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。     

The effect of Pd and Cu in the intermetallic growth of alloy Au wire

This is the new wire evaluation work for the reliability of the wire-bonding process. There is a trend for the plastic integrated-circuit package to function at higher junction temperature with thinner wire. New alloy Au wires have been developed to meet the reliability requirements. Two types of alloy Au wires, Au-Pd and Au-Cu, were evaluated in this study. These samples were aged between 155°C and 205°C under air from 0 h to 3,000 h. According to this study, the phase-formation sequence of Au₂Al, Au₅Al₂, and Au₄Al intermetallic is similar to the pure Au wire. There is a Pd-rich layer working as a diffusion barrier to slow down the growth rate of intermetallic phases in the Au-Pd wire. The Au-Cu wire also slowed down the growth rate with a different mechanism. Both wires have better reliability based on the microstructure examination. The reliability test results show longer working life at higher temperatures in comparison with the regular Au wire.     

浅谈镀钯铜线的特性

随着金线价格一路上涨并创下历史新高,大型封装厂正在加大对铜线制程的投入。通过封装厂多年的摸索,发现镀钯铜线是金线很好的替代品。文章分析了镀钯铜线作为键合线材料本身的基本性质,镀钯铜线引线键合的特征和镀钯铜线PCT实验的可靠性。通过分析发现镀钯铜线材料本身有优良的导电和导热特性,同时还有很好的抗氧化性。镀钯铜线在键合过程中需要保护气体的保护,通过硬度实验发现镀钯铜线的硬度较大,因此需要在键合过程中防止弹坑的出现。通过PCT实验证实镀钯铜线具有较好的可靠性。     

高温老化期间引线键合空洞形成探讨

在金-铝金属间化合物相中形成的空洞,降低了把金丝与焊盘键合的长期可靠性。文中通过一系列微结构研究来评定引线键合中空洞的形成。把形成的空洞分为初始、环形和极小三种类型。形成初始空洞的主要原因是探测标记和铝焊盘污染,初始空洞阻碍合金扩散并使金属间化合物生长减缓。环形空洞是由热超声引线键合的超声挤榨作用造成的,这些压焊缝隙可能导致会腐蚀并降低引线键合的一类卤化物的形成。极小的空洞是在Au4Al相阶段形成的。由于不同Au4Al相形成的反应,或与金球表层上晶粒界面影响的关系,在这些空洞中会出现两种Au4Al相的纹理。     

一种基于退化数据的元器件可靠性定量检验方法研究

针对高可靠元器件可靠性鉴定中缺乏可靠性级别定量评价的问题,基于失效物理,分析了键合强度参数退化及失效判据,并给出了退化模型的数学表达和参数估计方法,研究基于退化量分布的可靠性定量检验方法,并采用AD厂家的AD524SD作为试验器件,进行了相应的试验分析和验证。结果表明,提出的高可靠性级别器件鉴定检验方法具有很好的工程适用性和应用价值。     

高温老化期间引线键合空洞形成探讨

在金-铝金属间化合物相中形成的空洞,降低了把金丝与焊盘键合的长期可靠性。在该文中,通过一系列微结构研究来评定引线键合中空洞的形成。把形成的空洞分为初始、环形和极小三种类型。形成初始空洞的主要原因是探测标记和铝焊蕊污染,初始空洞阻碍合会扩散并使金属间化合物生长减缓。环形空洞是由热超声引线键合的超声挤摔作用造成的,这些压焊缝隙可能成为腐蚀并降低引线键合的一类卤化物形成的途径。极小的空洞是住Au4l相阶段形成的。由于不同Au4l相形成的反应,或与金球表层上品粒界面影响的关系,在这些空洞中会出现两种Au4l相的纹理。     

Ag and Cu migration phenomena on wire-bonding

After storing a plastic packaged sample at 250°C for 588 h, the Au plus 1% Pd wire composition was found to be changed. The Ag and Cu atoms can migrate from the wedge bond through the wire surface and arrive at the ball bond. At the same time, Ag and Cu atoms diffuse into the gold wire itself and form a layer type structure. The atom migration phenomena are due to three driving forces: diffusion, alloy formation, and Galvanic effect. The obtained diffusion rate constant is in the order of 10⁻¹² cm square per sec, which corresponds to an activation energy of 0.7∼0.76 eV. The phases sequence formed by diffusion is inconsistent with the equilibrium Ag-Au-Cu phase diagram which indicates that the present diffusion layer has reached thermodynamic equilibrium.     

