Research on Selective Shredding of Wasted Printed Circuit Boards

Electronic scrap, especially wasted printed circuit boards (PCBs), is regarded as an environmental challenge. At present, the physical separation is thought to be the environmental friendly and economical method of treating and reutilizing electronic waste. An effective liberation of metals from non metallic components is a crucial step towards mechanical separation and recycling of wasted PCBs. In this paper, the selective shredding theory and mechanics characteristics of wasted PCBs were analyzed, and the shredded experiments of wasted PCBs by hammer mill were investigated. The result shows that the selective shredding exists in the wasted PCBs shredded process by hammer mill. The shredding velocity of non metallic components is far greater than that of metals in the wasted PCBs shredding, which makes the metals concentrate in the coarser fraction. And the impact force of hammer mill is superior to metal liberation from non metallic components, a satisfied metal liberation degree can be achieved in the wasted PCBs shredding by hammer mill.

Optimization of low-temperature alkaline smelting process of crushed metal enrichment originated from waste printed circuit boards

A novel low-temperature alkaline smelting process is proposed to convert and separate amphoteric metals in crushed metal enrichment originated from waste printed circuit boards. The central composite design was used to optimize the operating parameters,in which mass ratio of Na OH-to-CME, smelting temperature and smelting time were chosen as the variables, and the conversions of amphoteric metals tin, lead, aluminum and zinc were response parameters. Second-order polynomial models of high significance and3 D response surface plots were constructed to show the relationship between the responses and the variables. Optimum area of80%-85% Pb conversion and over 95% Sn conversion was obtained by the overlaid contours at mass ratio of Na OH-to-CME of4.5-5.0, smelting temperature of 653-723 K, smelting time of 90-120 min. The models were validated experimentally in the optimum area, and the results demonstrate that these models are reliable and accurate in predicting the smelting process.

Efficient recovery of valuable metals from waste printed circuit boards by microwave pyrolysis

The recycling of waste printed circuit board(WPCBs) is of great significance for saving resources and protecting the environment. In this study, the WPCBs were pyrolyzed by microwave and the contained valuable metals Cu, Sn and Pb were recovered from the pyrolyzed WPCBs. The effect of pyrolysis temperature and time on the recovery efficiency of valuable metals was investigated. Additionally, the characterization for morphology and surface elemental distribution of pyrolysis residues was carried out to investigate the pyrolysis mechanism. The plastic fiber boards turned into black carbides, and they can be easily separated from the metals by manual. The results indicate that 91.2%, 96.1% and 94.4% of Cu, Sn and Pb can be recovered after microwave pyrolysis at 700 °C for 60 minutes. After pyrolysis, about 79.8%(mass)solid products, 11.9%(mass) oil and 8.3%(mass) gas were produced. These gas and oil can be used as fuel and raw materials of organic chemicals, respectively. This process provides an efficient and energy-saving technology for recovering valuable metals from WPCBs.

Pyrolysis kinetics and TG-FTIR analysis of waste epoxy printed circuit boards

Thermal decomposition of waste epoxy PCBs was performed in different atmospheres (nitrogen,argon,air and vacuum) at a heating rate of 10 °C/min by DSC-TGA,and the pyrolysis characteristic was analyzed. The gases volatilized from the experiment were qualitatively analyzed by TG-FTIR. Kinetics study shows that pyrolysis reaction takes place between 300 and 400 °C,and the activation energies are 256,212 and 186.2 kJ/mol in nitrogen,argon and vacuum,respectively. There are two mass-loss processes in the decomposition under air atmosphere. In the first mass-loss process,the decomposition is the main reaction,and in the second process,the oxidation is the main reaction. The activation energy of the second mass-loss process is 99.6 kJ/mol by isothermal heat-treatments. TG-FTIR analysis shows carbon dioxide,carbon monoxide,hydrogen bromide,phenol and substituent phenol are given off during the pyrolysis of waste epoxy PCBs.

