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。     

基于ADAMS引线键合机动态性能仿真分析

引线键合技术是半导体后续封装的关键技术,在集成电路制造产业领域,随着芯片尺寸的缩小、I/O密度的增大、封装工艺及材料的改进,对IC封装设备的动态响应速度和稳态定位精度提出更苛刻的要求。为节约开发成本,缩短开发时间,提高效率,可以利用MSC系列软件可以建立虚拟样机模型。同时为提高仿真效果,必须对一些影响键合机工作性能的外界干扰因素进行建模分析。本文利用有限元方法对关键部件进行模态分析,建立键合机的柔体模型,进行动态仿真,分析关键部件对引线键合效果的影响,提出改进的方案。     

玻璃与铝多层阳极键合接头力学性能分析

阳极键合是一种利用电和热相互作用实现固体电解质玻璃(陶瓷)与金属材料固态连接的一种新方法.运用共阳极法实现多层玻璃/铝的键合,并采用微拉伸试验和MARC非线性有限元分析软件,分析了玻璃与铝多层键合试件冷却后,接头的力学性能和残余应力分布状况.试验发现,在玻璃/铝/玻璃多层连接区,键合界面附近的残余应力和应变呈对称分布,多层结构的对称性有利于缓解接头应变和应力,表明应用公共阳极法可实现多层玻璃/铝/玻璃的良好键合.     

面向引线焊线工艺的参数预测模型与规律分析

芯片封装的引线键合质量受键合温度、功率、压力、速度、时间等多参数的影响,各参数间相互耦合,存在着非线性关系,难以用准确的数学模型来表达其间的关系,影响芯片键合质量的提高.应用方差分析法开展正交试验的数据分析,得出各工艺参数对键合质量关键评价指标(剪切力和压扁球直径)的影响程度,确定描述工艺模型的6个关键参数.提出基于自适应神经模糊推理系统的焊线工艺预测模型的构建方法,并通过焊线机上的多组试验数据进行模型训练.将所建模型的预测结果与实际数据相比较,结果显示剪切力和压扁球直径预测模型所产生的平均误差分别为3.16%和1.24%.基于所建预测模型,确定关键工艺参数对键合质量的影响规律,为进一步实现焊线工艺过程的最优参数组合提供支持.     

无铅BGA回流焊残余应力仿真分析

以热弹塑性理论为基础,建立无铅BGA焊点在回流焊工艺中的残余应力有限元模型,采用ANSYS进行热结构耦合分析,得到Sn3.5Ag0.75焊点回流冷却结晶后的残余应力分布规律。并针对焊点的直径、焊点的高度、PCB板的厚度和对流系数四个因素建立正交试验表,分析这四个因素对BGA冷却过程中残余应力影响规律,通过极差分析得出影响程度由大到小分别为对流系数、焊点高度、焊点直径、PCB板厚度,对控制BGA回流冷却残余应力提供理论指导。     

铝硅聚苯酯封严涂层切向载荷作用下应力分布的有限元分析

在封严涂层弹性模量试验的基础上,建立封严涂层摩擦有限元模型,对民航发动机铝硅聚苯酯封严涂层的摩擦过程进行有限元分析。分析了摩擦系数、涂层厚度和粘结层厚度等参数对涂层/粘结层/基体系统应力分布的影响。分析结果表明:在切向载荷的作用下,随着摩擦系数的增大,涂层表面、涂层与粘结层的界面以及粘结层和基体界面处的应力峰值均增大;随着涂层厚度的增大,涂层表面及两界面处的应力峰值均减小,但当涂层厚度达到一定程度后,继续增加涂层厚度对降低应力峰值的效果不明显;粘结层厚度在一定范围内的变化对涂层表面和涂层与粘结层界面处的应力变化影响不大,但随着粘结层厚度的减小,粘结层与基体界面处的应力峰值均增大。     

微晶玻璃与不锈钢阳极键合残余应力分析

微机电系统封装过程中产生的应力会影响其封装效果与使用寿命,针对微晶玻璃与不锈钢阳极键合温度引起的残余应力问题,采用MARC有限元软件对微晶玻璃与不锈钢键合冷却过程模拟。分析了微晶玻璃与不锈钢在不同厚度比值与面积比值键合结构下的残余应力分布规律。结果表明:微晶玻璃与不锈钢厚度比值越小,最大残余应力越小;随着不锈钢与微晶玻璃面积比值的增大,残余应力逐渐趋于平稳。研究结果为改善微晶玻璃与不锈钢阳极键合质量提供了理论参考与设计依据。     

基于自感知压电换能器的键合质量检测方法研究

将换能器耦合电信号作为识别键合质量的信息载体,研究了耦合信号的特征提取、模式识别方法及实际应用。提出了一种换能器耦合信号细化特征提取方法,该方法以三个关键键合过程即去除氧化膜、键合点塑性变形、应力扩散为依据,将瞬态耦合信号分段进行特征提取。采用主分量分析技术对提取的特征进行选择,通过BP神经网络对键合缺陷特征进行分析,有效地识别了无引线键合缺陷,预测了键合点剪切力。     

