热力耦合场下互连微焊点的疲劳寿命分析

该文设计热循环和跌落耦合冲击试验,选用Sn_(96.5)Ag_(3.0)Cu_(0.5)(SAC305)和Sn_(63)Pb_(37)(Sn-37Pb)两种焊料制成焊球,以芯片尺寸封装(CSP)芯片为研究基底,焊盘分别进行Ni/Au化学电镀和有机保焊膜涂覆两种工艺处理,研究该环境对CSP微尺度焊点疲劳寿命的影响。结果表明:CSP微尺度焊点的失效模式是先快后慢,初期失效的变化率最高,产品具有固有的耐耦合冲击能力,无铅焊点更适用于低周热循环和低能级跌落耦合冲击环境,有铅焊点的抗跌落冲击能力较强,Ni/Au处理的焊盘配合无铅焊球制成的CSP器件具有更高的耐高周耦合冲击可靠性,焊点的失效机制是由离散的空洞逐渐向界面裂纹转变。     

光纤定位激光钎焊键合过程中钎料与镀层的界面反应

光电子封装中,光导纤维的定位键合是一项关键技术,并且焊点界面处的显微组织对于焊点的可靠性有重要影响.本文选用80Au20Sn和52In48Sn钎料实现了激光钎焊条件下的光纤键合,采用扫描电子显微镜及能谱分析的方法对于两种钎料分别与硅片上的Au/Ti镀层和光纤上的Au/Ni镀层反应形成的界面微观组织形态及形成规律进行了分析.结果表明:对于80Au20Sn钎料,除了共晶组织ζ相+δ相,在AuSn/Au/Ti镀层界面形成了大量枝状的先共晶ζ相,在AuSn/Au/Ni镀层界面形成了针状的(Au,Ni)3Sn2;对于52In48Sn钎料,在InSn/Au/Ti镀层界面形成了连续层状的Au(In,Sn)2,随着输入能量的增加,其逐渐转变为不连续的块状化合物AuIn2,在熔融钎料流的作用下部分AuIn2脱离界面进入钎料中,在InSn/Au/Ni镀层界面形成了一层极薄的Au(In,Sn)2.     

Al/Cu键合系统中金属间化合物的形成规律及防止方法

Al/Cu键合界面金属间化合物的形成是导致微电子器件失效的重要因素之一,总结了微电子器件生产和使用过程中Al/Cu键合界面金属间化合物的生长规律,分析了Al/Cu键合系统的失效机制。热超声键合过程中,Al焊盘上氧化铝层的破裂使金属间化合物的形成成为可能,键合及器件使用过程中,金属间化合物和柯肯德尔空洞的形成和长大最终导致键合失效。采用在Al焊盘上镀覆Ti过渡层的方法,可有效降低键合系统中Cu原子的扩散速度,抑制金属间化合物的生长,从而提高电子元器件的可靠性。     

焊后时效对7046铝合金搅拌摩擦焊接头力学性能的影响

对厚度为3.5 mm的7046铝合金挤压板材进行搅拌摩擦焊接并对焊接接头进行人工时效,研究了焊后时效对接头力学性能的影响。结果表明,焊接接头时效前的硬度分布大致呈“W”形,抗拉强度为406.5 MPa,焊接系数为0.8,拉伸时在后退侧热影响区与热机影响区的过渡位置出现断裂,此处的硬度值最低,断裂面上有大量的韧窝;进行120℃×24 h时效后,接头的热影响区、热机影响区和焊核区的硬度都显著提高,母材区的硬度变化不大,硬度分布大致呈“一”形,抗拉强度大幅度提高到490 MPa,焊接系数达到0.96,拉伸时在焊核区中心断裂,断裂面有大量的沿晶裂纹。时效后接头区域的晶内GPI区转变成具有更好强化效果的η′亚稳相,使接头的硬度和强度提高;与其它区域相比,焊核区中晶界η相的分布更连续,晶界处无沉淀析出带的体积分数更大,因此容易成为拉伸时的断裂位置。     

Ti-22Al-25Nb合金惯性摩擦焊接头显微组织与力学性能EI北大核心CSCD

采用惯性摩擦焊技术焊接Ti-22Al-25Nb合金,研究热处理前后焊接接头微观组织和显微硬度的变化,分析接头在650℃和750℃高温拉伸力学性能.结果表明:接头原始态焊合区由B2相和极少量残余α2相构成,热处理后焊合区由B2相和O相构成,O相由B2相直接相变产生,相变过程无成分变化.原始态焊合区的显微硬度高于母材,780℃/3 h热处理后焊合区的显微硬度陡升,大量析出的细小O相促进硬度升高,800℃/3 h热处理后焊合区显微硬度介于原始态和780℃/3 h热处理之间.高温拉伸断裂位置均位于母材区域,650℃拉伸断口微观形貌呈韧性断裂特征,断口存在较多浅而小的韧窝.     

