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。     

平整度对细Al丝超声引线键合强度的影响

为避免双键合点破坏性拉力实验不易准确的缺陷和剪切力测试不能评价键合点整体特性的缺陷,采用了破坏性单键合点的测试方法.在尽量排除其他干扰因素的情况下,通过实验比较了10种不同平整度条件下细Al丝超声引线键合的结果.结果表明,平整度对超声引线键合的强度有影响,随着平整度的提高,键合强度和稳定度也随之提高.实际测试键合拉力时发现,键合良好断裂点均在跟键(heel)处,采取补强的方式使1.25 mil(3.125×10-3 cm)细Al丝超声键合后的键合强度均值可以达到0.156 8 N.分析了以上实验现象产生的原因,探讨了键合强度形成的机理.     

台面型焊盘的引线键合工艺研究

引线键合工艺是微电子封装的基础工艺,广泛应用于军品和民品芯片的封装。特殊结构焊盘的引线键合失效问题是键合工艺研究的重要方向。文章主要针对台面型焊盘,从热压键合、超声键合、热超声键合原理进行了分析,对台面型焊盘的工艺适应性给出了建议。使用热超声键合工艺进行台面型焊盘的引线键合需要尽可能降低超声功率,避免键合焊盘的机械损伤,并通过平衡其他各变量保证键合点的强度。侧重于热超声键合工艺的应用,分析台面型焊盘与热超声键合过程相关的失效现象,通过样件及小批量试制,对工艺参数进行了优化验证,针对故障件统计分类给出了相应的解决途径。     

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。     

超声功率对25μm铂金丝球形键合强度的影响及键合点质量评价

铂金丝作为低温器件封装中理想的键合丝,其键合质量的优劣决定着整个器件的性能和可靠性。通过25μm的铂金丝球形键合试验,并使用OLYMPUS SMT-6三轴测量显微镜观察键合点形貌并测量第一键合点根部直径。结果表明,当超声功率介于0.96～1.2 W时,增加超声功率有助于提高键合强度,增加工艺稳定性。在文中所设实验条件下,为保证键合强度和工艺稳定性,超声功率设置为1.2～1.28 W时最佳。第一焊点键合球平均直径为2.8 WD(WD表示键合线直径)时,键合强度最大,工艺稳定性最好。总结出了键合点直径与拉力值关系图,从而通过键合点直径来评价键合质量。     

基于DOE和BP神经网络对Al线键合工艺优化

Al丝超声引线键合工艺被广泛地应用在大功率器件封装中,以实现大功率芯片与引 线框架之间的电互连.Al丝引线键合的质量严重影响功率器件的整体封装水平,对其工艺参数的优化具有重要工业应用意义.利用正交实验设计方法,对Al丝引线键合工艺中的三个最重要影响因数(超声功率P/DAC、键合时间t/ms、键合压力F/g)进行了正交实验设计,实验表明拉力优化后的工艺参数为:键合时间为40 ms,超声功率为25 DAC,键合压力为120g;剪切推力优化的工艺参数为:键合时间为50 ms,超声功率为40 DAC,键合压力为120 g.基于BP神经网络系统,建立了铝丝超声引线键合工艺的预测模型,揭示了Al丝超声键合工艺参数与键合质量之间的内在联系.网络训练结果表明训练预测值与实验值之间符合很好,检验样本的结果也符合较好,其误差基本控制在10%以内.     

声表面波器件引线楔形键合跟部微损伤控制研究

声表面波器件内连的主流工艺是硅铝丝超声键合，而跟部微损伤是该工艺最大的质量隐患。该文从超声键合原理和工艺技术出发，对造成跟部微损伤的影响因素进行了分析，并给出了相应的解决方案。该方案使声表面波器件的键合点跟部微损伤得到有效控制。     

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.     

