热超声金丝键合工艺及其可靠性研究

采用单一变量法,研究了超声功率、超声时间和焊接压力对金丝球焊时金丝引线结合性能的影响,以及键合引线在不同测试温度和不同老化时间下的结合性能,并通过对键合界面的研究分析了影响界面可靠性的原因。研究结果表明,相比于超声功率和超声时间,焊接压力对金丝引线结合性能的影响最大,随着焊接压力的增大,金丝球焊第一焊点的剪切断裂载荷以及金丝引线的拉伸断裂载荷均增加;随着测试时基板加热温度的升高,金丝球焊第一焊点的剪切断裂载荷以及金丝引线的拉伸断裂载荷均逐渐降低。150℃老化试验结果表明,随着老化时间延长,金丝球焊第一焊点的剪切断裂载荷以及金丝引线的拉伸断裂载荷均呈现先增大后减小的规律。     

超声功率对引线键合强度的影响

采集键合试验的PZT驱动功率及对应键合点的剪切测试力数据,作为超声功率和引线键合强度的表征.试验中的键合力、温度和时间分别设置为4.7 N、室温和100 ms.在这种典型的工业工艺键合参数下,通过改变超声功率比(设定超声功率与最大可调功率之比)来改变超声功率,研究了超声功率对引线键合强度的影响规律.试验中超声功率比在15%～100%之间做了20种设置,共进行了20组1 000次键合试验.结果表明:超声功率小于3.5 W时,键合强度受超声功率的影响规律明显,即当超声功率小于1.0 W时,增加超声功率将增加键合强度,并减少剪切测试力为0的情况;大于1.6 W后则反之;而在1.0～1.6 W之间则可获得稳定可靠的键合强度,也就是在上述试验条件下的键合窗口;超声功率超过3.5 W后,规律不明显.此外,超声功率除受超声功率比这一可控因素影响外,还受基板质量不均匀、劈刀与铝丝间约束不确定等随机因素影响,超声引线键合是一个敏感的过程.     

微波毫米波T/R组件内键合引线熔断机理研究

键合引线的耐电流水平是影响键合可靠性的重要因素之一,直接决定了雷达微波毫米波T/R组件的使用寿命。文中结合雷达微波组件的实际应用需求,开展键合引线耐电流水平研究,并深入分析了引线熔断机理,探讨引线熔断的微观过程,为电讯设计提供数据和理论参考。研究发现,键合引线熔断过程是焦耳热作用下的原子热迁移过程。熔断电流水平受外部气氛影响,大气气氛下的熔断电流水平略高于真空气氛下,可为航天产品设计提供参考。     

七彩LED金丝球焊机图像识别系统设计

在对七彩LED引线键合工艺及芯片图像特征分析的基础上,通过芯片、焊点示教方案以及目标搜索、对中方案的规划,设计了一个七彩LED芯片、焊点自动识别及自动对中系统.将图像识别系统应用于七彩LED金丝球焊机上,实现了多芯片、多引线电子元器件的自动焊线作业,提高了生产效率,降低了焊线成本.     

超声功率对粗铝丝超声引线键合强度的影响

超声功率是影响粗铝丝引线键合强度的最主要因素之一。在尽量排除其他干扰因素的情况下，通过实验比较了11种不同超声功率条件下，粗铝丝引线键合的结果，观察到了超声功率对粗铝丝引线键合强度的影响：在超声功率较小情况下(超声功率比为20％～30％)，增大超声功率有助于提高键合强度；在超声功率较大的情况下(超声功率比为45％～70%)，增大超声功率反而会降低键合强度，出现过键合的情况；只有当超声功率适中时(超声功率比为35％～40%)，才能获得稳定且满意的键合强度。分析了验现象的产生原因。     

