Experiments on the aging of Sn–Ag–Cu solder alloys

Abstract

The microstructural stability of the Sn–3·8%Ag–0·7%Cu solder alloy was investigated by studying microstructural changes caused by heating small samples for various times, up to 1000 h, at 150°C. The first change, evident at high magnification after heating for 1 h, occurred from the as cast lamellar plus fibrous form of the Ag₃Sn and Cu₆Sn₅ interdendritic eutectic phases to a particulate form. With further heating, coarsening of the two compound phases occurred, gradually rendering the Sn dendrite pattern less distinct. Due to the very rapid diffusion of Cu in solid Sn, the Cu₆Sn₅ phase coarsened most rapidly, growing from its originally finely divided (200 nm) size in the ternary eutectic to form many particles up to 3 m m or more in size in a time of 100 h. At that time, nearly 50% of the total Cu was contained in these particles. The Ag₃Sn phase coarsened more slowly. Approximate measurements of average particle size as a function of time suggested that coarsening occurs by Ostwald ripening, controlled by diffusion in the Sn phase.     

高含量Ag,Mo,Sn光谱定量分析方法

地质试样中当被测元素含量高达某一值后,由于感光板乳剂的局限性,摄谱法光谱分析的精密度、准确度急剧降低,无法进行工作。本文试验与论述了采取某些特殊措施——三阶梯减光板滤光及小容量电极,氯化钠与碳酸锂冲液,以背景为内标,其相对标准7.25%,准确度为±10%。     

Features of the Sintering of Fe–Cu–Sn–Ni and Cu–Ti–Sn–Ni Powders during Hot Pressing

Powder Metallurgy and Metal Ceramics - The efficiency and durability of a diamond tool fabricated using powder metallurgy methods depend on several factors. These are the quality of diamond...     

Wetting Behavior and Evolution of Microstructure of Sn–3.5Ag Solder Alloy on Electroplated 304 Stainless Steel Substrates

In the present study, wetting characteristics and evolution of microstructure of Sn?C3.5Ag solder on Ag/Ni and Ni electroplated 304 stainless steel (304SS) substrates have been investigated. Solder alloy spread on Ag/Ni plated 304SS substrates exhibited better wetting as compared to Ni/304SS substrate. The formations of irregular shaped and coarser IMCs were found at the interface of solder/Ni/304SS substrate region whereas, solder/Ag/Ni/substrate interface showed continuous scallop and needle shaped IMCs. The precipitation of Ag₃Sn, Ni?CSn, FeSn₂ and lesser percentage of Fe?CCr?CSn IMCs were found at the interface of solder/Ag/Ni/substrate region whereas, solder/Ni/304 SS substrate exhibited predominantly FeSn₂ and Fe?CCr?CSn IMCs. Presence of higher amount of Fe?CCr?CSn IMCs at the solder/Ni/304SS substrate interface inhibited the further wetting of solder alloy.     

Forum on W,Sb,Sn and Zn policies

A forum was held recently in Beijing onChina's policies concerning tungsten, anti-mony, tin and zinc. Since China has ad-vantages in these metals resources in theworld and to improve China's export rev-enue from these metals, it is very impor-tant to strengthen export administrationand keep an orderly market.     

Thermodynamic Properties and Phase Equilibria in Ba–Sn Alloys

Powder Metallurgy and Metal Ceramics - The mixing enthalpies for liquid Ba–Sn alloys were determined by isoperibolic calorimetry at 1300 K over the entire composition range. Large exothermic...     

Friction Surfaces and Wear Products of Sn–Sb–Cu-Based Composite Materials

The structure and the tribological properties of the composite materials based on an Sn–Sb–Cu alloy (B83 babbit) and fabricated by hot pressing of powders are studied under dry sliding friction conditions. Modified schungite and silicon carbide are chosen as reinforcing materials. The composite material fabricated by a powder technology and reinforced by silicon carbide and modified schungite particles is found to have the doubled wear resistance as compared to a cast B83 alloy at a comparable friction coefficient.     

