Creep behavior of intermetallic compounds at elevated temperatures and its effect on fatigue life evaluation of Cu pillar bumps
Creep behavior of intermetallic compounds at elevated temperatures and its effect on fatigue life evaluation of Cu pillar bumps
复制标题
金属间化合物高温蠕变行为及其对铜柱凸块疲劳寿命评价的影响
DOI：
10.1016/j.intermet.2022.107526
复制
发表时间：
2022-05-01
期刊：
影响因子：
4.4
通讯作者：
Liu, Li
中科院分区：
文献类型：
--
作者：
Chen, Zhiwen;Yang, Fan;Liu, Li
在电子器件中，金属间化合物（IMC）通常存在于焊料互连中，它会对互连的机械完整性产生重大影响。在相关的力学模拟中，人们普遍认为IMC是脆性的，而通常认为IMC是弹性的。然而，在这项工作中，发现Cu6Sn5（一种常见的金属间化合物）在室温和高达180℃的高温下都存在温度依赖的非弹性变形行为，因此通过纳米压痕系统地研究了Cu6Sn5的非弹性变形行为。随着温度的升高，IMC的杨氏模量和硬度呈线性下降。证实了纳米压痕中IMC在停留期间的蠕变变形，并对其进行了进一步分析。最大蠕变位移从室温时的4.90 nm增加到180℃时的186.10 nm，随着温度的升高，蠕变应力指数从3.32降低到0.37，变形能力明显提高。考虑和不考虑IMC蠕变的有限元模拟表明，IMC的非弹性变形可以补偿相邻焊料与焊盘之间的不匹配。如果不考虑IMC蠕变，在建模中会严重低估铜柱碰撞的疲劳寿命。
In electronic devices, intermetallic compound (IMC) can normally be found in solder interconnects, and it can pose significant effects on mechanical integrity of interconnects. It is widely accepted that IMC is brittle and normally assumed to be elastic in related mechanical simulations. However, in this work, temperature-dependent inelastic deformation behavior of Cu6Sn5, a common intermetallic compound in lead-free solder joints, was identified to exist at both room temperature and high temperature up to 180 degrees C and therefore was systematically investigated by nanoindenation. Young's modulus and hardness of IMC generally decreased linearly with increasing temperature. Creep deformation of IMC during dwelling period in nanoindentation was confirmed and further analyzed. The maximum creep displacement was found to increase from 4.90 nm at room temperature to 186.10 nm at 180 degrees C. Creep stress exponent was found to decrease from 3.32 to 0.37 as temperature rose, indicating significant improvement of deformation capability. Finite element modeling with and without IMC creep shows that inelastic deformation of IMC can compensate the mismatch between adjacent solder and pad in interconnects. Without considering IMC creep, fatigue life of Cu pillar bump can be severely under estimated in modelling.