新型铜线键合技术

铜线以其良好的电器机械性能和低成本特点已在半导体分立器件的内引线键合工艺中得到广泛应用;但铜线的金属活性和延展性也在键合过程中容易带来新的失效问题.文中对这种失效机理进行了分析.     

功率模块铜线键合技术及其可靠性研究

由于铝线键合逐渐不能满足如今功率模块功率密度、工作温度不断提升的可靠性要求,因此采用铜线代替铝线,以实现更高的可靠性工作寿命。对比分析了铜线、铝线键合工艺的特点、结合强度和可靠性,证明了铜线键合工艺的可行性和高可靠性。同时分析了铜线键合工艺目前存在的问题和应对措施。     

铜线键合设备焊接一致性探索

相对于传统金线键合,铜线键合设备焊接过程工艺窗口更小,对焊接的一致性要求更高.通过对铜线键合工艺窗口的影响因素进行分析,探索了设备焊接过程的影响和提升办法,为铜线键合技术的推广应用提供技术指导.     

铜线键合优势和工艺的优化

半导体封装对于芯片来说是必须的,也是至关重要的.封装可以指安装半导体集成电路芯片用的外壳,它不仅起着保护芯片和增强导热性能的作用,而且还起到沟通芯片内部世界与外部电路桥梁和规格通用功能的作用.文章阐述了铜线键合替代金线的优势,包括更低的成本、更低的电阻率、更慢的金属问渗透.再通过铜线的挑战--易氧化、铜线硬度大等,提出...     

铜线键合塑封器件破坏性物理分析技术

铜线替代传统的金线键合已经成为半导体封装工艺发展的必然趋势,因其材料和制造工艺的特点,其破坏性物理分析方法不同于金线或铝线键合的器件。提出铜丝键合塑封器件破坏性物理分析的步骤及判据参照标准,讨论了器件激光开封技术的工艺步骤和参数值以及键合强度测试判据和典型断裂模式,以解决铜线键合塑封器件的破坏性物理分析问题。     

DBC铜线键合工艺参数研究

铜线作为最有发展潜力的新一代键合材料,与铝线相比,具有优异的导电及导热能力。因绝缘栅双极型晶体管（IGBT）需承载大电流,采用铜线可在键合线数量不变的基础上提高电流传输能力和散热能力。采用铜线超声楔形键合对覆铜陶瓷基板（DBC）第一键合点和第二键合点的键合工艺参数进行研究,以剪切力作为衡量键合质量的标准,采用单因素分析法研究各参数对键合点强度的影响,采用正交试验确定最佳工艺参数,为铜线键合工艺的参数设定提供参考及指导方法。     

国内外铜线键合拉力试验方法标准对比分析

为满足铜线键合拉力试验需求,从拉力施加位置、失效模式分类、最小拉力值以及试验结果的应用等4个方面对国内外铜线键合拉力试验方法标准的技术内容进行对比分析,并提出国内试验方法的修订建议。     

高温存储下铜线键合焊点分析

采用铜引线键合工艺生产的电子元器件在服役中会产生热,引起引线与金属化焊盘界面出现IMC(intermetallic compound,金属间化合物)。IMC的生长和分布将影响键合点的可靠性,严重时会出现"脱键",导致元器件失效。研究了焊点在服役过程中的演化,选取铜线键合产品SOT-23为试验样品,分析了在高温存储试验环境下焊点键合界面IMC的生长及微观结构变化情况。     

铜线键合二焊点参数正交试验探析

本文研究了影响二焊点键合力大小的关键因素：超声功率(A)、压力(B)、研磨次数(C)、振幅(D)、频率(E)对二焊点拉力的影响程度,采用正交试验法分析研究,得出各因素影响力大小为D>B>A>E>C,较优化的工艺方案为“A₁B₁C₁D₂E₂”。得出线性回归模型为Y=12.026-0.012A-0.017B-0.005C-0.174D-0.001E。通过实际验证,理论分析与实际相吻合。以上理论依据为20μm铜线键合的二焊点参数应用提供了指导方法。     

半导体封装行业中铜线键合工艺的应用

文章介绍了半导体封装行业中铜线键合工艺下,各材料及工艺参数(如框架、劈刀、设备参数、芯片铝层与铜材的匹配选择)对键合质量的影响,并总结提出如何更好地使用铜线这一新材料的规范要求。应用表明芯片铝层厚度应选择在0.025mm以上;劈刀应使用表面较粗糙的;铜线在键合工艺中使用体积比为95:5的氢、氮气混合保护气体;引线框架镀银层厚度应控制在0.03mm～0.06mm。     

