Characterization of electronic components of printed circuit boards for the recovery of gold and copper

Several studies are being carried out aiming the hydrometallurgical recovery of metals of high economic value from comminuted samples of printed circuit boards (PCB) of computers, however, few studies focus on the treatment of the electronic components present in PCB. The present work deals with the structural and chemical characterization of several types of components, after manual dismantling and removal of the nonmetallic materials present in each one of them. The samples, which were of numerous sizes (~ 0.5-4 cm in length), were initially characterized by MEV-EDS and EDX for the determination of the main metals contained, and later by quantitative chemical analysis by ICP-OES after digestion. A digestion block digestion method using reverse aqua regia (3HNO₃: ¹HCl) and sequential additions of HCl was developed. The SEM analyzes indicated that Au is present at the terminals as a thin coating layer on Ni, usually in the region of contact with the electronic devices. EDX analyzes confirmed the presence of Au in such regions, as well as identifying the main elements present in the sample, i.e. Au, Cu, Ni, Pb, Sn and Zn. The analysis by ICPOES indicated that the metals present distinct levels for each component, but Cu represents the major element in all types. Au and Cu contents varied between 58-1550 g/t and 612-883 kg/t, respectively. Considering these results, a global sample was prepared, after mixing all the characterized components, homogenization and mechanical blocking. This sample has the following composition: Cu 72.7% m/m; Zn 21.7% m/m; Sn 4.6% m/m; Pb 1.5% m/m; Ni 1,1% m/m; Au 168 ppm; Fe 103 ppm; Pd 90 ppm; and Ag 17 ppm. Based on these data, a promising route, from the technical, economic and environmental point of view, is being developed aiming at the recovery of Au and Cu. (author)