2024铝合金随机多弹丸喷丸后残余应力场的有限元模拟

基于有限元分析软件ABAQUS建立了2024铝合金随机多弹丸喷丸的三维有限元模型,首先模拟了不同弹丸数量下残余应力场的变化特征,然后分析了弹丸速度和直径对残余应力场的影响;最后进行了试验验证。结果表明:弹丸数量大于80颗后,残余应力基本不再变化;增加弹丸速度可显著提高残余压应力层的深度、各深度残余压应力值以及残余压应力的峰值,但对残余压应力峰值的深度影响不大;增大弹丸直径对0~0.1 mm深度内的残余压应力值影响不大,对残余压应力层的深度、0.1mm深度以下的残余压应力值、残余压应力峰值及残余压应力峰值的深度提高明显;有限元模拟结果与试验结果接近,说明模拟结果准确。     

浅析铜线键合工艺第二焊点不沾的管控方法

铜线键合工艺是半导体封装技术应用中最普遍的工艺,已成为主流。虽然其在生产成本、生产效率上比金线工艺更具有优势。但是铜线的储存和使用条件对环境的要求非常高,尤其是在生产过程中极其容易氧化,另外铜线材料在生产制造中,如果材料的特性、设备键合工艺参数设置不合理、夹具的选择、环境以及夹具的选择容易造成第二焊点不沾,不良现象主要体现在弹坑、虚焊、焊接不良以及芯片焊盘铝层破裂等,最终导致产品失效。本文就铜线键合工艺中第二焊点不沾的情况如何管控进行简单的分析,以确保铜线键合工艺的稳定及可靠性。     

表面粗糙度对扩散连接孔隙闭合时间的影响

为考察实际连接表面粗糙度分布的随机性对扩散连接孔隙闭合的影响，把由表面粗糙度决定的接触界面的孔隙高度和半径视为随机变量。在原有确定性模型的基础上考虑了粗糙度孔隙的概率分布，建立了扩散连接孔隙闭合的概率模型。采用蒙特卡罗模拟和数值积分方法，计算了不同扩散连接时间下孔隙闭合的概率大小，并进行了参数敏感性分析，讨论了蠕变指数和孔隙半径对孔隙闭合时间的影响规律。     

计入截面厚度均匀性的浪形保持架的工作应力分析

模拟了保持架梁与兜孔处相对弯曲半径为0.8和1.0的深沟球轴承浪形保持架的冲压成形过程,并将其截面厚度信息映射到保持架应力分析的有限元网格中,得到更接近于真实状况的保持架应力分布。结果表明:由冲压成形引起的保持架截面厚度不均匀性对相对弯曲半径为0.8的保持架圆角处应力分布状况影响较大,而对相对弯曲半径为1.0的保持架圆角处应力分布状况影响较小;保持架梁与兜孔处相对弯曲半径由0.8增大至1.0有利于改善圆角处应力分布状况。     

基于高速摄像的引线键合高尔夫球现象形成规律实验研究

利用高速摄像系统记录不同打火参数下打火杆放电、尾丝熔化成球的序列图像。通过MATLAB对图像进行图像处理,得到最终成球的直径及其球心与尾丝中心线的偏距。实验发现,在较大的打火电流(I=60mA)或较小的预设球直径(D=40.64μm(1.6mil))等条件下,球心与尾丝中心线的偏距不稳定且相差较大,易出现高尔夫球现象,严重影响引线键合的质量。     

热超声引线键合换能系统振动特性仿真研究

在建立热超声引线键合换能系统各子部分运动方程的基础上，利用有限元方法建立空载情况下换能系统的振动特性仿真模型，并采用正弦扫频方法验证仿真模型。结果表明：换能系统以第2阶变幅杆轴向振动与劈刀径向振动的模态作为其工作状态下的主振型；换能系统工作频率附近包含多种振动模态，键合过程极易被激发而表现出多模态性，由此会消耗部分超声能量且对芯片键合界面造成负面影响，这些振动模态必须得到抑制；仿真计算与试验结果相吻合，其中工作频率的相对误差只有1．2％。     

超声波线焊的两维非接触有限元分析

在超声波线焊中,虽然金线和焊接平台间的接触界面较大,但实验显示,焊接部位只发生在接触截面的周边,这是一种特别的焊接界面形态和超声波线焊的机理。本文采用弹塑性、大变形的非线性有限元方法,模拟了超声波线焊的过程,分析了接触界面的接触压强分布,发现不均匀的接触压强分布是导致这种焊点形态的主要原因。这种不均匀的焊点形态也将影响对压碶按压力作用的理解,过高的压碶按压力并不一定有助于超声波线焊。     