Pyrolysis behaviour and combustion kinetics of waste printed circuit boards

The effective recycling of waste printed circuit boards(WPCBs)can conserve resources and reduce environmental pollution.This study explores the pyrolysis and combustion characteristics of WPCBs in various atmospheres through thermogravimetric and Gaussian fitting analyses.Furthermore,this study analyses the pyrolysis products and combustion processes of WPCBs through thermogravimetric and Fourier transform infrared analyses(TG-FTIR)and thermogravimetry-mass spectrometry(TG-MS).Results show that the pyrolysis and combustion processes of WPCBs do not constitute a single reaction,but rather an overlap of multiple reactions.The pyrolysis and combustion process of WPCBs is divided into multiple reactions by Gaussian peak fitting.The kinetic parameters of each reaction are obtained by the Coats-Redfern method.In an argon atmosphere,pyrolysis consists of the overlap of the preliminary pyrolysis of epoxy resin,pyrolysis of small organic molecules,and pyrolysis of brominated flame retardants.The thermal decomposition process in the O_(2) atmosphere is mainly divided into two reactions:brominated flame retardant combustion and epoxy combustion.This study provided the theoretical basis for pollution control,process optimization,and reactor design of WPCBs pyrolysis.

Modeling of Micropores Drilling Force for Printed Circuit Board Micro-holes Based on Energy Method

The quality of printed circuit board(PCB)micro-hole processing directly determines the stability of the inner and outer circuit connections.Micro-hole drilling technology is a typical method for PCB micro-hole processing.The problem of optimal control of its drilling force is one of the main factors affecting the quality of micro-hole machining.To address this problem,the thrust forces and torques in PCB drilling were first modeled and analyzed,and the corresponding prediction models were established.The drilling force analysis was carried out through the micro-hole drilling experiment,the specific cutting energy under different feed rates was calculated,the influence of the size effect was clarified,and the accuracy of the prediction model was verified.The result shows that during the drilling of glass fiber cloth,changes in the material removal mechanism are induced as the feed per revolution is varied.When the feed per revolution is less than the tool edge radius,the glass fiber is not cut by the main cutting edge,but is crushed and broken.When the feed per revolution is greater than the radius of the tool edge,the glass fiber is cut by the main cutting edge.At the same time,the established analytical model can accurately reflect the influence of the size effect on the drilling torque in PCB micro-hole drilling,and the error is within 10%.This method has certain practical application value in controlling PCB micro hole processing quality.

Metals Recovery from Fine Printed Circuit Boards Using Falcon SB Concentrator

Physical methods show great potential and advantages on comprehensive reutilization of waste printed circuit boards (PCBs) because of lower investment and operation cost, higher efficiency and environment friendliness. However, metals contained in fine fraction of PCBs cannot be recovered effectively by conventional equipments such as high tension electrostatic separator or shaking table. In the paper, this conundrum was resolved successfully with the enhanced Falcon SB concentrator. The separation mechanism of Falcon SB concentrator was analyzed and main factors affecting separation efficiency such as magnitude of rotation frequency of bowl, water counter pressure and slurry concentration of feed were studied and interaction of factors above also were investigated using Design-Expert software. Experiment results show that complete liberation degree and great difference of density between metals and nonmetals are suitable to recover metals from -74 μm PCBs using enhanced Falcon SB concentrator and 80.77 % integration efficiency can be achieved when slurry concentration of feed is 40 g/L with the water counter pressure of 0.01 MPa and rotation frequency of 50 Hz.

Distribution of heavy metals during pyrolysis of waste printed circuit boards

<正> The volatilization behavior of Cu, Pb, Sn, Sb, Ni, Zn, Mn, Co, Cr, Cd during pyrolysis of waste printed circuit boards was investigated in a bench-scale fixed-bed pyrolysis system. It was found that volatility of heavy metals increases with operating temperature elevating, and bromine and vacuum have an obvious promoting effect on volatility of most of heavy metals. Over 99% weight of Cu and Ni are still remained in solid residue after pyrolysis, about 20% weight of Sb, Zn and Cd are transfered into liquid and gas during a pyrolysis process at 600℃, volatilization fractions of Pb, Sn, Mn, Co, Cr are less than 10% at the same conditions. The contents of heavy metals in liquid and gas products depend on not only volatility of metals, but also their initial contents in printed circuit boards, pyrolysis liquid and gas are primarily contaminated by Cu, Pb, Sn, Sb and Zn, their contents in liquid vary from 10~2 to 10~3 μg/mL, Mn, Co, Cr, Cd were detected only at very low level, less than 10 μg/mL.

