Role of substrate commensurability on non-reactive wetting kinetics of liquid metals

The dynamics of spreading of liquid metal atoms via molecular dynamics is considered vs. the commensurability of the solid surface with respect to the size of the liquid atoms. The solid surfaces are modeled as rigid (1 0 0) oriented Ni and, for two series of simulations, the lattice spacing of the substrate is varied from the regular equilibrium spacing to a commensurate situation with Au or Ag drops spreading spontaneously on top. The diffusion is calculated in the layered region of the liquid in contact with the two different solid surfaces and then compared. Then, the dynamic evolution of the contact angle is fitted to Molecular Kinetic Theory and compared with the two substrate geometries. It is observed that the friction parameter scales as the inverse of the diffusion in the interfacial region. The change in ordering induced by the commensurate substrate is characterized by examining the density profiles across the solid/liquid interface and fitting the curve by an exponential decay with a characteristic correlation distance 1/κ. It is shown that the commensurability/non-commensurability of the solid surface with respect to the liquid atoms changes the ordering, which plays a significant role in the dynamics, a feature not properly taken into account in the present formulation of Molecular Kinetic Theory.     

Thermodynamics and kinetics of dissolutive wetting of Si by liquid Cu

Wetting of Si single crystals by pure copper has been studied using the dispensed drop technique under high vacuum at 1100 °C. At this temperature copper dissolved large quantities of Si during spreading. CuSi droplets presaturated in silicon were also used to obtain non-reactive spreading. From the results obtained the different contributions to “dissolutive wetting” were determined. Moreover, a simple analytical model was formulated for analysing the influence on wetting of the interfacial atomic processes and of Si transport in the liquid. It is seen that, under our experimental conditions, solute transport by Marangoni convection controls the spreading kinetics.     

45钢表面制备V形凹槽及其摩擦学特性

采用声光调Q固体Nd:YAG激光器在45钢试样表面制备了V形凹槽织构,利用UMT2的销盘式摩擦方式考察了V形凹槽的几何参数对表面摩擦性能的影响。结果表明： 45钢表面制备的V形凹槽织构,在油润滑条件下能有效减小表面的摩擦因数;特别是在载荷较低、速度较大的工况下,织构面的平均摩擦因数最大可比未织构面减小64%。在试验范围内,平均摩擦因数普遍随着V形凹槽角度的增加而减小,随着边长的增大而减小,存在最优的横向和横向槽间距使得平均摩擦因数达到最小。     

不同实验装置测定粉尘湿润剂的湿润效果相关性

采用滴液法、正向渗透法和反渗湿润法分别研究了3种阴离子型湿润剂对10种硫化矿粉尘的湿润效果,比较了不同实验装置研究湿润剂湿润粉尘的相关性.结果表明:温度约20℃时,使用上述3种实验方法对相同的试剂和粉尘做湿润实验没有相关性,许多情况下还出现完全相反的结果;而对于相同的实验装置,3种湿润剂都具有较好的相关性.由此可以看出,实验室研究湿润剂所采用的方法在原理上要与应用现场的特征相适应,否则就将适得其反.     

Effect of Solder Thickness on Electromigration Behavior in Eutectic SnPb Solder Reaction Couples

The trend of miniaturization of electronic products induced the shrinking dimension of interconnects in the chip. When those interconnects are subjected to high current density (usually 10³ to 10⁴ A/cm²), electromigration (EM) could affect the reliability of the chip which would ultimately break the circuit. In this study, eutectic SnPb solders with thickness of 280, 128, and 50 μm were investigated under high current density (10⁴ A/cm²) and high ambient temperature (120 °C). The EM-induced surface undulations were more prominent at the shorter thickness, demonstrating that the diffusion of metal atoms/ions was controlled by the actual temperature in the bulk solder instead of the back stress. Bamboo groove features were observed on the surface of solder extrusion at the anode side for the three solder thickness, which indicated the metal atoms/ions that migrated parallel to the direction of flow of electrons.     

