MLCC三层镀中甲基磺酸镀锡体系工艺条件对锡镀层性能影响的研究(续)

针对了片式多层陶瓷电容器（MLCC）三层镀甲基磺酸镀纯锡体系,提高镀液中Sn^2＋离子浓度、添加剂浓度及增大阴极电流密度对电流效率、沉积速度、最大允许电流密度及镀层性能等几个方面的影响.结果表明,提高Sn^2＋离子浓度和阴极电流密度后,添加剂Ⅰ按Sn^2＋离子浓度比例相应提高,添加剂Ⅱ浓度不变,阴极电流密度提高至0.3～0.35 A/dm^2,沉积速度加快,即镀得相同厚度的镀层,其电镀时间可比原来工艺缩短三分之一,收到缩短电镀生产周期、提高生产设备利用率的效果.     

SnCl_4-HCl体系废电路板元器件的分离及锡的回收

针对现有废旧线路板元器件分离及锡回收工艺所存在环境污染严重、效率低、难以大规模推广应用等问题,采用超声辅助下SnCl_4-HCl体系退除元器件管脚处焊锡,达到废线路板元器件分离的目的;同时,采用隔膜电积技术回收退锡液中的锡并再生出SnCl_4-HCl退锡剂。结果表明:在反应温度50℃、Sn~(4+)浓度30 g/L、盐酸浓度4.0 mol/L、超声频率40 kHz、超声功率100 W的条件下,反应20 min后废线路板元器件管脚及过孔处的焊锡全被退除。以退锡后的液体为电解液,采用隔膜电积技术回收退锡液中的锡;在温度35℃、电流密度200 A/m~2、异极距5 cm、石墨板为阳极、不锈钢板为阴极的条件下进行隔膜电积8 h,阴极得到了平整致密的电积锡,阴极电流效率97.3%,电锡纯度99.9%,阳极电流效率为88.8%,阳极液再生出SnCl_4-HCl溶液,可作为退锡液返回用于超声退锡。     

电迁移诱发镀层锡须生长行为分析

分析了0.3×104 A/cm2恒定电流密度和四种不同加载时间（0,48,144和240 h）电迁移条件对6.5 μm厚镀锡层表面锡须生长行为的影响,以及不同电流密度对阴极裂纹宽度的影响.结果表明,电迁移加速了镀层表面锡须的形成与生长,随着电迁移时间的延长,锡须长度不断增加.此外,电迁移导致在阴极首先出现了圆形空洞,随后在两极均形成了圆形空洞,并且在阴极处还发现有微裂纹存在,随着电流密度增加,阴极裂纹宽度也随之增加,电流密度为0.5×104 A/cm2时,平均最大裂纹宽度约为9.2 μm.     

基于隔膜电积的硫酸铅渣湿法提铅新工艺及电化学机理

根据物料平衡和电荷平衡原理,对Pb(Ⅱ)-Ac~--H~+-H_2O体系进行热力学分析,分析结果表明在接近于实际浸出液的pH值范围内,溶液中PbAc~+平衡浓度最高。以湿法炼锌产出的硫酸铅渣为原料,采用单因素实验法优化"乙酸盐配位浸出-隔膜电积提取铅"的主要工艺条件,采用单因素试验法优化乙酸铅溶液隔膜电积工艺条件,采用线性扫描、循环伏安等电化学测试手段研究Pb(Ⅱ)-Ac~--H_2O体系铅电积过程中阴极电化学行为。结果表明:在反应时间1h、浸出温度70℃、乙酸铵浓度4mol/L、液固比4:1的优化条件下浸出硫酸铅渣,铅浸出率93.28%。在电积温度30℃、Pb~(2+)浓度50 g/L、电流密度100 A/m~2的条件下阴极电流效率98%左右,每吨Pb直流电耗约700 kW·h。在此条件下以硫酸铅渣浸出液直接作为电积液隔膜电积8 h在阴极可以获得纯度99.2%较为致密平整的电铅,阴极电流效率96.16%。铅的还原沉积过程是一个不可逆过程,铅在电沉积初期遵循三维连续成核与颗粒长大机制,升高温度和提高阴极液Pb~(2+)浓度可以促进溶液离子扩散,提高电流效率。     

