Qualitative and Semi-quantitative Estimation of Major Elements in Desktop Computer Motherboards

Abstract

The technical advancement and changing lifestyle have given rise to a new waste stream—‘electronic waste’ or ‘e-waste’ which is different from conventional municipal waste. The growing volume and complex composition of these items along with the absence of proper disposal mechanisms is a major area of concern today. Personal computer (PC) is one of the most widely used electronic products with limited life cycle. The present paper deals with qualitative and semi-quantitative estimation of major elements (mainly toxic and hazardous elements) in one of the key components of desktop computer viz. the motherboard. Wavelength dispersive X-ray fluorescence (WDXRF) spectroscopy and laser ablation inductively couples plasma mass spectroscopy (LA-ICP-MS) techniques have been used to find out the elemental composition of obsolete motherboards. By performing composition analysis, a noticeable change has been found in concentrations of some major elements as a function of technology. With the advancement of technology, concentrations of Al and Cu have increased whereas Pb concentration is found to decrease. The distribution of various elements in the motherboard based on different technologies will enable us to monitor the changing trends of hazardous elements and may also provide better insights into waste segregation and disposal methods.

Keywords

Desktop computer motherboard technology major elements qualitative semi-quantitative estimation

Introduction

With the development of science and technology, the electronic industry has become one of the fastest-growing sectors in the world (Wang & Xu, 2014) and such development resulted into an array of discarded, end-of-life (EOL) products (Kumar & Kumar, 2012), thereby introducing a new and very climacteric (Saoji, 2012) waste stream called ‘electronics waste’ or ‘e-waste’. E-waste, one of the fastest growing (Hasan, Abbasi, Mahapatra, Ahmed, & Abbasi, 2010) waste streams (Gupta, Sangita, & Kaur, 2011), already constitutes 8 per cent of municipal waste (Tsydenova & Bengtsson, 2011; Wath, Vaidya, Dutt, & Chakrabarti, 2010) and calls for efficient management (Khaliq, Rhamdhani, Brooks, & Masood, 2014).

Waste electrical and electronic equipment (WEEE) is the biggest challenge to sustainability (Menikpura, Santo, & Hotta, 2014) for the civilization not only for its ever-increasing volume but also for the complex composition due to the presence of different toxic and hazardous ingredients (Nnorom & Osibanjo, 2008). WEEE can be distinguished from other municipal solid waste (Gupta & Kumar, 2014; Khetriwal, Kraeuchi, & Widmer, 2009) because it contains valuable materials such as gold (Au), silver (Ag), platinum (Pt) and palladium (Pd) that can bring economic benefits as well as toxic elements such as chromium (Cr), lead (Pb), arsenic (As), mercury (Hg), cadmium (Cd), beryllium (Be) and nickel (Ni) that can create environmental as well as health problems (Bhat, Rao, & Patil, 2012; Jha, Kumar, Kumar, & Lee, 2011; Kiddee, Naidu, & Wong, 2013; Needhidasan, Samuel, & Chidambaram, 2014). The introduction of e-waste mainly the computer waste makes the solid waste management much more challenging (Joseph, 2007; Rajput, 2013; Rao, 2014). But unfortunately due to lack of appropriate e-waste recycling, in most of the countries, no proper disposal mechanisms are present and the handling of e-waste is done by incinerations, disposal in landfills or exporting overseas (Eswaraiah, Kavitha, Vidyasagar, & Narayanan, 2008; Khaliq et al., 2014) to developing nations which are not acceptable due to environmental pollution and health risks.

Personal computer (PC) is being considered to be one of the most essential and extensively used products among all EEEs. A desktop computer, a type of PC, has a number of components with a wide range of specifications (shape, size, function, type etc.) and compositions (Kolias, Hahladakis, & Gidarakos, 2014). With the advancement in technology, the life span of EEE in use is decreasing (Ashfaq & Khatoon, 2014), thereby decreasing the life of a PC. The average life span of a computer today has decreased from 4.5 to 2 years (Ashfaq & Khatoon, 2014; Widmer, Krapf, Khetriwal, Schnellmann, & Böni, 2005) resulting in a huge number of disposable computers (Kiddee et al., 2013) with a wide range of technology. In this scenario, the study of the composition of different components of desktop computer can prove to be a key area for researchers as well as environmental managers and policy makers because of the presence of environmental and health hazards. In this paper, the motherboards from a variety of PCs with different levels of technology have been examined.

