Ⅲ族锢源对LP－MOVPE方法生长In_（1－x）Ga_xAs材料的影响

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Eu(DBM)3超细微粒的分形聚集的TEM研究

本文利用透射电镜（ＴＥＭ）和Ｘ射线能谱（ＥＤＳ）对铕－二苯甲酰甲烷配合物（Ｅｕ（ＤＢＭ）３）在溶液中的分形聚集进行了研究，结果表明：Ｅｕ（ＤＢＭ）３超细微粒在表面活性剂形成的溶胶中，以及在溶胶中长时间静置后，其聚集体均具有分形特征，Ｈａｕｓｄｏｒｆｆ分形维数Ｄｆ分别为１．６６、１．６８。     

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TMS320C5X及其在复分胺器中的应用

重点介绍了ＴＩ（ＴＥＸＡＳ ＩＮＳＴＲＵＭＥＮＴＳ）公司的定点信号处理芯征－－ＴＭＳ３２０Ｃ５Ｘ。然后，描述利用ＴＭＳ３２０Ｃ５０实现的可变速率可变时序的复分接器。     

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Effects of Co Addition on Bulk Properties of Sn-3.5Ag Solder and Interfacial Reactions with Ni-P UBM

The effects of Co addition on the undercooling, microstructure, and microhardness of Sn-3.5Ag solder (all in wt.% unless specified otherwise) and interfacial reactions with Ni-P under bump metallurgy (UBM) are investigated when the Co content varies from 0.01 wt.% to 0.7 wt.%. When more than 0.02 wt.% Co was added to Sn-3.5Ag solder, the undercooling of the Sn-3.5Ag solder was significantly reduced and the microstructures coarsened with the increased eutectic region. In addition, the hardness value increased as the Co content in Sn-3.5Ag increased. In the interfacial reactions with Ni-P UBM, a spalling phenomenon of intermetallic compounds (IMCs) during reflow was prevented in the Sn-3.5Ag-xCo (x ≥ 0.02 wt.%). However, when more than 0.05 wt.% Co was added to Sn-3.5Ag, the IMC morphology changed from a bulky shape to a plate-like shape. The bulky IMCs were Ni₃Sn₄ and the plate-like IMCs were Sn-Ni-Co ternary compounds. The main issues discussed include the relations between the morphological changes and the IMC phases, the effects of Co addition on the prevention of IMC spalling, and the optimum level of Co addition.     

Effect of Aluminum Concentration on the Interfacial Reactions of Sn-3.0Ag-<Emphasis Type="Italic">x</Emphasis>Al Solders with Copper and ENIG Metallizations

Aluminum was added into Sn-3.0Ag (wt.%) solder to investigate the effect of aluminum concentration on the interfacial reaction of Sn-3.0Ag-xAl solders with copper or electroless nickel immersion gold (ENIG) metallizations. Four different Sn-3.0Ag-xAl solders (x = 0 wt.%, 0.1 wt.%, 0.5 wt.%, and 1.0 wt.%) were used for comparison. It was found that the composition, morphology, and thickness of interfacial reaction products were strongly dependent on aluminum concentration. At low aluminum concentration (0.1 wt.%), the typical Cu₆Sn₅ layer was formed at the interface. When the aluminum concentration was 0.5 wt.%, a continuous CuAl₂ layer spalled off from the interfacial Cu-Sn intermetallic compound (IMC) layer. Only a planar CuAl₂ layer was observed at the interface when the aluminum concentration was increased to 1.0 wt.%. In Sn-Ag-Al/ENIG reactions, Ni₃Sn₄ was formed and spallation occurred near the interface in the Sn-3.0Ag and Sn-3.0Ag-0.1Al solder joints. When the aluminum concentration was higher than 0.1 wt.%, a thin planar AuAl compound formed at the interface. There was no P-rich phase formation that retarded the spalling phenomenon. The aluminum additive in Sn-Ag solder inhibited the growth of IMCs in the reaction with copper or ENIG metallizations, which was favorable for the reliability of solder joints.     

Interfacial Reactions and Joint Strengths of Sn-<Emphasis Type="Italic">x</Emphasis>Zn Solders with Immersion Ag UBM

The solder joint microstructures of immersion Ag with Sn-xZn (x = 0 wt.%, 1 wt.%, 5 wt.%, and 9 wt.%) solders were analyzed and correlated with their drop impact reliability. Addition of 1 wt.% Zn to Sn did not change the interface microstructure and was only marginally effective. In comparison, the addition of 5 wt.% or 9 wt.% Zn formed layers of AgZn₃/Ag₅Zn₈ at the solder joint interface, which increased drop reliability significantly. Under extensive aging, Ag-Zn intermetallic compounds (IMCs) transformed into Cu₅Zn₈ and Ag₃Sn, and the drop impact resistance at the solder joints deteriorated up to a point. The beneficial role of Zn on immersion Ag pads was ascribed to the formation of Ag-Zn IMC layers, which were fairly resistant to the drop impact, and to the suppression of the brittle Cu₆Sn₅ phase at the joint interface.     