Sn1.0Ag0.5Cu和Sn3.0Ag0.5Cu钎料组织与性能对比研究

Sn3.0Ag0.5Cu无铅钎料已广泛应用于电子封装中,但是与传统的Sn Pb钎料相比,其抗冲击能力相对较差,且成本远远高于锡铅钎料。因此,为了改善抗冲击性能,降低钎料的成本,低银型无铅钎料成为研究热点。本文对比分析了Sn1.0Ag0.5Cu和Sn3.0Ag0.5Cu两种无铅钎料的润湿性及力学性能,同时研究了焊后和高温时效300 h后两种钎料焊点的显微组织。结果表明:随着Ag含量的增加,钎料的铺展面积显著增加,不同钎焊温度条件下,钎料的铺展面积随着钎焊温度的升高而明显增大。Sn3.0Ag0.5Cu钎料焊点的拉伸力和剪切力也明显高于Sn1.0Ag0.5Cu钎料,但随着时效时间的增加,高银型钎料的力学性能下降速度略高于低银型钎料。焊后两种钎料对应界面层为Cu6Sn5,经150℃时效300 h,界面金属间化合物的厚度随着时效时间的增加而增加。同时,界面层随着Ag含量的增加而增厚。     

Sintering Behaviour and Mechanical Properties of Al–Cu–Mg–Si–Sn Aluminum Alloy

The present study investigates the effect of compaction pressure and sintering temperature on densification response and mechanical properties of the Al–3.8Cu–1Mg–0.8Si–0.3Sn (2712) alloy. The compacts were pressed at 200 and 400 MPa and sintered at temperatures ranging from 570–630°C in vacuum (10^?6 Torr). The objective of the present work is to obtain an optimum sintering conditions for achieving higher sintered densities and mechanical properties. The effect of sintering temperature is evaluated by measuring the sintered density, densification parameter, microstructure, phase changes and mechanical properties. While a higher sintering temperature results in densification enhancement, it also leads to microstructural coarsening. Significant improvement in mechanical properties is obtained through age-hardening of sintered alloy under various ageing conditions (T4, T6 and T8).     

Microstructural Features and Mechanical and Tribological Properties of Fe–Cu–Ni–Sn Composites Precipitation-Hardened with CrB2 Additions

Powder Metallurgy and Metal Ceramics - The structural features, hardness, elastic modulus, and wear resistance of Fe–Cu–Ni–Sn composites with different CrB2 contents, produced by...     

Effect of Ca and Rare Earth Additions on the Texture,Microhardness, Microstructure and Structural Properties of As-Cast Mg–4Al–2Sn Alloys

In this work, alloys with nominal composition of Mg–4Al–2Sn–xRE–yCa (where RE = rare earth, x = 0, 1, 3 and y = 0, 1) have been prepared using tilt casting method. Prepared as-cast samples have been investigated by X-ray diffractometry, optical microscopy and scanning electron microscopy techniques as well as hardness measurement. The texture, microstructure and structural parameters of samples were also refined from X-ray diffraction patterns utilizing the Rietveld method and generalized spherical-harmonic model. It was found that with addition of rare earth and calcium elements, intermetallic phases of γ-Mg₁₇Al₁₂ and β-Mg₂Al₃ disappeared in cast alloys while small amount of Al₁₁RE₃ and CaMgSn intermetallics phases are formed. The texture factor of α-Mg as a main phase of samples was decreased with addition of rare earth up to 1 % and increased with more addition of rare earth elements. According to the results, with addition of rare earth elements, texture of Mg phase changes from 〈112〉 direction to 〈100〉 and 〈002〉 directions while Ca addition causes the texture in 〈002〉 direction. The microhardness of Mg–4Al–2Sn alloy was enhanced with addition of rare earth and calcium elements which is in agreement with the expected trend based on computed phase fraction of the samples. Addition of 1 wt% of calcium causes a dramatic change in the morphology and chemical composition of intermetallic phases, from acicular shape with composition of Al₁₁RE₃ into fine feather of CaMgSn intermetallic phase which accumulated in cluster morphologies in interdendritic regions.     