Review: Current Status of Recycling of Waste Printed Circuit Boards in India

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.

Study on High-power LED Heat Dissipation Based on Printed Circuit Board

In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents.The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB.However,PCB with low thermal resistance can be matched with smaller volume heat sink,so it is hopeful to reduce the size,weight and cost of LED lamp.

An Experimental Study of the Printed-Circuit Elliptic Dipole Antenna with 1.5-16 GHz Bandwidth

Printed-circuit board (PCB) elliptic antennas with useful bandwidth exceeding 10:1 ratio are suitable for wideband radar, wireless ultra wideband (UWB) and other wireless communication applications. We present wideband PCB elliptic dipole antennas which are capable of achieving the bandwidth requirements for all the applications. A set of elliptic dipole antennas with varying eccentricities have been fabricated for demonstration. We find one specific size (specific eccentricity) dipole that can yield an impressive 1.5-16 bandwidth exceeding the currently available. A couple of elliptic dipole antennas suitable for UWB application have been presented. We have measured swept frequency response, impedance and radiation patterns of all dipoles. An empirical formula is given for calculating the starting resonant frequency within the operating band. The calculated values are found in good agreement with measured results.

基于298/77 K循环处理回收PCB中非金属组分

为解决废印制电路板(PCB)中非金属组分回收难且二次污染率大的问题,引入298/77 K循环处理技术,首先分析温度改变对PCB内部结构所造成的影响及PCB内部力学性能的变化,测试静电分选和离心分选对PCB非金属组分回收率的实际影响,之后引入CaF_(2)作为精炼过程中的强氧化剂,测试PCB内部结构发生改变后的硅组分回收率,最后测定回收后硅元素的实际纯度。结果表明:PCB在经过298/77 K循环处理后,内部结构受温度循环影响发生明显变化;各项力学性能均实现明显下降;PCB非金属组分实际产出量和硅组分回收率,相比于传统处理方式实现了明显提升,且对原PCB中各项杂质有较好的去除效果,硅元素占比在97%以上。

废旧线路板综合回收利用技术研究进展

为了提高电子固体废弃物等二次资源综合利用水平,针对目前废旧线路板存量大,增速快的特点,以及暴力拆解、强酸浸出、污染严重、回收率低等问题,对其物理分选、火法处理、湿法处理等技术手段进行了综述,并分析了不同工艺技术优缺点。最后指出,废旧线路板等电子固废应当在高效拆解的基础上,使不同组分最大限度解离,再通过火法处理手段利用其中有机组分,通过湿法处理技术回收其中有价金属,最终实现全组分回收以及过程中使用的药剂都循环利用的目的。废旧线路板综合利用未来可在热解设备、新型萃取剂研发等方面进行更加深入的研究。

基于质量4.0的印制电路板智能缺陷检测研究

新一代信息技术的高速发展为制造业的转型与发展提供了机遇,同时也推动了制造质量管理方式的重大变革。本文结合制造业发展实际情况,概述了质量4.0的基本理论及关键技术,并进一步探讨了质量4.0的实施与落地应用。具体而言,将印制电路板(printed circuit board,PCB)缺陷检测作为研究案例,设计了基于质量4.0的PCB智能缺陷检测方案,并提出了缺陷检测的5个关键评价标准;提出的检测方案可有效帮助PCB制造企业过滤缺陷假点、控制产品良率、获取缺陷解决建议,并为员工掌握专业检测技能提供学习和培训平台。本文旨在研究质量4.0环境下的智能缺陷检测及其PCB中的应用,以推动制造业质量管理数字化和智能化转型。

PCB可靠性测试评估方法简述

印制电路板(PCB)技术向高密度、高集成化等方向发展,导致PCB可靠性问题日益凸显。针对PCB失效机理,并结合现有PCB标准及实践应用情况,详细介绍了3种PCB可靠性测试评估的方法——失效率预计法、加速试验预计法和试验鉴定法,以期为从业者开展PCB可靠性测试评估提供一定的帮助。