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。     

自动楔焊键合第一键合点跟部损伤控制

在自动楔焊键合中,要提高键合引线的抗拉强度,最重要的一点就是要减小第一键合点跟部的损伤。文章简述了自动楔焊键合的工艺过程,分析了在自动楔焊过程中造成第一键合点跟部损伤的主要原因：劈刀本身结构会对键合引线造成一定的摩擦损伤,劈刀在键合第一点后垂直上升所产生的应力会对第一键合点根部造成损伤,键合引线在拉弧过程中也会造成键合引线摩擦受损,送线系统的张力也会对第一键合点根部造成一定的损伤。文中还讨论了如何尽量减小摩擦和应力对第一键合点跟部所造成的损伤。     

Reliability model for Al wire bonds subjected to heel crack failures

In power electronic packages wire bonding is used for the electrical contact of the chips and for interconnections on the module substrate. Limiting factors for the reliability are solder fatigue and wire bond failures. In this work we investigate the material fatigue of aluminum bonding wires stressed by cyclic lateral bonding area displacement. Bond wire heel crack failures observed by experiments are found to be strongly dependent on the loop geometry. Based on a finite element model that accounts for elastic-plastic material properties, a life-time model for the Al wire (Coffin-Manson representation) is derived from the experiments.     

金丝楔形键合强度的影响规律分析

金丝楔形键合是一种通过超声振动和键合力协同作用来实现芯片与电路引出互连的技术。现今,此引线键合技术是微电子封装领域最重要、应用最广泛的技术之一。引线键合互连的质量是影响红外探测器组件可靠性和可信性的重要因素。基于红外探测器组件,对金丝楔形键合强度的多维影响因素进行探究。从键合焊盘质量和金丝楔焊焊点形貌对键合强度的影响入手,开展了超声功率、键合压力及键合时间对金丝楔形键合强度的影响研究。根据金丝楔焊原理及工艺过程,选取红外探测器组件进行强度影响规律试验及分析,指导实际金丝楔焊工艺,并对最佳工艺参数下的金丝键合拉力均匀性进行探究,验证了金丝楔形键合强度工艺一致性。     

铝丝键合焊点颈部损伤研究

在铝丝键合中,要提高键合铝丝的拉力强度,最重要的一点就是减少第一焊点颈部的损伤。该文简述了铝丝键合的工艺过程,分析了在自动键合过程中造成第一键合点颈部损伤的主要原因:焊接参数设置不当会造成焊点过应力损伤;焊接顺序不合理会造成超声波作用后,焊点颈部损伤;键合劈刀沾污以及劈刀本身的设计结构也会对焊点造成一定的损伤;键合引线在拉弧度的过程中也会因摩擦受损;压爪或垫块未完全固定基岛,引起键合过程中焊点颈部损伤。     

Process windows for low-temperature Au wire bonding

The process windows are presented for low-temperature Au wire bonding on Au/Ni/Cu bond pads of varying Au-layer thicknesses metallized on an organic FR-4 printed circuit board (PCB). Three different plating techniques were used to deposit the Au layers: electrolytic plating, immersion plating, and immersion plating followed by electrolytic plating. Wide ranges of wire bond force, bond power, and bond-pad temperature were used to identify the combination of these processing parameters that can produce good wire bonds, allowing the construction of process windows. The criterion for successful bonds is no peel off for all 20 wires tested. The wire pull strengths and wire deformation ratios are measured to evaluate the bond quality after a successful wire bond. Elemental and surface characterization techniques were used to evaluate the bond-pad surfaces and are correlated to wire bondability and wire pull strength. Based on the process windows along with the pull strength data, the bond-pad metallization and bonding conditions can be further optimized for improved wire bondability and product yields. The wire bondability of the electrolytic bond pad increased with Au-layer thickness. The bond pad with an Au-layer thickness of 0.7 μm displayed the highest bondability for all bonding conditions used. The bondability of immersion bond pads was comparable to electrolytic bond pads with a similar Au thickness. Although a high temperature was beneficial to wire bondability with a wide process window, it did not improve the bond quality as measured by wire pull strength.     

