镧对Sn3.5Ag0.5Cu钎料组织性能影响

运用莱卡显微镜、扫描电镜和能谱分析等手段,研究了稀土元素La的添加量对Sn3.5Ag0.5Cu钎料及其与Cu基体焊接后微观组织及性能的影响。结果表明:添加不同含量的稀土La均能使钎料及其与Cu基体焊接后组织与性能得到改善,其中以w(La)达到0.05%时为最优,显微硬度及剪切强度分别提高14%和10.7%。键参数函数计算结果表明La具有"亲Sn"倾向,可细化钎料组织,降低IMC(界面金属间化合物)的长大驱动力。     

低熔点SnBi合金对导电银胶性能的影响

以银粉为主要导电填料,选定环氧树脂体系,添加不同量低熔点共晶SnBi合金制得导电胶,利用四点探针法和万能材料试验机考察了SnBi合金添加量对导电胶导电性能和力学性能的影响.发现当SnBi合金添加量占填料质量分数的15%时,导电胶的体积电阻率可以达到3.4×10<,-4>Ω·cm,剪切强度为12.56 MPa.SnBi合...     

电迁移对Sn3.0Ag0.5Cu无铅焊点剪切强度的影响

通过热风回流焊制备了Cu/Sn3.0Ag0.5Cu/Cu对接互连焊点,测试了未通电及6.5 A直流电下通电36 h和48 h后焊点的剪切强度.结果表明,电迁移显著地降低了焊点的剪切强度,电迁移36 h使剪切抗力降低约30%,电迁移48 h降低约50%.SEM观察断口和界面形貌表明,界面金属间化合物增厚使断裂由韧性向脆性...     

Ce对SnAgCu系无铅焊锡力学性能的影响

通过向Sn-3Ag-2.8Cu钎料合金中添加微量稀土Ce,利用扫描电子显微镜(SEM)研究了不同稀土含量对Sn-3Ag-2.8Cu合金的力学性能的影响,同时对显微组织进行了分析.实验结果表明,微量的Ce稀土可以显著提高Sn-3Ag-2.8Cu钎料的延伸率、延长其焊接接头在室温下的蠕变断裂寿命,尤其是当稀土的质量分数为0.1%时,其蠕变断裂寿命可以达到Sn-3Ag-2.8Cu钎料的9倍以上,当稀土的质量分数超过0.1%时,接头的蠕变断裂寿命呈下降趋势.综合考虑,最佳的稀土质量分数为0.05%～0.10%.     

Sn-Bi二元合金应变速率敏感性的研究

基于合金的微观组织观察,考察了Sn-xBi(x=10,20,30,40,50和58)合金在拉伸载荷下的应变速率敏感行为。试验结果表明,Sn-xBi (x=10和20)合金的微观组织由β-Sn基体及分布于其上的Bi粒子组成,合金形变由晶界滑移控制,应力指数较大;Sn-xBi (x=30,40,50和58)合金微观组织以网状共晶组织为基体,其形变机制随着Bi含量的增大,转变为相界滑移,应力指数减小。当应变速率由0.0001 s^-1增大到0.1 s^-1时,Sn-20Bi的断裂模式由延性断裂转变为具有塑性形变的混合断裂。这一断裂模式的转变与合金在不同速率下的形变机制有关。     

Ni对Sn-0.7Cu焊料微观组织和力学性能的影响

研究了添加微量Ni元素对Sn-0.7Cu焊料的力学性能、微观组织和断裂特性的影响.结果表明,微量的Ni可已细化焊料合金的微观组织,显著提高焊料的塑性,从而提高焊料的综合力学性能;但Ni含量太高,焊料的塑性反而受到弱化,合适的Ni添加量为0.133%,此时焊料的拉伸强度为35.7 MPa,延伸率为50%.     

