微电子封装中焊锡接点的界面应力奇异性

采用界面力学理论计算了不同形状的含铅/无铅焊锡接点界面应力奇异性指数,建立了焊锡接点的有限元模型,计算了线弹性、弹塑性和Johnson-cook材料模型的界面应力分布.结果表明:随着焊锡接点接触角的增加,界面应力奇异性增强;Sn37Pb/Cu界面比Sn3.5Ag/Cu和Sn3.0Ag0.5Cu/Cu界面的应力奇异性明显;弹塑性变形和应变率效应降低界面应力.     

考虑损伤效应的无铅焊锡材料的率相关本构模型

考虑冲击过程中无铅焊锡材料试件中的损伤影响,根据实验数据确定了损伤演化参数,对原模型进行了修正,给出了Sn3.0Ag0.5Cu和Sn3.5Ag两种无铅焊锡材料考虑损伤效应的率相关本构模型.结果表明,修正后的模型与实验结果吻合较好.     

铅对Sn3.5Ag0.5Cu合金钎料性能的影响

利用显微硬度计、差热分析仪等仪器设备,研究了铅对Sn3.5Ag0.5Cu钎料合金性能的影响。实验结 果表明,铅对Sn3.5Ag0.5Cu钎料合金性能有较大的影响,添加铅后,Sn3.5Ag0.5Cu钎料合金熔化温度下降了8%; 钎料合金的润湿性得到改善;当w (Pb)达到0.5%时,Sn3.5Ag0.5Cu钎料合金显微硬度显微硬度值最大,达到21.5 HV之后快速下降。     

旋转磁场对无铅钎料组织及显微硬度的影响

为改善无铅钎料组织性能,研究了在0.125T、1250r/min的情况下旋转磁场对Sn3.0Ag0.5Cu、Sn-9Zn钎料组织和显微硬度的影响.结果表明：旋转磁场作用对Sn3.0Ag0.5Cu、Sn-9Zn钎料的物相构成没有影响,但可使钎料构成相的尺寸、形状及分布发生明显变化,其中部分Ag3Sn相发生弯曲,富Zn相变为细小且分布呈一定的旋转状.与未经旋转磁场作用相比,磁场作用后Sn3.0Ag0.5Cu、Sn-9Zn和Sn-9Zn钎料的显微硬度分别提高15.6%和10.2%,达到HV 24.5和HV 19.3.旋转磁场与感应电流间的Lorentz力具有驱动熔体随电磁场运动的趋势,将影响钎料组织凝固及其显微硬度.     

SABI333焊点拉伸性能及晶界对焊点拉伸性能影响

为了研究焊点拉伸力学性能,选取尺寸相同、晶体取向相似的Sn3.0Ag0.5Cu(SAC305)钎焊接头与Sn3.0Ag3.0Bi3.0In(SABI333)钎焊接头进行相同拉伸速度的拉伸实验.同时,选取SABI333钎焊接头中尺寸相同的单晶焊点与孪晶焊点进行相同拉伸速度的拉伸实验.利用EBSD与SEM对焊点的晶体取向和表面形貌进行表征.结果表明:SABI333焊点的抗拉强度远高于SAC305焊点,并且2种不同成分的焊点呈现完全不同的断裂方式. SAC305焊点发生韧性断裂,SABI333焊点在发生微量塑性变形之后断裂. SABI333焊点中单晶焊点和孪晶焊点在拉伸过程中表现出不同的拉伸性能.孪晶焊点在拉伸过程中未发生塑性变形,并且在钎料基体与铜棒交界处断裂.     