微波强化嗜酸氧化硫硫杆菌浸出废线路板中铜的条件优化

为提高电子废弃物中金属铜的生物浸出率,用微波强化嗜酸氧化硫硫杆菌(Aidithiobacillus thiooxidan)对废线路板中铜的浸出,采用Plackett-Burman法和Box-Behnken法优化强化浸出条件。Plackett-Burman法表明微波功率、辐照时间和浸出时间能够显著影响废线路板中铜的生物浸出率。最陡爬坡实验确定3因素的中心值为微波功率340 W、辐照时间3.60 min和浸出时间6.80 d。采用Box-Behnken法优化浸铜条件。研究发现,微波功率、浸出时间、微波功率和浸出时间及辐照时间和浸出时间的交互作用对浸铜有显著影响,辐照时间有影响但不显著。模型预测最优条件为微波功率336.10 W、辐照时间3.59 min和浸出时间6.82 d,预测最优浸出率为75.69%。调整微波强化废线路板中铜的生物浸出条件为微波功率336 W、辐照时间3.60 min和浸出时间6.80 d,实际铜浸出率为75.41%±0.76%,与模型预测结果相近。表明所得最优条件真实有效,可用于后续研究。

硫脲浸取回收废弃印刷线路板(PCBs)中的金银

研究用硫脲浸取金银技术从废弃印刷线路板中回收金银。结果表明,硫脲能够有效地从废弃印刷线路板中浸取金银,最佳浸出条件为固液比为1∶10,搅拌速度为300 r/m in,室温浸取（20-25℃）,浸取时间1h,硫脲浓度为12g/L,Fe^3＋质量分数为0.8%,pH为1.5。最佳条件下,金和银的浸取率分别达91.4%和80.2%。

基于网络层次分析法的废电路板树脂粉典型利用处置技术综合评价

面对产量快速增长的废电路板(WPCBs),通过机械物理等方法得到的废树脂粉若不能妥善利用处置会造成资源浪费和二次污染等一系列问题,亟须对现有WPCBs树脂粉典型利用处置技术进行综合评价。本研究运用基于网络层次分析法结合专家打分的综合评估方法,从资源、环境、经济、技术和社会五个方面构建网络层次关系,以确定其准则和指标间的联系与反馈,同时对WPCBs树脂粉三种典型利用处置技术填埋、焚烧和物理法进行优劣排序。研究结果表明,物理法以优异的环境、资源和经济准则获得最高的综合评价水平。最后以苏州某资源再生利用企业为例,应用本研究建立的评价模型对其开展在准则和指标方面的综合评价,验证了该模型的有效性,以期为WPCBs树脂粉工业化利用处置技术路线选择提供理论依据和参考。

废线路板利用过程重金属污染特征、迁移及风险评估

电子工业的发展和电器电子产品更新换代的加速使得废线路板产生量逐年增加.废线路板虽然资源回收价值高,但伴随其利用,重金属等污染物的释放会对生态环境和人体健康造成严重危害.因此,研究废线路板利用过程重金属的污染特征和迁移规律可为精准防控利用过程的重金属污染,保障人民群众健康和生态环境安全提供依据.本研究以采用机械分选工艺利用报废印刷线路板的企业为研究对象,通过采集车间内外不同环境介质样品,运用富集因子法和地累积指数法评价了废线路板利用过程重金属的富集和污染特征,并结合Pearson相关性分析、主成分分析等统计分析方法,阐明利用过程重金属的迁移规律,使用潜在生态风险指数法(RI)分析了潜在生态风险.结果表明,废线路板利用车间内灰尘和总悬浮颗粒物(TSP)中Cu浓度最高,Cd浓度最低;Sn、Cu、Pb、Cd、Zn在灰尘和TSP中表现出不同程度的富集;Sn、Cd、Pb在车间内主要分布于TSP中,但在车间外的富集程度和污染水平明显降低,表明其对车间外区域的影响范围有限.Cu、Pb、Sn、Cd等元素性质和在颗粒中的存在形态不同,其迁移特征也有所差异,但废线路板利用过程重金属的迁移规律总体可以总结为:破碎的小颗粒物料—车间内TSP—车间内灰尘/车间外—地表灰尘或土壤—扬尘—TSP.车间内灰尘和TSP的RI值分别为386、1706,Cu、Cd、Pb均是贡献最高的因子.因此,妥善处置定期清理的灰尘,保持车间相对密闭和微负压状态,并对收集的废气进行处理可有效控制废线路板利用过程重金属污染.