Determination of Elemental Content in Solder Mask Samples Used in Printed Circuit Boards Using Different Spectroanalytical Techniques

Elemental characterization of electronic waste: a review of research methodologies and applicability to the practice of e-waste recycling

Economic and environmental considerations have elucidated research interests on the best approach to managing electronic waste (e-waste), which has increasing social, environmental, and economic impacts. Proper e-waste managementis essential for resource recovery, environmental sustainability, and public health protection, and effective management of e-waste necessitates analytical techniques to assess and characterize their elemental composition. Despite expansive literature published on the topic of e-waste, there is scarce coverage of the various analytical techniques employed to characterize the inorganic contents of e-waste. This review discusses the various e-waste characterization techniques used in studies published between 2013 and 2023. Specifically, this review covers the analytical approaches employed to characterize the inorganic content of e-waste, the electronic devices or their components analyzed, the elements identified, the sample preparation methods adopted, and the merits and demerits of the analytical procedures. This review highlights the disparate approaches to e-waste characterization and the need for reliable and repeatable e-waste analysis and sample preparation methods.

Development of a fluorescent DNA sensor for dual detection of heavy metal ions utilising DAPI in distinct buffers

The DNA-based biosensor utilises a thymine/guanine(T/G)-rich ODN-4 scaffold with 4',6-diamidino-2-phenylindole(DAPI) as a fluorescent emissary to monitor mercury/lead(Hg(II)/Pb(II)) ions simultaneously. Key to its bifocal detection capability is the twin unbound cytosine(C) bases strategically bridging the G-quadruplex and T-rich sequences, enabling their synergistic interplay. It facilitates the recognition of Hg(II)/Pb(II) ions, characterised by high specificity, and effectively mitigates interference from silver(Ag(I)). The G-quadruplex, guided by the C bases, induces a conformational transition in T-Hg(II)-T complexes, resulting in intense fluorescence. Pb(II) causes a spatial shift in the G-quadruplex, relaxing the T-Hg(II)-T base pairs and attenuating the fluorescence signal. The ODN-4 exhibits a robust, linear correlation with Hg(II) concentration (4.09 nmol/L to 1000 nmol/L) and Pb(II) concentration (3.22 nmol/L to 5 μmol/L). Recovery rates in milk, tap water, and rice water specimens with both ions validate method accuracy (Hg(II): 95.19% to 104.68%, Pb(II): 98.20% to 103.46%). It holds promising prospects for practical food analysis.

Influence of Solder Mask on Electrochemical Migration on Printed Circuit Boards

Electrochemical migration (ECM) on the surface of printed circuit boards (PCBs) continues to pose a significant reliability risk in electronics. Nevertheless, the existing literature lacks studies that address the solder mask and solder pad design aspects in the context of ECM. Therefore, the objective of this study was to assess the impact of solder mask type with varying roughness and solder pad design on the susceptibility to ECM using a water drop test and thermal humidity bias test. Hot air solder leveling-coated PCBs were tested. Furthermore, the ECM tests were conducted on PCBs with applied no-clean solder paste to evaluate the influence of flux residues on the resulting ECM behavior. The results indicated that the higher roughness of the solder mask significantly contributes to ECM inhibition through the creation of a mechanical barrier for the dendrites. Furthermore, lower ECM susceptibility was also observed for copper-defined pads, where a similar effect is presumed. However, the influence of the no-clean flux residues can prevail over the effects of the solder mask. Therefore, the use of a rough solder mask and a copper-defined pad design is recommended if the PCB is to be washed from flux residues after the soldering process.

Past and emerging topics related to electronic waste management: top countries, trends, and perspectives

A bibliometric analysis was performed to assess historical and recent research trends regarding e-waste studies from 1998 to 2018. Documents related to e-waste were identified from the Clarivate Analytics Web of Science© (WoS) database, and a total of 3311 academic articles was retrieved. The analysis was performed from four main aspects: (1) publication activity by year, by WoS category, and by geographic distribution; (2) journals; (3) most-cited papers; and (4) top 10 countries and author keyword analysis. The number of publications concerning e-waste issues has increased substantially over the last 20 years, especially in the environmental science category, and more than a third of the publications were produced in China (1181 records). Waste Management and Environmental Science & Technology were the most sought-after journals for disseminating the results. Studies related to "e-waste flow analysis," "recycling," "recovery of precious metals," and "risk assessment of recycling areas" have been the most common for several years. The analysis of keywords suggested that there are many topics on electronic waste and that each country has presented a different focus of research. Overall, the bibliometric analysis proved to be an efficient tool with which to monitor historical and current research trends and to evaluate the sheer volume of currently existing scientific literature on e-waste topics.