互连焊点热电耦合下的电迁移行为研究

发布时间：2019-05-28 09:53

【摘要】：随着电子产品微型化趋势的不断推进,电迁移成为不可忽视的可靠性问题。微型化的推进迫使微焊点的尺寸不断减小,通过焊点中的电流密度持续增高,目前通过焊点的电流密度已经高达104A/cm2。另外,电子产品在无铅化过渡期间,势必存在着有铅和无铅的复合现象。目前对复合焊点的研究还停留在工艺和组织性能上,其电迁移可靠性的研究还存在空白。因此,对无铅焊点和复合焊点电迁移可靠性的研究具有重要意义。本研究中首先对不同Ag含量的Sn-Ag-Cu无铅焊点在热电耦合条件下的电迁移行为进行了研究,重点讨论了Ag含量和温度等影响因素对焊点界面电迁移行为的影响,同时研究了电迁移对焊点力学性能的影响。随后对Sn-3.0Ag-0.5Cu钎料和Sn-37Pb钎料复合焊点的电迁移行进行了研究,重点讨论了单一成分焊点和复合焊点电迁移中的界面行为,给出了界面IMC生长模型,并对焊点的电迁移平均失效时间进行了计算。研究结果表明,一定范围内Ag含量的增加,有效的提高了焊点的电迁移可靠性,温度对电迁移行为起到了促进作用。焊点基体中的β-Sn相具有强烈的各向异性,导致电迁移过程中流经β-Sn相的原子通量不平衡,晶粒发生旋转进而在焊点表明形成了晶界的凸起和凹陷。电迁移对焊点的拉伸性能具有明显影响,降低了焊点的拉伸强度,界面IMC的迁移削弱了界面和基板的结合强度,使焊点的断裂位置由钎料断裂向阴极界面断裂转变。在复合焊点电迁移行为的研究中,研究发现结构复合焊点中Sn-3.0Ag-0.5Cu网状共晶相在热电耦合的作用下发生粗化,并由阴极向阳极迁移。通电500h前,焊点阳极界面厚度没有明显的增加,通电超过500h后,Sn-3.0Ag-0.5Cu合金中大量的Cu6Sn5颗粒逐渐迁移至阳极界面,使其厚度快速增加。电迁移作用下,焊点阴极界面IMC厚度的变化受到其自身IMC厚度的影响,而阳极界面IMC的厚度受到钎料合金成分、焊点结构、通电时间和温度等多种因素的影响。通过有限元方法研究了焊点中电流密度分布和温度分布,结果表明,电流的加载方式对焊点中电流密度分布有明显影响,结构复合焊点的焦耳热生成介于有铅焊点和无铅焊点之间。Black方程计算结果表明,结构复合焊点的平均失效时间介于Sn-Ag-Cu焊点和Sn-37Pb焊点之间。
[Abstract]:With the development of the miniaturization trend of electronic products, the electrical migration becomes an unnegligible reliability problem. The microminiaturization of the push force forces the size of the microsolder joint to decrease continuously, and the current density through the welding spot continues to increase, and the current density through the welding spot is now up to 104A/ cm2. In addition, during the lead-free transition of the electronic product, there will be a combination of lead and lead-free. At present, the research of composite welding spot is still in process and organization performance, and the research of its electromigration reliability is also blank. Therefore, the research on the reliability of the electromigration reliability of the lead-free solder joint and the composite welding spot is of great significance. In this study, the electro-migration behavior of Sn-Ag-Cu lead-free solder joint with different Ag content under the condition of thermoelectric couple is studied. The influence of the influence factors such as Ag content and temperature on the electromigration behavior of the interface is discussed, and the effect of electromigration on the mechanical properties of the solder joint is also studied. In this paper, the electrical migration of Sn-3.0Ag-0.5Cu and Sn-37Pb composite solder joints is studied. The interface behavior of the single-component solder joint and the composite solder joint is discussed, and the growth model of the interface IMC is given, and the average failure time of the electric migration of the solder joint is calculated. The results show that the increase of Ag content in a certain range can effectively improve the reliability and the temperature of the solder joint. The Sn-Sn phase in the solder joint matrix has strong anisotropy, resulting in an imbalance of the atomic flux flowing through the Si-Sn phase during the electromigration process, and the rotation of the crystal grains further indicates that the grain boundary is formed and the depression is formed at the welding spot. The electrical migration has an obvious influence on the tensile property of the solder joint, the tensile strength of the welding spot is reduced, the migration of the interface IMC reduces the bonding strength of the interface and the substrate, and the fracture position of the welding spot is changed from the fracture of the graphite material to the cathode interface. In the study of electromigration behavior of composite solder joint, it was found that the Sn-3.0Ag-0.5Cu mesh eutectic phase in the structure composite solder joint was coarsened under the action of the thermo-electric coupling and migrated from the cathode to the anode. The thickness of the anodic interface of the solder joint was not obviously increased before 500 h, and the large amount of Cu6Sn5 particles in the Sn-3.0Ag-0.5Cu alloy gradually migrated to the anode interface and the thickness of the Sn-3.0Ag-0.5Cu alloy gradually increased. Under the action of electromigration, the change of the IMC thickness of the cathode interface of the welding spot is affected by the thickness of the IMC, and the thickness of the IMC in the anode interface is affected by various factors such as the composition of the alloy, the structure of the welding spot, the time of the energization and the temperature. The current density distribution and temperature distribution in the welding spot are studied by the finite element method. The results show that the current loading mode has a significant influence on the current density distribution in the welding spot, and the Joule heat of the structure composite welding spot is between the lead-free solder joint and the lead-free solder joint. The results of the Black equation show that the average failure time of the structural composite solder joint is between the Sn-Ag-Cu solder joint and the Sn-37Pb solder joint.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG40

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