Electromotive force study of the liquid silver-bismuth-tin alloys

The Ag−Bi−Sn alloy system has been assessed twice, so far, for its potential applications as a lead-free solder material. The first assessment was based on binary data only; the second assessment introduced ternary parameters. It was noted in conclusion that more experimental studies were needed, especially for the liquid phase. The electromotive force (emf) measurement method was used in this study to determine the thermodynamic properties of liquid Ag−Bi−Sn alloys using solid electrolyte galvanic cells as shown below: Re, Ag−Bi−Sn, SnO₂ |Yttria Stabilized Zirconia| Ni, NiO, Pt, Re, Sn, SnO₂ |Yttria Stabilized Zirconia| Ni, NiO, Pt. Alloy compositions for in vestigation were chosen along three constant Bi-to-Sn ratio lines (1/3, 1, and 3) and with the silver content changing from 10 up to 90 at.%, every 10 at.%, resulting in a total of 27 different alloy samples. The temperature of the measurements varied from 975 to 1400 K. A linear dependence of the emf on temperature was observed for all compositions, and the appropriate line equations were derived. Excess partial Gibbs energies of Sn were then calculated at 1200 K and compared with the results of the calculations of both assessments; Gibbs energy of formation of SnO₂ was determined as well. It was then shown that our new emf data fit better to the binary formalism-based calculations than to the second assessment results.     

无铅铜铋轴承合金的摩擦学特性

采用粉末冶金方法制备了几种典型铜基轴承合金,在HDM-20端面摩擦磨损试验机上进行了边界润滑条件下的摩擦磨损试验,分析了其摩擦学性能.结果表明:3.0％ Bi铜铋轴承合金具有较好的减摩、抗粘着性能,与典型铜铅轴承合金(Cu10Sn10Pb)相比,减摩性能稍好,耐磨性能稍差;两种轴承合金磨损量均随速度的增加而增加,而摩擦系数则随速度增加而降低.摩擦磨损过程中析出表面的铋可起减摩、抗粘着作用,并存在铋的析出、磨损脱落的过程.     

Sn-0.3Ag-0.7Cu-xNd钎料显微组织及性能

研究了稀土元素Nd的添加量对超低银无铅钎料Sn-0.3Ag-0.7Cu的润湿性能、显微组织和力学性能的影响.结果表明,微量Nd元素的加入可以显著改善Sn-0.3Ag-0.7Cu超低银无铅钎料的润湿性能和焊点的力学性能,并且能够起到细化基体组织的作用.当钎料中Nd元素的质量分数达到0.1%时,钎料的综合性能最佳,基体组织最为均匀细化.虽然Ag元素含量的降低使钎料的性能有所下降,但是加入适量Nd元素后钎料的润湿性能已接近传统Sn-3.8Ag-0.7Cu钎料.     

电子组装用无铅钎料的研究和发展

综述了近年来国际上无铅钎料的研发现状,重点介绍了无铅钎料的性能要求。指出研究无铅钎料,不只是简单地提供一种替代品,还需要考虑无铅钎料的力学性能、钎焊性能及焊点可靠性能够与传统的Sn-Pb钎料相近、钎焊设备与工艺尽量改动不大等因素,开展无铅钎料的研究具有十分重要的理论意义和实用价值。详细讨论了Sn-Ag系、Sn-Cu系和Sn-Ag-Cu系等三大系列的无铅钎料,指出无铅化电子组装面临着机遇与挑战,要想在激烈的国际竞争中赢得市场,我国必须重视无铅钎料产品的研究开发与产业化,这同时需要电子企业的全力支持与配合。     

Mechanical properties of QFP micro-joints soldered with lead-free solders using diode laser soldering technology

Soldering experiments of quad flat package(QFP) devices were carried out by means of diode laser soldering system with Sn-Ag-Cu and Sn-Cu-Ni lead-free solders, and competitive experiments were also carried out not only with Sn-Pb eutectic solders but also with infrared reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode as well as the fixed laser soldering time, an optimal power exists, while the optimal mechanical properties of QFP micro-joints are gained. Mechanical properties of QFP micro-joints soldered with laser soldering system are better than those of QFP micro-joints soldered with IR reflow soldering method. Fracture morphologies of QFP micro-joints soldered with laser soldering system exhibit the characteristic of tough fracture, and homogeneous and fine dimples appear under the optimal laser output power.     

Effect of cerium on microstructure and mechanical properties of Sn-Ag-Cu system lead-free solder alloys

The melting point, spreading property, mechanical properties and microstructures of Sn-3.0Ag-2.8Cu solder alloys added with micro-variable-Ce were studied by means of optical microscopy, scanning electron microscopy（SEM） and energy dispersive X-ray（EDX）. The results indicate that the melting point of Sn-3.0Ag-2.8Cu solder is enhanced by Ce addition; a small amount of Ce will remarkably prolong the creep-rupture life of Sn-3.0Ag-2.8Cu solder joint at room temperature, especially when the content of Ce is 0.1%, the creep-rupture life will be 9 times or more than that of the solder joint without Ce addition; the elongation of Sn-3.0Ag-2.SCu solder is also obviously improved even up to 15.7%. In sum, the optimum content of Ce is within 0.05%-0.1%.     

