Laser-induced breakdown spectroscopy (LIBS) combined with hyperspectral imaging for the evaluation of printed circuit board composition

doi:10.1016/j.talanta.2014.11.019

Talanta

Volume 134, 1 March 2015, Pages 278-283

https://doi.org/10.1016/j.talanta.2014.11.019 Get rights and content

Highlights

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LIBS/Chemometrics identified elements in waste electrical and electronic equipment.
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Spectral data treatment proposed to obtain more information from the signals.
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Score maps from Principal Component Analysis provided the location of elements.
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LIBS and Chemometrics offer a method of analysis of materials for recycling.

Abstract

In this study, laser-induced breakdown spectroscopy (LIBS) was combined with chemometric strategies (PCA, Principal Component Analysis) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS) to investigate the metal composition of a printed circuit board (PCB) sample from a mobile phone. Scanning electron microscopy–EDS was used for two main reasons: it was possible at the same time to visualize the sample surface, craters (made by the laser pulses) and also the chemical composition of the samples. A 30 mm×40 mm area of the mobile phone PCB sample, which was manufactured in 2011, was investigated. In this case, a matrix with 30 rows and 40 columns (1200 points) was analyzed, and 10 pulses were performed at each point. A total of 12,000 emission spectra were recorded in the wavelength range from 186 to 1040 nm. After an initial exploratory investigation using PCA, 18 emission lines were selected (representing the elements Al, Au, Ba, Ca, Co, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Sb, Si, Sn, Ti and Zn) and then normalized by the relative intensities, and a new PCA was calculated with the autoscaled data. For example, Au and Si were mainly observed in the superficial electrical contacts and in the bulk of the PCB, respectively. A second sample (a mouse PCB) was also analyzed and Pb (emission lines 357.273, 363.956, 368.346, 373.994 and 405.780 nm) was identified in the solders. In addition, this element was determined using FAAS (flame atomic absorption spectrometry) and the Pb concentration was around 25% (w/w). This study opens the possibility for improved recycling processes and the chemical investigation of solid samples measuring a few millimeters in dimension without sample preparation.

Graphical abstract

Introduction

Currently, the generation of waste electrical and electronic equipment (WEEE) is a major concern in EU countries and Brazil [1], [2], [3]. This type of waste is mainly composed of polymers and printed circuit boards (PCB). Printed circuit board is made of plastic material and chemical elements, mainly metals, that can be dangerous when improperly discarded. It is difficult to characterize this type of material due to its rich chemical composition, which includes a variety of elements [4]. However, the characterization of PCBs can be useful for the development of better recycling processes for the recovery of precious elements, such as Au. The size variation of PCB samples poses an additional problem; for example, mobile phones contain small PCBs, while computers contain large ones, leading to difficulty in obtaining representative samples for accurate wet sample preparation [5].

Conversely, it is also important to chemically characterize such materials in their initial life stage, specifically, when the focus of characterization is to control the quality of certain components in observation of any regulations related to public health and the environment. Taking these points into consideration, it is important to combine strategies for rapid and reliable analyses with little to no sample preparation. Laser-induced breakdown spectroscopy (LIBS) can fill this need, and when combined with chemometric strategies, this approach can solve many of the problems associated with sample characterization in this field [6], [7], [8], [9], [10]. Additionally, compositional mapping can be undertaken [11]. Therefore, the goal of this study is to demonstrate the use of LIBS for PCB characterization by combining hyperspectral images [12], [13], [14] and score maps obtained from principal component analysis (PCA). The use of hyperspectral images permits the simultaneous observation of the chemical distribution of multiple elements in a given sample. In a hyperspectral image [15] each pixel (picture element) is formed by one spectrum. In the case of LIBS each pixel has information about an emission spectrum. Energy-dispersive X-ray spectroscopy and scanning electron microscopy analyses were also performed.