三氯化铝/盐酸三甲胺离子液体中电沉积制备AI-Ni合金镀层

目的 研究离子液体中Ni2+浓度对Al-Ni合金镀层结构和成分的影响,同时考察电流密度对镀层表面形貌和织构的影响.方法 采用脉冲电流法,在含有不同浓度氯化镍的无水三氯化铝/盐酸三甲胺离子液体中,于不同电流密度下电沉积制备Al-Ni合金镀层.利用扫描电子显微镜、X射线衍射技术和能谱分析仪探究离子液体中Ni2+的浓度对Al-Ni合金镀层结构和成分的影响,考察电流密度对镀层表面形貌和织构的影响.结果 随着离子液体中Ni2+浓度的增加,镀层中镍的含量增多,表面胞状颗粒逐渐变小,表面趋于均匀,当Ni2+的浓度为0.2 mol/L时,形成铝镍金属间化合物.另外,随着电流密度的增加,镀层表面形貌由针状晶体变为棒状颗粒,并且颗粒逐渐增大.结论 离子液体中Ni2+的浓度和电流密度对Al-Ni合金镀层表面形貌、结构和成分有一定的影响.当溶液中Ni2+的浓度为0.2 mol/L、电流密度为6 mA/cm2时,电沉积4 h可制备得到厚度为10μm、由3μm大小晶粒组成、含有铝镍金属间化合物的合金镀层.     

基于数值模拟的电镀3D打印厚度均匀性研究

目的 优化电镀3D打印工艺,提高单层电沉积厚度的均匀性。方法 建立耦合电解液流动、物质传递、电极反应的多物理场模型,并数值求解,研究反应离子浓度和电解液电势的分布云图,以及沉积层截面形貌随时间的演化规律,分析影响沉积层厚度均匀性的直接因素。最后讨论抑制剂本体浓度C_S、对流流速u₀、电解液电导率κ及阴极电位φ_c等因素对沉积层厚度均匀性的影响规律。结果 随着沉积时间的增长,沉积层的形貌越发不平整,反应离子浓度和电解液电势的分布云图随沉积层截面形貌的变化而变化。加入40 μmol/L抑制剂后,沉积层表面的反应离子浓度和过电势的分布更加均匀。抑制剂本体浓度越高,沉积层截面形貌越平整,沉积层厚度均匀性越好,但存在一个饱和抑制剂浓度40 μmol/L。沉积层厚度均匀性随对流流速或电解液电导率的增大先增后减,随阴极电位增大单调递增。结论 阴极表面反应离子浓度和过电势的不均匀分布是导致沉积层厚度不均匀性的直接因素。添加抑制剂可有效改善沉积层厚度的均匀性,过大或过小的流速或电导率都会降低沉积层的厚度均匀性,适当提高阴极电位可提高沉积层厚度...     

基于超临界流体电铸耦合场分析及试验研究

利用COMSOL Multiphysics对超临界流体电铸耦合场进行数值模拟,研究分析电流密度分布和电铸层生长规律,并且试验测试与验证;同时对超临界流体镍纳米金刚石复合镀层的表面形貌和显微硬度进行研究和探讨。结果表明,阴极边缘处电流密度远高于阴极中间部分,电铸层生长情况与电流密度分布较为吻合,电铸层中部厚度预测值的误差较小;电铸层显微硬度HV最大可达9540 MPa,比普通情况下复合铸层提高80%;制备的复合电铸层表面平整,组织致密。     

碳纳米管／锡基轴瓦合金复合减摩镀层的制备

采用复合电沉积方法在铜基轴瓦合金的表面制备碳纳米管/锡基轴瓦合金复合减摩镀层,研究了电沉积工艺参数对碳纳米管/锡基复合镀层的组织与性能的影响.结果表明,当阴极电流密度为1.5A/dm2,镀液中碳纳米管的质量浓度为2 g/L、镀液的pH值为1时,镀层生长良好,碳纳米管分布均匀.     

基于阳离子型聚丙烯酰胺高聚物溶液的电化学沉积试验研究

以阳离子型聚丙烯酰胺(CPAM)高聚物为唯一添加剂,采用直流电源在超低电压下开展锌镀层电化学沉积试验,重点研究了CPAM离子度对锌镀层表面形貌、成分和电流密度的影响,考察了主盐Zn2+和CPAM的质量浓度对镀层微观形貌、晶粒平均直径的影响规律。结果表明:离子度20%的CPAM-ZnSO4高聚物溶液在0.3 V超低电压下获得的沉积层致密、晶粒尺寸均匀、表面平整光亮且电流密度达0.47 A/dm2;随着Zn2+和CPAM的质量浓度增加,镀层中锌含量增多,沉积层表面形貌由圆形颗粒变为片状晶体且表面晶粒细化;当Zn2+质量浓度40 g/L、CPAM质量浓度20 g/L、电压0.3 V时,电沉积5 min时,可制备出表面光亮、晶粒平均直径87 nm的镀锌层。     

