典型Sn基焊料凸点互连结构电迁移异同性

研究了Sn37Pb,Sn3.0Ag0.5Cu和Sn0.7Cu三种焊料BGA焊点在电迁移作用下界面的微观组织结构.在60℃,1×103 A/cm2电流密度条件下通电187h后,Sn37 Pb焊点阴极界面已经出现了空洞,同时在阳极有Pb的富集带;Sn3.0Ag0.5Cu焊点的阴极界面Cu基体大量溶解,阳极金属间化合物层明显比阴极厚;对于Sn0.7Cu焊料,仅发现阳极金属间化合物层厚度比阴极厚,阴极Cu基体的溶解不如SnAgCu明显,电迁移破坏明显滞后.     

电迁移对Sn3.0Ag0.5Cu无铅焊点剪切强度的影响

通过热风回流焊制备了Cu/Sn3.0Ag0.5Cu/Cu对接互连焊点,测试了未通电及6.5 A直流电下通电36 h和48 h后焊点的剪切强度.结果表明,电迁移显著地降低了焊点的剪切强度,电迁移36 h使剪切抗力降低约30%,电迁移48 h降低约50%.SEM观察断口和界面形貌表明,界面金属间化合物增厚使断裂由韧性向脆性...     

热循环条件下Sn基钎料接头电迁移行为研究

通过电迁移和热疲劳循环实验,研究了热循环和高电流密度耦合作用下Sn58Bi和Sn3.0Ag0.5Cu钎料焊接接头的失效形式。实验结果表明,在通电和高低温冲击的耦合作用下,两种钎料接头的失效都发生在升温阶段。热循环导致接头内部裂纹的萌生和扩展,导致局部电流密度持续增大,加速了电迁移的发生,最终导致焊点失效。在热电耦合作用下,Sn58Bi钎料接头的使用寿命要长于Sn3.0Ag0.5Cu钎料接头的使用寿命。     

SnAgCu无铅焊点原位电迁移IMC演变

在28℃.3.25A直流电下,对Cu/Sn3.0Ag0.5Cu/Cu对接无铅焊点进行原位电迁移实验,观察了通电120,168,384和504 h后焊点横截面的微观组织形貌.结果表明,电迁移初期,Cu<,6>Sn<,5>化合物遍布整个焊点截面,随时间延长,不断从阴极向阳极迁移聚集;当通电504 h后,焊点内已看不到金属间...     

SnAgCu焊点电迁移诱发IMC阴极异常堆积

为了研究电迁移过程中焊点与焊盘界面金属问化合物(IMC)的变化,在28℃下,对无铅Sn3.0Ag0.5Cu焊点进行了6.5A直流电下的电迁移实验.结果发现,通电144h后,阳极侧IMC层变厚,平均达到10.12 μm;阴极侧IMC层大部分区域变薄至0.86μm,局部出现Cu焊盘的溶解消失,但在界面边缘处出现Cu3Sn5...     

电迁移对Ni/Sn63Pb37/Cu焊点界面反应的影响

研究了在125℃,1×103 A/cm2条件下电迁移对Ni/Sn63Pb37/Cu BGA焊点界面反应的影响.回流后,在焊料/Ni界面处形成Ni3Sn4、在焊料/Cu界面处形成Cu6Sn5的金属间化合物.随着电迁移时间增加,芯片侧金属间化合物转变为(Cu,Ni)6Sn5类型化合物,印制板侧Cu6Sn5金属间化合物类型保...     

