【作者】 高翔；

【导师】 刘胜；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2014， 硕士

【摘要】 电子产品封装的可靠性决定着整个电子产品的可靠性，而且随着电子产品向着高I/O数、高密度的方向迅猛发展，对封装可靠性提出的要求更高，本文以电子封装的可靠性作为主要研究对象，研究了倒装芯片封装可靠性以及实现三维互连的关键技术——硅通孔（through silicon via, TSV）热机械可靠性设计。倒装芯片封装因其优异的高频性能和近乎理想的封装密度，获得了越来越多的关注，而且极有可能成为未来主流的封装模式之一。硅通孔是目前为止实现三维互连的最关键技术之一，其可靠性直接影响着整个三维封装产品的可靠性，对其结构参数进行优化设计可以为工艺加工提出指导，提高机械可靠性。本文基于有限元分析技术，主要研究内容如下：（1）分别研究了芯片与底充胶间沿水平和竖直两个方向的界面裂纹扩展行为，发现水平方向较竖直方向更易产生裂纹，而且当水平方向裂纹扩展一段距离之后，竖直方向的界面裂纹才可能开始萌生；对于芯片与底充胶间沿水平方向扩展的裂纹，研究了促使其扩展的驱动应力形式，分析表明，在裂纹萌生以及扩展较短距离阶段，剪切型应力起着主要的作用，但是当裂纹扩展较长一段距离后，张开型应力起着主要的作用。（2）分别研究了底充胶填充工艺所造成的缺陷以及芯片和底充胶间沿水平方向的界面裂纹对焊点寿命的影响，并对它们做了比较，研究结果表明，沿水平方向的界面裂纹对焊点寿命的影响更大，且一旦发生失稳扩展更容易造成整个封装结构的失效，对封装可靠性的影响更大。（3）研究了倒装芯片封装焊点的寿命预测，这包括无铅焊料本构模型的选择以及寿命预测模型的比较。结果表明，基于断裂参量和塑性应变的模型预测的寿命误差最大，基于蠕变的模型预测结果与实验结果最为接近，因此，蠕变是倒装芯片封装结构工作时的主要变形机制；而且，工作时焊点蠕变变形主要处在第二阶段，双曲正弦规律能较好拟合Sn-Ag-Cu焊料的蠕变变形机制。（4）对硅通孔三维芯片堆叠封装结构进行了热机械可靠性设计，提出了一种新型的硅通孔结构并与传统硅通孔结构的热机械可靠性做了比较。使用了正交设计实验和有限元仿真分析计算相结合的方法，研究了通孔间距、SiO2层、铜柱直径、芯片厚度、焊球直径和高分子保护胶的弹性模量等参数对TSV相关可靠性的影响，发现铜柱的直径和高分子保护胶的弹性模量对TSV可靠性的影响最大，且随着铜柱直径和保护胶弹性模量的增大，可靠性降低；新型硅通孔结构较之于传统硅通孔结构，其热机械可靠性明显提高。更多还原

【Abstract】 Electronic products’ reliability largely depends on their package reliability. Withelectronic products’rapid development to be of more I/Os and higher density, the requirementfor packaging reliability has been more strict. This thesis mainly focuses on electronicpackages’ reliability, especially, reliability for flip-chip package and TSV(through silicon via),which is the key technology to realize3D interconnection, in3D package. Because of itsexcellent performance in high frequency and almost ideal packaging density, flip-chippackage has attracted more and more attention and has the great potential to be one of themain packaging modes in the future. TSV has been seen as one of the most critical technologyto realize3D interconnect and its realiability can directly affect realiability of the whole3Dpackaging products. Structural optimization design for TSV can provide guidance forprocessing and enhance its mechanical reliability. Based on the finite element method, maincontents of this thesis are as follows:（1） Propagation behavior of interfacial delamination at chip/underfill interface inhorizontal and vertical direction are respectively studied. It turns out that it is more likely fordelamination in horizonal direction to take place and after the interfacial delaminationpropagates a certain distance, that in vertical direction begins to initiate; as for interfacialdelamination in horizontal direction, the mode of its driving force is studied, the results showthat when delamination initiates or crack is short, shearing stress plays the dominant role,however, when it propagates a relative long distance, opening stress makes the biggercontribution.（2） Effects of defects induced by underfill filling process and delamination alonghorizonal interface between chip and underfill on solder joints’ life are respectively analyzedand compared. It indicates that interfacial delamination has a bigger impact on solder joints’reliability and once unstable propagation happened, the whole flip-chip package may fail towork.（3） Life prediction for solder joints in flip-chip package is studied, which iscomposed of constitutive model selection for leadfree solder and comparing of different life prediction models. It is found that the life prediction models based on frature parameter andplastic strain respectively could lead to big error, and the model based on creep could predictsolder’s lifespan which could be very close to experimental results. Therefore, creep can beregarded as the main deformation mechanism when flip-chip works or undergoes thermalcycling. In addition, the creep deformation is mainly concentrated in the second stage (creepdeformation is composed of three stages in total) and the hyperbolic-sine law can describeSn-Ag-Cu solder’s creep deformation when flip-chip works.（4） Thermo-mechanical reliability design for the TSV stacked-dies3D package isimplemented and a new TSV structure is introduced and thermo-mechanical reliabilitycomparing between the new structure and the traditional copper-filled structure is made.Through combinating the design of experiment (DoE) with the finite element analysis, effectsof parameters, such as via pitch, copper via diameter, chip thickness, solder diameter andYoung’s Modulus of underfill, on TSV’s reliability, it is found that copper via’s diameter andYoung’s Modulus of underfill have the greatest effect on TSV’s reliability and the reliabilitydecreases with the increase of copper via’s diameter and Young’s Modulus. What’s more,compared with traditional copper-filled TSV structure, the new one has betterthermo-mechanical reliability.更多还原