第一顺序键合引脚失效分析及键合可靠性提高

文章分析了一例采用金丝热超声键合电路在工艺监控过程中的键合强度检测合格,在高温稳定性烘焙后其引线抗拉强度同样符合MIL-STD-883G方法2011．7的要求,但电路在使用中出现第一顺序键合引脚开路现象。经分析是由于芯片键合区（压点）的材料、结构、键合工艺参数处于工艺下界,以及此类缺陷不能通过键合引线抗拉强度在线监测（包括125℃下的24h高温贮存后的检测）检测出而导致。最后针对缺陷所在,通过改进检测方法、键合工艺设置等消除了键合缺陷,并提高了键合可靠性。     

Effect of plasma treatment of Au-Ni-Cu bond pads on process windows of Au wire bonding

The wire bondability of Au-Ni-Cu bond pads with different Au plating schemes, including electrolytic and immersion plates, are evaluated after plasma treatment. The plasma cleaning conditions, such as cleaning power and time, are optimized based on the process window and wire pull strength measurements for different bond pad temperatures. Difference in the efficiency of plasma treatment in improving the wire bondability for different Au plates is identified. The plasma-cleaned bond pads are exposed to air to evaluate the recontamination process and the corresponding degradation of wire pull strength. The changes in bond pad surface characteristics, such as surface free energy and polar functionality, with exposure time are correlated to the wire pull strength, which in turn provides practical information about the shelf life of wire bonding after plasma cleaning.     

Influence of surface contamination on metal/metal bond contact quality

The influence of surface cleanliness of Au/Ni coated multichip materials (MCMs), Ag plated Cu lead frames, and Al bond pads on semiconductor chips on the strength of Au wire bond contacts has been investigated. A clean surface is important for good adhesion in any kind of attachment process. Investigations by means of x-ray photoelectron spectroscopy have been performed on the bond substrates to determine the chemical composition, the nature as well as the thickness of the contamination layer. The influence of contamination on bond contact quality has been examined by pull force measurements, which is an established test method in semiconductor packaging industry for evaluating the quality of wire bonds. The results clearly show that a strong correlation between the degree of contamination of the substrate and pull strength values exists. Furthermore, a contamination thickness limiting value of 4 nm for Au and Ag substrates was determined, indicating good wire bond contact quality. The effect of plasma cleaning on wire bondability of metallic and organic (MCMs) substrates has been examined by pull force measurements. These results confirm the correlation between surface contamination and the strength of wire bond contacts for Au/Ni coated MCMs and Ag plated Cu lead frames. Atomic force microscopy measurements have been performed to determine the roughness of bond surfaces, demonstrating the importance of nanoscale characterization with regard to the bonding behavior of the substrates. Finally, bonding substrates used in integrated circuit packaging are discussed with regard to their Au wire bonding behavior. The Au wire bonding process first results in a cleaning effect of the substrate to be joined and secondly enables the change of bonding energy into frictional heat giving rise to an enhanced interdiffusion at the interface.     

Direct gold and copper wires bonding on copper

The key to bonding to copper die is to ensure bond pad cleanliness and minimum oxidation during wire bonding process. This has been achieved by applying a organic coating layer to protect the copper bond pad from oxidation. During the wire bonding process, the organic coating layer is removed and a metal to metal weld is formed. This organic layer is a self-assembled monolayer. Both gold and copper wires have been wire-bonded successfully to the copper die even without prior plasma cleaning. The ball diameter for both wires are 60 μm on a 100 μm fine pitch bond pad. The effectiveness of the protection of the organic coating layer starts from the wafer dicing process up to the wire bonding process and is able to protect the bond pad for an extended period after the first round of wire bond process. In this study, oxidization of copper bond pad at different packaging processing stages, dicing and die attach curing, have been explored. The ball shear strength for both gold and copper ball bonds achieved are 5 and 6 g/mil² respectively. When subjected to high temperature storage test at 150 °C, the ball bonds formed by both gold and copper wire bond on the organic coated copper bondpad are thermally stable in ball shear strength up to a period of 1440 h. The encapsulated daisy chain test vehicle with both gold and copper wires bonding have passed 1000 cycles of thermal cycling test (−65 to 150 °C). It has been demonstrated that orientation imaging microscopy technique is able to detect early levels of oxidation on the copper bond pad. This is extremely important in characterization of the bondability of the copper bond pad surface.     

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。