Sn3.8Ag0.7Cu和Sn37Pb焊点界面显微结构研究

利用扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究了Sn3.8Ag0.7Cu（Sn37Pb）/Cu焊点在时效过程中的界面金属间化合物（IMC）形貌和成份。结果表明：150℃高温时效50、100、200、500h后,Sn3.8Ag0.7Cu（Sn37Pb）/Cu焊点界面IMC尺寸和厚度增加明显,IMC颗粒间的沟槽越来越小。50h时效后界面出现双层IMC结构,靠近焊料的上层为Cu6Sn5,邻近基板的下层为Cu3Sn。之后利用透射电镜观察了Sn37Pb/Ni和Sn3.8Ag0.7Cu/Ni样品焊点界面,结果显示,焊点界面清晰,IMC晶粒明显。     

Sn0.7Cu无铅焊点的电迁移失效模拟及优化分析

基于ANSYS有限元软件,综合考虑电子风力、温度梯度、应力梯度和原子密度梯度四种电迁移驱动机制,采用原子密度积分法(ADI)对倒装芯片球栅阵列封装(FCBGA)的Sn0.7Cu无铅焊点进行电迁移失效模拟。针对焊点直径、焊点高度、焊点下金属层(UBM)厚度三个关键参数进行电迁移失效的正交试验优化,探究焊点尺寸对电迁移失效的影响。研究表明:焊点直径和高度的增加会缩短焊点的电迁移失效寿命(TTF),而UBM层厚度对焊点失效寿命的影响相对较小;焊点局部拉应力对焊点的失效寿命影响较大,通常会加剧焊点的空洞失效。     

SnAgCu凸点互连的电迁移

研究了无铅Sn96Ag3 sCuo s凸点与镀Ni焊盘互连界面的电迁移现象.在180℃条件下,凸点及互连界面在电迁移过程中出现了金属间化合物沿电子流运动方向的迁移,其演化过程呈现出显著的极性效应:阴极互连界面发生了金属间化合物的熟化、剥落和迁移;阳极互连界面则出现了金属间化合物的大量聚集.金属间化合物的演化和迁移造成了阴极处的物质减少,从而诱发空洞的形成和聚集,导致互连面积减小,整体电阻增大,可靠性降低.     

倒装芯片互连凸点电迁移的研究进展

电子产品向便携化、小型化、高性能方向发展,促使集成电路的集成度不断提高,体积不断缩小,采用倒装芯片互连的凸点直径和间距进一步减小和凸点中电流密度的进一步提高,由此出现电迁移失效引起的可靠性问题.本文回顾了倒装芯片互连凸点电迁移失效的研究进展,论述了电流聚集和焊料合金成分对凸点电迁移失效的影响,指出了倒装芯片互连凸点电迁移研究亟待解决的问题.     

SnAgCu凸点互连的电迁移

研究了无铅Sn96Ag3 sCuo s凸点与镀Ni焊盘互连界面的电迁移现象.在180℃条件下,凸点及互连界面在电迁移过程中出现了金属间化合物沿电子流运动方向的迁移,其演化过程呈现出显著的极性效应:阴极互连界面发生了金属间化合物的熟化、剥落和迁移;阳极互连界面则出现了金属间化合物的大量聚集.金属间化合物的演化和迁移造成了阴极处的物质减少,从而诱发空洞的形成和聚集,导致互连面积减小,整体电阻增大,可靠性降低.     

Impact Behavior of Thermomechanically Fatigued Sn-Based Solder Joints

Impact behavior of Sn-3 wt.%Ag-0.5 wt.%Cu (SAC 305) solder joints subjected to thermomechanical fatigue in different temperature regimes was investigated. This study was aimed at understanding the roles of distributed cracks that develop near the solder/substrate interface region during early stages of thermal excursions. Two specimen geometries were employed to evaluate mode I and mode II types of fracture under impact in solder joints several hundred microns thick. The peak stress that could be withstood in mode I fracture under impact decreased with increasing number of thermomechanical fatigue cycles, while mode II fracture was insensitive to the same. No observable influence on the impact strength due to the temperature regimes was noted. However, the fracture surfaces of specimens subjected to thermal excursions at the lower-temperature regime were predominantly along the Cu₆Sn₅/solder interface, while specimens subjected to the higher-temperature regime predominantly fractured along the Sn-Sn grain boundaries. These observations are consistent with the findings of prior studies dealing with damage accumulation in the early stages of thermal excursions in these temperature regimes.     

