In recent years, Sn-Bi solder has been widely used in the electronic packaging industry due to its low melting point. However, the segregation and coarsening of Bi will degrade the mechanical properties of solder joints. In this paper, the shear strength of Sn-Bi/(111)Cu joints is enhanced by refining the distribution of Bi in the composite solder. Bi diffuses in the Sn-Sn58Bi layered composite structure in the reflow process, resulting in inhibition of coarsening. In addition, the growth behavior and orientation of Cu6Sn5 in Sn58Bi/(111)Cu and Sn-Sn58Bi/(111)Cu solder joints are also investigated.

Ni-Co alloys with different compositions have been electroplated, followed by anodizing and annealing. Subsequently, the impact of metal composition and treatment on the morphology and glucose catalytic properties for the samples are characterized. Results indicate that the samples become loose and porous after anodization and annealing accompanied by the appearance of fluoride and oxides. The highest catalytic sensitivity (2820 mu A mM(-1) cm(-2)) and fast current response (<2 s) are obtained in the anodized Co sample. This pioneering work not only offers a promising strategy for the convenient construction of nanoporous alloy composites, but also broads the scope of application of Ni-Co alloys and their compounds in the field of glucose catalysis.

In this study, three-dimensional nanostructured electrodes were synthesized by one-step electrochemical anodizing of the brass. Composites based on different oxides/hydroxides including ZnO, Cu2O, Cu(OH)(2), and CuO are selectively prepared by potential modulation for the first time. With the increase of potential, the nano-oxide transforms from granular morphology into uniformly distributed nanosheet clusters, and the size of the nanosheet decreases gradually with the increase of potential, finally, the double-layer nanosheet structure is formed. Attributed to the finely regulated composition and nanostructure, high-performance non-enzymatic glucose sensor electrodes are developed, which can exhibit prominent sensitivity for glucose catalytic up to 2817 mu A.mM(-1).cm(-2) with a response time within 3 s and outstanding selectivity. This pioneering work not only offers a promising strategy for the rational construction of high-performance glucose catalytic nanostructured electrodes, but also provides a fresh pathway for the selective oxidation of alloys to form functional materials that meet practical needs.

室温Ga基液态金属兼具金属的导电性和液体的流动性,是柔性电子器件的首选材料.在电子产品微型化趋势下,Ga基液态金属导体面临着更大的电流密度、更高的焦耳热效应等问题,严重影响着液-固电极界面的微观结构及结构稳定性.利用实验数据与数值模拟相结合的方法,通过改变通电过程中的换热介质研究了焦耳热对Cu/Ga-21.5In-10Sn/Cu液-固电极界面微观结构演化的影响.结果表明,在400 A/cm2的电流密度下通电24 h后,Cu/Ga-21.5In-10Sn/Cu界面会生成CuGa2,阴极和阳极界面生成的CuGa2层厚度没有显著差异,并且在阴极Cu电极表面出现明显的溶蚀坑,表现出极性效应,而且通电过程中产生的焦耳热会导致阴极Cu电极表面溶蚀坑的快速生成.

In the 3D advanced packaging process, solder joints undergo multiple reflows and the intermetallic compounds will continue to grow on the Cu6Sn5 layer. However, the nucleation and growth mechanism of intermetallic compounds on the Cu6Sn5 layer is not clear. In this paper, the Cu6Sn5 layer was prefabricated on (001) Cu and the reaction between the prefabricated Cu6Sn5 layer and the Sn-based solder under the influence of solder composition was investigated. Results show that when the prefabricated Cu6Sn5 layer has a preferred orientation, the orientation can be retained after reflowing. When the orientation of the prefabricated Cu6Sn5 layer is randomly distributed, small Cu6Sn5 grains nucleate on the surface of the prefabricated Cu6Sn5 layer and grow along the <0001> crystal direction. Besides, the addition of Ag is beneficial to the heritability of orientation and inhibits the nucleation of small Cu6Sn5 grains on the surface of the prefabricated Cu6Sn5 layer.

The high reliability of solder joints is the guarantee for the miniaturization, ultra-high density, multi-functional and high performance of integrated chips. The growth of interfacial intermetallic compounds determined by solder composition, substrates, reflow temperature et al., is the key factor to achieving good bonding. In this paper, the effects of substrate surface roughness on interfacial reaction at Sn-3.0Ag/(001)Cu interface were investigated. Confocal Laser Scanning Microscope (CLSM), Scanning electron microscope (SEM), Electron backscatter diffraction (EBSD) and Shanghai Synchrotron Radiation Facility (SSRF) were used to characterize the interface reaction. Results suggest that higher Ra favors to form thicker IMC layer and more voids, as well as degrades the preferred orientation of IMC. The results have a significant meaning in improving the reliability of solder joints in the real work environment.