Section snippets

Materials and equipment

In this experiment, two printed circuit boards (PCB) obtained from (1) a mobile phone manufactured in 2011 with dimensions of 30 mm×40 mm (see details in Fig. 1, Fig. 2) and a computer mouse with no specification (for example, year of production) were studied. There is not a particular reason to select a mobile phone manufactured in 2011, but in the authors opinion this sample is too new for a waste mobile. Both PCBs samples presented around 1–2 mm thickness and the surface was very irregular.

Hyperspectral image interpretation

A PCA was performed for each set of 10 pulses. The score values were arranged to build score maps, which were then correlated with loading values (information regarding the analyzed elements). Fig. 3 shows the obtained results. In the initial observation, two micrographs were obtained from the metallic layer located at the superior left corner of the sample (P1, see Fig. 4). The first and second micrographs were obtained from the surface and the crater, respectively. Observing the crater, it is

Conclusions

This study demonstrates the application of LIBS and chemometric tools for the analysis of PCBs based on the use of PCA score maps. The positions of 18 elements were highlighted inside the sample, and the proposed method was successfully used to detect precious and toxic elements in WEEE samples, which has the potential to facilitate the efficiency of the recycling process or other sample characterization procedures.

The use of hyperspectral images can foster new routes for improved recycling

Acknowledgments

The authors are grateful for the financial support of Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq (Grants 304772/2012-7 and 474357/2012-0) and Grants 2012/01769-3, 2012/50827-6 and 2013/04688-7 from the São Paulo Research Foundation (FAPESP) and Thermo Scientific-Analítica for the FAAS instrument.

References (20)

O. Tsydenova et al.
Waste Manag.
(2011)
F.O. Ongondo et al.
Waste Manag.
(2011)
L.H. Yamane et al.
Waste Manag.
(2011)
R. Noll et al.
Spectrochim. Acta Part B
(2008)
R. Noll et al.
Spectrochim. Acta Part B
(2014)
R.L. Carneiro et al.
Spectrochim. Acta Part A
(2014)
R.L. Carneiro et al.
J. Pharm. Biomed. Anal.
(2012)
M. Vidal et al.
Chemom. Intell. Lab. Syst.
(2012)
P. Geladi et al.
Chemom. Intell. Lab. Syst.
(2004)
H. Xia et al.
Talanta
(2014)

There are more references available in the full text version of this article.