Motherboard is the main and largest printed circuit board (PCB) of a PC (Kolias et al., 2014) whereas PCB is a key component of discarded e-scraps (Eswaraiah et al., 2008; Park & Fray, 2009). In PCB, there is a non-conductive substrate on which semi-conductive or conductive electronic components (ECs) are mounted and based on the arrangements of these ECs the elemental composition of PCBs vary (Eswaraiah et al., 2008). FR-2 is the most common type of PCB which is mainly used in PC. The PCB of PC consists of 27 wt.% polymers, 28 wt.% ceramics and 45 wt.% metals. Lead and tin are mainly used for welding of ECs on the PCBs. Copper is present in the highest percentage in PCBs, with copper concentration being 20 wt.%. To prevent oxidation in place of electrical contacts in computers a small layer of gold is used because of its chemical stability (Yamane, Moraes, Espinosa, & Tenorio, 2011).

Several studies (Park & Fray, 2009; Veit, Bernardes, Ferreira, Tenório, & Malfatti, 2006; Yamane et al., 2011) indicated that composition of PCBs probably changes based on applied methodologies and introduction of technological innovations over time.

Objective

The objective of the study is to quantify the major elements (mainly toxic and hazardous elements) of obsolete desktop computer motherboards.

Methodology

As a consequence of the rapid innovation of electronic industries, EEE sizes are getting reduced and the constituents are becoming more complicated. Desktop computer is no exception to it. In order to find out the change of materials in motherboards with the advancement of technology, motherboards are being categorized based on the processor technology. The categorization has been shown in Table 1.

Table 1.

The Categorization of Desktop Computer Motherboards Based on Processor Technology

Product	Component	Categorization Technology (Processor Technology)
Desktop Computer	Motherboard	Pentium 3	Pentium 4	Core 2 Duo

Source: Authors’ own.

Materials and Methods

Sample Collection

All the samples used in this study are collected from old, out of warranty, discarded desktop computers. At first, three motherboards (one with Pentium 3 processor, one with Pentium 4 processor and one with Core 2 Duo processor) are collected. Before performing the destructive analysis, the specifications of all samples are documented and depicted in Table 2.

Table 2.

The Detailed Specifications of Samples Under Study

Components	Specifications
	Processor Technology	Make	Size		Weight
	Processor Technology	Make	Dimension	Thickness (avg.)	Weight
Motherboard	Pentium 3	Dell	28.5 × 20.8 cm	1.68 mm	641.1 g
	Pentium 4	Asus	24.5 × 24.5 cm	1.7 mm	979.1 g
	Core 2 Duo	Intel	24.5 × 24.5 cm	1.68 mm	1059.4 g

Source: Authors’ own.

Sample Preparation

For the three motherboards same processes have been carried out for sample preparation. A schematic flow diagram of sample preparation from waste motherboards has been shown in Figure 1. In order to analyze the composition of motherboards by instrumental analysis, the parts, sections and modules of motherboards are dismantled. To start with, plastics (fan) and other selected components, such as, CPU, CPU socket, Li-ion battery, heat sink and back panel port, are separated out which are not crushable (Figure 1a). This is followed by snipping of the PWB and other remaining components into small pieces of dimensions approximately 10 × 8 cm using hammers, screw drivers and pliers. The samples are then subjected to a Scutter crusher to obtain a particle size of 3–5 mm. After crushing, a sample of about 100 g is taken by using coning and quartering method so as to get homogeneous sample for grinding. Vibration cup mill grinder is used for this purpose. After grinding operation, the sample particle size further reduced to –100 mesh (Figure 1b). The mass distributions of three motherboards have been shown in Table 3.

Figure 1.

(a) Separation of Different Parts of Motherboard. (b) Crushing and Grinding of Selected Parts

Table 3.

Mass Distribution of Three Motherboards

Mass Distribution of Three Motherboards
Motherboards with Three Processors	Separated Metals (g)	Separated Plastics (g)	PWB and Other Remaining Components (g)
Pentium 3	198.7	40.7	400
Pentium 4	360.4	103.4	513.8
Core 2 Duo	416	114	528.8

Source: Authors’ own.

