基于田口方法的微波组件金丝键合工艺优化

为了提高微波组件金丝键合的可靠性,采用楔形金丝键合工艺进行了金丝互连,通过田口试验方法设计 和试验验证,确定了金丝键合最优化的工艺参数组合。研究结果表明：键合金丝质量的影响因素依次是超声功率、键 合压力和键合时间,优化的工艺参数组合依次为超声功率、键合压力、键合时间,优化的工艺参数组合为超声功率 15、键合压力16、键合时间50;采用优化后的工艺参数进行金丝键合操作,获得了稳定性良好的互连金丝,完全满 足混合集成微波电路金丝键合互连应用的需求。     

键合丝随机振动应力极限仿真分析

利用Pro/E与ANSYS联合仿真,对不同材料、 丝径、 键合形式和跨度的键合丝的振动应力极限进行了分析研究.基于键合工艺及其特点在Pro/E中建立了键合丝参数化三维模型,并利用ANSYS对参数化模型进行了模态及随机振动仿真分析,获得了球键合金丝与楔键合硅铝丝在不同丝径、 跨度等条件下的极限功率谱密度,研究结果可为键合丝的选型提供参考.     

铜丝键合工艺研究

键合铜丝作为微电子工业的新型研发材料,已经成功替代键合金丝应用于IC后道封装中。随着IC封装键合工艺技术及设备的改进,铜丝应用从低端产品如DIP、SOP向中高端QFP、QFN、多层线、小间距焊盘产品领域扩展。因封装制程对键合铜丝的性能要求逐步提高,促进了铜丝生产商对铜丝工艺性能向趋近于金丝工艺性能发展,成为替代金丝封装的新型材料。本文首先讲述了铜丝键合的优点,列举了铜丝在键合工艺中制约制程的瓶颈因素有两个方面：一是铜丝储存条件对环境要求高,使用过程保护措施不当易氧化;二是铜丝材料特性选择、制具选择、设备键合参数设置不当在生产制造中易造成芯片焊盘铝挤出、破裂、弹坑等现象发生,最终导致产品电性能及可靠性问题而失效。本文通过对铜丝键合机理分析,提出解决、预防及管控措施,制定了具体的生产管控工艺方案,对实现铜丝键合工艺有很好的指导意义。     

铜丝键合工艺研究

键合铜丝作为微电子工业的新型研发材料,已经成功替代键合金丝应用于IC后道封装中。随着IC封装键合工艺技术及设备的改进,铜丝应用从低端产品如DIP、SOP向中高端QFP、QFN、多层线、小间距焊盘产品领域扩展。因封装制程对键合铜丝的性能要求逐步提高,促进了铜丝生产商对铜丝工艺性能向趋近于金丝工艺性能发展,成为替代金丝封装的新型材料。文章首先讲述了铜丝键合的优点,指出铜丝在键合工艺中制约制程的瓶颈因素有两个方面：一是铜丝储存条件对环境要求高,使用过程保护措施不当易氧化;二是铜丝材料特性选择、制具选择、设备键合参数设置不当在生产制造中易造成芯片焊盘铝挤出、破裂、弹坑等现象发生,最终导致产品电性能及可靠性问题而失效。文章通过对铜丝键合机理分析,提出解决、预防及管控措施,制定了具体的生产管控工艺方案,对实现铜丝键合工艺有很好的指导意义。     

微组装技术中的金丝键合工艺研究

金丝键合是微组装工艺中的一道关键工艺,金丝键合质量的好坏直接影响微波组件的可靠性以及微波特性.对金丝键合工艺的影响因素进行了分析,并通过设计实验方案对25 μm金丝进行键合实验.对键合金丝进行拉力测试,测量结果全部符合军标GJB 548B-2005要求.根据测量结果寻求最佳键合参数,对实际生产具有一定的指导意义.     