20#钢/锡青铜偶对在流动海水中的电偶腐蚀行为研究

20#钢穿舱件和锡青铜阀电偶腐蚀是船舶海水管路系统严重腐蚀部位之一。为控制20#钢/锡青铜电偶腐蚀延长海水管路系统寿命,本文通过原位测量20#钢管材和ZCuSn5Pb5Zn5锡青铜管材在静态以及1、3和5 m/s流速海水中的电偶电位和电偶电流,分析电偶腐蚀速率随时间和流速的变化规律;同时采用扫描电镜(SEM)和激光Raman光谱仪分析腐蚀形貌和腐蚀产物组分。结果表明,在不同流速海水中,20#钢与ZCuSn5Pb5Zn5合金间存在明显的电偶腐蚀倾向,20#钢作为阳极加剧腐蚀,ZCuSn5Pb5Zn5合金作为阴极受到保护;相比于静态海水,20#钢阳极极化电流密度和ZCuSn5Pb5Zn5合金阴极极化电流密度在流动海水中显著增加,电偶腐蚀显著加剧,1 m/s流速下的电偶腐蚀速率是静态下的17.5倍;当海水流速达到5 m/s后,20#钢表面形成了致密性较高、活性低的腐蚀产物沉积层,电偶腐蚀速率减小。     

Current density limitation and diffusion boundary layer calculation using CFD method

The knowledge of limiting current density and thickness of diffusion boundary layer is particularly important in improving space-time-yield of electrolysis and especially of high current-density electrolysis. Both natural and forced convection of electrolyte flow are considered in the presented computational fluid dynamics model for calculation of these values. Natural convection is modeled by implementation of a source term at the cathode surface for copper concentration according to Faraday’s law, which allows calculation of electrolyte density for each volume cell of the grid. Forced convection is considered as flow of electrolyte through the cell generated by electrolyte inlet and outlet. By variation of current density, the limiting current density can be calculated with a copperion concentration of zero at the cathode surface after reaching the steady-state conditions in electrolyte. Time dependency of diffusion boundary layer thickness is shown for a chosen cell geometry. Literature data and measured and calculated values of both quantities are in good agreement.     

切割用等离子弧的数值分析

以转移型直流电弧等离子体切割炬为研究对象,根据局部热力学平衡假设和磁流体动力学理论构建了电弧数学模型,采用数值模拟方法分析了等离子体炬内等离子体的传热和流动特性,阴极形状、锥角、内缩量和喷嘴形状对切割气流的速度和等离子温度分布的影响.并对五种常用形状阴极和两种不同内缩量的割炬内等离子流体速度场和温度场进行了比较.从数值分析的角度验证了阴极斑点较小的阴极能产生较大的焰流速度和热量,以及内缩量的增加对电弧的压缩具有显著作用.     

Fabrication of microprism mould by electroforming with high electrolyte flowrate

Abstract

Electroforming is applied to fabricate microprism moulds, however only low working current density is employed because the higher current density at the edge limits the usable value of the working current density. Reduction of current density at the edge is a key in the enhancement of the working current density. In this paper, a secondary cathode was introduced to lower the edge current density. By this technique, the edge current density of the primary cathode surface is not only weakened obviously but can be even lower than that of the others. In addition, a high electrolyte flow rate has been introduced to improve working current density. Experimental results show that both the microhardness and tensile strength of the electroformed layer increase with electrolyte flowrate. By using both secondary cathode and high speed electrolyte flow, the electroforming time could be reduced significantly and mechanical properties of the electroformed layer are not adversely affected in electroforming of microprism moulds.     

片状偏钨极电弧特性的数值模拟

基于流体力学和麦克斯韦方程组,建立片状偏钨极电弧三维数学模型,计算得到电弧温度场、流场、电场及电流密度分布.结果表明,片状偏钨极厚度方向电弧温度场、流场、电场及电流密度呈对称分布;相同焊接工艺参数下,片状偏钨极电弧最高温度、最大流速及电流密度小于圆柱钨极电弧;电流密度受片状偏钨极前端斜边引导作用和电弧惯性后拖效应的共同影响,其分布范围沿钨极宽度方向扩展,且电弧等温线在该方向上扩张;片状偏钨极前端斜边倾角的改变,会引起电流密度在钨极前端局部集中,并导致阴极下方高温区和阴极射流沿斜边偏移.     