Sample Analysis

The powdered samples are analyzed using X-ray fluorescence (XRF) spectroscopic analysis to determine their chemical compositions. Boric acid (H₃BO₃) is used as a binder in the process of pelletization. Pellets of thickness 2 mm are prepared using hydraulic pellet press metre. Two numbers of pellets for each of the three samples are used. In this study, for each pellet the qualitative and semi-quantitative analysis is performed using wavelength dispersive X-ray fluorescence (WDXRF) spectrometer of PANalytical make (AXIOS model). Rhodium (Rh) is used as the X-ray source; gas flow proportional counter and Scintillation counter are used as detectors.

However, some of the elements such as arsenic, cadmium, tin and mercury that are supposed to be present in the motherboard (Kolias et al., 2014) are not detected as the XRF spectrometer has the limitation of detecting a fixed number of elements.

So we carried out inductively coupled plasma mass spectroscopy (ICP-MS) analysis of samples to find out the concentrations of those elements. The use of ICP-MS was chosen for its capability of scanning all elements simultaneously with a high speed, precision and sensitivity. No binder is used in the process of pelletization. Thin pellets are prepared using hydraulic pellet press metre. Two numbers of pellets for each of the three samples are used. In this work, laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) is done by using Varian 820-MS ICP mass spectrometer. For each and every sample four number spots are taken during the analysis.

However, this analysis technique still failed to detect cadmium and mercury. So, in future further studies could be performed to find out the concentrations of these two elements.

Results and Discussion

The concentrations (in percentage) of major elements of motherboards are determined by WDXRF and LA-ICP-MS analysis for these three samples. To find out the change of elemental concentrations in motherboards with the change of technology, the comparative study has been done. Concentrations of different elements in three motherboards with three different technologies determined by WDXRF and LA-ICP-MS have been presented in Tables 4 and 5, respectively.

Table 4.

Concentration (in per cent) of Major Elements in Three Motherboards Determined by WDXRF

Name of Elements	Pentium 3 (Conc. per cent)	Pentium 4 (Conc. per cent)	Core 2 Duo (Conc. per cent)
Al	10.355	15.410	16.541
Cu	9.627	10.414	10.733
Fe	2.674	4.780	3.414
Ni	0.399	0.267	0.300
Pb	0.083	0.085	0.005
Zn	0.173	0.691	0.495
Cr	0.016	0.013	0.013
Co	0.002	0.002	0.002
Si	38.500	26.084	24.237
Mn	0.199	0.073	0.068
Ba	0.318	0.253	0.514
Br	2.092	1.824	2.190

Source: Authors’ own.

Table 5.

Concentration (in per cent) of Elements in Three Motherboards Determined by LA-ICP-MS

Name of Elements	Pentium 3 (Conc. per cent)	Pentium 4 (Conc. per cent)	Core 2 Duo (Conc. per cent)
As	0.006	0.006	0.006
Sn	19.338	14.170	34.871

Source: Authors’ own.

With the advancement of technology, concentrations of aluminum and copper are increasing. Increase in copper concentration indicates the extensive replacement of single layer PCBs by multilayer ones. Likewise the increase in aluminum concentration indicates the introduction of aluminum clad or metal clad PCBs. The concentration of lead is decreasing with the advancement of processor technology which indicates the use of lead free soldering in future generation PCBs. Decrease in silicon concentration indicates the extensive replacement of large-sized integrated circuits to small ones. Also a high concentration of bromine is indicative of the use of brominated flame retardants in PCBs.

Arsenic is used in PCBs because of its efficiency as a conductor. It is also used in manufacturing silicon-based semiconductors. The result indicates that the arsenic concentration remains same in three technologies whereas concentration of tin is changing.

Conclusion

By performing review of literature it could be analyzed that a very few number of articles are available in composition analysis of desktop computer motherboards. This study provides valuable information in this area.

By performing spectroscopic analysis, this work presents the variations of concentrations of different elements in motherboards with the change of processor technology and indicates how materials are changing with time. The results also support the technology.

This information may be useful to design proper e-waste management scheme. By composition analysis this result highlights that before performing the operations, the e-waste materials should not be mixed. At first, materials should be segregated and then category-wise proper disposal and/or recycling mechanisms should be taken. It also provides guidelines to PCB manufacturers and designers in choice of materials selection. It can help them to think of substituting materials to replace toxic and hazardous elements in motherboards and to plan and implement environment friendly (less toxic) and renewable products.

Despite these encouraging results, in this work, two elements (cadmium and mercury) that are supposed to be present in motherboards are not detected. So, further studies could be performed to find out the concentrations of these two elements of interest.

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