Reaction of Liquid Sn-Ag-Cu-Ce Solders with Solid Copper

Small amounts of the rare-earth element Ce were added to the Sn-rich lead-free eutectic solders Sn-3.5Ag-0.7Cu, Sn-0.7Cu, and Sn-3.5Ag to improve their properties. The microstructures of the solders without Ce and with different amounts (0.1 wt.%, 0.2 wt.%, and 0.5 wt.%) of Ce were compared. The microstructure of the solders became finer with increasing Ce content. Deviation from this rule was observed for the Sn-Ag-Cu solder with 0.2 wt.% Ce, and for the Sn-0.7Cu eutectic alloy, which showed the finest microstructure without Ce. The melting temperatures of the solders were not affected. The morphology of intermetallic compounds (IMC) formed at the interface between the liquid solders and a Cu substrate at temperatures about 40°C above the melting point of the solder for dipping times from 2 s to 256 s was studied for the basic solder and for solder with 0.5 wt.% Ce addition. The morphology of the Cu₆Sn₅ IMC layer developed at the interface between the solders and the substrate exhibited the typical scallop-type shape without significant difference between solders with and without Ce for the shortest dipping time. Addition of Ce decreased the thickness of the Cu₆Sn₅ IMC layer only at the Cu/Sn-Ag-Cu solder interface for the 2-s dipping. A different morphology of the IMC layer was observed for the 256-s dipping time: The layers were less continuous and exhibited a broken relief. Massive scallops were not observed. For longer dipping times, Cu₃Sn IMC layers located near the Cu substrate were also observed.     

Electrical Conductivity of Film Composites Based on Polyvinyledene Fluoride with Carbon Nanotubes

The results of a study of film composites based on polyvinylidene fluoride with carbon nanotubes (CNTs) by dielectric relaxation spectroscopy are presented. For composite samples containing more than 0.5 wt % of nanotubes, nonlinear current–voltage characteristics are obtained. The concentration dependences of the electrical conductivity of the composites are examined and the percolation threshold for the samples under study is determined. It is shown that an insignificant increase in the electrical conductivity of the composites is observed even upon filling with 0.2 wt % of CNTs, whereas the electrical conductivity becomes three orders of magnitude higher upon the introduction of 1 wt% of CNTs and is seven orders of magnitude higher at more than 3 wt %, compared with the unfilled polymer. This confirms that CNTs are promising for the development of electrically conducting composites and film materials on the basis of polyvinylidene fluoride.     

Effect of Amount of Cu on the Intermetallic Layer Thickness Between Sn-Cu Solders and Cu Substrates

In the present study, Sn-Cu solders were synthesized using pure tin with varying weight percentage of nanosized copper particles (0 wt.%, 0.25 wt.%, 0.43 wt.%, 0.86 wt.%, and 1.35 wt.%) by a powder metallurgy route incorporating microwave-assisted sintering. Intermetallic compound (IMC) layer formation between Sn-Cu solders and Cu substrates was investigated following a reflow process. Isothermal aging studies were also conducted on selected Sn-Cu solders at 150°C for up to 4 weeks. Results revealed that the average IMC layer thickness decreases with the addition of nanocopper up to 0.43 wt.%. Beyond 0.43 wt.% Cu addition, the IMC layer thickness started to increase, and the maximum IMC layer thickness was found for Sn with 1.35 wt.% Cu addition. An attempt was made in this study to correlate the effect of nanocopper additions and aging time on the IMC layer thicknesses.     

Microstructural Evolution of Sn-Ag-Sb Solder with Indium Additions

The effects of 1 wt.%, 5 wt.%, and 10 wt.% additions of indium (In) on the microstructure and compound morphology of Sn-Ag-Sb lead-free solder joints␣were examined. The results showed that In prompts the formation of Ag₃(Sn,In), Ag₂(In,Sn), and InSb compounds within the solder matrix. As the amount of In was increased, the Sn atoms in the Ag₃Sn compound were gradually replaced by In atoms, prompting a transformation from Ag₃Sn to Ag₃(Sn,In) and finally to Ag₂(In,Sn). This transformation occurs more readily under high-temperature conditions. The Ag₂(In,Sn) compound formed in Sn-Ag-Sb-xIn/Cu solder joints was found to have either a leaf-like morphology or an antler-like morphology. Finally, with In additions greater than 5 wt.%, the Cu₆Sn₅ interfacial compounds in the solder/Cu joints transformed into Cu₆(Sn,In)₅.     

