印制板的表面终饰工艺系列讲座 第二讲 超薄型超高密度挠性印制板的置换镀锡工艺

新型NCI-8888置换镀锡工艺获得的锡镀层致密、无铅、无锡须,能承受长时间高温烘烤和多次回流,可用于超高密度超薄型挠性印制板。介绍了该工艺的特点、工艺流程及规范,以及镀液的维护、镀液成分的分析。测定了不同置换锡镀层在不同条件下的焊接性能。结果表明,置换锡镀层焊接性能都较好。     

STRAIN EFFECT ON TRANSPORT PROPERTIES OF Nb3Sn MULTIFILAMENT STRANDS PREPARED BY INTERNAL TIN ROUTE

采用Pacman弹簧装置测量了4.2 K, 12 T条件下Nb₃Sn多芯股线的I_c--ε特征曲线. 材料轴向应变变化范围在-0.9%---+0.6%. 通过偏量比例模型模拟了材料临界电流I_c随应变状态的变化规律. 研究了轴向应变条件下超导材料载流能力(I_c)的衰退和lg V--lg I曲线斜率n值的变化, 通过临界电流随轴向应变的变化规律比较了不同制备工艺Nb₃Sn股线的轴向应变敏感性.     

微量Sn元素对高纯Cu线再结晶行为的影响

利用扫描电镜、强度测试仪分析了高纯铜线与微Sn合金铜线不同热处理温度下组织结构及强度、伸长率的差异,研究了高纯铜线、微Sn合金铜线再结晶行为及微量合金元素Sn对高纯铜线再结晶温度的影响机理。结果表明:Sn原子与铜原子间的化学交互作用与弹性交互作用,引起高纯铜的点阵畸变,阻碍再结晶过程中铜的晶界迁移,抑制再结晶和晶粒长大,使微Sn合金铜线再结晶温度由高纯铜线的400℃提高至450℃,且高纯铜线在热处理过程中晶粒增长与热处理时间呈四次方关系;微量Sn合金减少了无空气焊球热影响区长度,热影响区长度由150μm减少至120μm。     

SiC和Al2O3颗粒对Ti-25Nb-3Mo-3Zr-2Sn合金微磨损行为的影响

本文研究了SiC和Al₂O₃颗粒对生物医用植入材料Ti-25Nb-3Mo-3Zr-2Sn合金的微磨损行为的影响。在文中研究了合金的比磨损率、摩擦系数、磨损机制以及微磨损与腐蚀之间的协同作用。研究结果显示,合金的比磨损率随磨粒尺寸的增加而增加。由于SiC磨粒的硬度和切削性均优于Al₂O₃磨粒,由此在同尺寸磨粒下SiC磨粒所造成的材料的损失比Al₂O₃磨粒造成的要大。摩擦系数的结果显示,在同一种磨粒作用下,Hank’s溶液中所获得的摩擦系数的平均值大于蒸馏水中所获得的摩擦系数平均值,且由于Hank’s溶液的腐蚀性所致在Hank’s溶液中获得的摩擦系数的稳定性要比在蒸馏水中的稳定性差;在同尺寸磨粒下,Al₂O₃磨粒所造成的摩擦系数要大于SiC磨粒所造成的。随磨粒尺寸的减小,磨损机制由三体磨损转变为混合磨损之后再转变为二体磨损。从磨损机制图中可以看出腐蚀对材料损失的贡献是不容小视的,磨损机制为以磨损为主的磨损腐蚀。     

RE及Ni对Zn20Sn高温无铅钎料显微组织及性能的影响

在Zn20Sn高温无铅钎料合金中添加0.1%RE及0.2%~0.8%Ni(质量分数,下同),研究了RE及Ni对钎料合金显微组织及性能的影响。结果表明,在Zn20Sn中同时添加0.1%RE及0.2%~0.8%Ni后,钎料合金的固相线变化不大,而液相线温度降低;RE及Ni对钎料合金的润湿性能及显微硬度有明显的影响,当RE为0.1%、Ni为0.4%时,钎料合金的润湿性能最好、显微硬度最高;随着RE及Ni的添加,在钎料合金中形成了含Ni金属间化合物,且随着Ni含量的提高,金属间化合物的形状、钎料合金的组织结构发生显著变化。     

