3D reconstruction and defect pattern recognition of bonding wire based on stereo vision

Non-destructive detection of wire bonding defects in integrated circuits(IC)is critical for ensuring product quality after packaging.Image-processing-based methods do not provide a detailed evaluation of the three-dimensional defects of the bonding wire.Therefore,a method of 3D reconstruction and pattern recognition of wire defects based on stereo vision,which can achieve non-destructive detection of bonding wire defects is proposed.The contour features of bonding wires and other electronic components in the depth image is analysed to complete the 3D reconstruction of the bonding wires.Especially to filter the noisy point cloud and obtain an accurate point cloud of the bonding wire surface,a point cloud segmentation method based on spatial surface feature detection(SFD)was proposed.SFD can extract more distinct features from the bonding wire surface during the point cloud segmentation process.Furthermore,in the defect detection process,a directional discretisation descriptor with multiple local normal vectors is designed for defect pattern recognition of bonding wires.The descriptor combines local and global features of wire and can describe the spatial variation trends and structural features of wires.The experimental results show that the method can complete the 3D reconstruction and defect pattern recognition of bonding wires,and the average accuracy of defect recognition is 96.47%,which meets the production requirements of bonding wire defect detection.

基于视觉技术的Wire Bonding中焊点质量的自动检测方法

用WireBonder(引线键合机)进行键合后的芯片,其焊点可能会出现位置偏移、断线和线尾(Pigtail)过长等缺陷。该文针对上述几种质量问题,利用WireBonder现有的硬件,运用图象处理及模式识别技术,提出了一套自动视觉检测的方法。实验表明,该方法所需硬件低廉,操作方便,能很好地检测WireBonding中焊点的质量。

Mechanism of microweld formation and breakage during Cu-Cu wire bonding investigated by molecular dynamics simulation

Currently,wire bonding is the most popular first-level interconnection technology used between the die and package terminals,but even with its long-term and excessive usage,the mechanism of wire bonding has not been completely evaluated.Therefore,fundamental research is still needed.In this study,the mechanism of microweld formation and breakage during Cu-Cu wire bonding was investigated by using molecular dynamics simulation.The contact model for the nanoindentation process between the wire and substrate was developed to simulate the contact process of the Cu wire and Cu substrate.Elastic contact and plastic instability were investigated through the loading and unloading processes.Moreover,the evolution of the indentation morphology and distributions of the atomic stress were also investigated.It was shown that the loading and unloading curves do not coincide,and the unloading curve exhibited hysteresis.For the substrate,in the loading process,the main force changed from attractive to repulsive.The maximum von Mises stress increased and shifted from the center toward the edge of the contact area.During the unloading process,the main force changed from repulsive to attractive.The Mises stress reduced first and then increased.Stress concentration occurs around dislocations in the middle area of the Cu wire.

Factors governing heat affected zone during wire bonding

In the wire bonding process of microelectronic packaging,heat affect zone(HAZ)is an important factor governing the loop profile of bonding.The height of loop is affected by the length of the HAZ.Factors governing the HAZ were studied.To investigate this relationship,experiments were done for various sizes of wire and free air ball(FAB).Electric flame-off(EFO)current, EFO time,EFO gap and recrystallization were also studied.The results show that as the size of FAB becomes larger,the length of HAZ increases.With the increase of EFO current and time,the length of HAZ becomes longer.When FAB forms at the same parameter the length of HAZ becomes shorter with the high temperature of recrystallization.

Temperature effect in thermosonic wire bonding

The temperature effect on bonding strength and ultrasonic transmission in a PZT transducer system was investigated. The results show that, the temperature change influences the material features of the bonding interface, such as elastic modulus, tensile strength of gold ball and Ag substrate, which results in different bonding strengths. Moreover, the temperature change also influences the impedance and dissipative ultrasonic energy in the PZT system. The current signal of PZT transducer was analyzed by join time-frequency analysis, which can reveal the current change in a bonding process more clearly and completely. The analysis shows that the bonding parameters influence mutually. These results can help build some criteria for parameter match and optimization in wire bonding processes.

Bonding mechanism of ultrasonic wedge bonding of copper wire on Au/Ni/Cu substrate

The ultrasonic wedge bonding with d25 μm copper wire was achieved on Au/Ni plated Cu substrate at ambient temperature.Ultrasonic wedge bonding mechanism was investigated by using SEM/EDX,pull test,shear test and microhardness test.The results show that the thinning of the Au layer occurs directly below the center of the bonding tool with the bonding power increasing.The interdiffusion between copper wire and Au metallization during the wedge bonding is assumed negligible,and the wedge bonding is achieved by wear action induced by ultrasonic vibration.The ultrasonic power contributes to enhance the deformation of copper wire due to ultrasonic softening effect which is then followed by the strain hardening of the copper wedge bonding.