Ti-22Al-25Nb合金惯性摩擦焊接头显微组织与力学性能

采用惯性摩擦焊技术焊接Ti-22Al-25Nb合金,研究热处理前后焊接接头微观组织和显微硬度的变化,分析接头在650℃和750℃高温拉伸力学性能。结果表明:接头原始态焊合区由B2相和极少量残余α_2相构成,热处理后焊合区由B2相和O相构成,O相由B2相直接相变产生,相变过程无成分变化。原始态焊合区的显微硬度高于母材,780℃/3 h热处理后焊合区的显微硬度陡升,大量析出的细小O相促进硬度升高,800℃/3 h热处理后焊合区显微硬度介于原始态和780℃/3 h热处理之间。高温拉伸断裂位置均位于母材区域,650℃拉伸断口微观形貌呈韧性断裂特征,断口存在较多浅而小的韧窝。     

1Cr18Ni9Ti不锈钢管焊接接头断裂原因分析

某飞机用1Cr18Ni9Ti不锈钢管在进行弯曲疲劳试验时焊接接头发生断裂。通过宏观分析、微观分析、金相检验等方法,对焊接接头的断裂原因进行了分析。结果表明:焊接结构不合理(焊接热影响区处于截面过渡位置),是导致该1Cr18Ni9Ti不锈钢管焊接接头疲劳寿命降低的主要原因;焊接区域存在未焊透情况,需要对焊接工艺进行优化。     

ZL205A大厚板铝合金TIG堆焊组织与性能研究

目的 解决壁厚25 mm的ZL205A铸造铝合金在多层多道TIG焊过程中接头易出现气孔和虚焊等问题,进而实现大厚板ZL205A的高质量焊接。方法 采用TIG堆焊方法对25 mm厚的ZL205A进行焊接,研究不同层间焊接电流对接头组织和力学性能的影响。结果 焊后接头焊核区存在明显的气孔缺陷,随层间焊接电流的增大,气孔缺陷数量和尺寸显著增加。焊接接头根据组织特征分为焊核区、熔合区、热影响区和母材区,其中焊核区晶粒尺寸最小,约为20 μm,仅为母材晶粒尺寸的1/5左右。在焊核区晶界处弥散分布了大量Al2Cu、AlCu及少量Al12CuMn2颗粒相。随焊接电流的增大,接头拉伸强度及伸长率呈现先增大后减小的趋势,其最大拉伸强度为母材强度的94%,最大伸长率仅为母材伸长率的41.72%。在最优焊接电流下,接头拉伸断裂位置为母材处和焊缝处,气孔缺陷是导致焊缝断裂的主要原因,而母材断裂的主要原因为晶界间存在较多脆硬性AlCu/颗粒相。结论 采用TIG多层多道的焊接方法通过控制不同层间电流可以实现25 mm厚ZL205A的高强度焊接。     

12Cr1MoV联箱与支管焊缝裂纹分析

为研究某厂联箱与支管运行1.4×105h后发生开裂的原因,采用宏观渗透及光学显微镜、扫描电镜、能谱仪、显微硬度计等测试方法对失效管进行检测.研究表明:焊后存在焊接缺陷,大量的裂纹垂直于焊缝,加速裂纹的扩展,改变应力分布状态;部分夹杂物沿直线分布,使材料受力具有方向敏感性,导致材料开裂失效;断口表面主要是Fe的氧化物,焊件长期过热,外表面形成不均匀氧化层,产生应力集中,致使焊缝从管壁外侧开裂;母材硬度超标.优化焊接工艺方案,焊前预热焊后回火,消除管件外壁的氧化层及减少设备停机次数均能有效防止同类焊接结构开裂失效.     

镍钢复合板压力容器的制造

主要介绍了镍钢(N6与16MnR)复合板制造的压力容器工艺.根据多年制造纯镍容器的经验,结合镍钢复合板的特点,重点解决了镍与钢过渡层的焊接,镍层与钢之间使用Ni112焊条过渡,然后用氩弧焊ERNi-1焊丝成形,严格控制加工工艺.筒体与封头相连的A、B类焊缝棱角度控制在3mm以下,错边量0.5mm,不直度1.5mm.从而保证了镍与钢过渡层的焊接.采用特殊的焊接工艺,选用小电流,多道次,减小焊接速度,控制层间温度在80℃以下等工艺措施.使焊接接头既满足了强度要求又减少熔池中钢的稀释,避免了镍在焊接高温过程中与氧形成氧化镍而导致焊缝及热影响区裂纹,并减少了镍的过量烧损而降低焊缝的耐蚀性.     

