Kinetic analysis of the thermal degradation of printed wiring boards

The non-isothermal pyrolysis of printed wiring boards (PWBs) was investigated by simultaneous thermogravimetric and differential thermal analysis (TG-DTA) in the temperature range of 300–1200 K. Pyrolysis experiments were carried out on PWBs samples at three different heating rates of 10, 20, and 30°C/min. In this study, the kinetic parameters of PWBs pyrolysis have been estimated using model free and model fitted methods.     

废弃电路板金属资源特点及其湿法冶金再生技术的发展现状

介绍了我国金属资源面临的挑战、废弃电路板中的金属资源特征和循环利用的重要意义,并重点综述了废弃电路板中金属资源的湿法冶金再生技术的发展与现状.     

从废弃印刷线路板中回收金的试验

试验研究了采用硫脲法有效地从废弃印刷线路板中回收金。试验结果表明，硫脲回收金的主要影响因素有：温度、硫脲质量浓度、Fe^3＋质量分数、浸出时间、硫酸体积分数；合适的浸出条件是：固液比为1：5，浸出温度为35℃，硫脲质量浓度为10g／l，Fe^3＋抖质量分数为0．3％，浸出时间为1h，硫酸体积分数为5％。     

从废弃印刷线路板中回收金的试验

试验研究了采用硫脲法有效地从废弃印刷线路板中回收金.试验结果表明,硫脲回收金的主要影响因素有温度、硫脲质量浓度、Fe3+质量分数、浸出时间、硫酸体积分数;合适的浸出条件是固液比为15,浸出温度为35℃,硫脲质量浓度为10g/l,Fe3+质量分数为0.3%,浸出时间为1h,硫酸体积分数为5%.     

Electric discharge in the process for recovering the wastes of printed circuit boards

This paper proposes a new process to separate components at the recovery of waste printed circuit boards and probably other waste of electronic equipment production.     

Pressure leaching of metals from waste printed circuit boards using sulfuric acid

Printed circuit boards (PCBs) are essential components of electronic equipments which contain various metallic values. This paper reports a hydrometallurgical recycling process for waste PCBs, which consists of the novel pretreatment consisting of organic swelling of PCBs followed by sulfuric acid leaching of metals from waste PCBs. To recycle the waste PCBs, experiments were carried out for the recovery of copper from the crushed and organic swelled materials of waste PCBs using sulfuric acid leaching in presence of hydrogen peroxide under atmospheric and pressure condition. The leaching of PCBs at 90°C, pulp density 100 g/L under atmospheric condition, using 6M sulfuric acid resulted in the dissolution of a minor amount of copper due to the presence of plastic coating on the surface of metallic layers. On the other hand, when the liberated metal sheets from organic swelled PCBs were treated with dilute sulfuric acid of concentration 2M along with hydrogen peroxide in an autoclave under oxygen atmosphere, the percentage recovery of copper was found to increase from 59.63% to 97.01% with an increase in hydrogen peroxide concentration from 5 to 15% (v/v) keeping constant pulp density 30 g/L.     

The inspection of solder joints on printed circuit boards by phase-shift holographic interferometry

The principle of inspecting solder joints on printed circuit boards (PCBs) by phase-shift holographic interferometry is described. By using this technique, defective solder joints can be easily distinguished from good ones without analysing complicated holographic interferograms. Experiment shows that most defects in solder joints, such as breaks and voids, can be detected successfully.     

Automated assembly of electro-optical components onto printed circuit boards with integrated optical waveguides

The performance of information- and communication-systems will be defined in the future increasingly by their interior capacity of signal transmission. The feasible bandwidth of the conventional electrical signal transmission is limited because of physical properties like wave propagation and length of conductors. Due to the different nature of optical signal transmission inside printed circuit boards, those effects are avoided and therefore with this technology, a significant increase in data transfer rates can be achieved. For this reason, optical signal transmission finds its way into conventional electronic systems and substitutes electrical based high frequency transmission lines. This type of assembly results in hybrid systems where electrical and optical technology coexist. In view of promising system solutions, increased research and development activities take place with a focus especially on assembly and packaging technologies. This article describes the conceptual design and implementation of a continuous process chain for manufacturing electro-optical packages, which makes it possible to interlink the so far incompatible technologies of electrical and electro-optical assembly.     

A process for extracting precious metals from spent printed circuit boards and automobile catalysts

In this work, a novel process to simultaneously extract precious metals such as gold, palladium, and platinum from spent printed circuit boards (PCBs) and honeycomb-type auto catalysts by smelting without the addition of any collector metals has been developed. The process uses metal components such as copper, tin, and iron contained in spent PCBs as the collector metal and spent auto catalysts as a slag formative. In each experiment, spent PCBs and auto catalysts were crushed, incinerated, and melted after adding fluxes and carbon. Up to 90% of the gold, palladium, and platinum in the raw materials were extracted in a Cu-Sn alloy phase. For more information, contact Jae-chun Lee, Korea Institute of Geoscience & Mineral Resources, Minerals & Materials Processing Division, 30 Gajeong-dong, Yuseong-gu, Daejeon 305-350, Korea; 82-42-868-3020; fax 82-42-861-9727; e-mail jclee@kigam.re.kr.     

