Complementary results of non-destructive elemental assay and liberation analysis of waste printed circuit boards

This chapter summarized the non-destructive characterization results of complex and heterogeneous composition of printed circuit boards (PCBs) based on elemental assay and liberation analysis. PCBs are the essential components of any electrical and electronic equipment. The rate of increase in Waste PCBs has been raised over the last two decades and keeps on growing at 3%-5% per year. Thus, global attention has been shifted to recycling the valuable components from WPCBs instead of their disposal. PCBs contain high concentrations of base metals (e.g., Cu, Al, Sn, Pb, and Fe), precious metals (PMs) (e.g., Au, Ag, Pd, and Pt), and other valuable components. To recover these valuable metals, precise characterization is quite important to develop an economical and environmentally-friendly recycling process. However, the characterization of the complex and heterogenous composition of PCBs has become one of the main challenges in their recycling purposes. To capture the heterogeneity and deportment behavior of valuable substances in the WPCBs and their processed products, various characterization methods have been applied and developed. Some of them state the average percentage composition of a particular substance or limited information on a small section of the sample with some uncertainty. With a large amount of sample, the characterization results can be imprecise, and limited. These results can also be highly dependent on the liberation size of valuable metal in powdered PCBs. Thus, the objective of this chapter was to summarize and compare the complementary results of various non-destructive characterization methods applied in PCB characterizations, such as XRF, and SEM-EDS. Those methods have some similarities and discrepancies in their results. Based on our studies and literature, some advantages and disadvantages are also highlighted in this chapter.