Studies of CrNAu as an improved die attach metallization system

The increased incidence of premature integrated circuit die attach failure in ceramic packages has recently become a problem of major concern. It appears that the conventional “back-side gold” process has become marginal from the standpoint of bond strenght and reliability when used in conjunction with the conventional “eutectic die attach” process. This study shows that this trend may be due, in part, to the basic metallurgical instability of the “back-side gold” process, i.e. heat treatment of this metallization in the eutectic bonding temperature range (375–425°C) is shown to result in rapid and extensive growth (about 10 nm min^?1) of silicon oxide over the gold metallization. The resultant oxide film is known to degrade profoundly the bondability of the gold metallization. The movement of the silicon through the gold layer is thought to proceed via grain boundary interdiffusion. Thus, dice which were initially easily bondable can become non-bondable by extended storage at room temperature prior to the die attach step in processing.In this study we describe a metallization scheme (CrNAu) which can easily withstand eutectic bonding temperatures for short periods with minimal oxide growth. Additionally, data comparing shear force strength and thermal shock testing between the two metallization will be presented. It is shown that use of the CrNAu system results in considerable die attach yield improvement and greater strength and reliability over the conventional “back-side gold” process. The use of Auger electron spectroscopy for such an investigation is shown to be a very definitive tool.     

低温非晶硅/金圆片键合技术(英文)

本文研究了低温非晶硅/金圆片键合技术.具有不同金硅比的键合片在400℃键合温度和1 MPa键合压力下维持30 min,其键合成功区域均高于94%,平均剪切强度均大于10.1 MPa.键合强度测试结果表明键合成品率与金硅比大小无关,平均剪切强度在10～20 MPa范围内.微观结构分析表明键合后单晶硅颗粒随机分布在键合层内,而金则充满其他区域,形成了一个无空洞的键合层.无空洞键合层确保不同金硅比非晶硅/金键合片均具有较高的键合强度,可实现非晶硅/金键合技术在圆片键合领域的应用.     

镀Au键合Ag线性能对键合质量的影响研究

利用扫描电镜、能谱仪、拉力-剪切力测试仪等研究了不同镀Au厚度的镀Au键合Ag线Free Air Ball(FAB)特性和不同力学性能的镀Au键合Ag线对键合强度及其可靠性的影响规律，研究结果表明：镀Au键合Ag线镀层厚度过小会造成Electronic-Flame-Off(EFO)过程中的FAB偏球及球焊点形状不稳定，镀层厚度过大会导致FAB变尖；高强度、低伸长率会造成焊点颈部产生裂纹而造成焊点的拉力偏低并在颈部断裂，低强度、高伸长率引起颈部晶粒粗大进而降低颈部连接强度；镀Au键合Ag线颈部应力集中或内部组织结构不均匀，在冷热冲击周期性形变作用下，球焊点颈部产生裂纹并引起电阻增加，进而导致器件失效.     

铜线性能及键合参数对键合质量的影响

为了提高铜线性能及其键合质量,采用拉力-剪切力测试仪、扫描电镜等研究了不同力学性能铜线及相应的键合参数对其键合质量的影响,分析了不同伸长率和拉断力、铜线表面缺陷、超声功率和键合压力对铜线键合质量的作用机制.结果表明:伸长率过小和拉断力过大会造成焊点颈部产生微裂纹,从而导致焊点的拉力和球剪切力偏低;表面存在缺陷的铜线其颈部经过反复塑性大变形会造成铜线表面晶粒和污染物脱落而出现短路和球颈部断裂;键合过程中键合压力过大能够引起的焊盘变形,同时较大的接触应力引起铝层溢出;过大的超声功率使键合区域变形严重产生明显的裂纹和引起键合附近区域严重的应力集中,致使器件使用过程中产生微裂纹而降低器件的使用寿命.     

Irregular Characteristics of Bond Interface Formation in Ultrasonic Wire Wedge Bonding

The mechanism of ultrasonic wire wedge bonding, one of the die/chip interconnection methods, was investigated based on the characteristics of the ultrasonic wire bonding joints. The Al-1%Si wire of 25 μm in diameter was bonded on Au/Ni/Cu pad and the joint cross-section was analyzed by scanning electron microscopy （SEM） and energy-dispersive X-ray spectroscopy （EDX）. The results indicated that it is irregular for the ultrasonic bond formation, non-welded at the centre but joining well at the periphery, especially at the heel and toe of the joint. Furthermore, the diffusion and/or reaction at the cross-section interface are not clear at C-zone, while there exists a strip layer microstructure at P-zone, and the composition is 78.96 at. pct Al and 14.88 at. pct Ni, close to the Al3Ni intermetallic compound. All these observations are tentatively ascribed to the plastic flow enhanced by ultrasonic vibration and repeated cold deformation driving interdiffusion between AI and Ni at bond interface.     