厚膜导带上的粗丝键合

文章给出了混合集成电路厚膜导带膜厚、键合丝直径、以及加热老化的一系列数据，讨论了选用金合金浆料或银合金浆料所形成的金属化导带在可靠性提高方面的不同情况，论述了热老化对键合强度的影响以及键合丝的电气集成性能，并对大电流流经一组键合丝所形成的加热效应进行了测量。探讨了键合点接触电阻和键合强度衰减问题的动力学成因及产生机理。     

基于变焦显微测量技术的键合金丝参数测量

欧美国家在半导体行业一直以来对我国实行技术封锁政策,我国许多关键技术和设备只能依靠进口,其中就包括键合金丝参数测量设备。键合金丝参数测量设备主要用于自动检测键合金丝的拱高和跨度等参数。由于键合金丝的回波损耗、驻波等微波传输特性与键合金丝的拱高、跨度等参数呈对应关系,因此可以通过测量相关参数的方法来检测键合金丝的微波传输特性是否合格。通过这一方法可以解决人工测量导致的速率低下的问题,提高键合质量检测效率,降低检测成本。本文基于变焦显微测量技术实现了键合金丝参数的测量。该方法通过自主设计的图像采集平台,获取到键合金丝的一组图像,然后进行聚焦区域提取,从而实现键合金丝的三维重建及参数测量。该方法对键合金丝拱高的测量精度<0.01 mm,相对误差<1.5%,对键合金丝跨度的测量精度<0.005 mm,相对误差<0.7%,可以满足自动检测键合金丝参数的设计需求。     

专利视角下的键合金银丝合金体系及组分构成分析和展望

键合金银丝是一种以金银合金为基体的导电合金丝,因兼具性能和成本优势近年来广受关注。为促进我国相关产业的技术进步,采用专利导航分析并结合文献综述、标准对比等手段综合分析了键合金银丝的技术发展概况,并就键合金银丝的专利申请、技术分布、区域布局等展开了论述,为键合金银丝研制提供技术溯源、启示参考和知产风险预警。结果表明,键合金银丝的专利申请已成为键合引线行业的主要热点,其中金基键合丝的合金成分范围(质量分数)涵盖Au:45%～75%、Ag:25%～50%、Pd:3%～5%的区域,银基键合丝的合金成分范围(质量分数)涵盖Au:0～20%、Pd:0～20%的区域,特别是Au、Pd含量(质量分数)在1%～5%的区间,并均有进一步合金化的研发趋势。结合专利布局现状,建议行业未来应重点强化技术研发、瞄准技术空白和扩大国际市场。     

面向射频微系统应用的圆片-芯片集成工艺技术研究

利用Au-Sn共晶合金反应实现硅基圆片-芯片(Die to Wafer)键合是一种可行的集成方案,通过优化关键实验条件改善圆片-芯片键合层质量及键合强度,探索出适合射频微系统应用的D2W集成工艺条件;使用扫描电子显微镜(SEM)观察各组圆片-芯片界面质量状态,分析其键合层元素组成;在常温及300℃高温下完成水平推力测试,分析了键合样片键合强度和耐高温水平。结果表明:键合压力、Sn浸润时间、Au-Sn共晶合金温度及时间、芯片键合前处理等条件对键合层质量影响较大;对芯片进行前处理,使用少量助焊剂,240℃浸润2 min,并在温度为290℃、压力为4 N的条件下键合6 min,可以得到具备良好键合层质量的键合样片,水平推力达到55 N。     

一种用于毫米波的共面波导间的宽带互联结构

在多芯片组件中,微波传输线间一般使用金丝键合的方式进行连接。受金丝自身的等效电感和其与基板及壳体间存在的寄生电容的影响,键合金丝结构在毫米波频段下带来了较大的阻抗失配。为了解决该问题,文中从等效集总元件角度出发,对阻抗变换公式进行了推导,分析得出串联低阻抗传输线可以等效为并联集总电容的结论,可以与键合金丝的等效模型一起,构成等效低通滤波器,完成阻抗匹配。文中使用共面波导结构制作了键合金丝匹配结构测试件,测试结果显示,在30～40 GHz内S_(11)<-20 dB、S_(21)>-0.2 dB,具有优良的传输性能。该结构具有较强的实用性,可以用于毫米波频段下的微波组件设计。     