真空热解预处理对回收废线路板中铜的影响

先采用间歇式固定床真空热解中试装置对废线路板进行真空热解前处理,然后利用剪切破碎和气流分选方法对真空热解渣中的金属铜进行回收,着重分析与讨论真空热解过程中线路板的分层机理,真空热解对破碎过程中铜单质解离度及破碎规律的影响,真空热解对气流分选过程中铜品位及回收率的影响。结果表明:真空热解强化线路板各材料层之间的分层效果显著,增大了粗粒级破碎物料中铜单质的解离度及铜的质量分布率,大幅度提高了分选产品中的铜品位及回收率,铜的回收指标远远优于未经真空热解前处理的线路板。尺寸为40mm×40mm的线路板先在升温速率15℃/min、反应温度600℃、绝对压力20kPa及恒温时间60min的条件下进行真空热解前处理,再经剪切破碎,对于粒级为0.45～4.0mm的破碎产物,铜单质的解离度大于97.06%,铜的质量分布率为98.64%,回收产品中铜品位为99.50%,铜的总回收率为99.86%。     

Preparation of pure SnO_2 powders from tin slag of printed circuit boards waste

The recycling method and principle of SnO2 from the tin slag of printed circuit boards(PCB) waste were investigated. In this study, pure SnO2 powders were obtained through a multi-step process including ball-milling, roasting, dissolving, precipitating, and pickling. The total recovery rate of tin can be up to 91 %. The SnO2 powders obtained is the single phase, and the content of SnO2 is up to 99.9 %. However, the SnO2 particles are easier to agglomerate during the precipitation process. The agglomerate SnO2 particles are about 7.778 lm in mean particle size(D50). This preparation method presents a viable alternative for the tin slag recycling. The tin is not only recycled, but also reused directly to prepare pure SnO2 powders.     

Nanolayer CrNx/WNy coatings used on micro drills for machining of printed circuit boards

A series of CrNx/WNy nanolayer coatings were synthesized using an industrial-scale four-target DC closed-field unbalanced magnetron sputtering ion plating system (CFUBMSIPS?), employing one W target and three Cr targets. For comparison, a monolayer CrN coating was also grown on the same deposition system. Characterization was conducted using EDX, SEM, TEM, AFM, XRD, nanohardness indentation tester, and scratch tester. Performance of cutting tools with the nanolayer coatings was carried out via machining tests using the coated micro drills to continuously make through-thickness holes on printed circuit boards. The results showed that nanolayer CrNx/WNy coatings with various modulation period (λ) could be obtained on an industrial-size deposition machine by means of control in the current applied to the W target. Of the studied nanolayer CrNx/WNy coatings, the one with λ = 27 nm showed the highest nanohardness and best micro drilling performance. This nanolayer coating showed significant improvements in cutting performance as compared with the referred monolayer CrN coating.     

Recovering plastics for recycling by mineral processing techniques

Patents and other literature on recycling post-consumer plastics from various sources (e.g., municipal solid waste) indicate that unit operations common to minerals processing have been seriously considered at various times. A review of the available literature and statistics on recoverable plastics reveals that only 2.4 percent is recycled. This article presents a flowsheet that we developed and tested in a bench-scale pilot plant. It shows that a combination of mineral processing techniques, including comminution, heavy media separation, and flotation, can be successfully adapted to the recycling of post-consumer plastics. The gamma flotation process, which operates on the basis of solution surface tension control to facilitate the separation of inherently hydrophobic solids, combined with the alkali-treatment of a mixed polyvinal chloride-polyethylene terephthalate feedstock generates clean polymer concentrates at high recoveries.     

Application of magnetic pulse welding technique for flexible printed circuit boards (FPCB) lap joints

The magnetic pulse welding (MPW) is a high speed solid state welding process which has been used successfully to provide metallurgical and electrical bonds between flexible printed circuit board (FPCB) with using: (1) welding with aluminum driver sheet and (2) without driver sheet. The optimum bank energy for reliable bonding was about 1 kJ with 160–180 kA maximum current. The maximum tensile shearing for most welded samples was nearly same as tensile shearing strength of copper layer of FPCB sheet.     

图像处理方法在自动化加工中的应用

在自动化加工中,有时需要识别产品或工件的颜色、形状、中心等综合性状.在简单分析传统图像处理系统的缺点的基础上,设计了一种新的嵌入式图像采样处理系统.该系统包括CMOS图像传感器OV7620、SRAM帧存储器IS61LV25616、CPLD/FPGA控制器EPF10K10LC84-3及数字信号处理器TMS320VC5416.提出了一种RGB空间到HIS空间的方法.系统可明显提高自动化生产线灵活性和可靠性.