贵金属Pd-X(X=Ag,Ni,Sn)体系的相图热力学研究

对贵金属Pd-X(X=Ag,Ni,Sn)体系的相图热力学文献数据进行严格评估的基础上,采用替代溶液模型描述该3个二元系中液相和FCC＿A1相的吉布斯自由能,分别采用亚点阵模型(Pd,Sn)₁Sn₂、(Pd)_0.25(Pd,Sn)_0.75和(Pd)_0.2(Pd,Sn)_0.8描述Pd Sn₂、PdSn₃和PdSn₄相,通过CALPHAD(calculation of phasediagram)方法获得描述贵金属Pd-X (X=Ag,Ni,Sn)体系的热力学参数。相较于文献报道,本研究得到的热力学参数能更合理地描述Pd-X (X=Ag Ni,Sn)体系的实验相图数据和热力学数据,尤其在Pd-Ag相图、Pd-Ag体系和Pd-Ni体系FCC＿A1的混合焓及Pd-Sn相图富Sn端零变量反应的描述方面。计算结果与实验数据的比较表明本工作获得的热力学参数的准确性。     

Kinetics of discontinuous precipitation and dissolution in Cu–Ag alloys

The kinetics of discontinuous precipitation and dissolution of the cellular precipitate have been studied in Cu-3 at.% Ag and Cu-4 at.% Ag alloys. The growth rates of the cells were measured using optical microscopy. The interlamellar spacings of the primary cells and compositions of the depleted matrix were measured using scanning electron microscope and X-ray diffraction, respectively. The Cu–Ag alloys were observed to decompose into a lamellar structure consisting of alternate lamellae of the α (Cu-rich) and β (Ag-rich) phases when a solid solution of the alloy was aged below the solvus temperature. The rod shaped morphology of the β phase dispersed in the matrix of α was observed at all temperatures. The primary cell growth data were analysed using the theories of Cahn, Hillert, Sundquist, Turnbull and Petermann and Hornbogen. From the diffusivity values, it has been shown that the growth of primary cells occurs by the diffusion of Ag along the grain boundaries. The results are consistent with the diffusivity values reported in the literature in the same temperature range.The discontinuous dissolution of the primary cells occurred above the solvus temperature as well as 30–40 K below it. The dissolution occurred primarily at the prior positions of grain boundaries as well as at the primary cells intersection, at least in the initial stages of dissolution. The discontinuous dissolution occurred by the diffusion of Ag along the interface boundary between the primary and dissolution cells. The diffusivity and mobility values obtained during dissolution are one order of magnitude smaller than those obtained for the discontinuous precipitation. This has been explained by volume diffusion ahead of the interface and not all of the free energy being used to drive the interface boundary.     

Sn—In—Ag系焊料的热力学

不但通过试验，而且通过热力学模型对Ｓｎ－Ｉｎ－Ａｇ系无铅焊料进行了研究。根据得到的热力学和相平衡数据，完善了对Ａｇ－Ｉｎ和Ｉｎ－Ｓｎ两个二元系的热力学描述，并与已知的Ａｇ－Ｓｎ二元系相结合，得到完整的Ｓｎ－Ｉｎ－Ａｇ三元体系的热力学描述。得到的热力学参数作为凝固过程中温度的函数和扩散偏析的影响因数，用相关的相图和微观结构图模拟了合金的凝固过程。讨论了不同铁凝固过程及其与合金微观结构和机械性能的关系     

Effect of Gd on microstructure,mechanical properties and wear behavior of as-cast Mg–5Sn alloy