微连接用碳基纳米颗粒增强无铅复合钎料的研究新进展

综合评述含碳纳米管、石墨烯纳米片等碳基纳米颗粒增强微连接用无铅复合钎料的研究现状,介绍了碳纳米管、石墨烯纳米片、富勒烯、金属改性碳纳米管(石墨烯纳米片)等增强相对无铅钎料和钎焊接头组织与性能的影响。简述了无铅复合钎料的制备方法、熔化特性、导电性、润湿性、力学性能和无铅复合钎料焊点可靠性等,指出了碳基纳米颗粒增强无铅复合钎料存在的问题、解决措施及发展趋势。     

Ag元素含量对SnAgCuX无铅钎料性能的影响

分析了SnAgCuX系无铅钎料中Ag异元素含量的变化对熔化温度、润湿性能的影响,同时研究了时效前和高温时效后钎焊接头的抗剪强度和显微组织,其中X包含Ni,P和Ce三种元素.结果表明,添加微量X元素能够在一定程度上弥补snAgCu钎料中Ag元素含量的降低引起的性能下降.X元素的添加对SnAgCu钎料的熔化温度影响不大,但能改善钎料合金的润湿性能,提高钎焊接头的抗剪强度,并抑制时效引起的接头强度下降.这与微量X元素的添加改善了钎料的显微组织和金属间化合物的形貌有很大的关系.     

电子互连无铅钎料及焊点蠕变行为研究进展

针对近年来无铅钎料及焊点的蠕变失效问题,综合评述了蠕变变形行为及其在焊点可靠性评估中的应用。首先系统地介绍无铅钎料的蠕变行为,探讨含合金元素/颗粒无铅钎料蠕变性能改性机制。其次评述焊点蠕变行为,探讨焊点成分以及不同基板材料对焊点蠕变特性影响的研究进展。再次结合具体电子器件,采用有限元模拟,分析基于有限元的焊点蠕变响应及疲劳寿命预测,评估焊点可靠性。最后针对无铅钎料及焊点蠕变行为的未来发展进行展望,分析其研究中存在的问题及解决办法,为焊点可靠性进一步研究提供理论支撑。     

Thermodynamic study of the phase equilibria in the Sn−Ti−Zn ternary system

The Sn−Ti−Zn ternary phase diagram has been constructed using the CALPHAD technique. The Ti−Zn binary system phase boundaries were determined using differential scanning calorimetry and the solid-liquid diffusion couples method. In addition, the formation energy of some stoichiometric compounds was obtained using first-principle band energy calculations. For the ternary system, some alloys were prepared by equilibration at 600 or 700 °C, and the compositions of the precipitates were analyzed using electron probe microanalysis. Thermodynamic assessment of the Ti−Zn and Sn−Ti−Zn systems was performed based on the experimental information and by adopting reported values of the thermodynamic properties of the Sn−Zn and Sn−Ti binary systems. Microstructural observation showed that Sn₃Ti₅Zn₁₂ exists in the ternary system. Seven types of invariant reaction on the Sn-rich liquidus surface of the ternary system are predicted by the phase diagram calculations. The ternary eutectic point falls at 0,0009 mass% Ti and 8.69 mass% Zn, at T=192.40°C, which is slightly lower than the calculated eutectic point of Sn−Zn binary alloy (T=192.41°C). Based on these results, a nonequilibrium solidification process using the Scheil model was simulated. This paper was presented at the International Symposium on User Aspects of Phase Diagrams, Materials Solutions Conference and Exposition, Columbus, Ohio, 18–20 October, 2004.     

两种雾化无铅焊锡粉末特性及钎焊接头显微组织

采用扫描电镜(SEM)和激光粒度分析仪研究了无铅焊锡粉末Sn3Ag2.8Cu和Sn3Ag2.8cu旬.1Ce的特性诸如球形度、粒度分布、润湿性及钎焊接头的显微组织,并与对应合金的润湿性及钎焊接头显微组织进行了对比.结果表明:Sn3Ag2.8Cu和Sn3Ag2.8Cu-0.1Ce粉末都具有较好的粒度分布和球形度;与传统Sn37Pb粉末和Sn3Ag2.8Cu粉末相比,Sn3Ag2.8cu_o.1Ce粉末均具有更好的润湿性;在与铜基板的钎焊中,Sn3Ag2.8Cu-0.1Ce粉末的扩散层比Sn3Ag2.8Cu粉末更薄,但两种粉末与铜基板形成的扩散层均比其对应合金与铜基板的扩散层更厚.因此,Sn3A萨.8Cu-0.1Ce粉末具有更好的综合性能.     

