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Pyrolysis of Printed Circuit Boards
International Journal of Metallurgical Engineering , 2012, DOI: 10.5923/j.ijmee.20120106.01
Abstract: Printed Circuit Board (PCB) is an essential component of almost all electrical and electronic equipments. The rapid growth of the use of such equipments has contributed enormously to the generation of large quantity of waste PCBs. The WPCBs not only contain valuable metals but also a large variety of hazardous materials. Conventional treatments of such WPCBs have their own limitations. By pyrolysis of WPCBs, it is not only possible to obtain the organic part of it as a fuel or useful chemical but can make further processing to recover metals much easier and efficient. In the present work, a kinetic study on the low temperature pyrolysis of WPCBs using a thermogravimetric analyser has been attempted. The TG analysis was conducted in nitrogen and air atmospheres in the temperature range of 200-600℃ at a heating rate of 40℃/min. The kinetic expressions for both the environments were determined and the activation energies were found to be 110.7 and 90.2 kJ/mol for nitrogen and air, respectively. The effect of thermal pre-treatment on the subsequent copper leaching in nitric acid for untreated, pyrolysed and air-burned PCB was also studied. Copper recoveries from these samples were 30.4%, 92.5% and 96.2%, respectively indicating the importance of thermal pre-treatment in leaching of the metal content.
Review: Current Status of Recycling of Waste Printed Circuit Boards in India  [PDF]
Rashmi Kumar, Dahyalal. J. Shah
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.51002

Printed Circuit Boards (PCBs) are an integral part of any electronic equipment. The growth of e-waste as end-of-life electronic equipments at an exponential rate is producing large quantities of discarded PCBs. In India, current recycling and processing of PCBs is managed almost entirely by the informal sector or the unskilled labor (95%). The crude recycling activities cause irreversible health and environmental hazards and the loss of valuable materials due to the poor recovery of base and precious metals. With the disclosures of the recycling being done by unskilled labor, alternative recycling strategies are being sought with the aim of higher recovery of materials in an environment friendly manner. There is an urgent need to establish effective and efficient methods for recycling the metals presented in the waste PCBs. In this study, the existing methods practiced for recycling of waste PCBs in India and the management strategies for handling them are assessed.

Mass analysis of the components separated from printed circuit boards
Hana Charvátová,Dagmar Janá?ová,Miloslav Fialka,Karel Kolomazník
Acta Montanistica Slovaca , 2010,
Abstract: Methods of effective and ecological recycling of printed circuit boards (PCBs) are searched all over the world at this time.The material composition and temperature properties of PCB are necessary to be known for an optimal recycling technology. For thispurpose we analyzed weight ratio of the electronic components moulded on the selected kinds of PCBs and next we formulatedmathematic model of temperature field in PCB during a grinding process in that the metal layers are separated from the plasticelements. We present the obtained results in this paper.
A tool for errors detection in printed circuit boards production
A. de Luca Pennacchia,L. G. de la Fraga,U. Martínez Hernández
Journal of applied research and technology , 2009,
Abstract: The progressive implementation of software functions in Integrated Circuits (ICs) has considerably increased the number oftransistors and pin connections of ICs. For that reason, Printed Circuit Boards (PCBs) are fabricated with the Surface MountTechnology (SMT) nowadays and IC mounting on PCB is a crucial process that requires high precision. An Automatic MechanicalMontage (AMM) system is used to mount ICs on the sockets using a couple of reference points for every IC in order to find thecorrect positions for mounting the IC. Due to some factors in the process of PCB development, there are differences betweendesigned and manufactured PCBs, which could generate delays in their production. In this work, a software tool which allows towork with digital images of PCBs is described. This tool finds the differences generated in PCB development, especially thedifferences in IC reference points using Digital Image Processing (DIP) techniques.
Recovery of tin and copper by recycling of printed circuit boards from obsolete computers
Castro, L. A.;Martins, A. H.;
Brazilian Journal of Chemical Engineering , 2009, DOI: 10.1590/S0104-66322009000400003
Abstract: this paper presents the experimental results for the leaching of printed circuit boards (pcb) from obsolete computers for extracting and recovering tin and copper by means of leaching followed by precipitation. printed circuit boards were dismantled, cut into small pieces, and fed into a cylinder mill. the powder obtained was leached by using the aqueous solutions 2.18n h2so4, 2.18n h2so4 + 3.0n hcl, 3.0n hcl, and 3.0n hcl + 1.0n hno3. the lowest values for the percentage of metal extraction were obtained with 2.18n h2so4 (2.7% for sn and lower than 0.01% for cu), while the 3.0n hcl + 1.0n hno3 leach system exhibited an extraction of 98% for sn and 93% for cu. precipitates were obtained at different ph values by neutralizing the leach liquors using naoh. the 3.0n hcl + 1.0n hno3 leach system presented the highest recovery values from the powder feed (84.1% for sn and 31.9% for cu), as well as from the leach liquor (85.8% for sn and 34.3% for cu).
Microwave assisted leaching and electrochemical recovery of copper from printed circuit boards of computer waste
Iv?nu? R.C.,Iv?nu? D.,C?lmuc F.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100614001
Abstract: Due to the rapid technological progress, the replacement of electronic equipment is very often necessary, leading to huge amounts that end up as waste. In addition, waste electrical and electronic equipment (WEEE) contains metals of high commercial value and others that are supposed to be hazardous for the environment. Consequently, WEEE could be considered as a significant source for recovery of nonferrous metals. Among these wastes, computers appear to be distinctive, as far as further exploitation is concerned. The most ″useful″ parts of the computers are the printed circuit boards that contain many metals of interest. A study on microwave assisted electronic scrap (printed circuit boards of computer waste – PCBs) leaching was carried out with a microwave hydrothermal reactor. The leaching was conducted with thick slurries (50-100 g/L). The leaching media is a mixed solution of CuCl2 and NaCl. Preliminary electrolysis from leaching solution has investigated the feasibility of electrodeposition of copper. The results were discussed and compared with the conventional leaching method and demonstrated the potential for selective extraction of copper from PCBs.