La对Sn3.5Ag0.5Cu钎料界面组织和性能的影响

通过SEM和EDAX等,研究了La添加量对Sn3.5Ag0.5Cu钎料与Cu基体焊合界面IMC微观组织及性能的影响。结果表明:添加不同量的La均对Sn3.5Ag0.5Cu与Cu基体焊合后的组织有细化作用并增强其力学性能。其中以w(La)达到0.05%时最优,剪切强度可提高10.7%。材料热力学理论计算结果表明,La具有"亲Sn"倾向,添加少量La到Sn3.5Ag0.5Cu钎料中,可减小Cu6Sn5/Cu界面Sn的活度,降低IMC的长大驱动力。     

添加SAC微粒对SnBi锡膏焊后性能的影响

采用机械混合的方法,向Sn58Bi(Sn Bi)共晶锡膏中添加不等量的Sn-3.0Ag-0.5Cu(SAC)微粒,制备Sn Bi-SAC复合锡膏。在不改变Sn Bi锡膏低温焊接工艺的前提下,改善Sn Bi锡膏焊后合金硬脆缺陷。实验结果表明:Sn Bi-SAC复合锡膏中SAC微粒含量分别为质量分数0,3%,5%,8%时,采用180℃低温焊接均可获得良好的钎焊效果。与Sn Bi共晶锡膏焊后合金相比较,Sn Bi-SAC复合锡膏中SAC微粒含量的增加促使焊后合金微观组织中的β-Sn相含量与晶粒尺寸增大,改善了Sn Bi焊后合金中富Bi相的致密网状结构。当锡膏中SAC微粒含量由0增大至质量分数8%时,合金硬度从213.9 m Pa下降到117 m Pa,对Sn Bi锡膏焊后合金硬脆缺陷起到改善效果。     

覆Ag层对用于LD封装的In焊料性能的影响

In焊料由于其优越的可塑性以及优良的导电、导热特性,被广泛用于半导体激光器(LD)的封装。但是In焊料遇空气易氧化,尤其在焊接加热的过程中,氧化现象更加明显,因此一般当天制备当天使用。为防止氧化,可以在In焊料表面镀一层Ag或Au作为保护层,因为Ag成本较Au低,可作为首选的保护层。关于In-Ag合金性能的研究已有过相关报道,但关于In-Ag合金的表面形貌及Ag层厚度对内部In的影响的报道还很少。文章通过扫描电子显微镜、XRD对不同样品进行了表面和成分的分析,得到了关于Ag对内部焊料的影响以及不同冷却速率下焊料的表面形貌。     

时效温度和Ag对Al-Zn-Mg合金力学性能与微观结构的影响

本文研究了在不同时效温度条件下Ag对Al-Zn-Mg铝合金力学性能与微观结构的影响。结果表明,随着时效温度的提升,Ag对合金硬度的影响增大,合金晶界无析出带宽度明显减小。时效温度为120℃时,含Ag和不含Ag的Al-Zn-Mg铝合金均以η系列相析出为主,但含Ag合金的晶内析出相分布更为细小弥散,尺寸减小的同时径厚比增大。当时效温度升高至160℃和180℃,Ag对合金峰值硬度的提升作用显著增加。此时,Al-Zn-Mg合金主要强化相由η系列相转变为T系列相,同时尺寸明显增大,而含Ag合金中主要强化相类型与120℃时相同,仍然为η系列相,且尺寸并未明显增大。     

Effects of cooling rate on creep behavior of a Sn-3.5Ag alloy

The effect of cooling rate on microstructure and creep behavior of bulk, eutectic Sn-3.5Ag solders was studied. The cooling rate is an important processing variable that significantly affects the microstructure of the solder and therefore determines its mechanical behavior. Controlled cooling rates were obtained by cooling specimens in different media: water, air, and furnace, which resulted in cooling rates of 24°C/s, 0.5°C/s, and 0.08°C/s, respectively. The cooling rate decreased the secondary dendrite arm size and the spacing of the Sn-rich phase, as well as the morphology of Ag₃Sn. The Sn-dendrite arm size and spacing were smaller at fast cooling rates, while slower cooling rates yielded a nearly eutectic microstructure. The morphology of Ag₃Sn also changed from relatively spherical, at faster cooling rates, to needlelike for slower cooling. The effect of cooling rate on creep behavior was studied at 25°C, 60°C, 95°C, and 120°C. Faster cooling rates were found to increase the creep strength of the solder due to the refinement of the solder microstructure. Stress exponents, n, indicated that dislocation climb was the controlling mechanism. Activation energies, for all cooling rates, indicated that the dominant diffusional mechanism corresponded to dislocation pipe diffusion of Sn. Grain boundary sliding (GBS) measurements were conducted, using both scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was observed that GBS had a very small contribution to the total creep strain.     

