어 있기 때문에 두 금속 간에 일어나는 간섭현상이 있어 음극 액 중 Cu 농도 제어에 문제점이 있었으며, 이를 해결하는 방안으로 RGB 칼라 센서와 ORP센서를 이용하여 음극액 중 구리농도를 제어하였다. 전류 밀도는 350mA/cm2일 때, 음극액의 철 이온 조성은 Fe2+의 비율이 높을수록, 음극액의 구리 이온 농도는 14g/L일 때, 음극액의 구리 이온 조성은 Cu+의 비율이 높을수록 높은 구리 석출 효율(g/Ah)을 나타냈다. 이러한 최적 조건으로 회분식, 반-회분식, 순환식, 반-순환식 등 다양한 방식의 공정운전을 시행하였다. 그중 반-순환식 공정이 장기 운전 시 가장 뛰어난 효율을 나타내었고, 실제 공정에 이용 시 가장 유리한 공정임을 나타내었다. | Electrochemical etching of PCB waste to use it at the anode and cathode for the deposition of copper in the experiments were carried out. The etching ability of iron chloride etchant that is used during the etching process is decreased gradually as with the concentration of copper is increased and, the ORP is decreased as well. This etchant is currently recycled by a chemical method but, it can cause many environmental problems so, the recycle process by electrochemical method might be more eco-friendly. In this research, the basic tests for the development of electrochemical recycling devices and control experiments were executed. All the process of the experimental presents were automatically controlled by using MATLAB program and DAQ system and, anion exchange membrane is placed between anode and cathode in an electrolytic cell to avoid mixing each other. The etching waste was used as anode and, the diluted etching waste with 0.5N hydrochloric acid was used as cathode. The reaction was proceeded by inserting DSA electrode in anode and carbon electrode in cathode. The reduction reaction occurred at the cathode and, Cu ions were deposited on the electrode plates as particulate Cu. At the anode Cu+ ions and Fe2+ were oxidized followed by the formation of Cu2+ ions and Fe3+ ions and thus, the etching ability of etchant waste was recovered. There was a problem to control copper concentration because two metallic ions, the copper and iron, were contained in ferric chloride etching waste at the same time. RGB color sensor and ORP sensor were used to solve this problem. The best conditions were 350mA/cm2, Cu 12g/L, the higher Fe2+ ratio than Fe3+, the higher Cu+ ratio than Cu2+. Experiments were performed in various ways such as batch, semi-batch, continuous and semi-continuous processes with this optimum conditions. Among those four kinds of reactions, semi-continuous process showed the best efficiency at longer reaction times and, it could be successfully applied at commercial scale.; Electrochemical etching of PCB waste to use it at the anode and cathode for the deposition of copper in the experiments were carried out. The etching ability of iron chloride etchant that is used during the etching process is decreased gradually as with the concentration of copper is increased and, the ORP is decreased as well. This etchant is currently recycled by a chemical method but, it can cause many environmental problems so, the recycle process by electrochemical method might be more eco-friendly. In this research, the basic tests for the development of electrochemical recycling devices and control experiments were executed. All the process of the experimental presents were automatically controlled by using MATLAB program and DAQ system and, anion exchange membrane is placed between anode and cathode in an electrolytic cell to avoid mixing each other. The etching waste was used as anode and, the diluted etching waste with 0.5N hydrochloric acid was used as cathode. The reaction was proceeded by inserting DSA electrode in anode and carbon electrode in cathode. The reduction reaction occurred at the cathode and, Cu ions were deposited on the electrode plates as particulate Cu. At the anode Cu+ ions and Fe2+ were oxidized followed by the formation of Cu2+ ions and Fe3+ ions and thus, the etching ability of etchant waste was recovered. There was a problem to control copper concentration because two metallic ions, the copper and iron, were contained in ferric chloride etching waste at the same time. RGB color sensor and ORP sensor were used to solve this problem. The best conditions were 350mA/cm2, Cu 12g/L, the higher Fe2+ ratio than Fe3+, the higher Cu+ ratio than Cu2+. Experiments were performed in various ways such as batch, semi-batch, continuous and semi-continuous processes with this optimum conditions. Among those four kinds of reactions, semi-continuous process showed the best efficiency at longer reaction times and, it could be successfully applied at commercial scale.