超声键合换能系统的非稳态特性试验

测得超声键合振动系统的输入电流、电压,用激光多普勒测速仪测得换能杆系统的响应速度,研究了超声引线键合工艺中超声振动系统的非稳态动力学特性.据此对超声加卸载过程分段,进行频谱分析和非稳态特性建模,并研究了相关的试验方法.结果表明,振动系统拟共振态腹点的速度均方值可作为系统机械能的等效量,供系统动力学特性试验研究;快速键合时系统惯性使功率源的开关不等同于键合机超声振动系统的启停.这些均有助于键合机换能系统的工艺建模和优化.     

热超声键合压电换能器的动力学特性

基于有限元方法和试验测试,研究了芯片封装用压电超声换能器的动力学特忡。借助ANSYS压电耦合和非线性接触分析功能,对换能器自由和约束状态下的振动特性进行了分析。探讨了超声能量在空间域、时域和频域的传递规律。由模态分析得到换能器的振动形式,通过谐响应分析提取其在正弦电压激励下的振动信息,经瞬态分析获得换能器的瞬态响应。结果表明,螺栓径向尺寸和预紧力影响换能器的模态分布和动态特性,压电晶堆加载电压的频率影响超声能量传递特性。通过键合试验考察了焊点质量与螺栓径向尺寸的关系。分析和试验结果为换能器设计和键合工艺优化提供了指导。     

面向微电子超声键合的精密气浮定位平台特性分析

基于有限元方法,详细考察了两自由度气浮支撑定位平台的静动态特性.建立了定位平台的有限元模型,分别对其进行了静态、模态和瞬态分析.通过静态分析,考察了系统在静力载荷作用下的响应特性;经模态分析,获取了定位平台的固有频率以及模态振型;通过施加脉冲力激励,探讨了系统的脉冲响应,通过方波力信号模拟定位平台的实际工作状态,得到了定位平台的瞬态响应特性.结果表明,该定位平台具有良好的静动态特性,为该类气浮支撑定位平台的结构优化设计与控制提供了重要信息.     

不同温度对热超声键合工艺连接强度的影响

在有规律地改变键合温度的条件下,分析不同温度对热超声键合工艺连接强度的影响规律,并研究温度因素对整个系统的PZT换能器输入功率及阻抗的影响。试验研究发现,温度过低（低于601℃）导致键合不成功或连接强度很低,温度过高（高于300℃）导致连接强度降低,最佳的键合窗口出现在200～240℃区间,此时连接强度达20g左右。对推荐使用的大于5．4g的连接强度标准,文中试验条件下可键合窗口为120～360℃。而且,对于恒定额定功率设置的PZT换能器系统,温度的改变导致PZT换能器实际加载的功率及阻抗的改变。这些试验现象和分析结果可作为整个键合系统工艺参数匹配及优化的依据。     

超声振动内圆磨头主轴系统的优化设计

基于限元分析方法,揭示了超声振动内圆磨头的主轴部件的振动规律,对超声振动内圆磨头的主轴部件进行了结构优化设计。给出了使用激光多普勒测振仪测试超声振动内圆磨头主轴系统的方法,并对主轴系统进行了振动特性试验研究,验证了超声振动内圆磨头的主轴系统优化设计的结果,并制造了超声振动内圆磨头样机。     

基于振动试验建模的不平衡状态预测研究

本文采用不同不平衡量的高速精加工铣削刀具开展铣削振动试验,研究在三种切削速度下,刀具的不平衡量与振动量的关系,利用统计学中回归方法建立相应的数学模型,并通过显著性分析和验证试验证明了三种数学模型的有效可行性。试验结果表明,在使用具有相同不平衡量的高速精加工铣削刀具情况下,切削速度越大,刀具振动量也相应变高;在相同切削参数情况下,刀具不平衡量越高,其振动量也相应变高。同时在不同切削条件下,通过数学模型可以有效对刀具动平衡状态进行预测,从而诊断出刀具的高速精密加工切削性能。     

热超声倒装键合工具和芯片振动的频率特征

采用激光多普勒振动测量系统,监测了热超声倒装键合过程工具末端和芯片的振动速度。由工具和芯片的振动速度有效值曲线,发现了“速度分离”现象,即键合启动数毫秒后,芯片的振动速度突然下降而工具的振动速度继续增大;“速度分离”表明金凸点／焊盘界面已初步形成键合强度。研究了工具和芯片振动速度信号的频率特征,发现芯片振动信号的3倍频成分的产生时刻就是“速度分离”发生的时刻,小键合力有利于“速度分离”发生,也就是有利于初始键合强度的形成,提出了以3倍频产生时刻为临界点的变键合力加载思路。     

激光相变强化非稳态温度场的研究

采用有限差分方法计算激光相变强化三维非稳态温度场。用间歇跳跃式移动光源来模拟激光的连续扫描，考虑了涂层在热传递过程中的“媒介”作用以及相变潜热、材料热物性参数随温度改变等因素的影响。对计算结果进行分析，并与实验数据和其它模型相比较。     

引线键合中多向超声波能量传输特性研究

引线键合主要是采用超声波热键合技术，而超声波振动传播和能量传递是超声波键合设备中一个非常关键和复杂的问题。利用波在弹性体中传播的机理，给出超声波聚能杆和劈刀的振动传递特性，利用多普勒振动计PSV-300-F(1．5MHz)测量了振动位移和速度，证实了理论分析结果，并对双向垂直传输超声波能焊具的性能进行了研究，阐明垂直双向加载是一种高效的传能模型。     

