铝带超声键合界面损伤机理分析与优化设计

铝带超声键合过程中需要极大的键合能量和键合力作用在芯片表面,易造成芯片焊点界面损伤,从而引起产品质量与可靠性问题。详细分析了铝带超声键合工艺中造成芯片界面损伤的主要因素与作用机理,并通过键合参数的试验设计（Design of experiment,DOE）来解决芯片焊点界面损伤问题,从而提升最终产品良率。     

不同状态的Si-Al丝对键合点根部损伤的影响

键合点根部损伤是Al丝超声键合工艺中最常见的问题,严重的根部损伤不仅使焊点的键合强度降低,甚至会使键合点失效。通过优化键合机器的工艺参数、分析键合丝的组分和采取不同的退火条件,研究Al丝超声键合中,键合点根部损伤的程度,为键合丝的选用和提高Al丝超声键合强度提供依据。     

不同状态的SiAl丝对混合集成电路键合点根部损伤的影响

键合点根部损伤是Al丝超声键合工艺中最常见的问题之一，严重的根部损伤不仅使焊点的键合强度降低，甚至会使键合点失效。本通过优化键合机器的工艺参数，分析键合丝的组成成份和采取不同的退火条件，研究Al丝超声键合中键合点根部损伤的程度，为键合丝的选用提供依据，也为进一步提高Al丝超声键合强度做一些基础工作。     

厚膜Au导体的超声键合技术研究

Al丝超声键合技术是混合电路组装中使用得最为普遍的一种键合技术。本文使用焊点破坏性拉力试验和焊点的接触电阻测试两种方法，研究了导体材料（Au、Pd—Au）、膜层厚度、125℃、300℃热老练和温度循环对焊点键合强度的影响。分析了键合强度降低和焊点失效的原因。     

Pt-Pd-Ag厚膜导体的粗Al丝键合

采用破坏性拉力试验和焊点接触电阻测量两种方法测试Ｐｔ－Ｐｄ－Ａｇ三元合金导体的粗Ａｌ丝超声键合的性能。分别在１２４℃，１０００ｈ和３００℃，１０ｈ条件下进行热老练和温度循环等环境试验，然后测量焊点的键合强度。在室温和１２５℃高温条件下，观察了Ａｌ／Ｐｔ－Ｐｄ－Ａｇ超声键合系统抗电流冲击的能力。试验结果表明：Ｐｔ－Ｐｄ－Ａｇ厚膜导体适于粗Ａｌ丝超声键合，键合强度能满足要求。     

一种内引线键合脱键失效模式及其预防

通过对硅铝丝超声键合机理及键合检验方法的介绍，针对单片集成电路加工过程中遇到的键合脱键失效模式，详细叙述了分析过程，找出了键合脱键的失效原因，提出了预防失效的方法。     

一种内引线键合脱键失效模式及其预防

通过对硅铝丝超声键合机理及键合检验方法的介绍，针对单片集成电路加工过程中遇到的键合脱键失效模式，详细叙述了分析过程，找出了键合脱键的失效原因，提出了预防失效的方法。     

键合功率对银线键合质量的影响

铜线键合技术是半导体封装的关键技术之一,影响键合质量的因素有很多。本文基于热压超声键合的方法,对影响铜线键合质量的主要工艺参数——键合功率,进行DOE研究分析。通过对键合后的产品进行焊点剪切失效模式、拉伸失效模式以及弹坑实验分析,研究键合功率对键合质量的影响,进而确定合理的工艺参数,最终应用于大批量生产。     

一种内引线键合脱键失效模式及其预防

通过对硅铝丝超声键合机理及键合检验方法的介绍，针对单片集成电路加工过程中到的键合脱键失效模式，详细叙述了分析过程，找出了键合脱键的失效原因，提出了预防失效的方法。     

超声引线键合点形态及界面金属学特征

采用超声键合的方法,研究了键合点的形成原因,通过SEM及EDX分析发现超声键合过程中存在扩散现象.对键合点进行了老化试验,考察了键合点上25μm直径的质量分数为Al 1%Si引线的组织演变情况,在170℃下,随着老化时间的延长,键合点上引线内部形成了大量的微裂纹和孔洞,连接成线,与超声振动方向平行,分析了产生原因以及对键合点可靠性的影响.     

