Au线改Cu线的新发展及可靠性研究

Au线作为内引线一直占据着键合的主导地位,而由于Cu线具有优良的电性能和价格优势,随着键合技术的发展,以Cu丝代替Au丝作为键合用内引线已经成为现在的主要趋势。介绍了Cu线相对于Au线的优势、存在的可靠性问题,并对Cu引线键合新的发展趋势、如何进行可靠性验证等问题进行了研究。     

引线带楔焊键合技术

引线带楔焊键合和引线(圆形)楔焊键合是不同的。对于高频器件应用来说,引线带键合较之于圆形引线键合更为有利。为了让更多的人了解该项技术,文章对部分相关技术,其中包括键合工艺过程、键合引线的断丝方式、键合引线带规格以及键合劈刀的选择作了介绍。     

混合集成电路的外引线键合技术

混合集成电路外引线键合的方式很多。与混合集成电路的内引线键合不同，外引线键合时，键合丝的1端在管壳的引线柱上。因此，管壳外引线金属镀层的结构、镀层材料、键合丝的性能和键合工艺因素都将影响混合电路外引线键合的质量。本文主要对Au丝球焊、Au丝点焊、SiAl丝超声焊等不同的键合工艺及其对应的金属学系统进行研究，并对其结果进行比较。采用Au丝点焊工艺键合混合电路外引线的效果最佳。     

银键合丝力学性能对键合质量的影响

通过调节微合金元素的含量获得3种具有不同力学性能的银键合丝.利用拉伸试验、键合试验、焊线挑断力、焊球推力测试等手段,研究了银键合丝力学性能对键合质量的影响.结果表明,在延伸率相同的条件下,随着微合金元素含量的降低,3种键合丝的断裂负荷降低,初始模量先减小后增大,键合后焊线挑断力和焊球推力均降低,电极金挤出率先减小后增大.银键合丝初始模量较低时在超声和压力的作用下易于变形,焊线内残余应力较低且第二焊点与引线框架结合较好,因此挑断测试时第二焊点与框架材料界面处不易发生脱离,有利于获得更高的键合成功率.     

镀Pd Cu线键合工艺中Pd行为研究

由于Cu线热导率高、电性能好、成本低,将逐渐代替传统Au线应用于IC封装.但Cu线键合也存在Cu材料本身固有特性上的局限:易氧化、硬度高及应变强度等.表面镀Pd Cu线材料的应用则提供了一种防止Cu氧化的解决方案.然而,Cu线表面的Pd层很可能会参与到键合界面形成的行为中,带来新的问题,影响到Cu线键合的强度和可靠性.对镀Pd Cu线键合工艺中Pd的行为进行了系统的研究,使用了SEM,EDS等分析手段对cu线、烧结Cu球(FAB)、键合界面等处Pd的分布状况进行了检测,结果证明Pd的空间分布随着键合工艺的进行发生了很大的变化,同时还对产生Pd分布变化的原因进行了分析和讨论.     

键合拉力测试点对键合拉力的影响分析

随着现代封装技术的高速发展,对于封装产品质量的检测要求越来越严格,而键合拉力测试是封装产品质量检测中的重要一项,而在相关标准上并未对键合拉力测试点及键合线弧度对测量结果所产生的影响给出明确的规定。基于此,文章介绍了测量点位置、引线弧度、测量速度等因素对引线键合拉力测试准确性的影响。然后通过客观的分析提出了科学合理的键合强度测试的方法,为客观准确的测量键合拉力奠定了基础。     

铜键合线的发展与面临的挑战

介绍了当今微电子封装中重点关注的铜键合引线,指出了铜键合线的优缺点.铜线键合是一种代替金和铝键合的键合技术,人们关注它不仅因为它的价格成本优势,更由于铜线特有的机械和电学等方面的优良性能,当然,铜线键合技术还存在不少问题和挑战,针对这些存在的问题,进行了简要的介绍并提出相应的解决办法.     

起步中的载带自动键合技术(TAB)

<正> 载带自动键合(TAB)是一种封装技术,该技术使用了一种覆有金属引线框架的聚酰亚胺带。裸露的芯片被键合到内引线框架上,而键合好的引线框架/管芯或是被单个地置于载体上或是被送到卷带上的定位/键合装置上。图1是一个装在典型的内引线框架上的单个载带自动键合的示意图。 TAB、带式封装、微封装和PILL封装的引线均不穿过电镀通孔(PTH),这一点与SMT相似。不同的是,SMT的典型间距在0.020～0.050in之间,而载带引线则在0.008～0.020in之间,属于精细间距技术(FPT)。     

多排焊盘外壳封装IC金丝球焊键合技术

在多层多排焊盘外壳封装电路的引线键合中,由于键合的引线密度较大,键合引线间的距离较小,键合点间的距离也较小,在电路的键合中就需要对键合点的位置、质量、键合引线的弧线进行很好的控制,否则电路键合就不能满足实际使用的要求。文中就高密度多层、多排焊盘陶瓷外壳封装集成电路金丝球焊键合引线的弧线控制、外壳焊盘常规植球键合点质量问题进行了讨论,通过对键合引线弧线形式的优化以及采用"自模式"植球键合技术大大提高了电路键合的质量,键合的引线达到工艺控制和实际使用的要求。同时,外壳焊盘上键合的密度也得到了提高。     

半导体器件组装技术的突破——Cu丝球焊将替代Au丝球焊

评述了A1、A1合金、Ag和Cu四种引线材料在半导体器件组装技术中作为球焊键合引线的前途.Cu的情况最喜人,Cu丝焊技术将应用到年导体器件的大批量生产中去.     