Evaluation of flow behavior in copper electro-refining cell with different inlet arrangements

The arrangement of electrolyte inlet in the copper electro-refining (ER) cell has a great influence on the local flow field, which affects the distribution of electrical current density in consequence. In order to understand the complicated phenomena of electrolyte flow behavior in vertical counter electrodes in full-scale copper ER cell, the three-dimensional computational fluid dynamics (CFD) models with four different arrangements of electrolyte inlets, i.e., single inlet (SI), central bottom inlets (CBI), top side interlaced inlets (TII), and bottom side interlaced inlets (BII), were established to simulate the flow behavior. Simulation results have revealed that the parallel injection devices help to improve the electrolyte velocity between electrodes, and while the relative range of electrolyte velocity in CBI exceeds that of TII and BII, which is more than 4 times, indicating its severer unequal flow distribution. Meanwhile, the average velocity of electrolyte in BII is 4 times larger than that of SI due to its higher turbulence intensity. Generally, one of the efficient ways to supply fresh copper solution rapidly and uniformly into the inter-electrode space is to adapt the arrangement of BII. By utilizing such an arrangement, the electro-refining under high electrical current density is possible, and the productivity can be increased in sequence.     

A numerical model for deep penetration welding processes

The general features of a numerical model, and of its extensions, for calculating the temperature and fluid velocity field in a three-dimensional workpiece undergoing deep penetration laser beam welding are described. In the current model, the deposition of power from the beam is represented by time-dependent boundary conditions on the equations of energy and momentum transfer. These boundary conditions are specified at each timestep on a surface whose configuration can change with time and upon which energy is deposited according to a specified power distribution. This model also includes the effects of the buoy-ancy force on the melt pool and of the surface tension gradient on the surface of the fluid. The coupled equations of energy, momentum transfer, and continuity combined with the time-dependent boundary conditions representing the keyhole and the moving boundaries of the workpiece are solved by using a specific implementation of the SIMPLE algorithm. The important features of the numerical methods used in the model are discussed. Isotherms and convection patterns calculated using the current model are presented, and their significance for predicting weldment properties is discussed. A significant result of the simulations is that they demonstrate the overwhelming influence of the keyhole vapor/liquid inter-face on fluid convection and conduction in deep penetration welding.     

SPCC钢碱性无氰直接预镀铜工艺研究

目的提高LED支架的性价比,减少SPCC钢表面镀银预镀铜工艺的镀液污染,简化现有的预镀镍-镀铜施镀工艺,提高预镀层质量。方法采用HEDP碱性无氰直接预镀铜方法来简化工艺,用单因素实验法,系统研究了电流密度、镀液pH、电镀温度、HEDP/Cu~(2+)摩尔比、电镀时间等参数,对镀层镀速、孔隙率及镀层表面质量的影响,并表征镀层的微观组织及镀层结合力。结果在阴极电流密度为1.41 A/dm~2,pH值为9.5,温度为50℃,HEDP/Cu~(2+)摩尔比为3.75:1(Cu~(2+)为10 g/L),时间为11 min的条件下,可获得镀速约为1.7 mg/(cm~2·min)的预镀铜层,且镀层与基体的结合力良好,无孔隙,呈良好的光亮/半光亮状的细晶镀层。结论与钢铁表面氰化镀铜及镀银前预镀铜工艺相比,推荐的HEDP直接预镀铜工艺的镀层质量好,可满足直接镀铜和镀银前预镀铜工艺要求,可有效减少镀液污染和简化施镀工艺,对SPCC钢的镀铜工艺改善具有较好的推广价值。     

电镀锌铁合金工艺及光亮剂的研究

介绍了一种硫酸盐电镀锌铁合金工艺及新型光亮剂。研究了镀液中FeSO4.7H2O浓度、锌铁总离子浓度、光亮剂用量、阴极电流密度、pH值、温度等因素对镀层含铁量的影响。结果表明:随着镀液中锌铁总离子浓度和温度的升高,镀层的含铁量降低;随着阴极电流密度和pH值的增大,镀层的含铁量先增加,后降低;随着FeSO4.7H2O浓度的升高,镀层的含铁量增加。探讨了新型光亮剂对镀层的影响,获得了最佳电镀方案。     

镍-氧化锆纳米复合电铸层微观形貌影响因素的分析

用SEM分析了诸如电铸时间、电流密度、镀液中纳米ZrO2颗粒悬浮量、电流形式和阴极表面粗糙度等因素对Ni-ZrO2纳米复合电铸层微观形貌的影响.结果表明,电铸时间、阴极电流密度以及镀液中纳米ZrO2悬浮量对纳米复合电铸层微观形貌有一定程度的影响,采用脉冲电沉积工艺有助于获得表面光滑平整、显微组织均匀致密的纳米复合电铸层.