Effects of bonding frequency on Au wedge wire bondability

This paper studies the effect of bonding frequency on bondability of Au wire on a PCB bond pad. The wire bonding was performed at two different frequencies, 62 kHz and 138 kHz, and at varying bond pad temperatures between 60 and 110 °C. It is shown that the bond strengths of the wires bonded at a high frequency were generally higher than those bonded at a low frequency for all temperatures studied. Two distinct wire failure modes were observed for the wires bonded at the high frequency: the wires with high pull strengths failed at the bond neck, while those with low pull strengths failed mainly within the bonded wire body. This resulted in a large pull strength data scatter, which was explained by the high Q factor of the high frequency transducer. The bondability obtained for the high bond power end was much higher for the high frequency, giving rise to a wider process window in terms of bond power for the high frequency bonding. The wire bonding performance was compared between the “open” and “closed” loop bonding systems. The minimum bond powers required for successful bonds in the closed loop system were significantly lower than those required in the open loop system (e.g. 20–40 mW vs. 110–135 mW at 90 °C). The closed loop system was able to correct the resonance frequency shift, thus maintaining an almost constant bond power during bonding. In the open loop system, in contrast, a high bond power needs to be continuously supplied because of the power drop. This causes an excessive energy to be transmitted to the bonded wire, resulting in weakened wire due to excessive deformation.     

Gold-to-alumina solid state reaction bonding

This paper describes methods by which strong vacuum-tight bonds between gold and alumina can be fabricated in an air atmosphere. Temperature was found to be a sensitive factor in bond formation; the higher the temperature, the stronger the bond, provided that the temperature remained below the melting point of gold. Intimate contact between the bonding gold and alumina surfaces during formation of the bond was also an important consideration. This was achieved by using an optically flat and polished ceramic surface and applying a low pressure of about 1 MPa to the bonding couple. Further enhancement of the contact can be achieved by depositing an additional thin layer of gold onto the ceramic surface by evaporation or by other means, and by thorough cleaning by high temperature heat treatment prior to bonding. Good bonding occurs in the range of 1 to 100 h. Bond strengths as high as 80 MPa were achieved.     

表面粗糙度对PS-PVD YSZ陶瓷层性能的影响EI北大核心CSCD

采用PS-PVD工艺在预制有NiCoCrAlYTa黏结层的K417G高温合金上制备YSZ陶瓷层;采用万能拉伸试验机、粒子冲刷仪、静态氧化炉等设备测试PS-PVD YSZ陶瓷涂层的结合强度、抗粒子冲刷和抗高温氧化性能;采用SEM和EDS分析涂层表面、截面形貌和元素分布等。结果表明:表面粗糙度对YSZ陶瓷层拉伸结合强度、抗粒子冲刷和抗高温氧化性能的影响很大。随着粗糙度的增大,结合强度先增大而后减小。Ra=0.40μm表面上沉积的YSZ涂层,其结合强度最高,达到23.5 MPa。拉伸断裂发生在涂层内部,并距离黏结层40~70μm的位置。随着表面粗糙度的增大,冲刷速率先减小而后增大,Ra=0.40μm涂层的抗粒子冲刷性能最好,冲刷速率仅为2.8×10^-3 g/g,表面起伏小和孔隙率低是涂层具有良好抗粒子冲刷性能的重要原因。不同表面粗糙度制备的YSZ涂层均能生成致密连续的热生长氧化物(TGO)层。粗糙度大则生长的TGO起伏大,更容易导致局部增厚和应力集中而失效。     

High-temperature reliability of sintered microporous Ag on electroplated Ag,Au, and sputtered Ag metallization substrates

Ag sinter joining technology has been used in the advanced power applications to replace conventional soldering technology due to its high temperature stability, along with its excellent electrical and thermal conductivity. In this paper, we report the high-temperature reliability (250 °C for 1000 h) for die-attachment structures using Ag sintering technology on Cu substrates with different top metallization layers (Au and Ag), formed via different deposition processes (electroplating and sputtering). The bonding strength over 40 MPa and high-temperature reliability of sintered Ag on the sputtered Ag surface was the best among the systems studied here. Bonding quality and the bonding fracture behavior of sintered Ag on the different metallization substrates were characterized. Ag–Au solid solution was formed due to metallizaion Au atoms diffused into sintered Ag layer, leading to decreased shear strength under high temperature process. The influence of grain structure on the bonding quality at the interface between sintered Ag and the metallization Ag layers were discussed. It revealed that the grain size and orientation of the top metallization Ag layer influenced the bonding quality. The sintered Ag layer formed by Ag hybrid particles may have a selective orientation of metallization layer on the surface (111) of the Ag crystal. These results will be helpful to understand both technological perspectives for design and the applications of sintered Ag from the viewpoint of high-temperature reliability, as well as the fundamental understanding of its bonding quality mechanism with top metallization layers.