Thermodynamic prediction of the composition of Fe-based amorphous alloys

The liquidus univariant lines of the Fe-Nb-B ternary system have been thermodynamically calculated by means of CALPHAD method and Fe-based thermodynamic data. It is found that there are two eutectic reactions in the Fe-rich corner,that is,（1） L（Fe-3Nb-15B） →α＋γ＋ M2B （1430 K）,and （2） L（Fe-10Nb-27B） → FeB ＋ Lc14 ＋ M2B （1575 K）. Moreover,the eutectic points are very close to the compositions with high glass forming ability determined experimentally. This means that it is feasible to design the compositions of multicomponent bulk metallic glasses by looking for the eutectic points in the Fe-Nb-B system by means of thermodynamic calculation.     

液相三元Al-Ni-Zn合金的热力学性质计算(英文)

将用于热力学预测的最新版本的通用模型用来计算液相三元Al-Ni-Zn合金的热力学性质。对9个具有不同Ni与Zn,Zn与Al和Al与N摩尔比的截面在1800~2000K的热力学性质进行研究。对液相三元Al-Ni-Zn合金的局部和整体的摩尔热力学性质进行了测定,并对结果进行了讨论。     

原位合成Mo-Si-B三元系多相合金的热力学评估

对Mo-Si-B三元系中各化合物不同温度下的标准生成自由焓和不同开始温度下合成Mo-Si-B三元系多相合金反应的绝热温度以及生成物的熔化比进行了计算和分析评估。结果表明,在元素配比合适的情况下,原位合成热力学稳定的α-Mo+Mo3Si+Mo5SiB2(T2)和Mo3Si+Mo5Si3(T1)+T2多相合金是完全可行的,合成反应的绝热温度以及生成物的熔化比与开始温度有关,原位合成这些多相合金不宜采用燃烧合成的SHS(自蔓延高温合成)模式,适合采用燃烧合成的热爆模式。     

Study of Mn activities in Mn–Ni–C alloys by EMF measurements

The activities of manganese in Mn–Ni–C alloys have been studied by solid-state galvanic cell technique with CaF₂ as the solid electrolyte. The measurements of electromotive force (EMF) have been carried out in the temperature range 920–1240 K. The main phase compositions of the alloys have been analyzed by X-ray diffraction (XRD). It was established that the substitution of Mn by Ni in the (MnNi)₂₃C₆ carbide was limited, that the lattice parameter decreased slightly with increase in the Ni content and that a solid solution is formed between Mn and Ni. It was also found that the activity of manganese decreases with increase in the nickel content when the ratio of C/(Mn+C) is less than 8.3 wt.%, and that the negative effect of Ni on the activity of Mn in Mn–Ni–C ternary system decreases as the carbon content increases. However, when the ratio of C/(Mn+C) is equal to 8.3 wt.% or more, the activity of manganese is independent of the nickel content.     

Modified cellular automaton model for modeling of microstructure and microsegregation in solidification of ternary alloys

A modified cellular automaton （MCA） model has been extended to the ternary alloy system by coupling thermodynamic and phase equilibrium calculation engine PanEngine. In the present model the dendrite growth is driven by the difference between the local equilibrium liquidus temperature and local actual temperature, incorporating the effect of curvature. The local equilibrium liquidus temperature is calculated with PanEngine according to the local liquid concentrations of two solutes, which are determined by numerically solving the species transport equation in the domain. Model validation was carried out through the comparison of the simulated values to the prediction of the Scheil model for solute profiles in the primary dendrites. The simulated data with zero solid diffusivity and limited liquid diffusivity were increasingly close to the Scheil profiles as the solidification rate decreased. The simulated microstructure and microsegregation in an Al-Cu-Mg ternary alloy were compared with those obtained experimentally.     

Mg-Al-Ca合金系金属间化合物的力学性质与热力学性能第一原理计算

采用基于密度泛函理论Castep和Dmol程序软件包,计算了Mg-Al-Ca合金系金属间化合物的力学性质与热力学性能。结果显示:DI3型结构Al4Ca为延性相,C15型结构Al2Ca与C14型结构Mg2Ca为脆性相,C15型结构Al2Ca塑性最差;采用弹性常数计算结果预测的Al2Ca熔点与实验值很接近,误差仅为4.06%;而不同温度下热力学性能的计算结果表明,在298.15~425K温度范围内,Al2Ca的Gibbs自由能最小,对应其相结构的热稳定性最好;而Al4Ca次之,Mg2Ca最差;随着温度的升高,Mg2Ca的Gibbs自由能下降最快,对应结构的热稳定性增强也最快;在525K以上时,Mg2Ca的结构热稳定性最好,其次是Al2Ca,而Al4Ca最差。     

Model on medium range order in liquid Al-Fe alloys

Numerical analysis confirms that in some cases the prepeak in the structure factor causes obvious change in the coordination number, but change in the interatomic distance can be neglected for the study of the medium range order(MRO). In order to model the MRO, it is not possible to get enough information based on the pair correlation function; however the quasi-Bragg equation can be employed to characterize the quasi-period of MRO corresponding to the prepeak position. By assuming that the interatomic distance between Fe and Al atoms hardly varies with composition, structural models were constructed based on the B2-type structure units of ordered FeAI alloy. The quasi-periods for different alloys obtained from the model structures are in reasonable agreement with the experimental ones.