微电阻焊及其在雷达T/R组件互连中的应用

微电阻焊技术成熟且操作简便,被广泛应用于电子及机械制造领域。文中将其创新性地应用到了雷达T/R组件微波模块的内部互连中。文中首先分析了微波组件中电阻焊的实现工艺与方法,然后应用该技术分别实现了T/R组件的低频连接器与基板之间、射频电路模块之间以及高频连接器接头内部电路的互连。利用该工艺技术方法,可以突破常规引线键合时焊接面可焊性要求较高的限制,可以实现高频、射频电路中金属丝、带（如镀金铜丝、金带、镀金铜箔）的互连。初步验证表明,其焊接质量良好。     

通用型耐高温微型压力传感器封装工艺研究

针对通用型高温微型压力传感器的测量要求,采用SIMOX(separation by implanted oxygen)技术SOI(silicon on insulator)晶片4层结构Pt5Si2-Ti-Pt-Au合金化引线系统,解决了高温压力传感器引线的难点。制作了静电键合实验装置,完成了硅／玻璃环静电键合,制作了压焊工作台,选用退火后的金丝,金金连接完成内引线键合。自制了耐高温覆铜传引板,定制了含Ag的高温焊锡丝,选用了耐高温导线作为外导线,完成了耐高温封装的关键部分。研制了高精度、稳定性的压阻式压力传感器。     

引线键合工艺参数的有限元分析

运用Ansys/LS-DYNA模拟引线键合过程,研究分析了键合力、焊盘材料属性、摩擦系数等参数在引线键合过程中对焊球和焊盘应力分布及变形的影响,并将仿真分析结果应用于实验室开发的引线键合机,为键合机的研发和调试提供了理论参考,改善了键合机的键合质量和键合稳定性。实验测量结果表明,有限元分析方法是有效的,结果是合理的,有一定的参考价值。     

面向IC封装的机器视觉定位算法研究

在IC封装过程中,为了解决引线键合理论位置与实际位置不重合的问题,本文提出采用最小外接矩形拟合法求解芯片各个焊点和引线框架实际位置,实时校正在芯片引线键合工艺中由于贴片和装夹产生的位置误差。根据芯片引线键合批量化生产的特点分别建立软件的实验模块和批处理模块。在实验模块中,对芯片图像特征采用软件智能识别和人工辅助定义相配合的方法来实现芯片特征区域和类型的快速定义,形成与特定类型芯片相对应的特征信息文件和算法配置文件。在进行批量化生产时根据实验模块中建立的芯片特征和算法文件来进行焊点和引线框架的快速定位。这种方法在批处理运行时简化了算法的复杂度,提高了芯片焊点和引线框架的位置检测效率和引线键合质量。     

金铝键合体系服役寿命评价方法研究

金铝键合是单片集成电路、微波T/R组件中实现硅芯片与基板互连的最主要手段。它是一种异质键合工艺,不可避免地会在键合界面生成金属间化合物,这也给金铝键合的可靠性带来了严峻挑战。文中研究了一种新型Au-Al键合体系服役寿命评价方法。采用金丝键合的破坏性拉力数据作为判定对象,基于高温加速寿命理论Arrhenius模型和威布尔模型设计Au-Al键合的可靠性评价方案,测试过程易于开展,评价数据直观,系统测试误差小。在室温25 ℃条件下,失效寿命为22.0年;在80 ℃工作温度下,失效寿命为9.1年。该评价方法可为Au-Al键合体系在型号装备中的应用提供支撑,为异质材料键合可靠性评价提供方法参考。     

Evolution of matt surface topography in aluminium pack rolling. Part II: effect of material properties

A model has been presented in a companion paper [1] to predict the generation of roughness on the matt surface in pack rolling of aluminium foil. The model is based on the finite element method using isotropic plasticity. This model is used in the current paper to investigate the effect of material properties on the generation of surface roughness. There is a large inhomogeneity of strain during deformation, with harder grains generally deforming less than softer ones. It is found that the roughness amplitude is roughly proportional to the standard deviation of the initial grain yield stress distribution, normalised by the initial mean yield stress, so that a wider distribution of the initial yield stress results in greater surface roughness. It is shown that a suitable linear hardening law can be used to approximate the roughening behaviour for real material flow stress curves.     

