力学学报 ›› 2018, Vol. 50 ›› Issue (3): 487-496.doi: 10.6052/0459-1879-18-077

所属专题: 热应力专题(2018年第3期)

• 热应力专题文章 • 上一篇    下一篇

多物理场下FCBGA焊点电迁移失效预测的数值模拟研究

张元祥1, 梁利华2, *, 张继成2, 陈俊俊2, 盛玉峰2   

  1. 1 衢州学院机械工程学院, 浙江衢州 324000;
    2 浙江工业大学机械工程学院, 杭州 310014
  • 收稿日期:2018-01-30 出版日期:2018-05-15 发布日期:2018-06-11
  • 通讯作者: 梁利华, 教授, 主要研究方向:计算固体力学和微电子封装技术研究. E-mail:lianglihua@zjut.edu.cn
  • 基金资助:
    国家自然科学基金资助项目(51605252, 51375447).

MODELING OF ELECTROMIGRATION FAILURE PREDICTING FOR FCBGA SOLDER BUMP UNDER MULTI-PHYSICAL FIELD LOADS

Zhang Yuanxiang1, Liang Lihua2, *, Zhang Jicheng2, Chen Junjun2, Sheng Yufeng2   

  1. 1 College of Mechanical Engineering, Quzhou University, Quzhou 324000, Zhejiang, China;
    2 College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014, China
  • Received:2018-01-30 Online:2018-05-15 Published:2018-06-11

摘要: 随着微电子封装技术的快速发展, 焊点的电迁移失效问题日益受到关注. 基于有限元法并结合子模型技术对倒装芯片球栅阵列封装(flip chip ball grid array, FCBGA)进行电-热-结构多物理场耦合分析, 详细介绍了封装模型的简化处理方法, 重点分析了易失效关键焊点的电流密度分布、温度分布和应力分布, 发现电子流入口处易产生电流拥挤效应, 而整个焊点的温度梯度较小. 基于综合考虑“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的原子密度积分法, 并结合空洞形成/扩散准则及失效判据, 分析FCBGA焊点在不同网格密度下的电迁移空洞演化过程, 发现原子密度积分算法稳定, 不依赖网格密度. 采用原子密度积分法模拟真实 工况下FCBGA关键焊点电迁移空洞形成位置和失效寿命, 重点研究了焊点材料和铜金属层结构对电迁移失效的影响. 结果表明, 电迁移失效寿命随激活能的增加呈指数级增加, 因此Sn3.5Ag焊点的电迁移失效寿命约为63Sn37Pb的2.5倍, 有效电荷数对电迁移寿命也有一定的影响;铜金属层结构的调整会改变电流的流向和焊点的应力分布, 进而影响焊点的电迁移失效寿命.

关键词: 电迁移|电-热-结构耦合分析|互连焊点|失效寿命|空洞演化

Abstract: With the rapid development of microelectronics packaging technology, more attention has been paid to the electromigration (EM) failure on solder bump. The electric-thermal-structural multi-physical coupled analysis for flip chip ball grid array (FCBGA) packaging is performed in this paper based on FEM and submodeling technique. The simplified method of package model is introduced in detail. The current density distribution, temperature distribution and stress distribution of the key solder bump is investigated. It is found that the current crowding effect is easily generated at the location where electrons enter the bump from Cu metal layer, and the temperature gradient of the whole key solder bump is small. This paper presents the atomic density integral (ADI) method which considers four driving forces for electromigration such as electron wind force, stress gradient, temperature gradient and atomic density gradient. According to ADI method and the failure rule on void formation and diffusion, the electromigration void evolution process of the key solder bump is simulated with different mesh density. In can be found that the ADI method is stable and almost independent on the mesh density. The EM void location and time to failure (TTF) of key solder bump in FCBGA package is also simulated in the real service condition by ADI method. And the effect of solder material and Cu metal layer on EM failure is investigated in detail. We can see that the TTF of lead-free solder (Sn3.5Ag) is about 2.5 times than leaded solder (63Sn37Pb) because the TTF is determined to increase exponentially with the activation energy. And the EM failure is also influenced by the effective charge number. The adjustment of Cu metal layer structure will change the current flow direction and the stress distribution of the solder bump, which will affect the time to failure of solder bump.

Key words: electromigration|electric-thermal-structural coupled analysis|solder bump|time to failure|void evolution

中图分类号: 

  • O346