New Type Gold Bonding Wire

The influences of additive elements on properties of gold wire and the technology of homogeneously adding those elements to gold matrix were studied. A BJ-type gold bonding wire for automatic bonders was developed, which has high bond strength and stable uniform mechanical properties and is capable of forming good spherical shape of melting-ball observed by SEM. The bonding wire is fully suitable to the requirements of the automatic bonding technology and satisfies the performance requirement of IC products.

Effect of Conduction Pre-heating in Au-Al Thermosonic Wire Bonding

This paper presents the recent study by investigating the vital responses of wire bonding with the application of conduction pre-heating. It is observed through literature reviews that, the effect of pre-heating has not been completely explored to enable the successful application of pre-heating during wire bonding. The aim of wire bonding is to form quality and reliable solid-state bonds to interconnect metals such as gold wires to metalized pads deposited on silicon integrated circuits. Typically, there are 3 main wire bonding techniques applied in the industry;Thermo-compression, Ultrasonic and Thermosonic. This experiment utilizes the most common and widely used platform which is thermosonic bonding. This technique is explored with the application of conduction pre-heating along with heat on the bonding site, ultrasonic energy and force on an Au-Al system. Sixteen groups of bonding conditions which include eight hundred data points of shear strength at various temperature settings were compared to establish the relationship between bonding strength and the application of conduction pre-heating. The results of this study will clearly indicate the effects of applied conduction pre-heating towards bonding strength which may further produce a robust wire bonding system.

New Generation Semi-Automatic Thermosonic Wire Bonder

The physical and technological aspects of wire ball-wedge bonding in the assembly of integrated circuits are considered.The video camera and the pattern recognition system(PRS)of new bonder helps to provide accurate positioning of the bonding tool on the chip pads of integrated circuits.The formation of the loop wire cycle is ensured by the synchronous movement of the bonding head along the Z axis and the working table along the XY axes based on the servo drive.A feature of the bonder is that it can bond all the wire loops of the electronic device according to the pre-recorded program without needing to align the bonding points.

Wire Bonding Using Offline Programming Method

Manual process of creating bonding diagram is known to be time consuming and error prone. In comparison, offline programming (OLP) provides a much more viable option to reduce the wire bonding creation time and error. OLP is available in two versions, i.e., vendor specific OLP and direct integration offline pro- gramming (Di-OLP). Both versions utilize the bonding diagram and computer aided design data to speed up bonding program creation. However, the newly proposed Di-OLP is more flexible as it can be used to create bonding program for multiple machine platforms in microelectronics industry. Some special features of Di-OLP method are presented. The application of generic OLP however, is applicable to machines that recognize ASCII text file. The user needs to know the data format accepted by machine and convert the data accordingly to suit its application for different machine platforms. Di-OLP is also a practical method to replace the time consuming manual method in production line.

接地共面波导与芯片级联结构设计与优化

针对传输线与芯片级联时产生阻抗突变,导致传输效率下降的问题,基于接地共面波导与芯片级联结构,提出了一种适用于X~Ka波段的匹配带线解决方法。通过S参数提取芯片的输入阻抗,并对射频电路中的阻抗不连续点进行分析,设计阻抗匹配电路并建立三维仿真模型。通过有限元仿真分析,讨论了匹配电路和键合引线中心间距对射频传输性能的影响,对比分析了不同结构及不同匹配电路的传输性能差异。仿真结果显示:在X~Ka波段范围内,匹配电路可令接地共面波导与芯片级联结构的S11<-21 dB,S21>-0.19 dB。优化后的接地共面波导与芯片级联结构可在降低传输损耗的同时显著提高射频信号的隔离度,减少信道串扰,为厘米波频段下射频电路的设计提供理论参考。

一种基于开通栅极电压的新型IGBT键合线老化监测方法

绝缘栅双极型晶体管(insulated gate bipolar transistors,IGBT)的可靠运行是牵引变流器安全和性能的重要保障。键合线老化作为IGBT的一种常见失效模式,对其进行监测具有重要意义。文中提出一种基于开通栅极电压ugem的键合线老化监测方法,该方法可有效避免温度和负载电流带来的影响。首先,基于IGBT等效电路模型,系统分析ugem受键合线断裂影响的原因;其次,利用双脉冲测试进行验证,同时对温度和负载电流带来的影响进行分析;在此基础上,考虑到使用ugem局部特征将受到温度和电流的干扰,提出将开通栅极电压整体波形用于键合线老化的监测,并进一步利用有监督的线性判别分析进行数据降维以及采用支持向量机实现键合线断裂根数的检测。最后,通过实验对所提监测方法的有效性进行验证。

金合金中Ce和Lu晶界偏聚的第一性原理研究

元素在晶界的偏聚通常会引起材料性能的变化。基于第一性原理研究了Ce和Lu元素在纯金晶界的偏聚行为,计算得出Ce和Lu的最小晶界偏聚能分别为-0.89和-0.28 eV,这表明Ce在晶界的偏聚倾向较大,而Lu的偏聚倾向较小;同时,在此基础上进一步研究了Ce和Lu在金合金中的原子结构和电子结构,揭示了晶界偏聚的物理成因。