Optimal phosphorous content selection for the soldering reaction of Ni-P under bump metallization with Sn-Ag-Cu solder

Nickel plating has been used as the under bump metallization (UBM) in the microelectronics industry. The electroplated Ni-P UBM with different phosphorous contents (7 wt.%, 10 wt.%, and 13 wt.%) was used to evaluate the interfacial reaction between Ni-P UBM and Sn-3Ag-0.5Cu solder paste during multiple reflow. (Cu,Ni)₆Sn₅ intermetallic compounds (IMC) formed in the SnAgCu solder/Ni-P UBM interface after the first reflow. For three times reflow, (Ni,Cu)₃Sn₄ IMC formed, while (Cu,Ni)₆Sn₅ IMC spalled into the solder matrix. With further increasing cycles of reflow, the Ni-Sn-P layer formed between (Ni,Cu)₃Sn₄ IMC and Ni-P UBM for Ni-10wt.%P and Ni-13wt.%P UBM. However, almost no Ni-Sn-P layer was revealed for the Ni-7wt.%P UBM even after ten cycles of reflow. In consideration of the wettability of Ni-P UBM, the interfacial reaction of SnAgCu/Ni-P, and dissolution of Ni-P UBM, the optimal phosphorous selection in Ni-P UBM was proposed and also discussed.     

The influence of solder composition on the impact strength of lead-free solder ball grid array joints

This study aims to investigate the shear and tensile impact strength of solder ball attachments. Tests were conducted on Ni-doped and non-Ni-doped Sn-0.7wt.% Cu, Sn-37wt.% Pb and Sn-3.0wt.% Ag-0.7wt.% Cu solder ball grid arrays (BGAs) placed on Cu substrates, which were as-reflowed and aged, over a wide range of displacement rates from 10 to 4000 mm/s in shear and from 1 to 400 mm/s in tensile tests. Ni additions to the Sn-0.7wt.% Cu solders has slowed the growth of the interface intermetallic compounds (IMCs) and made the IMC layer morphology smooth. As-reflowed Ni-doped Sn-0.7wt.% Cu BGA joints show superior properties at high speed shear and tensile impacts compared to the non-Ni-doped Sn-0.7wt.% Cu and Sn-3.0wt.% Ag-0.7wt.% Cu BGAs. Sn-3.0wt.% Ag-0.7wt.% Cu BGAs exhibit the least resistance in both shear and tensile tests among the four compositions of solders, which may result from the cracks in the IMC layers introduced during the reflow processes.     

Microstructure and Tensile Properties of Sn-1Ag-0.5Cu Solder Alloy Bearing Al for Electronics Applications

This work investigates the effects of 0.1?wt.% and 0.5?wt.% Al additions on bulk alloy microstructure and tensile properties as well as on the thermal behavior of Sn-1Ag-0.5Cu (SAC105) lead-free solder alloy. The addition of 0.1?wt.% Al reduces the amount of Ag₃Sn intermetallic compound (IMC) particles and leads to the formation of larger ternary Sn-Ag-Al IMC particles. However, the addition of 0.5?wt.% Al suppresses the formation of Ag₃Sn IMC particles and leads to a large amount of fine Al-Ag IMC particles. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions suppress the formation of Cu₆Sn₅ IMC particles and lead to the formation of larger Al-Cu IMC particles. The 0.1?wt.% Al-added solder shows a microstructure with coarse ??-Sn dendrites. However, the addition of 0.5?wt.% Al has a great effect on suppressing the undercooling and refinement of the ??-Sn dendrites. In addition to coarse ??-Sn dendrites, the formation of large Sn-Ag-Al and Al-Cu IMC particles significantly reduces the elastic modulus and yield strength for the SAC105 alloy containing 0.1?wt.% Al. On the other hand, the fine ??-Sn dendrite and the second-phase dispersion strengthening mechanism through the formation of fine Al-Ag IMC particles significantly increases the elastic modulus and yield strength of the SAC105 alloy containing 0.5?wt.% Al. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions worsen the elongation. However, the reduction in elongation is much stronger, and brittle fracture occurs instead of ductile fracture, with 0.5?wt.% Al addition. The two additions of Al increase both solidus and liquidus temperatures. With 0.5?wt.% Al addition the pasty range is significantly reduced and the differential scanning calorimetry (DSC) endotherm curve gradually shifts from a dual to a single endothermic peak.