引线键合技术进展

引线键合以工艺简单、成本低廉、适合多种封装形式而在连接方式中占主导地位.对引线键合工艺、材料、设备和超声引线键合机理的研究进展进行了论述与分析,列出了主要的键合工艺参数和优化方法,球键合和楔键合是引线键合的两种基本形式,热压超声波键合工艺因其加热温度低、键合强度高、有利于器件可靠性等优势而取代热压键合和超声波键合成为键合法的主流,提出了该技术的发展趋势,劈刀设计、键合材料和键合设备的有效集成是获得引线键合完整解决方案的关键.     

焊线机超声波闭环控制

超声波是焊线机焊接过程中的重要参与元素,超声波控制效果决定着焊接的品质和速度。在分析超声换能器频率特性和电流响应的基础上,给出了频率自动跟踪和电流受控输出的闭环控制方案,提高了超声波效率,缩短了响应时间,增强了超声波输出的稳定性。实验结果表明,此方法实现了受控的上升时间和较小的超调     

LTCC基板金丝热超声楔焊正交试验分析

引线键合是微组装技术中的关键工艺,广泛应用于军品和民品芯片的封装。特殊类型基板的引线键合失效问题是键合工艺研究的重要方向。低温共烧陶瓷(LTCC)电路基板在微波多芯片组件中使用广泛,相对于电镀纯金基板,该基板上金焊盘楔形键合强度对于参数设置非常敏感。文章进行了LTCC基板上金丝热超声楔焊的正交试验,在热台温度、劈刀安装长度等条件不变的情况下,分别设置第一键合点和第二键合点的超声功率、超声时间和键合力三因素水平,试验结果表明第一点超声功率和第二点超声时间对键合强度影响明显。     

LTCC电路基板上金丝热超声楔焊正交试验分析

进行了LTCC基板上金丝热超声楔焊的正交试验,在热台温度和劈刀安装长度等条件不变的情况下,分别设置第一键合点和第二键合点的超声功率、超声时间和键合力三因素水平,试验结果表明第一点超声功率和第二点超声时间对键合强度影响明显。     

Investigation of ultrasonic vibrations of wire-bonding capillaries

Ultrasonic energy is widely used in wire bonding for microelectronics packaging. It is necessary to ensure that the maximum ultrasonic vibration displacement occurs at or near the tip of the bonding tool (capillary) for optimal performance. In this study, amplitude profiles of ultrasonic vibrations along capillaries were measured with load using a laser interferometer. This provided valuable information in understanding and improving capillary performance. The method was applied to real time applications to optimize capillary designs and bonding processes for specific bonding applications. First, the application of a new capillary material with different zirconia compositions was evaluated. The new material with certain amount of zirconia composition showed that it was the capillary material of choice for ultra-fine pitch wire bonding. Next, comparative analysis was conducted to investigate the ultrasonic energy transfer of a new ‘slimline’ bottleneck and the conventional bottleneck. The actual bonding response of the molded slimline bottleneck showed comparable performance with the ground conventional bottleneck using the same bonding parameters. Finally, optimization of a 60-μm-bond-pad-pitch process was performed on a wire bonder. Within the optimized parameter ranges, the ultrasonic displacement of the capillary was monitored. For all possible combinations of bond force and bond power, the ultrasonic displacement of the capillary increased with increasing bond power, without drastic changes caused by bond force changes. This indicated that the selected process window was located in a stable region.     