挤压-弯曲一体化成型铝合金弯曲型材的质量与性能

通过改造传统挤压机,增加弯曲装置,对铝合金型材进行挤压-弯曲一体化成型,研究了辊轮半径和辊轮移动速度对成型质量的影响,基于有限元模拟获得了辊轮半径和辊轮移动速度等最佳工艺参数。结果表明:当型材挤出速度与辊轮移动速度相同时,铝合金型材的成型性较好;挤压-弯曲一体化成型工艺避免了传统拉弯工艺存在的回弹、表面划伤和截面变形等缺陷,提高了弯曲型材力学性能的均匀性。     

三辊非对称滚弯成形的数值仿真及试验验证

基于有限元法对三辊非对称滚弯成形工艺进行了研究,对比分析了三辊非对称滚弯成形和三辊对称滚弯成形过程中,变形区应力场、板材上表面的塑形应变场及卷制力的变化规律。仿真结果表明：侧辊位移进给量相同的工况下,三辊非对称滚弯成形的卷制力大于三辊对称滚弯成形的卷制力;三辊非对称滚弯变形区的纵向应力和径向应力均大于三辊对称滚弯成形的纵向应力和径向应力;三辊非对称滚弯成形板材压弯段的成形质量高于三辊对称滚弯成形的成形质量。最后,经三辊非对称滚弯试验验证,有限元模型的成形误差为6.8%,有较高的精度。     

Contact simulation for predicting surface topography in metal forming

A surface contact model that takes account of flattening, roughening and tool elastic microwedge effects on workpiece surface is developed. The model can be implemented in FEM codes to predict the final surface qualities of the products in metal forming. As an example, the proposed model has been combined with a membrane finite element code of sheet metal forming process to predict the contact area ratio, surface roughness and mean asperity spacing. Numerical results showed good agreement with the experiments.     

Knowledge-based substep deterministic optimization of large diameter thin-walled Al-alloy tube bending

Regarding increasing applications with mass quantities, diverse specifications, and close quality tolerance, the precision bending of large diameter thin-walled (LDTW) Al-alloy tube should be efficiently achieved. However, bending of LDTW Al-alloy tube is a highly tri-nonlinear process with possible multi-defect, needing strict coordination of various bending tools and processing parameters. Considering the coupling effects of various forming parameters on multiple defects, this study developed a knowledge-based substep methodology to solve the deterministic optimization of LDTW Al-alloy tube bending with multi-objective and multi-variable under multiple factor constraints. Considering narrow forming window under small bending radii (R _b?<?2D, R _b—bending radius, D—initial tube diameter), a finite element (FE)-based stepwise iterative search method is proposed to optimize key forming parameters of LDTW Al-alloy tube under small R _b, and the search direction is based on bending knowledge. While for large R _b bending with wide optional ranges of forming parameters, a hybrid optimization approach is used by combining virtual design of experiment, FE simulation, approximate response surface model, sequential quadratic programming algorithm, or genetic algorithm. Using orthogonal experimental method, three-dimensional (3D)-FE simulation, experiential data, and analytical formulae, knowledge on key forming parameters, coupling effects on multiple defects, effect significance, and design rules are obtained as well as initial values and design ranges. By several practical bending scenarios with D up to 100 mm, the proposed substep deterministic optimization methodology for LDTW Al-alloy tube bending is evaluated.     