焊料凸点倒装焊技术

介绍了倒芯片面阵式凸点制作、多层陶瓷基板焊盘制作及倒装焊各关键技术 ,并成功地获得了芯片与基板的互连。     

Prediction of Solder Bump Formation in Solder Jet Packaging Process

Precise solder bump shape prediction is crucial for the application of the solder jet bumping process to microelectronic component packaging. In the present study, numerical simulation of both the dynamics and phase change responses during a metal droplet impingement is conducted by introducing a nonconstant interfacial heat transfer coefficient, which varies with time and position. Comparison between the numerical and experimental results for a large metal droplet demonstrates the validity of the numerical method. The results of many simulation cases are presented corresponding to typical solder jet bumping conditions. Variations in the impact velocity, initial droplet size, and droplet temperature and substrate temperature are investigated to understand their impact on the formation of solder bumps.     

Thermomigration Versus Electromigration in Microelectronics Solder Joints

Competing mechanisms of electromigration and thermomigration in flip chip SnAgCu (SAC) solder joints were studied experimentally. A daisy chain of solder joints were stressed at $2.0times 10^{4} {rm Amps/cm}^{2}$, $2.4times 10^{4} {rm Amps/cm}^{2}$, and $2.8times 10^{4} {rm Amps/cm}^{2}$ current density levels at room temperature. In the test vehicle, some solder joints were exposed to a combination of electromigration and thermomigration, while some others were exposed to thermomigration alone. The changes in the intermetallic compound (IMC) microstructure were observed with scanning electron microscope (SEM) under thermomigration alone and when both migration processes are present. In all cases, ${rm Cu}_{6}{rm Sn}_{5}$ IMC at the hot side disintegrated while at the cold side thickened. The dissolution of the IMC at the hot side and the thickening at the cold side is a result of temperature and diffusion driving forces. It is observed that thermomigration driving force, when present, is much larger than electromigration.      

Cu-Ni/Solder/Ni-Cu互连结构的电迁移

采用Cu-Ni/Solder/Ni-Cu互连结构,在加载的电流密度为0.4×104 A/cm2的条件下,得到了界面阴极处金属原子的电迁移.数值模拟揭示了其原因是由于凸点互连结构的特殊性,电子流在流经凸点时会发生流向改变进而形成电流聚集,此处的电流密度超过电迁移的门槛值,从而诱发电迁移.运用高对流系数的热传导方法降低了互连焊点的实际温度,在电迁移的扩展阶段显著减小了高温引起的原子热迁移对电迁移的干扰;因此电迁移力是原子迁移的主要驱动力.在电迁移的快速失效阶段,原子的迁移是热迁移和电迁移共同作用的结果:电迁移力驱动阴极处原子的迁移,造成局部区域的快速温升,从而加剧此处原子的热迁移.     

无铅焊料的研究（4）——电迁移效应

电迁移是金属原子沿着电流方向的移动。阐述了无铅焊料中电迁移的物理特性,由于焊点的特殊几何形状,电流拥挤效应将发生在焊点与导线的接点处;电迁移效应导致无铅焊料中金属间化合物(IMC)的生成与溶解,以及焊点下的金属化层(UBM)的溶解和消耗,使原子发生迁移并会产生孔洞,造成焊点破坏,缩短了焊点平均失效时间(MTTF),从而带来可靠性问题。     

Electromigration of Sn-9wt.%Zn Solder

The morphological evolution of Sn-9wt.%Zn solder under electromigration at a current density of about 10⁵ A/cm² was examined. Sn extrusion was observed, suggesting that Sn is the dominant moving species under electromigration. In contrast, Zn appeared to be immobile. It was also found that the microstructure of the solder had a significant effect on the electromigration behavior. For the solder with fine Zn precipitates, the surface morphology of the solder was almost unchanged except for the formation of Sn extrusion sites at␣the anode side after electromigration. However, for the solder with coarse Zn precipitates, more Sn extrusion sites were observed, and they were located not only at the anode side but also within the solder. Coarse Zn precipitates appeared to block Sn migration, thus Sn migration was intercepted in front of the Zn precipitates. The Sn atoms accumulated there, which led to its extrusion. The blocking effect was found to depend strongly on the size and orientation of the Zn precipitates.