Allocation of Component Types to Machines in the Automated Assembly of Printed Circuit Boards
Mehmet Bayram Yildirim,Ekrem Duman,Dilek Duman,Coskun Cetinkaya
Journal of Computers , 2007, DOI: 10.4304/jcp.2.7.11-19
Abstract: Although the use of electronic component placement machines has brought reliability and speed to the printed circuit board (PCB) assembly process, to get higher utilization, one needs to solve the resulting complex operations research problems efficiently. In this study, the problem of distributing the assembly workload to two machines deployed on an assembly line with two identical component placement machines to minimize the line idle time is considered. This problem is NP-Complete even in its simplest form. A mathematical model and several heuristics have been proposed to solve this problem efficiently.
Using Mathematical Morphology to Detect the Imperfections of the Printed Circuit Boards
Ionut Balan
Journal of Applied Computer Science & Mathematics , 2008,
Abstract: Image processing is a form of signal processing(analysis, interpretation, and manipulation of signals) forwhich the input is an image, such as photographs; the outputof image processing can be either an image or a set ofcharacteristics or parameters related to the image. Typicaloperations of image processing are geometrictransformations such as enlargement, reduction androtation, color corrections such as brightness and contrastadjustments, quantization, or conversion to a different colorspace, interpolation and recovery of a full image from a rawimage format, image editing, image differencing, imagestabilization, image segmentation and other. Applications ofthese operations are encountered in computer vision, facedetection, feature detection, medical image processing,microscope image processing, morphological imageprocessing, remote sensing and many other disciplines.Morphological image processing is a collection of techniquesfor digital image processing based on mathematicalmorphology. By combining these morphological operatorswe can obtain algorithms for many image processing tasks,such as feature detection, image segmentation, imagesharpening, image filtering, and granulometry. Likewise,using this technology we can detect some imperfections of theprinted circuits, imperfections that allow us to repair it,opportunely. So in this way, we can eliminate some costs inthe technological process.The paper presents an introduction in mathematicalmorphology, describes “hit and miss transform”, dilationand erosion and, after all, we present the usage of two ofthese operations in printed circuit error detection.
Kinetic Study of the Pyrolysis of Waste Printed Circuit Boards Subject to Conventional and Microwave Heating  [PDF]
Jing Sun,Wenlong Wang,Zhen Liu,Qingluan Ma,Chao Zhao,Chunyuan Ma
Energies , 2012, DOI: 10.3390/en5093295
Abstract: This paper describes a kinetic study of the decomposition of waste printed circuit boards (WPCB) under conventional and microwave-induced pyrolysis conditions. We discuss the heating rates and the influence of the pyrolysis on the thermal decomposition kinetics of WPCB. We find that the thermal degradation of WPCB in a controlled conventional thermogravimetric analyzer (TGA) occurred in the temperature range of 300 °C–600 °C, where the main pyrolysis of organic matter takes place along with an expulsion of volumetric volatiles. The corresponding activation energy is decreased from 267 kJ/mol to 168 kJ/mol with increased heating rates from 20 °C/min to 50 °C/min. Similarly, the process of microwave-induced pyrolysis of WPCB material manifests in only one stage, judging by experiments with a microwave power of 700 W. Here, the activation energy is determined to be only 49 kJ/mol, much lower than that found in a conventional TGA subject to a similar heating rate. The low activation energy found in microwave-induced pyrolysis suggests that the adoption of microwave technology for the disposal of WPCB material and even for waste electronic and electrical equipment (WEEE) could be an attractive option.
Leaching of Gold from the Waste Mobile Phone Printed Circuit Boards (PCBs) with Ammonium Thiosulphate
International Journal of Metallurgical Engineering , 2012, DOI: 10.5923/j.ijmee.20120102.02
Abstract: The rapid growth in the use of electronic equipments, combined with early obsolescence has contributed enormously to the generation of large quantity of electronic (e) waste. One such e-waste, the mobile phone printed circuit boards (PCBs) contain various precious metals which can be extracted by different hydrometallurgical routes. The present work deals with the recovery of gold using ammonium thiosulfate as a leaching agent from waste mobile PCBs containing 0.021% Au, 0.1% Ag, 56.68% Cu, 1.61% Ca, 1.42% Al, 1.40% Sn, 0.24% Fe, 0.22% Zn, 0.01% Pd etc.. The cutting granules of 0.5 -3.0 mm PCBs were used for leaching in a 500 mL glass beaker in open atmosphere. The effect of various parameters viz. ammonium thiosulfate concentration, copper sulfate concentration, pH and pulp density was studied. A leaching of 56.7% gold was obtained under the optimum condition of 0.1M ammonium thiosulfate, 40 mM copper sulfate, pH: 10-10.5, pulp density: 10 g/L at room temperature and stirring speed of 250 rpm in 8h duration. The maximum leaching of gold in the pH range 10-10.5 may be attributed to the higher stability of the ammonium thiosulfate. The decomposition of ammonium thiosulfate in the different pH ranges was chemically analysed by iodometric method. The ammonium thiosulfate contents in the leach liquors were in agreement with the quantity of gold leached in the respective pH ranges. In this process the copper sulfate worked as a catalyst. The experiment conducted with complete PCBs scrap exhibited a maximum leaching of 78.8% gold at the above optimised condition.
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