多场载荷作用下FCBGA焊点的电迁移失效研究

RESEARCH OF ELECTROMIGRATION FAILURE FOR FCBGA SOLDER JOINT IN MULTI-PHYSICAL FIELD

基于有限元法,结合子模型技术对倒装芯片球栅阵列封装(FCBGA)进行电-热-结构耦合分析,获得关键焊点的电流密度分布、温度分布和应力分布,采用原子通量散度法(AFD)和原子密度积分法(ADI)对关键焊点的电迁移(EM)特性及影响因素进行研究。结合焊点电迁移失效的SEM图,发现综合考虑电子风力、应力梯度、温度梯度以及原子密度梯度四种电迁移驱动机制的原子密度积分法能比较准确地预测焊点的电迁移失效位置,原子密度梯度(化学势)通常会延缓电迁移现象。

Based on FEM and submodel technique, the electric-thermal-structural coupled analysis for flip chip ball grid array （FCBGA） package is performed to obtain the distribution of current density, temperature and stress for the key solder joint. By using atomic flux divergence （AFD） method and atomic density integral （ADI） method, the electromigration （EM） characteristics and influence factors of the key solder joint are studied. The SEM image of the key solder joint under EM demonstrates that the ADI method with the consideration of four driving mechanisms, such as electron wind force, stress gradient, temperature gradient and atomic density gradient, can effectively predict the EM failure location. The atomic density gradient （chemical potential） usually can retard EM phenomenon.