Thermosonic Wire Bonding Process Simulation and Bond Pad Over Active Stress Analysis

In this paper, a transient nonlinear dynamic finite element framework is developed, which integrates the wire bonding process and the silicon devices under bond pad. Two major areas are addressed: one is the impact of assembly 1st wire bonding process and another one is the impact of device layout below the bond pad. Simulation includes the ultrasonic transient dynamic bonding process and the stress wave transferred to bond pad device and silicon in the 1st bond. The Pierce strain rate dependent model is introduced to model the impact stain hardening effect. Ultrasonic amplitude and frequency are studied and discussed for the bonding process. In addition, different layouts of device metallization under bond pad are analyzed and discussed for the efforts to reduce the dynamic impact response of the bond pad over active design. Modeling discloses the stress and deformation impacts to both wire bonding and pad below device with strain rate, different ultrasonic amplitudes and frequencies, different friction coefficients, as well as different bond pad thickness and device layout under pad. The residual stress, after cooling down to a lower temperature, is discussed for the impact of substrate temperature.     

Hardening and Softening in AlSi1 Bond Contacts During Ultrasonic Wire Bonding

Ultrasonic wedge-wedge bonding of 25- $mu$m AlSi1 wires is characterized as a dynamic process of hardening and softening. In the first phase of wire bonding, the wedge is predeformed and cold worked by the bondforce. After ultrasonic energy has been switched on, recrystallization starts at the interface. During the bonding time hardening and softening processes alternate and a maximum in hardness is measured. Hardening and softening processes correlate well with the grain structure, the measured grain sizes and a typical plateau in the z-deformation curve of the contact. At the end of the wire bonding process the wedge is recrystallized and softer than the predeformated wedge, but harder than the as-received wire.      

超声换能系统电特性实验研究

超声换能系统是引线键合设备的核心部件,对其工作特性的深入了解有助于理解引线键合过程.通过实验,观察分析了超声引线键合过程中不同劈刀安装长度对换能系统电流、电压及功率的影响,发现电流及功率在不同劈刀安装长度时有较为明显的变化.并进一步采用小波分析方法展现了电流信号在时频域内变化的细节情况,为充分了解换能系统电学特性提供了可靠依据和新的方法.     

In situ ultrasonic force signals during low-temperature thermosonic copper wire bonding

Ultrasonic in situ force signals from integrated piezo-resistive microsensors were used previously to describe the interfacial stick-slip motion as the most important mechanism in thermosonic Au wire ball bonding to Al pads. The same experimental method is applied here with a hard and a soft Cu wire type. The signals are compared with those obtained from ball bonds with standard Au wire. Prior to carrying out the microsensor measurements, the bonding processes are optimized to obtain consistent bonded ball diameters of 60 μm yielding average shear strengths of at least 110 MPa at a process temperature of 110 °C. The results of the process optimization show that the shear strength c_pk values of Cu ball bonds are almost twice as large as that of the Au ball bonds. The in situ ultrasonic force during Cu ball bonding process is found to be about 30% higher than that measured during the Au ball bonding process. The analysis of the microsensor signal harmonics leads to the conclusion that the stick-slip frictional behavior is significantly less pronounced in the Cu ball bonding process. The bond growth with Cu is approximately 2.5 times faster than with Au. Ball bonds made with the softer Cu wire show higher shear strengths while experiencing about 5% lower ultrasonic force than those made with the harder Cu wire.     

Footprint study of ultrasonic wedge-bonding with aluminum wire on copper substrate

The effects of the process parameters of ultrasonic power and normal bonding force on bond formation at ambient temperatures have been investigated with scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) analysis. A model was developed based on classical microslip theory¹ to explain the general phenomena observed in the evolution of bond footprints left on the substrate. Modifications to the model are made due to the inherent differences in geometry between ball-bonding and wedge-bonding. Classical microslip theory describes circular contacts undergoing elastic deformation. It is shown in this work that a similar microslip phenomenon occurs for elliptical wire-to-flat contacts with plastically deformed wire. It is shown that relative motion exists at the bonding interface as peripheral microslip at lower powers, transitioning into gross sliding at higher powers. With increased normal bonding forces, the transition point into gross sliding occurs at higher ultrasonic bonding powers. These results indicate that the bonding mechanisms in aluminum wire wedge-bonding are very similar to those of gold ball-bonding, both on copper substrate. In ultrasonic wedge-bonding onto copper substrates, the ultrasonic energy is essential in forming bonding by creating relative interfacial motion, which removes the surface oxides.