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。     

热声焊机在电子封装业中的应用

热声焊技术可实现金丝的高质量焊接。介绍了热声焊的原理、焊接材料、工艺、设备,热声焊机已应用于微波器件、组件的制造及其相关工艺的研究。     

Fine pitch copper wire bonding in high volume production

Wire bonding is the predominant mode of interconnection in electronic packaging. Gold wire bonding has been refined again and again to retain control of interconnect technology due to its ease of workability and years of reliability data. Economic realities are now enabling fine diameter copper wire to compete with gold wire. It needs to be demonstrated however that known challenges in the assembly process and long term reliability can be managed successfully. Here, a rigorous methodology has been established to introduce copper wire bonding on new as well as converted dice into manufacturing. Manufacturing efficiencies and yields have been driven to be equivalent to gold wires. Reliability testing has passed the usual criteria and has been extended to demonstrate the viability of this technology. Interfacial analysis has confirmed the observations that intermetallic compounds form and grow slowly.     

Optimization of the Cu wire bonding process for IC assembly using Taguchi methods

The yield of IC assembly manufacturing is dependent on wire bonding. Recently, the semiconductor industry demands smaller IC designs and higher performance requirements. As such, bonding wires must be stronger, finer, and more solid. The cost of gold is continuously appreciating, and this has become a key issue in IC assembly and design. Copper wire bonding is an alternative solution to this problem. It is expected to be superior over Au wires in terms of cost, quality, and fine-pitch bonding pad design. To obtain the best wire bonding quality, we employed Taguchi methods in optimizing the Cu wire bonding process. With Cu wire bonding technology, the production yield increased from 98.5% to 99.3% and brought approximately USD 0.7 million in savings.     

金丝楔形键合强度的影响规律分析

金丝楔形键合是一种通过超声振动和键合力协同作用来实现芯片与电路引出互连的技术。现今,此引线键合技术是微电子封装领域最重要、应用最广泛的技术之一。引线键合互连的质量是影响红外探测器组件可靠性和可信性的重要因素。基于红外探测器组件,对金丝楔形键合强度的多维影响因素进行探究。从键合焊盘质量和金丝楔焊焊点形貌对键合强度的影响入手,开展了超声功率、键合压力及键合时间对金丝楔形键合强度的影响研究。根据金丝楔焊原理及工艺过程,选取红外探测器组件进行强度影响规律试验及分析,指导实际金丝楔焊工艺,并对最佳工艺参数下的金丝键合拉力均匀性进行探究,验证了金丝楔形键合强度工艺一致性。     

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。     

自动焊接技术在SPRITE探测器内引线联接工艺中的应用

为使自动金丝球焊接技术应用于碲镉汞红外器件的研制工艺，在大量试验的基础上，摸索出一套使用自动金丝球焊接技术进行了ＳＰＲＩＴＥ红外器件内引线焊接的可靠方法。文中还对自动焊接的精度和最小间距进行了探讨。     

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.     

Direct gold and copper wires bonding on copper

The key to bonding to copper die is to ensure bond pad cleanliness and minimum oxidation during wire bonding process. This has been achieved by applying a organic coating layer to protect the copper bond pad from oxidation. During the wire bonding process, the organic coating layer is removed and a metal to metal weld is formed. This organic layer is a self-assembled monolayer. Both gold and copper wires have been wire-bonded successfully to the copper die even without prior plasma cleaning. The ball diameter for both wires are 60 μm on a 100 μm fine pitch bond pad. The effectiveness of the protection of the organic coating layer starts from the wafer dicing process up to the wire bonding process and is able to protect the bond pad for an extended period after the first round of wire bond process. In this study, oxidization of copper bond pad at different packaging processing stages, dicing and die attach curing, have been explored. The ball shear strength for both gold and copper ball bonds achieved are 5 and 6 g/mil² respectively. When subjected to high temperature storage test at 150 °C, the ball bonds formed by both gold and copper wire bond on the organic coated copper bondpad are thermally stable in ball shear strength up to a period of 1440 h. The encapsulated daisy chain test vehicle with both gold and copper wires bonding have passed 1000 cycles of thermal cycling test (−65 to 150 °C). It has been demonstrated that orientation imaging microscopy technique is able to detect early levels of oxidation on the copper bond pad. This is extremely important in characterization of the bondability of the copper bond pad surface.