Effect of minor Gd addition on the microstructure, mechanical properties and wear behavior of as-cast Mg–5Sn-based alloy was investigated by means of OM, XRD, SEM, EDS, a super depth-of-field 3D system, standard high-temperature tensile testing and dry sliding wear testing. Minor Gd addition has strong effect on changing the morphology of the Mg–5Sn binary alloy. Gd addition benefits the grain refinement of the primary α-Mg phase, as well as the formation and homogeneous distribution of the secondary Mg₂Sn phase. The mechanical properties of the Mg–5Sn alloys at ambient and elevated temperatures are significantly enhanced by Gd addition. The wear behavior of the Mg–5Sn alloy is also improved with minor Gd addition. The alloy with 0.8% Gd addition exhibits the best ultimate tensile strength and elongation as well as the optimal wear behavior. Additionally, the worn surface of the Mg–5Sn–Gd becomes smoother in higher Gd-containing alloys. The best wear behavior of alloy was exhibited when Gd addition was up to 0.8%, showing a much smoother worn surface than that of control sample. The improvement of tensile properties is mainly attributed to the refinement of microstructure and the increasing amount and uniform distribution of Mg₂Sn phase. The larger amount of Mg₂Sn phase uniformly distributed at the grain boundary of Mg–Sn–Gd alloys act as a lubrication during sliding, and combined with smaller grain size improve wear behavior of the binary alloy.     

Sn—Ag基无铅焊料的研究与进展

研究开发无铅焊料是我国电子材料行业面临的新课题,Sn-Ag系是一种有希望替代铅焊料的无铅焊料。本文综述了该合金系研究的主要成果,包括微观组织、焊料与基体的相互作用、拉伸和剪切性能、疲劳性能及蠕变性能,指出了此合金系作为软钎焊材料尚待解决的问题。采用合金化、基体涂层、发展新焊剂等手段可使该合金系发展为较理想的无铅焊料。     

Electrochemical Corrosion and Impedance Studies of Porous Ti–xNb–Ag Alloy in Physiological Solution

Porous titanium (Ti) and its alloys are promising materials for orthopedic applications due to their low elastic modulus, high strength, excellent corrosion resistance, and biocompatibility. In this study, the porous Ti–xNb–5Ag (x = 25, 30 and 35 wt%) alloys were synthesized using the powder metallurgy approach. The effects of Nb content on the porosity, mechanical properties, and electrochemical corrosion behavior of the alloys were investigated. XRD analysis revealed that the porous alloys mainly consist of α-Ti, β-Ti, intermetallic compound (Ti₄Nb), and oxides of TiO₂ and NbO phases. Porous alloys possess the porosity ranging from 57 to 65%, due to the addition of NH₄HCO₃ (45 wt%). Increase in Nb content lead to a reduction in the elastic modulus and compression strengths of the sintered porous Ti–xNb–5Ag alloys. All three developed porous Ti–xNb–5Ag alloys show the optimum combination of elastic modulus and compression strength, which is suitable for orthopedic applications. These porous alloys exhibit excellent electrochemical corrosion resistance in the simulated body fluids, and the samples having low porosity exhibit higher corrosion resistance than high-porosity samples.

     

Cold Sintering of Fe–Ag and Fe–Cu Nanocomposites by Consolidation in the High-Pressure Gradient

Russian Journal of Non-Ferrous Metals - The results of fabricating dense Fe–Ag and Fe–Cu nanocomposites from mixtures of powders consolidated by high-pressure cold sintering and from...     

The Effect of Precipitation Characteristics on Hardening Behavior in Cu–Cr–Sn Alloy with Sn Variation

Powder Metallurgy and Metal Ceramics - The influence of minor solute additions of Sn on hardening behavior and microstructure evolution of the Cu–Cr–Sn alloys has been investigated with...     

Effect of Vacuum Hot Pressing Temperature on the Mechanical and Tribological Properties of the Fe–Cu–Ni–Sn–VN Composites

Powder Metallurgy and Metal Ceramics - The mechanical (hardness and elastic modulus) and tribological (friction force and wear rate) properties of the Fe–Cu–Ni–Sn–VN...