Effects of cooling rate on mechanical properties of near-eutectic tin-lead solder joints

This paper reports the results of a study on the effect of the cooling rate during solidification on the shear creep and low cycle shear fatigue behavior of 60 Sn/40 Pb solder joints, and on bulk solder tensile properties. Solder joints were made with three different initial microstructures by quenching, air-cooling and furnace-cooling. They have similar steady-state strain rates under creep at relatively high shear stresses (i.e. in the matrix creep region) but creep at quite different strain rates at lower shear stresses (i.e. in the grain boundary creep region). These results are ascribed to the refined grain size and less lamellar phase morphology that results on increasing the cooling rate. Tensile tests on bulk solders that were cold-worked, quenched and furnace-cooled show that a faster cooling rate decreases the ultimate strength and increases the ductility at low strain rates. The fatigue life of quenched solder joints is shown to be longer than that of the furnace-cooled joints.     

Thermal ageing induces drastic changes on mechanical and damage behavior of Sn3.0Ag0.5Cu alloy

For the SnAgCu alloys, previous hardness test results suggested that high temperature thermal ageing causes a quick and significant drop in the mechanical properties. However, to date, the acceleration law of thermal ageing and the relationship between thermal ageing and fatigue mechanical behavior of SnAgCu alloys are still unknown.The aim of this paper is to understand the mechanical changes during thermal ageing of Sn3.0Ag0.5Cu alloy and their impact on solder joint reliability under mechanical stresses. In a first part, influence of thermal ageing on mechanical behavior is analyzed by means of hardness tests, reversed tensile tests on dog-bone specimens and compression test on solder balls used for electronic components. In the second part, the impact of thermal ageing on the solder joint reliability is analyzed thanks to torsion tests on assembled boards.The results show systematically a decrease of 20–60% of the mechanical properties or of the number of cycles to failure (in the case of torsion test). These results lead to enlarge tests conditions in order to define the fields where the influence of thermal ageing cannot be neglected.     

Effects of dopant,temperature, and strain rate on the mechanical properties of micrometer gold-bonding wire

An experimental study on the thermomechanical properties of microelectronic gold-bonding wires was conducted using high-precision, microforce tensile tests. The load-displacement behavior of three types of gold wire (GL-2 type, FA type, and SR type) was carefully recorded for determining the elastic modulus and stress-strain curves. Tests were conducted with miniature specimens at temperatures ranging from room temperature to 250°C and load rates on the order of 1 mm/min and 10 mm/min. The testing results indicated that the tensile strength of all three types of wire decreased with temperature, especially the SR type. The load strain rate has a significant effect on the SR type but little effect on the GL-2 and FA wires. The stress-strain curves from these tests were analyzed to fit into empirical constitutive models that account for the strain, temperature, and strain-rate effects.     

AZ91镁合金激光冲击强化力学性能研究

为了研究激光冲击强化对镁合金力学性能的影响以及不同激光冲击模式的效果,采用双束无叠加钕玻璃脉冲激光对AZ91镁合金进行冲击处理;冲击后在试样表面得到椭圆冲击斑,对光斑形貌和形状进行了观测分析,并与传统单点叠加冲击模式的结果对比。采用Triboindenter纳米压痕仪测试了冲击和未冲击区域的纳米硬度,得到测量值分别为1.59GPa和1.47GPa;采用X2350A型X射线应力衍射仪测试冲击区域残余应力分布情况,并用有限元软件ABAQUS对残余应力进行了数值模拟,得到实验测量和模拟结果在加载区域都有高达-120MPa左右的残余应力分布,且模拟结果与实验结果一致。结果表明,采用双束无叠加冲击模式可以提高冲击效率;激光冲击处理提高了镁合金的纳米硬度和力学性能,增强了其抗外物冲击损伤和抗疲劳性能。     