Thermal Fatigue in Solder Joints

Thermal fatigue in shear is an important cause of failure in electronic devices. Microstructures of solder joints with 5Sn-95Pb and 60Sn-40Pb solder contacts on copper have been studied and their performance in both isothermal and thermal fatigue investigated. In 5Sn-95Pb joints the shear fatigue failure is always through the solder rather than the solder-copper interface and occurs in an intergranular fashion. In 60Sn-40Pb joints, the shear fatigue failure occurs along bands of concentrated shear, but the shear induces a rapid coarsening of the eutectic microstructure which helps to concentrate the deformation.     

Solder paste metamorphism

Solder paste quality can be improved from microstructure and surface status of the solder powder.In this work,the micro-morphology of solder paste was observed ...     

金锡合金钎料焊膏与箔材钎焊性能对比研究

研究和比较了自制金锡合金焊膏与金锡合金箔材的相关性能。实验结果表明:金锡合金钎料焊膏的铺展性及润湿性优于箔材钎料;接头的显微组织和结构基本相同;在大气条件下,焊膏的钎焊性能比箔材钎料好;焊膏的剪切强度略低于箔材钎料。     

焊点形态对表面贴装元件无铅焊点可靠性的影响

表面组装焊点的几何形态是影响焊点可靠性的重要因素之一.本文采用有限元方法,重点讨论了润湿角对低银Sn2.5Ag0.7CuRE焊点的应力应变分布和热疲劳寿命的影响,并与Sn37Pb和Sn3.8Ag0.7Cu钎料焊点的热疲劳寿命进行了对比分析.研究表明,片式元件的理想接头形态为微凹形;在此形态下,与Sn37Pb和Sn3.8Ag0.7Cu钎料焊点相比,低银Sn-2.5Ag-0.7CuRE钎料的表面贴装元件焊点具有更高的热疲劳寿命.这一结果对于焊点的优化设计及新型无铅钎料的研制具有一定的指导意义.     

Initial rapid wetting in metallic systems

The initial rapid wetting of a solid surface by a liquid phase is an important step in many industrial processes. Liquid-phase sintering of powder metallurgical steels is one such industrial process, where metallic powders of micrometer size are used. Investigating the dynamic wetting of a high-temperature metallic drop of micrometer size experimentally is very challenging. Here, a phase-field-based numerical model is first implemented and verified by accurately capturing the initial dynamic wetting of millimeter-sized metal drops and then the model is extended to predict the dynamic wetting of a micrometer-sized metal drop. We found, in accordance with recent observations, that contact line friction is required for accurate simulation of dynamic wetting. Our results predict the wetting time for a micrometer-sized metal drop and also indicate that the dynamic wetting patterns at the micro- and millimeter length scales are qualitatively similar. We also found that the wetting process is much faster for a micrometer-sized metal drop compared to a millimeter-sized metal drop.     

纳米压痕法测量Sn-Ag-Cu无铅钎料BGA焊点的力学性能参数

对Sn-3．0Ag-0．5Cu无铅体钎料和Sn-4．0Ag-0．5Cu无铅钎料BGA(ball grid array)焊点进行了Berkovich纳米压痕法实验,通过改变不同的加载速率研究了钎料的蠕变特征．钎料压痕载荷位移曲线蠕变部分表现出了明显的加载速率相关性．基于Oliver-Pharrr法确定的体钎料和BGA焊点的Young’S模量分别为9．3和20GPa．基于压痕做功概念确定的体钎料和BGA焊点的应变速率敏感指数分别为0．1111和0．0574．钎料的力学性能有着明显的尺寸效应。     

SnAgCu系无铅钎料合金力学性能及钎焊性能研究

利用光学显微镜、扫描电子显微镜(SEM)和能谱分析仪(EDX)及Instron电液伺服疲劳拉伸试验机,对SnAgCu系无铅钎料合金的力学性能和钎焊性能进行了研究.结果表明,适量的稀土元素Ce的添加显著地延长了Sn3Ag2.8Cu钎焊接头在室温下的蠕变断裂寿命,Sn3Ag2.8Cu-0.1Ce钎焊接头的蠕变断裂寿命超过Sn3Ag2.8Cu钎料的9倍;同时,使Sn3Ag2.8Cu合金的延伸性能也得到了显著改善,伸长率达到15.7%;Sn3Ag2.8Cu-0.1Ce与铜基板的扩散层厚度比Sn37Pb厚,但是比Sn3Ag2.8Cu薄.     

