Novel Recycle Technology for Recovering Gallium Arsenide from Scraped Integrated Circuits

摘要

From the environmental safety and resource recovery viewpoint, a novel method of recycling gallium arsenide (GaAs) from scrapped GaAs-based integrated circuits (ICs) was proposed in this study. A hydrothermal-buffering method (HBM) has been developed in which an oxidant (H2O2) in the presence of phosphate buffer solution reacted with ICs under hydrothermal conditions. The results have shown that the packaging material was effectively decomposed without any significant loss of GaAs under the HBM condition. Gallium and arsenic recovery rates were 99.9 and 95.5%, respectively. In addition, thermodynamically stable regions of Ga and As species in aqueous systems were identified by an Eh-pH diagram. The function of HBM has been studied and discussed in detail. Results have shown that Na+ and OH (-) ions provided by a buffer system accelerate the degradation of packaging materials. Meanwhile, the OH- plays an irreplaceable role in the recovery of GaAs. The states of As on the surface of the recovered GaAs were mainly positively trivalent and pentavalent, and the corresponding compounds were As2O3 and Na2HAsO4, respectively. Under optimum conditions, without releasing any toxic gases to the environment, 91.2% of the packaging materials were decomposed, probably the free radical reaction being the main mechanism; the probable decomposition pathways of packaging materials were investigated. The study provides an efficient and environmentally friendly process to treat the IC packaging material and recover maximum GaAs for further use.