IC键合铜线材料的显微力学性能研究

用于IC(集成电路)的键合铜线材料具有低成本、优良的导电和导热性等优点,但其高硬度容易对铝垫和芯片造成损伤,因此对其硬度的测量是一项关键技术。纳米压痕测量技术可以方便、准确地测量铜线材料的显微硬度值和其他力学性能参数。描述了纳米压痕测量技术的原理以及对铜线材料样品进行纳米压痕测量的参数选择,进行了测量试验。结果表明,原始铜线、FAB(金属熔球)、焊点的平均硬度分别为1.46,1.51和1.65GPa,为键合铜线材料的选择和键合工艺参数的优化提供了依据。     

Deformation and bonding processes in aluminum ultrasonic wire wedge bonding

The ultrasonic wire bonding (UWB) process has been examined using transmission electron microscopy (TEM) and standard wire pull testing techniques. Al-0.5 wt.% Mg wires 75 μm in diameter were bonded to pure and alloyed Al substrates. The bonding parameters, surface roughness, and surface contamination levels were variables in the experiments. Cross-section TEM specimens were made from these samples. TEM analysis was conducted on the wire, wire/substrate interface and substrate. Pull tests showed that for the Al substrates the surface roughness or the presence of contamination did not effect the bond strength, whereas for contaminated stainless steel substrates, a three μm surface finish resulted in the highest bond pull strength. The TEM observations revealed features such as low-angle grain boundaries, dislocation loops and the absence of a high dislocation density, indicating that the wire and substrate were dynamically annealed during bonding. Based on the width of a zone near a grain boundary in the wire which was depleted of dislocation loops, it was estimated that local heating equivalent to a temperature of 250° C for 90 msec was achieved in the wire during bonding. No evidence was found for melting along the bond interface, indicating that UWB is a solid-state process. Based on the TEM observationsof the bond interface and the pull tests, it is concluded that the ultrasonic vibrations clean the surfaces to be joined to the extent that a good bond can be obtained by intimate metal-metal contact in the clean areas.     

Development of a thermosonic wire-bonding process for gold wire bonding to copper pads using argon shielding

To improve the bondability and ensure the reliability of Au/Cu ball bonds of the thermosonic (TS) wire-bonding process, an argon-shielding atmosphere was applied to prevent the copper pad from oxidizing. With argon shielding in the TS wire-bonding process, 100% gold wire attached on a copper pad can be achieved at the bonding temperature of 180°C and above. The ball-shear and wire-pull forces far exceed the minimum requirements specified in the related industrial codes. In a suitable range of bonding parameters, increasing bonding parameters resulted in greater bonding strength. However, if bonding parameters exceed the suitable range, the bonding strength is deteriorated. The reliability of the high-temperature storage (HTS) test for Au/Cu ball bonds was verified in this study. The bonding strength of Au/Cu ball bonds increases slightly with prolonged storage duration because of diffusion between the gold ball and copper pad during the HTS test. As a whole, argon shielding is a successful way to ensure the Au/Cu ball bond in the TS wire-bonding process applied for packaging of chips with copper interconnects.     

Thermosonic bonding of gold wire onto a copper pad with titanium thin-film deposition

A novel thermosonic (TS) bonding process for gold wire bonded onto chips with copper interconnects was successfully developed by depositing a thin, titanium passivation layer on a copper pad. The copper pad oxidizes easily at elevated temperature during TS wire bonding. The bondability and bonding strength of the Au ball onto copper pads are significantly deteriorated if a copper-oxide film exists. To overcome this intrinsic drawback of the copper pad, a titanium thin film was deposited onto the copper pad to improve the bondability and bonding strength. The thickness of the titanium passivation layer is crucial to bondability and bonding strength. An appropriate, titanium film thickness of 3.7 nm is proposed in this work. One hundred percent bondability and high bonding strength was achieved. A thicker titanium film results in poor bond-ability and lower bonding strength, because the thicker titanium film cannot be removed by an appropriate range of ultrasonic power during TS bonding. The protective mechanism of the titanium passivation layer was interpreted by the results of field-emission Auger electron spectroscopy (FEAES) and electron spectroscopy for chemical analysis (ESCA). Titanium dioxide (TiO₂), formed during the die-saw and die-mount processes, plays an important role in preventing the copper pad from oxidizing. Reliability of the high-temperature storage (HTS) test for a gold ball bonded on the copper pad with a 3.7-nm titanium passivation layer was verified. The bonding strength did not degrade after prolonged storage at elevated temperature. This novel process could be applied to chips with copper interconnect packaging in the TS wire-bonding process.     