Effects of Laser Excitation and Temperature on Ag/GaSe0.5S0.5/C Microwave Filters

The effects of temperature, illumination, and microwave signals on Ag/GaS_0.5S_0.5/C Schottky-type microwave filters have been investigated. The devices, which were produced from thin layers of GaSe_0.5S_0.5 single crystal, had room temperature barrier height and ideality factor of 0.65 eV and 3.28, respectively. Barrier height increased uniformly with increasing temperature, at 2.12 × 10^?2 eV/K, and the ideality factor approached ideality. The devices can even function at 95°C. A current switching phenomenon from low to high injection (“On/Off”) was also observed; this current switching appears at a particular voltage, V _s, that shifts toward lower values as the temperature is increased. When the devices were reverse-biased and illuminated with a laser beam of wavelength 406 nm, a readily distinguishable V _s was observed that shifted with increasing laser power. When the devices were run in passive mode and excited with an ac signal of power 0.0–20.0 dBm and frequency 0.05–3.0 GHz they behaved as band filters that reject signals at 1.69 GHz. Device resistance was more sensitive to signal amplitude at low frequencies (50 MHz) than at high frequencies. The features of these Ag/GaS_0.5S_0.5/C Schottky devices imply that they may be used as optical switches, as self standing, low band-pass, band reject filters, and as high band-pass microwave filters.     

High strain rate compression behavior for Sn-37Pb eutectic alloy, lead-free Sn-1Ag-0.5Cu and Sn-3Ag-0.5Cu alloys

This paper emphasized on studying the high strain-rate compression behavior of the unleaded Sn-3Ag-0.5Cu (SAC305), Sn-1Ag-0.5Cu (SAC105) solders and the traditional Sn-37Pb eutectic solder. The split Hopkinson pressure bar (SHPB) apparatus was used to conduct high strain rate tests in order to characterize the associated high rate mechanical response of these alloys. Specimens were tested at strain rates ranging from 380 to 3030 s⁻¹ to obtain the dynamic stress-strain relationship for the Sn-37Pb, SAC305 and SAC105 alloys. The tested soft and ductile samples experienced a large amount of elastoplastic deformation due to impact test. In the high strain rate range studied, limited strain rate hardening effect was observed for SAC305, SAC105 and Sn-37Pb alloys studied. The strain rate sensitivity parameter (m) related to the power law creep equation was also calculated for the present solder materials at specific strain values. In addition, the saturation stresses for the leaded and lead-free solders at the strain rate range studied are also reported.     

凝固冷却速率影响下Al-Pd-Co复杂合金相的形成及分布特征

复杂合金相具有不同于传统金属的结构特征。为了搞清凝固冷却条件对铸态Al-Pd-Co复杂合金相存在状态的影响,本文应用TEM、SEM、HREM、EDS等多种电子显微学手段,分析了不同凝固冷却速率下Al70Pd10Co20三元合金中复杂合金相形成和分布特征。通过比较不同凝固冷却速率下凝固组织的形貌和成份的变化,推断出Al70Pd10Co20合金凝固过程中,M-Al13Co4和O-Al13Co4型复杂合金相的高温形成具有宽化的成分区间。随着凝固冷却速率的提高可导致另一具有复杂结构的W相的形成并与M-Al13 Co4和O-Al13 Co4型相共生,其结构包含与Al-Pd-Co十面体准晶同类的十面体原子团结构单元。     

Effects of mechanical strain on TFTs on spherical domes

In this paper, amorphous-silicon (a-Si:H) thin-film transistors (TFTs) were fabricated on a plastic substrate, which was then permanently deformed into a spherical dome shape after the device fabrication process. The TFTs were patterned in an island structure to prevent cracking in the device films during the substrate deformation. In the majority of the TFTs, the off-current and gate leakage current do not change substantially. Depending on the island structure, the electron mobility either increased or decreased after deformation. This change in mobility was correlated with the mechanical strain in the device islands determined by finite element modeling of the deformation process. Tensile strain caused slightly higher mobility in planar structures. In a mesa-type structure, silicon films on top of the pillars could be in compression after the dome deformation, leading to a slight decrease in mobility.