Study of factors affecting the hardness of ball bonds in copper wire bonding

Copper wire bonding has gained popularity due to its economic advantage and superior electrical performance. However, copper is harder than gold, and replacing gold wire with copper wire introduces hardness related issues. This article reports investigations of the properties including microhardness of the copper balls bonded using ?25.4-μm copper wire and different combinations of electronic-flame-off (EFO) current and firing time settings with forming gas (5%H₂ and 95%N₂) as the inert cover gas. FABs with an identical diameter, obtained under different EFO firing conditions, were ball bonded with the same wire bonding parameters established using design of experiments. Microhardness tests were then performed on the cross-section of the bonded balls. The study revealed that ultrasonic generator current is the most significant factor to increase the bonded mashed ball diameter, ball shear and shear per unit area and to decrease the ball height. The microhardness of bonded copper balls is related to the EFO parameters, with FABs obtained by higher EFO current being softer. The lower hardness is attributed to the higher maximum temperature during the FAB melting state.     

铜丝球键合工艺及可靠性机理

文章针对铜丝键合工艺在高密度及大电流集成电路封装应用中出现的一系列可靠性问题,对该领域目前相关的理论和研究成果进行了综述,介绍了铜丝球键合工艺、键合点组织结构及力学性能、IMC生长情况、可靠性机理及失效模式。针对铜丝球键合工艺中易氧化、硬度高等难点,对特定工艺进行了阐述,同时也从金属间化合物形成机理的角度重点阐述了铜丝球键合点可靠性优于金丝球键合点的原因。并对铜丝球键合及铜丝楔键合工艺前景进行了展望。     

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。     

金属外壳引线键合可靠性研究

引线键合以工艺简单、成本低廉、适合多种封装形式的优势,在连接方式中占主导地位。其中把内部电路与金属外壳内引线柱之间的连接称为引线键合,目前90%以上的封装管脚采用引线键合连接。引线键合强度和可靠性不仅与键合工艺有关（比如键合工艺参数、键合设备、操作技能等因素）,而且与外壳引线的镀覆结构、镀层厚度、内引线柱高度等因素密切相关。文章简要介绍了引线键合工艺的基本原理,通过试验分析并比较了金属外壳镀覆结构、镀层厚度、内引线柱高度对键合可靠性的影响,提出了优化键合可靠性的外壳设计原则。     

Photovoltaic failure and degradation modes

The extensive photovoltaic field reliability literature was analyzed and reviewed. Future work is prioritized based upon information assembled from recent installations, and inconsistencies in degradation mode identification are discussed to help guide future publication on this subject. Reported failure rates of photovoltaic modules fall mostly in the range of other consumer products; however, the long expected useful life of modules may not allow for direct comparison. In general, degradation percentages are reported to decrease appreciably in newer installations that are deployed after the year 2000. However, these trends may be convoluted with varying manufacturing and installation quality world‐wide. Modules in hot and humid climates show considerably higher degradation modes than those in desert and moderate climates, which warrants further investigation. Delamination and diode/j‐box issues are also more frequent in hot and humid climates than in other climates. The highest concerns of systems installed in the last 10 years appear to be hot spots followed by internal circuitry discoloration. Encapsulant discoloration was the most common degradation mode, particularly in older systems. In newer systems, encapsulant discoloration appears in hotter climates, but to a lesser degree. Thin‐film degradation modes are dominated by glass breakage and absorber corrosion, although the breadth of information for thin‐film modules is much smaller than for x‐Si. Copyright © 2017 John Wiley & Sons, Ltd.     