In this study, the effects of reflow temperature, reflow time, and substrates (polycrystalline and (001/110/111) monocrystalline Cu substrates) on the growth of Cu3Sn at the Cu/Sn3Ag interface were investigated. Results show that the growth of Cu3Sn on the interface shows grain boundary diffusion regardless of the orientation of Cu substrates. The formation of Cu3Sn is considered as the reaction between Cu atoms and Cu6Sn5 at Cu6Sn5/Cu3Sn interface due to the similar interfacial outline to Cu substrate. In addition, the growth of interfacial Cu3Sn is positively correlated with reflow temperature and time. And the preferred plane orientation of Cu substrate has a significant effect on the growth rate of Cu3Sn during reflowing. In this experiment, the growth of Cu3Sn shows grain boundary diffusion. The growth of Cu3Sn on polycrystalline Cu substrate is faster because it has a lot grain boundaries. And the growth rate on (110)Cu single crystals is the fastest among single-crystal Cu substrates because the high surface free energy of single-crystal oriented (110)Cu substrates promotes the growth of Cu3Sn and the diffusion distance of Cu atoms is the shortest in this direction.

The Cu6Sn5 intermetallic, which commonly forms at the solder interconnects, is a critical component contributing to the reliability of solder joints. In this paper, the growth behavior during the isothermal stage of Cu6Sn5 grains in the Sn-xAg/(0 0 1)Cu (x = 0, 3, 3.5) joint was investigated. A new phenomenon, the Cu6Sn5 with cellular boundary, is found in the isothermal stage of Sn-3Ag/(0 0 1)Cu and Sn-3.5Ag/(0 0 1)Cu joint, but not found in the Sn/(0 0 1)Cu joint. The result suggests that the Ag3Sn play an important role in the formation of the cellular boundary. High-pressure air blowing was used to uncover the morphology of Cu6Sn5 at the isothermal stage. Scanning electron microscopy and electron backscatter diffraction were employed to characterize the morphology and grain orientation, respectively. The result has a great meaning in understanding the growth of Cu6Sn5 during the isothermal stage and improving the reliability of solder joints.

In this paper, the mechanism on the nucleation of orientation-preferred Cu6Sn5 at different temperatures and solder compositions was investigated. Results suggest that affected by temperature and solder composition, the distribution of clusters in solder plays an important role in the formation of preferred orientation. Higher temperature, Ag element and an appropriate amount of Cu element are favorable for the nucleation of orientation-preferred Cu6Sn5. However, the increase of Cu-Sn clusters size with the increase of Cu addition will lead to the nucleation of Cu6Sn5 in liquid solder, which does not need to follow the rule of the minimal lattice mismatch between Cu6Sn5 and Cu substrate. Meanwhile, the addition of Cu and Ag is conducive to the increase of grain size. Besides, the difference in solder volume between the central and edge region results in the difference in grain orientation. Furthermore, a model is established to illustrate that how the reflow temperature, Cu and Ag content affect the nucleation of orientation-preferred Cu6Sn5 through affecting the cluster evolution. The results have significant meaning in understanding and controlling the formation of Cu6Sn5 preferred orientation and improving the reliability of solder joints. (c) 2021 Elsevier B.V. All rights reserved.

The growth of Cu3Sn is associated with the formation of Kirkendall voids and is important to the reliability of solder joints. In this paper, the effect of Ag on the growth behavior of Cu3Sn on (001) Cu and polycrystalline Cu during aging was compared. Besides, the orientation evolution of Cu6Sn5 on (001) Cu during aging was also investigated. Results suggested the growth rate of Cu3Sn on (001) Cu is higher than that of polycrystalline Cu during solid-state aging and the difference in the Cu3Sn layer thickness increases with the increases of Ag content in the solder. Moreover, the addition of Ag is beneficial to maintaining the preferred orientation of Cu6Sn5 on (001) Cu during solid-state aging. The results have great help to deepen the understanding of the difference in growth behavior of intermetallic compounds on (001) Cu and polycrystalline Cu during aging.