单磨粒磨削对表面残余应力影响的仿真分析

通过分析单磨粒仿真模型中磨削参数对材料表面残余应力的影响,得到使材料表面残余应力稳定性更好的磨削参数值,针对Ti6Al4V合金建立热—力耦合的单磨粒平面仿真模型。单磨粒磨削深度取相应磨粒刃圆半径大小相近的数值,并得到两组使表面残余应力数值稳定性较好的磨削参数值:一组是圆锥角θ=60°、刃圆半径r=10μm的磨粒,磨削后的残余应力约为100MPa;另一组是圆锥角θ=60°、刃圆半径r=1μm的磨粒,单磨粒磨削后的残余应力约为400MPa。分析发现:磨削温度的热软化效应会使残余应力的数值降低;单磨粒圆锥角对材料表面残余应力的影响比刃圆半径的更加显著。     

Effects of wafer curvature caused by film stress on the chemical mechanical polishing process

A theoretical model based on two-body contact theory is established to simulate the contact pressure distribution arising from wafer curvature which is caused by film stress during CMP process. Both wafer and pad deformations during the contact process are considered. The profiles of the contact pressure distribution for wafers with different curvature radius are simulated. The influences of wafer curvature on mean removal rate and within wafer removal rate nonuniformity (WIWNU) are simulated and compared with the experimental data. According to the two-body contact model, when the pad is in contact completely with the wafer, the profile of the contact pressure has almost the same trend whether the wafer has an upward or a downward curvature. The mean value of the contact pressure will increase with increasing of radius of downward curvature. WIWNU will decrease with increasing pre-polish wafer bow from concave (upward curvature) to convex (downward curvature). The results from the simulation correlated with the experimental data and demonstrated the validity of the model. The results are helpful for controlling and reducing the wafer to wafer removal rate nonuniformity and within wafer removal rate nonuniformity in CMP.     

A mixed elastohydrodynamic lubrication model with layered elastic theory for simulation of chemical mechanical polishing

Mixed elastohydrodynamic lubrication (mixed EHL) model has been successfully used to study phenomena in chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, a polishing pad's deformation cannot correctly be described by adopted models for pad deformation such as elastic half-space model and Winkler elastic foundation model. Thus, a more accurate model for pad deformation is needed, since this is the prerequisite for an accurate prediction of contact pressure and material removal rate, which is critical for improvement of polishing quality. In this paper, a layered elastic theory, which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. It is found that this theory has a similar accuracy to the traditional 3D finite element method for calculating the pad deformation. However, its computational cost is much lower, which is especially important for accurate and efficient simulation of mechanical behavior and material removal rate (MRR) in CMP. In order to highlight benefits of the proposed theory, simulations are carried out based on three different pad deformation models with the mixed EHL model. The pad deformation behavior is found to have a significant influence on the final simulation results, especially the MRR prediction. By comparing the different simulation models, the proposed layer elastic theory is found to be an optimal model for describing the polishing pad deformation behavior in CMP and can provide accurate simulation results on contact pressure distribution and the material removal rate.     

A statistical model for material removal prediction in polishing

This paper develops analytically a statistical model for predicting the material removal in mechanical polishing of material surfaces (MS). The model was based on the statistical theory and the abrasive–MS contact mechanisms. The pad-MS and pad-abrasive-MS interactions in polishing were characterised by contact mechanics. Two types of active abrasive particles in the polishing system were considered, i.e., Type I – the particles that can slide and rotate between the pad and MS, and Type II – those embedded in the pad without a rigid body motion. Accordingly, the material removal is considered to be the sum of the contributions from the two types of abrasive interactions. It was found that the mechanical properties and microstructure of the polishing pad and polishing conditions have a significant effect on the material removal rate, such as the porosity and elastic modulus of the pad, polishing pressure, volume concentration of abrasives, particle size, pad asperity radius and pad roughness. It was also found that different types of active particles contribute quite differently to the material removal. When the mean particle radius is small, the material removal is mainly due to the Type II particles, but when the mean particle radius becomes large, the Type I particles remove more materials. The model predictions are well aligned with experimental results available in the literature and can be used for the material removal prediction in chemo-mechanical polishing if a proper treatment of the chemical effect is introduced.     

抛光垫特性对抛光中流体运动的影响分析

抛光垫表面特性能可大大改变抛光液的流动情况,从而影响化学机械抛光的抛光性能。考虑抛光垫粗糙度和孔隙等对抛光液流动的影响,提出了一个初步的晶片级流动模型,并用数值模拟方法研究了不同参数条件(载荷和速度的变化等)下抛光液的流动特征。计算结果表明增加外载荷将导致粗糙峰的磨损概率增加,增加剪切速率则提高了剪切应力,均可导致高材料去除率。模型能较好理解材料去除机制和输运,从而有助于对化学机械抛光机制的了解。