微电子器件封装铜线键合可行性分析

虽然在集成电路封装工艺中金导线键合是主流制程,但是目前采用铜导线替代金导线键合已经在半导体封装领域形成重要研究趋势。文章对微电子封装中铜导线键合可行性进行了分析,主要包括铜导线与金导线的性能比较(包括电学性能、物理参数、机械参数等),铜导线制备和微组织结构分析,铜导线焊合中的工艺研发及铜导线焊合可靠性分析等。当今半导体生产商关注铜导线不仅是因为其价格成本优势,更由于铜导线具有良好的电学和机械特性,同时文中也介绍了铜导线键合工艺存在的诸多问题和挑战,对将来铜导线在集成电路封装中的大规模应用和发展具有一定的参考意义。     

LDO失效分析及改善

低压差线性稳压器(Low Dropout Regulator,LDO)新品导入中,过强的铜线焊接会使焊球下芯片层间电介质层(Interlayer Dielectric,ILD)产生裂纹,从而导致器件测试漏电流失效或可靠性失效。通过对芯片结构的分析,指出LDO漏电流失效的原因,同时详细讨论了如何确定合理的铜线焊接参数、如何检测失效以及失效分析步骤。     

Cu丝超声球焊及楔焊焊点可靠性及失效机理研究

Cu丝由于具有优良的导热性能、机械性能以及低成本等优点使得用铜丝替代传统的Au丝和Al丝已经成为半导体工艺发展的必然方向.综述了Cu丝超声球焊以及楔焊焊点可靠性问题,对焊点的各种失效模式与机理进行探讨.     

Photovoltaic module reliability model based on field degradation studies

Crystalline silicon photovoltaic (PV) modules are often stated as being the most reliable element in PV systems. This presumable high reliability is reflected by their long power warranty periods. In agreement with these long warranty times, PV modules have a very low total number of returns, the exceptions usually being the result of catastrophic failures. Up to now, failures resulting from degradation are not typically taken into consideration because of the difficulties in measuring the power of an individual module in a system. However, lasting recent years PV systems are changing from small isolated systems to large grid‐connected power stations. In this new scenario, customers will become more sensitive to power losses and the need for a reliability model based on degradation may become of utmost importance. In this paper, a PV module reliability model based on degradation studies is presented. The main analytical functions of reliability engineering are evaluated using this model and applied to a practical case, based on state‐of‐the‐art parameters of crystalline silicon PV technology. Relevant and defensible power warranties and other reliability data are obtained with this model based on measured degradation rates and time‐dependent power variability. In the derivation of the model some assumptions are made about the future behaviour of the products—i.e. linear degradation rates—although the approach can be used for other assumed functional profiles as well. The method documented in this paper explicitly shows manufacturers how to make reasonable and sensible warranty projections. Copyright © 2008 John Wiley & Sons, Ltd.     

加强管壳检验工作,提高SAW器件的键合可靠性

现在，SAW器件的键合可靠性已成为影响器件性能的主要指挥之一。器件键合失效主要表现为温度试验后管壳上的键合点脱落，而引起失效的原因与工艺过程和键合所涉及的材料有关。该文介绍了采用正交试验的方法，通过大量的对比试验，从键合工艺和管壳质量两个方面入手，找到了导致器件大量失效的原因，并采取了相应的处理措施，从而提高了键合质量和产品的可靠性。     

RBF网络用于性能退化的可靠性评估

针对无法用数学式准确描述退化量与环境因子间复杂非线性关系的问题,提出了一种基于RBF网络的退化轨迹建模方法.利用RBF网络能够逼近任意非线性函数的特性,进行退化轨迹的建模,并结合失效值预测产品寿命.将所有估计寿命作为完全失效数据进行可靠性评估,有效地解决了失效数据少的问题.通过对疲劳裂纹增长数据的RBF网络建模分析,证明RBF网络具有很好的函数逼近能力,寿命预测结果非常理想.经验证,在更少的退化数据下,RBF网络仍能够较好地模拟退化轨迹,寿命预测精度较高.     

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。     

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。