电子封装用银合金线性能的研究

研究了不同钯(Pd)含量银合金线的电阻率、铝挤出、可靠性及横截面的情况,并分析了Pd抑制银离子迁移的原理。结果表明,银合金线中加入Pd后,Pd的含量越高,线材的FAB硬度越大,铝挤出越多,Pd有助于提高合金线的可靠性,同时Pd的质量分数到3%以上时其可靠性更好。Pd能够抑制银离子迁移的原因是表面形成了一个PdO层,PdO富集在表面阻碍银离子扩散及迁移。银合金线的Ag-Al焊球界面主要形成Ag2Al及Ag3Al,Ag2Al比Ag3Al具有更高的抗腐蚀能力。     

铜丝键合在实际应用中的失效分析

研究并总结了铜丝键合塑封器件在实际应用环境中工作时发生的几种不同失效模式和失效机理,包括常见封装类型电路的失效,这些封装类型占据绝大部分铜丝键合的市场比例。和传统的实验室可靠性测试相比,实际应用中的铜丝失效能够全面暴露潜在可靠性问题和薄弱点,因为实际应用环境存在更多不可控因素。实际应用时的失效或退化机理主要包括:外键合点氯腐蚀、金属间化合物氯腐蚀、电偶腐蚀、键合弹坑、封装缺陷五种类型。对实际应用中的数据和分析为进一步改善铜丝键合可靠性、提高器件稳定性提供了依据。     

Silver metallization for advanced interconnects

Silver metal has the highest room-temperature electrical conductivity of any substance; however, it has found limited acceptance in the electronic industry (e.g., silver filled epoxy) due to the high rate of metal corrosion and migration causing dendrites and electrical failures. With decreasing transistor feature sizes, device-operating voltages have scaled down considerably. In this paper, the reliability of silver and potential benefits of silver metallization are discussed in terms of future trends in microelectronic interconnections. Experimental data supports existing reliability models indicating that electrochemical migration failure modes may not be operative at low voltages. Silver metal corrosion and migration are studied under accelerated test conditions to obtain a qualitative understanding of the failure mechanism     

F&K 6400键合机在SMD封装中的应用

键合是SMD封装中的一道重要工序,F&K 6400键合机是德国F&K公司专门面向细铝丝键合的设备,采用超声作为键合能量。在键合工艺中不同材质的金属管座会形成不同的冶金系统,有些情况下会造成接触面腐蚀或者柯肯德尔空洞,并最终影响产品的可靠性。键合时采用的超声功率、键合时间、键合压力、键合方式等工艺参数直接影响到产品的产量和性能。在批量生产的基础上,作者分析了适合F&K 6400键合机在生产中采用的键合材料及工艺参数,并列出了生产过程中设备常见的故障及可能原因。     

PCB表面涂覆用的浸镀银现状

概述了浸镀银作为PCB的最终表面精饰的现状和浸银的诸特性（焊接性、线粘结性、迁移性、电池腐蚀、蠕变腐蚀）。     

Effect of the direct current on microstructure,tensile property and bonding strength of pure silver wires

In the microelectronics assembly and packaging industry, the wire bonding has become an important process to connect lead frames and pads. In the past, gold and copper were the main materials of wire bonding. However, the cost of gold wires is getting higher nowadays and yet wire bonding cannot be wholly replaced by copper wire; thus silver wires become a novel bonding material in recent years. The reliability test of wires was a static method; this study leads electrical current into the wires to estimate the structural changing and interface properties of Al pads (positive and negative pad). After leading 90% critical fusing current density (CFCD) into a 23 μm silver wire, some grains of silver wire had grown up and formed into equal-diameter grains (EDG). After the current test, the fracture position of bonded wires moved from heat affect zone (HAZ) of electric flame-off (EFO) to the neck of HAZ. Otherwise, the current test would reduce the tensile strength of wire. The bonding strength of the positive pad was lower than that of the negative pad. The intermetallic compound (IMC) of bonding interface was AgAl₂.     