研究了界面金属间化合物Cu6Sn5在多次回流过程中的微观结构和生长行为.利用场发射扫描电镜、 电子背散射衍射以及同步辐射实时表征技术对界面处Cu6 Sn5微观结构和生长行为进行表征.利用有限元软件COMSOL对焊点在多次回流过程中的热应力分布进行模拟.此外,对Cu/Sn3Ag/(001)Cu接头在多次回流过程中剪切强度的变化以及接头断裂方式进行了评估.结果表明,在多次回流过程中,Cu6 Sn5始终处于生长-溶解的动态平衡,在升温和保温阶段为扇贝状形貌,在冷却阶段为屋顶状形貌.冷热循环引起的热应力促使择优取向的Cu6 Sn5晶粒发生旋转,其<0001>晶向倾向朝着Cu化学势减小的方向旋转以获得最大Cu扩散能力.而且在多次回流过程中,Cu6 Sn5层厚度由于其取向的改变出现先增加后减小再增加的趋势.随着回流次数的增加,Cu/Sn3Ag/(001)Cu接头的断裂模式会由韧性断裂转变为脆性断裂,导致接头剪切强度下降.

The intermetallic compounds at the reaction interface will continue to grow during solid-state aging and the reliability of the solder joint will be affected by the growth behavior and orientation of intermetallic compounds. In the paper, the effect of solder composition, i.e., Sn and Sn3Ag, on the growth behavior of Cu3Sn on (001) Cu and polycrystalline Cu during aging are compared. Besides, the effect of solder composition on the orientation evolution of Cu6Sn5 on (001) Cu is investigated. Results indicate that the thickness of the Cu3Sn layer in the Sn3Ag/(001)Cu joint is larger than that in Sn3Ag/polycrystalline Cu joint, but the difference in Cu3Sn thickness between Sn/(001)Cu and Sn/polycrystalline Cu is small. Besides, the addition of Ag is beneficial to maintaining the preferred orientation of Cu6Sn5 on (001) Cu during solid-state aging. The results are beneficial to improve the reliability of solder joints.

Cu 6 Sn 5 is the main intermetallic compound between the Sn-based solder and Cu substrate. And the orientation of Cu 6 Sn 5 is one of the key factors affecting its electrical, thermal, and mechanical properties. Besides, under bump metallization may only contain one grain in a limit case due to the decrease of the solder joint. Therefore, the orientation-preferred Cu 6 Sn 5 on Cu single crystal attracts a great of attention from researchers in the electronic packaging industry. During the thermal aging process, the solid-solid reaction will take place in the solder joint and the intermetallic compounds will continue to grow, consequently affecting the performance of the joints. In this paper, the growth behavior of Cu 6 Sn 5 for the different kinds of as-soldered joints in the aging process was investigated. The as-soldered joints were reflowed at 300 °C for 1 s and 120 s, respectively, consequently resulting in the difference in the Cu 3 Sn layer thickness and Cu 6 Sn 5 grain size. Then, the solder joints were aged at 150 °C for a different time. The results suggest that in the aging process, the Cu 6 Sn 5 layer increases gradually and the Cu 3 Sn layer increases rapidly for the two kinds of solder joint. Moreover, the thinner the initial Cu 3 Sn layer is, the faster the Cu 3 Sn layer grows during aging. Besides, the morphology of Cu 6 Sn 5 grains gradually changed from roof to scallop and the preferred orientation of Cu 6 Sn 5 disappeared as the aging time increased. Besides, for the as-soldered joint reflowed at 300 °C for 1s, there are many voids at the reaction interface when the aging time is 20 d.

The anodization of several carbon steels with typical metallographic structures were systematically investigated. It was shown that the anodized iron oxide films were inherited from the microstructural characteristics of the original metallographic structure by employing metallographic regulation. Different characteristics of the original metallographic structures could affect the rate of the anodization reaction and determine the thickness of the oxide layer on the substrate. Meanwhile, the connection of nanopore size with the original microstructure of the substrate was also revealed by the statistical analysis of pore size on the anodized iron films. The methodology and techniques could obtain tunable micronano structure and might be applicable in similar alloy systems. (C) 2021 Elsevier B.V. All rights reserved.

The multiple reflows process is widely used in 3D packaging in the field of electronic packaging. The growth behavior of interfacial intermetallic compound (IMC) is more important to the reliability of solder joints. In this paper, experimental measurement combined with simulation calculation were preformed to investigate the evolution of Cu concentration in solders during multiple reflows, as well as its effects on the growth behavior of IMC and solder properties. The concentration of Cu in solder fluctuated, increasing with the increase of reflow times, which led to the fluctuation in the growth rate of the IMC. Furthermore, the Vickers hardness and melting point of the solder fluctuated during the multiple reflow processes due to the fluctuation in the Cu concentration. The data generated during this study could help to develop machine learning tools in relation to the study of interfacial microstructure evolution during multiple reflows.