Three-dimensional topography of the matt surface in aluminium pack rolling

A model has been presented in a companion paper (Utsunomiya et al., Int. J. Mech. Sci., in press) to predict the generation of roughness on the matt surface in pack rolling of aluminium foil. This model was based on a two-dimensional (2D) finite element analysis using an isotropic plasticity model for the material. The spread of crystallographic grain orientations was simulated by ascribing different material properties to each grain. The predictions showed good qualitative agreement with experiments. It was found that the formation of shear bands causes roughening of the matt surface. The effect of material properties was further explored in Utsunomiya et al. (Int. J. Mech. Sci., in press).In the current study the model for evolution of the matt surface roughness is extended to a three-dimensional (3D) analysis and compared with predictions using a 2D analysis, a full crystallographic 3D model and experiments. The amplitude of the predicted roughness for the 3D model is lower than for the corresponding 2D analysis. In the 3D model, grains deform more uniformly due to the homogeneous constraint from adjacent grains. The predicted roughness shows good quantitative agreement with experiments, as well as with the predictions of the crystal plasticity model. The influences of grain shape and deformation mode are investigated. It is found that peaks or valleys running perpendicular to the first principal axis of strain are generated at the matt surface, regardless of initial grain shape.     

Evolution of matt surface topography in aluminium pack rolling. Part I: model development

Roughening of the matt surface of pack rolled aluminium foil has been modelled. The model is based on the finite element method using isotropic plasticity. A distribution in material properties has been used to simulate the distribution of grain orientations through the material. It is found that the formation of shear bands causes roughening of the matt surface. The length of these shear bands allows individual grains or the hard roll to influence the roughness a significant distance away. Results show the effect of the ratio of the grain size to the strip thickness on the predicted roughness generated. The predictions show good qualitative agreement with the reported experiments. It is concluded that the model is able to simulate efficiently the effect of the granular behaviour of polycrystals on the matt surface roughness.     

Analysis and finite element simulation of the tube bulge hydroforming process

To investigate the effect of the loading path on the forming result and get the reasonable range of the loading path in tube bulge hydroforming process, a mathematical model considering the forming tube as an ellipsoidal surface is proposed to examine the plastic deformation behavior of a thin-walled tube during the tube bulge hydroforming process in an open die, and thus different loading paths are gained based on this model. The finite element code Ls-Dyna is also used for simulating the tube bulge hydroforming process. The effect of the loading paths on the bulged shape and the wall thickness distribution of the tube are discussed, and then the reasonable range of the loading path for the tube bulge hydroforming process is determined.     

Analysis and finite element simulation of the tube bulge hydroforming process

To investigate the effect of the loading path on the forming result and get the reasonable range of the loading path in tube bulge hydroforming process, a mathematical model considering the forming tube as an ellipsoidal surface is proposed to examine the plastic deformation behavior of a thin-walled tube during the tube bulge hydroforming process in an open die, and thus different loading paths are gained based on this model. The finite element code Ls-Dyna is also used for simulating the tube bulge hydroforming process. The effect of the loading paths on the bulged shape and the wall thickness distribution of the tube are discussed, and then the reasonable range of the loading path for the tube bulge hydroforming process is determined.     

Effect of die corner radius on the formability and dimensional accuracy of tube shear bending

Tube shear bending is a beneficial technique to realize considerable small bending radii. The authors have investigated the tube shear bending process of circular tubes experimentally. Moreover, an elastoplastic 3D finite element simulation has been conducted, aimed at clarifying the forming mechanism. Both the experiment and simulation results indicate that, in order to perform successful forming, the value of the applied pushing force on the tube must be appropriate. In this paper, the mechanism of defect generation was clarified. Two failure criteria were introduced and employed to recognize the occurrence of defects in the simulation. The effects of the die corner radius, as the main parameter, on the defect generation of circular A1050 aluminum tubes were investigated both by experiments and numerical simulation. From the results, the formability of tube on dies with different corner radii applying various pushing pressures was clarified. Moreover, the influence of the die radius on the dimensional accuracy of the deformed tube regarding cross-section ovality and thickness changes of the deformed tube was evaluated. The results of this study indicate that, whilst a small bending radius results in high cross-section ovality, increasing the die corner radius raises the wrinkling tendency of the tube. However, the die radius has a small effect on the suitable values of pushing pressure required for a successful shear bending deformation. Moreover, the effect of the die corner radius on the thickness strain of the deformed tube is insignificant.