Silver Nanoparticle Paste for Low-Temperature Bonding of Copper

Silver nanoparticle (NP) paste was fabricated and used to bond copper wire to copper foil at low temperatures down to 160°C. The silver NP paste was developed by increasing the concentration of 50 nm silver NP sol from 0.001 vol.% to 0.1 vol.% by centrifugation. The 0.001 vol.% silver NP sol was fabricated in water by reducing silver nitrate (AgNO₃) using sodium citrate dihydrate (Na₃C₆H₅O₇·2H₂O). The bond was formed by solid-state sintering among the individual silver NPs and solid-state bonding of these silver NPs onto both copper wire and foil. Metallurgical bonds between silver NPs and copper were confirmed by transmission electron microscopy (TEM). The silver NPs were coated with an organic shell to prevent sintering at room temperature (RT). It was found that the organic shell decomposed at 160°C, the lowest temperature at which a bond could be formed. Shear tests showed that the joint strength increased as the bonding temperature increased, due to enhanced sintering of silver NPs at higher temperatures. Unlike low-temperature soldering techniques, bonds formed by our method have been proved to withstand temperatures above the bonding temperature.     

Thermosonic bonding of gold wire onto silver bonding layer on the bond pads of chips with copper interconnects

A copper pad oxidizes easily at elevated temperatures during thermosonic wire bonding for chips with copper interconnects. The bondability and bonding strength of a gold wire onto a bare copper pad are seriously degraded by the formation of a copper oxide film. A new bonding approach is proposed to overcome this intrinsic drawback of the copper pad. A silver layer is deposited as a bonding layer on the surface of copper pads. Both the ball-shear force and the wire-pull force of a gold wire bonded onto copper pads with silver bonding layers far exceed the minimum values stated in the JEDEC standard and MIL specifications. The silver bonding layer improves bonding between the gold ball and copper pads. The reliability of gold ball bonds on a bond pad is verified in a high-temperature storage (HTS) test. The bonding strength increases with the storage time and far exceeds that required by the relevant industrial codes. The superior bondability and high strength after the HTS test were interpreted with reference to the results of electron probe x-ray microanalyzer (EPMA) analysis. This use of a silver bonding layer may make the fabrication of copper chips simpler than by other protective schemes.     

A study of large area die bonding materials and their corresponding mechanical and thermal properties

We tested the ability of Au/Sn eutectic, silver paste, and solder paste to bond to a large area as well as the bonding of a high power LED die to a highly conductive submount. The samples ran through several tests including ultrasound image, shear force, and thermal resistance measurement. Finite element analysis (FEA) models were built for comparison and analysis. Au/Sn bonding shows the best thermal and mechanical properties. Silver paste shows lower contact thermal resistance compared with solder paste. Although the thickness of the silver paste bonding layer is greater than the solder paste bonding layer, the average total thermal resistance is noticeably lower than the solder paste bonded samples.     

The reliability of wire bonding using Ag and Al

The combination of aluminum (Al) and silver (Ag) for wire bonding is long established: aluminum (Al) heavy wire bonding on silver (Ag) metallization, such as pastes consisting of Ag as main component or comprising Ag alloys, was first established in the 1970s and was widely discussed (particularly in terms of reliability under high temperature and relative humidity) until the 1990s. Recently, discussion of the Ag/Al material system has reemerged in the literature, albeit within the context of a new bonding approach – thermosonic (TS) ball/wedge (B/W) bonding with Ag or Ag alloy wires, instead of gold (Au) or copper (Cu) wires, on Al-metallized chips. Several forms of Ag wire are currently being evaluated, including pure Ag, Ag alloys and a preliminary version of a palladium (Pd) -coated Ag. The present paper bridges the gap in the literature between the two bonding approaches by reviewing reliability studies for both Ag-on-Al and Al-on-Ag bonding.