扩散焊接头缺陷超声C扫描检测能力分析

扩散焊界面缺陷的检测是目前无损检测领域的难点之一. 为研究超声C扫描对钛合金扩散焊接头小缺陷的检测能力,以钛合金为研究对象,制作了含有不同尺寸和类型缺陷的扩散焊试件,研究了步进长度和检测频率对检测能力的影响,最后通过破坏性测试结果对其进行验证. 结果表明,使用较小的步进长度和较高的检测频率,可提高检测的准确度,但扩散焊界面存在大量接触型和微小型缺陷,因此采用超声法难以对其进行精确定量.     

Effect of ultrasonic power and bonding force on the bonding strength of copper ball bonds

Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.     

热超声键合换能系统振动多模态分析

研究了换能系统的振动多模态性及其对键合质量的影响.利用激光多谱勒测振仪提取变幅杆和工具末端各特征点的速度信号,发现换能系统的运动为多种模态耦合的结果,并得到各非主模态与主模态的速度比值,其中非主模态以垂直弯曲振动为主.这种垂直弯曲振动对芯片造成"拍击"的负面效应,从而影响多凸点与基板的键合面积、键合强度以及芯片与基板的平行度.利用FEM方法分析系统多模态产生的原因,并提出抑制方法.     

Improvement of ultrasonic testing of concrete by combining signal conditioning methods, scanning laser vibrometer and space averaging techniques

This paper deals with the combination of several techniques to improve the ultrasonic pulse echo testing of concrete elements when a laser doppler interferometer is used as the ultrasonic receiver. This techniques involves specially designed ultrasonic probes, a pulse compression technique, random speckle modulation and space time signal processing methods. The pulse echo technique is carried out by sending frequency modulated chirp signals and performing a cross-correlation between the received and the transmitted signals. In combination with the application of recently available ultrasonic concrete probes as transmitter, this leads to an improvement in the signal-to-noise ratio. A laser doppler interferometer, equipped with a random speckle modulator, is used as detector of the ultrasound. Finally, the data sets are processed with various methods, involving time signals of several space points. Examples are the space averaging and the synthetic aperture focusing technique (SAFT). The advantage of the suggested technique is demonstrated by practical measurements on a test specimen. The improvement in results as compared to standard laser interferometric measurements will increase the feasibility of laser interferometric detection for non-destructive testing in civil engineering.     

铂金丝超声键合正交试验及焊点质量评价

采用正交试验法对直径为20μm的铂金丝进行超声波键合试验,并通过三轴测量显微镜观察键合区域形貌和测量键合点根部高度.结果表明,在研究的4个参数中,键合时间、搜索高度和超声功率的影响都较大,而键合力的影响较小.通过正交试验法可以快速获得较优的键合参数,最佳工艺条件为:键合力0.013 N,键合功率0.325W(W为键合区宽度),键合时间30 ms,搜索高度0.2 mm.键合点质量可以通过测量键合点根部高度进行评价,当根部高度在4~10μm之间时,引线拉力均在0.03 N以上.而且,当键合区接近椭圆形,且当W≈2D(D为引线丝直径)时,引线拉力较高,当键合区形貌为矩形或有裂纹出现时,拉力则较小.     

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

The ultrasonic wedge bonding with d 25 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.     

Effect of bonding conditions on the bonding strength in an aluminum bonding using ultrasonic vibrations and high-frequency induction heating in an atmosphere

ABSTRACT

The needs of aluminium joints have grown in recent years. However, as aluminium forms strong oxide layers on the surface in an atmosphere, joining of these materials is difficult. This is why we conceived a new atmosphere solid-phase bonding method that uses high-frequency induction heating and ultrasonic vibration. The effects of ultrasonic vibration and bonding conditions on this new bonding method were investigated. As a result, we were able to confirm the efficacy of ultrasonic waves on bonding. The bonding mechanism of new bonding method was also clear.     

Interface structure of ultrasonic wedge bonding joints of Ni/Al

Nickel plated on a copper plate was selected as a bond surface for ultrasonic aluminum wedge bonds, and a series of experiments were carried out to study the microstructure characterization of the wedge bond interface. Bond lift-off characteristics were studied by using scanning electron microscopy （SEM） with EDS-test. Characteristics of input power of PZT transducer were analyzed by the driving electric signal measured with GDS-820 Digital Oscilloscope. The results show that the pattern of partially bonded material at the Ni-Al interface of ultrasonic wedge bonds exposed by peeling underdeveloped bonds simulates a ridged torus with an unbonded central and external region rubbed along pulse direction. Bond strength is located between the severely ridged torus and the non-adhering central and external area of the bond. For the same machine variables, ridge-peak and transforming ultrasonic energy of the first wedge bond are greater than that of the second wedge bond. For constant other machine variables, with the increasing load, the total area of bond pattern increases in size, and minor axis of torus extends major axis; with the increasing time, the ridged periphery spreads a whole torus, and the ridged location of the bonded region moves closer to the bond center; the sliding trace and the ridge-like of the bond pattern strengthen when more power is applied. Moreover, the machine variables have an optimal range for microstructure characteristics.