等离子喷涂参数对Ta／W／Sn复合涂层组织性能的影响

采用等离子喷涂方法在LY12铝上制备了Ta/W/Sn复合涂层。研究了各种工艺参数对涂层材料熔化程度和沉积效率的影响。采用扫描电子显微镜观察了复合涂层的表面及界面，精密机械天平称量涂层的增重，力学拉伸机测量涂层的抗拉结合强度，能谱和化学方法分析涂层的化学成分。结果表明，等离子喷涂工艺可以制作组织致密，厚度均匀的Ta/W/Sn复合涂层；喷涂功率和送粉速率对材料的熔化状态影响较大，在特定喷距范围内喷距的影响则较小。     

Cu 5Ni 4Sn 3Al合金的时效强化

根据合金的力学和电学性能, 利用ＸＲＤ,ＴＥＭ 和ＳＥＭ 技术研究了Ｃｕ５Ｎｉ４Ｓｎ３Ａｌ 合金的时效强化。结果表明：３５０ ℃下时效时, 力学性能增加; 边带分析有边带效应, 且随时效时间的增加调幅波长增加。电镜下观察到调幅结构, 说明该合金是调幅分解强化的合金。同时, 铝的加入没有改变合金的相结构, 但是, 对合金的强化起着重要作用。实验结果还表明, 合金在时效过程中, 调幅分解的同时还形成ＤＯ２２（ＴｉＡｌ３） 型结构的Ｎｉ３Ｓｎ 化合物相     

纯Sn焊料表面高温氧化膜的腐蚀演化行为（英文）

对150℃高温时效条件下纯锡焊料表面氧化膜形貌、组成、厚度及耐蚀性的演化行为进行研究。结果表明,高温时效加速焊料表面原有自然氧化膜层中的Sn(OH)₄向SnO₂转变,同时加速新鲜Sn基体的氧化,从而使纯Sn焊料表面氧化膜厚度和粗糙度随时效时间的延长逐渐增加。然而,表面氧化膜层的耐蚀性随时效时间的延长呈先增强而后减弱的趋势。此外,还对纯Sn焊料表面氧化膜层的成膜机制及膜层演化机制进行讨论。     

Numerical simulation of critical current performance in Nb3Sn strand subjected to periodic bending deformation

In the ITER Engineering Design Activity (EDA), four NB₃Sn model coils were developed and successfully tested. However, it was revealed that the critical current of the conductor degraded with the increase of electromagnetic force. One of the explanations of this phenomenon is a strand bending caused by enormous electromagnetic force. The authors therefore developed a simulation code using the distributed circuit model to investigate dependency of the critical current performance on the periodic bending deformation. The simulation results were in good agreement with the experiments. The dependence of the critical current on the periodic transverse load, temperature, periodic load pitch, thickness of Ta barrier which prevents Cu stabilizer from being contaminated by Sn, twist pitch of the strand, and RRR of the bronze matrix was investigated using the developed code. The results showed that the critical current degraded less with decreasing the pitch of the transverse load and increasing the Ta barrier thickness. It suggests that the shorter cabling pitch and the larger bending stiffness prevent the critical current degradation. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 7–15, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20923     

Interpolymer radical coupling: A toolbox complementary to controlled radical polymerization

The current review focuses on the relevance and practical benefit of interpolymer radical coupling methods. The latter are developing rapidly and constitute a perfectly complementary macromolecular engineering toolbox to the controlled radical polymerization techniques (CRP). Indeed, all structures formed by CRP are likely to be prone to radical coupling reactions, which multiply the available synthetic possibilities. Basically, the coupling systems can be divided in two main categories. The first one, including the atom transfer radical coupling (ATRC), silane radical atom abstraction (SRAA) and cobalt-mediated radical coupling (CMRC), relies on the recombination of macroradicals produced from a dormant species. The second one, including atom transfer nitroxide radical coupling (ATNRC), single electron transfer nitroxide radical coupling (SETNRC), enhanced spin capturing polymerization (ESCP) and nitrone/nitroso mediated radical coupling (NMRC), makes use of a radical scavenger in order to promote the conjugation of the polymer chains. More than a compilation of macromolecular engineering achievements, the present review additionally aims to emphasize the particularities, synthetic potential and present limitations of each system.