低银系无铅焊料合金界面结构研究

电子锡焊料合金的焊接界面的金属间化合物具有硬而脆的特性,在应力影响下易产生裂纹,进而引发断裂失效.研究界面金属间化合物层的结构、形貌和服役条件下的变化,对提高焊料合金的可靠性具有重要意义.采用实验和数值计算的方法,研究Sn0.1 Ag0.7 Cu、Sn0.3 Ag0.7 Cu、Sn0.5 Ag0.7 Cu、Sn0.8 Ag0.7 Cu、Sn1.0 Ag0.7 Cu焊料合金的金属间化合物结构和形貌,并进行了室温和高温高湿条件下的老化试验,研究界面形貌,厚度变化.研究表明:焊接完成后的界面形貌不平滑,部分金属间化合物异常长大,经过高温高湿试验后,焊接界面变得比较均匀、平滑;随着Ag含量的升高,界面的生长活化能呈先升高后降低,当Ag含量为0.3％时,具有最大的活化能78.9 kJ/mol,界面金属间化合物较为稳定,服役可靠性较高.     

Ag对Sn-0.7Cu焊料压入蠕变性能的影响

采用自制的蠕变装置研究了Sn-0.7Cu及Sn-0.7Cu-0.5Ag无铅焊料在温度为80～120℃、压力为25～43.2MPa下的压入蠕变性能,并利用光学显微镜和XRD对合金蠕变前后组织的演化进行了分析.结果表明:在加入0.5wt%Ag后,在相同温度和压力下,Sn-0.7Cu-0.5Ag合金的蠕变速率和总蠕变量均比Sn-0.7Cu小;形成的金属问化合物cu6sn5与Ag3Sn颗粒强化了β-Sn基体,从而提高了合金的抗蠕变性能.     

合金元素对Sn-Bi-Sb-Ag-Cu-Re系无铅钎料性能和组织的影响

研究了合金元素Bi、Sb、Ag、Cu、Re对锡基无铅多元钎料性能和组织的影响.研究结果表明，增加Bi、Ag、Cu含量可以降低液相线温度，Sb可以提高液相线温度；Bi、Cu有提高润湿性能的作用，Sb、Ag、Re在低含量范围内可提高润湿性能；Cu有提高剪切强度的作用，Bi明显使剪切强度降低.钎料的相组成是由在β Sn的基体上分布着金属间化合物Ag3Sn、SnBi和Cu6Sn5构成的，Sb和Re则基本上是固溶在基体中.     

Effect of adding Ce on interfacial reactions between Sn-3.0Ag-0.5Cu solder and Cu substrate

The formation and the growth of Cu-Sn intermetallic compound （IMC） layer at the interface between Sn-3.0Ag-0.5Cu-xCe solder and Cu substrate during soldering and aging were studied. The results show that Cu6Sn5 IMC is observed at the interface between solder and Cu substrate in all conditions. After aging for 120 h,the Cu3Sn IMC is then obtained. With increasing aging time,the scalloped Cu6Sn5 structure changes to a plate structure. The Cu3Sn film always forms with a relatively planar interface. By adding a small amount of the rare earth element Ce （only 0.1%,mass fraction） into the Sn-3.0Ag-0.5Cu solder alloy,the growth rate of the Cu-Sn IMC at the interface of solder alloy system is decreased. When the time exponent is approximately 0.5,the growth of the IMC layer is mainly controlled by a diffusion over the studied time range.     

Cu-9Ni-6Sn弹性铜合金的组织及性能研究

铜基弹性合金广泛应用于医疗、航天航海导航仪器、机械制造、电子电力和仪表制造等行业．本文以铜镍锡系合金为研究对象,研究了熔炼铸造以及形变热处理工艺对Cu-9Ni-6Sn合金组织和性能的影响．研究表明：通过对Cu－9Ni－6S11合金铸态组织观察,发现Cu－9Ni－6Sn合金铸态组织枝晶发达,均匀化退火能一定程度消除Sn的偏析,本实验适宜的均匀化退火工艺为：850℃×6h;综合考虑合金的显微硬度、导电率以及抗拉强度,合金最佳时效工艺为：390℃×5h．在冷变形量为90％、390oCx5h条件下,Cu－9Ni－6Sn合金弹性极限为774MPa,显微硬度为Hmv390,导电率为17．5％IACS,抗拉强度可达990MPa．     