Two capillary solutions for ultra-fine-pitch wire bonding and insulated wire bonding

In this article, the new challenges and requirements in wire bonding are discussed, the problems in ultra-fine-pitch wire bonding and insulated wire bonding are analyzed, and then two capillary solutions to the problems are presented. Actual bonding experiments using the new capillaries were carried out and the results were satisfactory. Compared to the standard design, a new capillary design has a larger inner chamfer, a larger chamfer diameter and a smaller chamfer angle. This new capillary design has proved to improve the ball bondability and smaller ball size control for ultra-fine pitch wire bonding. A unique surface characteristic on the capillary tip surface has also been derived. The new finishing process developed creates a new surface morphology, which has relatively deep lines with no fixed directions. Compared to the standard capillary, this capillary has less slipping between the wire and the capillary tip surface in contact, and provides better coupling effect between them and better ultrasonic energy transfer. This capillary has been used to effectively improve the bondability of the stitch bonds for insulated wire bonding.     

基于正交试验的芯片堆叠封装引线键合工艺研究

选取0.2032 mm (8 mil)金线采用热压超声键合工艺进行烧球、拉力和线尾等一系列正交试验,分析各个键合参数对键合质量的影响。研究结果表明,最优的引线键合工艺窗口为键合温度180℃或190℃、键合功率35 mW、键合时间15 ms或20 ms、键合压力0.12 N、烧球电流3200 mA、烧球时间350μs和尾丝长度20μm。在影响键合质量的各因素中,键合功率和键合压力对键合质量的影响显著,过大的键合功率会引起键合区被破坏,键合强度降低,过小的键合功率因能量不足会引起欠键合,键合强度降低。过大的键合压力会引起键合球变形而导致键合强度降低,过小的键合压力因欠键合而导致键合强度降低。     

Microstructural study of copper free air balls in thermosonic wire bonding

Copper wires are increasingly used in place of gold wires for making bonded interconnections in microelectronics. In this paper, a microstructural study is reported of cross-sectioned free air balls (FABs) made with 23 μm diameter copper bonding wire. It was found that the FAB is comprised of a few columnar grains and a large number of fine subgrains formed within the columnar grains around the periphery of the FAB. It was determined that conduction through the wire was the dominant heat loss mechanism during cooling, and the solidification process started from the wire-ball interface and proceeded across the diameter then outward towards the ball periphery.The microstructure of the Cu ball bond after thermosonic bonding was investigated. The result showed that the subgrain orientations were changed in the bonding process. It is evident that metal flow along the bonding interface was from the central area to the bond periphery during thermosonic bonding.     

铝线邦定的可靠性及其应用

通过对铝线邦定在芯片上的可靠性进行研究和试验．结果表明影响其可靠性的因素非常多，如邦定功率、压力以及时间等。本文引用了国际上数篇有关邦定论文的结论，从实际应用出发，阐述了它们的失效状态、干扰因素及控制方法。最后介绍了邦定线在实际应用中的判定方法和技术革新．从而使工程师们在实际应用中能够进一步了解其特性。     

铜引线键合工艺研究

传统的半导体封装以铝线和金线为基础。功率器件使用铝线作为连接裸片焊盘与引线框架的互联通道,非功率器件使用金线为互联通道。由于金的价格昂贵,人们一直在寻找替代材料。铜作为物理和化学性质与金接近而价格低廉的金属材料,自然引起人们的关注。文章对铜引线键合工艺的关键问题进行了系统研究。这些研究内容包括自动焊线机的机器参数调整、焊球显微硬度测试、击穿电压测试、焊球高温老化形变、焊球接触电阻测试等内容。这些是铜焊线替代金焊线后影响产品可靠性及产品特性参数的关键问题。通过对机器参数的调整试验得出了适合于大规模生产的工艺参数。     

基于LTCC技术的Ku波段金丝线匹配的研究

基于低温共烧陶瓷(LTCC)技术,设计了Ku波段金丝键合线宽带匹配电路,该电路应用多节1/4波长传输线对两根金丝键合线在Ku波段进行了具有二项式响应的宽带匹配.三维电磁场仿真表明,匹配后在Ku波段的回波损耗达到-20 dB.以下,有效提高了信号的通过率.该匹配电路在LTCC基板上所占面积小、实现较为简单.