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It is extremely important for material analysis to visualize the elemental distribution of the sample surface quickly, sensibly, and high-resolution. Most point-to-point methods, such as laser-induced breakdown spectroscopy (LIBS), are incapable of achieving high spatial resolution at a reasonable time cost, while surface scanning methods such as hyperspectral imaging (HSI) is insensitive to concentration and material composition. In this work, we proposed a method coupling LIBS with HSI for rapid and high-resolution elemental distribution analysis of material surface. The method of point-to-point laser ablation and region of interest (ROI) segmentation were primarily employed. We further processed the LIBS and HSI spectra and distinguished different ROIs of material surface using principal component analysis. Significant LIBS and HSI lines that contributed to the classification of ROIs were also identified. Moreover, we examined the relationship between the principal component scores of LIBS and HSI spectra based on the Spearman correlation coefficient. Finally, the element visualization images of LIBS and LIBS-HSI were presented and compared. Compared with LIBS imaging, LIBS-HSI imaging offers a better spatial resolution that is at least 90.75 folds higher and a scanning time that is at least 6 times shorter. These results, together with the experimental process, indicate that LIBS-HSI appears to be a promising contender for rapid and high-resolution visual element analysis of material surface.
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Nowadays, Laser-Induced Breakdown Spectroscopy (LIBS) is one of the most relevant spectroscopic techniques in the framework of multi-element hyperspectral imaging [1–4], comparable to techniques such as micro-XRF mapping [5,6].
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Data fusion of LIBS and PIL hyperspectral imaging: Understanding the luminescence phenomenon of a complex mineral sample
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Analytical and reclamation technologies for identification and recycling of precious materials from waste computer and mobile phones
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Waste electrical and electronic equipment (WEEE) is one of the world's fastest-growing class of waste. WEEE contain a large amount of precious materials that have aroused the interest to develop new recycling technologies. Hence, effective recycling strategies are extremely necessary to promote the proper handling of these materials as well as for environmentally sound recovery of secondary raw resource. This paper reviews important existing methods and emerging technologies in WEEE management, with special emphasis in characterization, extraction and reclamation of precious materials from waste computer and mobile phones. Traditional pyrometallurgical and hydrometallurgical technologies still play a central role in the recovery of metals. More recently, emerging greener recycling technologies using microorganisms (i.e. biometallurgical), plasma arc fusion method and pretreatments (i.e. ultrasound and mechanochemical technologies) combined with other recycling methods (e.g. hydrometallurgical), and using less toxic solvents such as ionic liquids (ILs) and deep eutectic solvents (DESs) have also been attempted to recycle metals from computer and mobile phone scrap. The role of analytical method development, especially using spectroanalytical methods for chemical inspection and e-waste sorting process at industrial applications is also discussed. This confirmed that most direct sampling techniques such as laser-induced breakdown spectroscopy (LIBS) and X-ray fluorescence (XFR) have several advantages over traditional sorting methods including rapid analytical response, without use of chemical reagents or waste generation, and greater reclamation of precious and critical materials in the WEEE stream.
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Semi-quantitative LIBS analyses were performed for Ba, using as reference ICP-OES data. In the cited papers [4–6,8,10–14] scanning was performed by moving the sample on xy-stages relative to the stationary laser beam (e.g. 30 × 40 mm2 in [13]). In contrast, in this paper we present a scanning LIBS method where the laser beam is deflected by galvo-scanners thus enabling fast scans of PCBs with dimensions of up to 500 × 500 mm2 and height variations of up to 60 mm.
Inverse production strives for a selective dismantling of industrial mass products at their end-of-life (EOL) with the goal to generate highly enriched fractions of valuable materials for subsequent tailored recovery procedures. Since in many cases there is only fragmentary or even no information available about the chemical composition of such EOL-products and their components, there is a need for a fast, inline, multi-element, stand-off analyzing methodology, that can be integrated in an inverse production line. Within the European project ADIR, LIBS was studied to identify valuable materials in electronic components and to allocate this analytical information to the location of the measuring object on the printed circuit boards of the EOL-product. The fused data set of physical – gained via 2D, 3D geometry measurements – and chemical data allows for a selective disassembly and sorting of such electronic components. This paper describes the developed scanning LIBS method, gained results, and the integration of the LIBS measurements in the worldwide first inverse production line to process printed circuit boards of servers and cell phones.
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The huge consumption of modern plastic with improper disposals has posed a great threat to the environment and human beings. To put these post-consumer plastics into the recycling chain, laser induced breakdown spectroscopy (LIBS) has been established as a potential tool for rapid grading of plastics online. Meanwhile, LIBS is a powerful tool for plastic investigations in the laboratory with the capacity of simultaneous qualitative and quantitative analysis. The present review describes the development and prospect of plastic investigations using LIBS, highlighting the intrinsic advantages of LIBS for plastic recycling. Moreover, the selection of hardware components and analysis methods are discussed, which may help to start a research on plastic using LIBS.

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Laser-induced breakdown spectroscopy (LIBS) combined with hyperspectral imaging for the evaluation of printed circuit board composition

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials and equipment

Hyperspectral image interpretation

Conclusions

Acknowledgments

Waste Manag.

Waste Manag.

Waste Manag.

Spectrochim. Acta Part B

Spectrochim. Acta Part B

Spectrochim. Acta Part A

J. Pharm. Biomed. Anal.

Chemom. Intell. Lab. Syst.

Chemom. Intell. Lab. Syst.

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