低银Sn-Ag-Cu-Bi-Er焊料及其焊点的拉伸性能研究

采用差热分析、润湿性和力学性能试验研究了自主研发的一种新型低银无铅焊料Sn-XAg-0.3Cu-3Bi-0.05Er(SACBE)(X=1.0,1.5,2.0)及其焊点的拉伸性能。结果显示,与Sn-3.0Ag-0.5Cu(SAC)焊料相比,SACBE焊料具有较低的起始熔化温度(204～206℃)和较好的润湿性。Cu/SACBE/Cu焊点的拉伸强度与Cu/SAC/Cu焊点相当,但是其韧性显著改善。表明新型低银SACBE焊料,在保持SAC焊料优良物理力学性能基础上所具有的成本优势。     

新型船舶制造技术-搅拌摩擦焊

对搅拌摩擦焊的原理、特点以及在船舶制造工业中的应用进行了阐述，并且对搅拌摩擦焊在中国船舶制造领域的应用进行了展望。     

Solder engineering for optoelectronic packaging

In addition to providing electrical connections, solder is useful in the formation of passive, precision alignments for optoelectronic packaging. Different designs have demonstrated micrometer-level alignment accuracies, and the aligned structures are becoming more and more complex. Solder engineering has been successfully introduced into the field of optoelectronics, and it is expected to be applied to many other areas demanding low-cost, precision alignments.     

银基焊膏的研究进展

银具有高导电导热、耐腐蚀、抗氧化、延展性好等特性,制粉后添加不同合金元素与助焊剂以合适的比例混合制得的焊膏,在金属焊接与电子表面装联领域有着广泛的应用。结合近年来银基焊膏的最新研究进展,综述了银基焊膏中焊粉与助焊剂的研究现状,展望了银基焊膏的发展趋势。     

High-Temperature Oxidation of a Sn-Zn-Al Solder

The oxidation of 91Sn-9(95Zn-5Al) solder in theliquid state, 250°C, was studied by thermalgravimetric analysis (TGA). The oxidation behavior of63Sn-37Pb, 91Sn-9Zn, 99.4Sn-0.6Al, and Sn was alsoinvestigated for comparison. The weight gains per unitsurface area descend in the order: 63Sn-37Pb > Sn> 91Sn-9Zn > 91Sn-9(95Zn-5Al) > 99.4Sn-0.6Al.The initial weight gains of the materials investigated increase linearly with reaction time, whileparabolic behavior exists after the linear stage. Therate constants of the oxidation reaction for the tworeaction stages were determined. Activation energies for oxidation of the five materials weredetermined in the range of 250 to 400°C. Theactivation energies, derived from the linear rateconstants for the early stages of oxidation, are 27.7kJ/mole for 99.4Sn-0.6Al, 23.3 kJ/mole for 91Sn-9Zn, 21.4kJ/mole for 91Sn-9(95Zn-5Al), 20.5 kJ/mole for63Sn-37Pb, and 19.8 kJ/mole for Sn. Thesurface-oxidation behavior was investigated further withelectron spectroscopy for chemical analysis (ESCA) and Auger electronspectroscopy (AES). AES profiles showed that oxides ofZn and Al formed on 91Sn-9Zn and 91Sn-9(95Zn-5Al)solders, while tin oxide is formed on 63Sn-37Pbsolder.     

考虑定位误差的PCB焊点检测方法

定位误差会对AOI检测算法的性能产生影响.通过试验,定量研究了定位误差与误判率之间的关系.在现有AOI检测算法的基础上,提出在焊点统计学习阶段,通过对在位置、角度和尺度上存在定位误差的虚拟样本进行学习,使得系统能够学习到可能的定位误差.在评价AOI算法时,将定位误差考虑进来,定义了综合误判率作为AOI算法的性能评价方法...     

AgCuTi活性钎料的研究进展

AgCuTi系活性钎料是连接金属众多陶瓷及碳材料的理想钎料,解决了很多传统钎焊的难题。列举了常用商业AgCuTi的牌号及成分,简要分析了AgCuTi钎料的润湿性及影响AgCuTi润湿性的重要因素,综述了AgCTi活性钎料的一般制备方法与技术,以及AgCuTi活性钎料连接的典型应用与研究进展。