Modeling uniaxial tensile deformation of polycrystalline Al using CPFEM

The crystal plasticity finite element modeling (CPFEM) is realized in commercial finite element code ABAQUS with UMAT subroutine on the basis of the crystal plasticity theory of rate dependent polycrystal constitutive relations in the mesosocpic scale. The initial orientations obtained by electron backscatter diffraction (EBSD) are directly input into the CPFEM to simulate the mechanical response of polycrystalline 1050 pure AI in uniaxial tensile deformation. Two polycrystal models and two tensile strain rates were used in the simulations. The stress-swain curves of tensile deformation were analyzed. The predictions and the corre-sponding experiment result show reasonable agreement and slight deviation with experiments. The flow true stress of strain rate 0.01 s-1 is higher than that of strain rate 0.001 s-1. At the strain less than 0.05, the stress saturated rate of the experiment is higher than the simulated results. However, the stress saturated rate of the experiment becomes gentler than the corresponding simulated predictions at the strain over 0.05. Also, necking was simulated by the two models, but the necking strain is not well predicted. Tensile textures at swain 0.25 were predicted at the low strain rate of 0.001 s-1. The predictions are in good accord with the experimental results.     

两种不同大理岩SHPB动态劈裂实验

利用SHPB试验系统,结合高速摄影技术,研究了冬瓜山铜矿深部采集的两种不同大理岩在动态劈裂下的应变率和强度、破坏应变之间的关系。实验数据表明,应变率对试样抗拉强度的影响较为显著,两种大理岩的动态抗拉强度随着应变率的增加而增大;灰色大理岩当应变率小于50s-1时,随着应变率的增加,动态拉伸强度敏感系数变化较大,当应变率大于50s-1时,动态拉伸强度敏感系数则变化不大,而白色大理岩则是在应变率大于120s-1后;随着应变率的增加,试样的破坏应变也随之增加。     

Testing of High-Strength Zr-Based Bulk Metallic Glass with the Split Hopkinson Pressure Bar

The split Hopkinson pressure bar(SHPB) was used to determine the dynamic compressive strength of the high-strength Zr38Ti17Cu10.5Co12Be22.5 bulk metallic glass at strain rate on the order of 102 s-1.It is shown that at high strain rates beyond about 1 000 s-1,uniform deformation within the metallic glass specimen could not be achieved and dispersion in the transmitted pulse can lead to discrepancies in measuring the dynamic failure strength of the present Zr-based bulk metallic glass.Based on these reasons,a copper insert was placed between the strike bar and the input bar to obtain reliable and consistent experimental data for testing of the Zr38Ti17Cu10.5Co12Be22.5 bulk metallic glass using the SHPB.Negative strain rate sensitivity was found in the present Zr-based bulk metallic glass.     

Parameter fitting of constitutive model and FEM analysis of solder joint thermal cycle reliability for lead-free solder Sn-3.5Ag

The experimental tests of tensile for lead-free solder Sn-3.5Ag were performed for the general work temperatures range from 11 to 90 °C and strain rate range from 5×10⁻⁵ to 2×10⁻² s⁻¹, and its stress—strain curves were compared to those of solder Sn-37Pb. The parameters in Anand model for solder Sn-3.5Ag were fitted based on experimental data and nonlinear fitting method, and its validity was checked by means of experimental data. Furthermore, the Anand model was used in the FEM analysis to evaluate solder joint thermal cycle reliability. The results show that solder Sn-3.5Ag has a better creep resistance than solder Sn-37Pb. The maximum stress is located at the upper right corner of the outmost solder joint from the symmetric center, and thermal fatigue life is predicted to be 3.796×10⁴ cycles under the calculated conditions. Foundation item: Project(50376076) supported by the National Natural Science Foundation of China