红外探测器芯片高可靠性键合工艺研究

金丝键合工艺广泛应用于红外探测器的封装环节。实验选用25μm金丝,基于正交试验法,根据键合拉力值确定键合的最佳工艺参数。通过优化超声压力、超声功率、超声时间及接触力等工艺参数组合,改善了键合引线的电气连接性能和连接强度,从而提高芯片系统的信号传输质量。提出的引线键合工艺参数组合适用于红外探测芯片的键合。

TO-3封装器件键合丝热机械可靠性与寿命预测

为解决双芯片功率放大器的过电应力烧毁问题,对器件电路进行改进并探究其可靠性。首先,重新设计和制备基片上金属带线,并进行温度循环与拉力检测试验;然后,基于有限元方法在温度循环载荷作用下对键合丝应力应变分布情况进行了分析,并通过Coffin-Manson模型对器件的疲劳寿命进行预测分析。结果表明,高温下应力降低了3.23 MPa,低温下应力下降了97.7 MPa。改进后的器件寿命提高了11.6%,且经历过温度循环后仍满足最小键合拉力极限值要求。该研究结果可为复杂键合丝结构及寿命预测提供参考。

基于电-热-结构耦合分析的SiC MOSFET可靠性研究

作为应用前景广阔的功率器件,SiC金属氧化物半导体场效应晶体管(MOSFET)的可靠性分析至关重要。基于结构几何、材料特性和边界条件的建模方法可以显著缩短失效分析周期。考虑器件电阻随温度变化的特性,构建电-热-结构耦合的有限元模型,针对健康状态及不同失效模式进行温度和应力研究。结果表明,功率循环过程中键合线与芯片连接处受到的热应力最大,焊料层与芯片接触面的边缘位置次之;键合线失效对器件寿命影响最大,且焊料层中心空洞产生的应力大于边缘空洞产生的应力。仿真结果可为提升器件可靠性提供重要参考。

基于硅凝胶灌封温循载荷下的键合丝疲劳失效机理仿真分析

针对某型混合集成电路在温度循环试验后出现的硅凝胶灌封区域键合丝疲劳失效,对键合丝的键合强度和疲劳断裂失效进行了试验分析,建立了单根键合丝和硅凝胶局部灌封区域的有限元简化模型,拟合了硅凝胶材料的本构模型参数,基于ANSYS Workbench软件对不同胶体材料参数条件和温循载荷作用下的键合丝应力分布情况进行了热力耦合仿真分析,并基于仿真结果对混合集成电路的硅凝胶灌封工艺进行了优化和加严温度循环试验。仿真和实验结果表明,键合丝第一键合点颈部和第二键合点根部的应力值较大,存在明显的塑性应变,与疲劳断裂失效分析一致;通过减小硅凝胶的热膨胀系数和灌封体积的方式进行工艺优化后,键合丝的应力值显著减小,样品经过温度循环试验后实测良率从167%提升至100%。研究结果对于提高硅凝胶灌封区域中的金丝键合疲劳强度有一定的指导意义。

针对IGBT固态断路器的在线监测系统设计

针对固态断路器(SSCB)和功率半导体器件在长期工作下的系统级在线监测手段匮乏的问题,设计了绝缘栅双极晶体管(IGBT)固态断路器的在线监测系统,采用微控制器单元、测量回路以及模拟实验回路相互配合,实现了对IGBT老化状态的监测与数据提取。实验结果表明,该系统能够对400 V直流母线电压下的114 A故障电流进行连续重复关断,而测量回路则能够实时监测待测器件(DUT)的导通压降V_(CE,on),可监测到IGBT在循环过程中出现的导通压降升高这一老化特征,所有待测器件的V_(CE,on)均在上百次循环过程中升高了10%以上。通过扫描电子显微镜(SEM)分析可知,其键合线处的缝隙宽度增大了142.44%,实际验证了IGBT的键合线老化机理。

金丝球焊近壁键合技术

在引线键合工艺应用中,由于球焊键合工艺具有键合方向灵活、键合速度快等优势,在半导体芯片的封装互联领域被广泛应用。针对金丝球焊键合工艺中的近壁键合问题进行了研究,从键合方式、劈刀设计两个方面进行优化、改进,制定了两种不同的解决方案,并分析了两种方案的应用局限性。

一种涂胶封装半导体绑定金线断裂失效原因分析及改善方法

在半导体封装工艺中,芯片键合是非常关键的一环,其中绑定是芯片键合的一种普遍方式,它用高纯度金线把芯片接口和基板接口键合,从而实现信号的传输和电气连接[1]。然而使用过程中绑定容易出现一些故障,金线断裂是绑定常见的故障原因之一。本文通过对一种PCBA上涂有防护胶的传感器进行不良解析,采用故障树梳理金线断裂的可能因素,结合CT扫描、金线断面SEM对比分析等方式,找出金线颈部断裂的根本原因并提出改善方法,为金线断裂分析提供了一种有效的解析方式。