The preferred orientation of Cu6Sn5 formed on (001) Cu single crystals has attracted great attention due to its feature of strong anisotropy. Lots of researchers believe that the formation of preferred orientation is closely related to the reaction temperature but do not have a unified conclusion. In this study, a temperature-increased multiple reflow process was designed and utilized to investigate the grain rotation and coarsening behavior of orientation-preferred Cu6Sn5 formed at the Sn-3Ag/(001)Cu interface. Results demonstrate that the temperature-increased multiple reflow process facilities the annexation and rotation of Cu6Sn5 grains as well as their morphology transformation from scalloped-type to small facet. The results have significant meaning in understanding and controlling the formation of Cu6Sn5 preferred orientation and improving the reliability of solder joints. (C) 2021 Elsevier B.V. All rights reserved.

The competitive growth of Cu3Sn and Cu6Sn5 in the multi-reflow processes induced by temperature, time, and cooling rate was systematically studied in this work. Results indicated that the thickness proportion of Cu3Sn in the IMC layer was highly promoted in the temperature-increased multi-reflow process and slightly increased with a fluctuation in the isothermal multi-reflow process, while obviously decreased in the temperature-decreased multi-reflow process. The proportion of Cu3Sn grew following the increase of reflow temperature, time, and cooling rate and the thickness of Cu3Sn formed at the central of the Cu6Sn5 bottom was higher than that formed at the edge. The results have a significant meaning in understanding and controlling the competitive growth of Cu3Sn and Cu6Sn5 and improving the reliability of solder joints.

The effect of Sn crystal orientation on the solid-solid interfacial reactions of the Sn?Ag system at 150 ?C were systematically investigated. XRD, EBSD and SEM were employed to reveal the microstructure evolution behavior of Ag/Sn films. The experimental data indicated that lattice matching degree between Ag and Sn film was quite different due to the various preferred orientations. The results confirmed that crystal orientation of Sn had a substantial influence on the electroplating speed, surface morphology as well as the resulting reflectivity of Ag films. After annealing treatment, the reflectivity of as-prepared Sn/Ag films decreased, attributing to the grain size changing from nano-scale to submicron and/or micron scale and the as-formed Ag3Sn phase. At the research field of Ag-based reflective coatings, it was firstly proposed and implemented the evaluation on sulfidization resistance of Sn/Ag films by analyzing the potentiodynamic polarization information. Based on the thermodynamics calculation, the types of intermetallic compounds(IMCs) formation were discussed. This paper provides a guiding principle for improving the optical properties and chemical stability of multilayer Sn/Ag reflective materials from the optimized selection view of Sn bottom materials.

In this paper, multilayer interfacial linear solder joints were prepared by dip soldering. The effects of soldering temperature, soldering time, soldering distance and soldering layer number on IMC growth of Cu / multilayer Sn-Cu-Sn / Cu solder joints were studied. The linear solder joint of multilayer interface was obtained by dip soldering at 250°C for 30s. And then reflowing at 250°C, 300°C, 320°C for 30s, 60s, 120s, 5min, 10min, 30min. EPMA results show that there are Cu3Sn and Cu6Sn5 phases at the interface of each layer between solder and Cu substrates. At the same time, both reflow temperature and reflow time have effect on the interfacial compound, and the size of the interfacial compound increases with the increase of reflow temperature; With the increase of reflow time, the size of interfacial compound also increases; While decreases with the increase of dip soldering distance, the IMC of the sample with larger distance is thicker than small distance.

The package interconnect in integrated electronic components is realized by Interfacial intermetallic compounds (IMC). Meanwhile, the downsizing of µ-bumps to tens of microns in advanced 3D packaging will result in the overgrowth of IMC and the number of grains contained in UBM decreased sharply, which bring new challenge for the reliability of solder joints. For this condition, numerous researches about the growth of IMC generated at the solder/Cu single crystal interface have been reported. For this paper, the growth of IMC at the interface between different solder, i.e., Sn, Sn-2Ag, Sn-3Ag, and (110) Cu single crystal at different temperature, i.e., 230°C, 250°C, 300°C, were investigated. Scanning electron microscope (SEM) and electron backscattered diffraction (EBSD) was used to characterize the morphology and orientation of Cu6Sn5, respectively. Results shows that the CU6Sn5 formed on (110) Cu exhibit worm type at lower temperature and were tends to transform into facet type at higher temperature. Furthermore, the reflow temperature make a difference in the formation of Cu6Sn5 orientation. Besides, the coarsening rate of CU6Sn5 was promoted following the increase of the Ag. The results have a significant meaning in controlling the orientation and improving the reliability of micro solder joints.