摘要
钎焊过程中在焊锡接点中形成的金属间化合物(IMC)对焊锡接点可靠性具有重要影响.在原子扩散效应下,回流焊和等温时效过程中IMC层的生长会在其内部产生应力,其微结构也发生变化,致使IMC层和整个焊锡接点的力学性能下降.论文基于扩散反应机制,研究了由于原子扩散产生的IMC层的扩散应力.首先建立了描述焊锡接点IMC层生长早期微结构特征的2界面(Cu/Cu6Sn5/Solder)分析模型,然后运用Laplace变换法求解扩散方程得到了Cu原子在IMC层中的浓度分布;采用把原子扩散作用转换为体应变方法,计算了IMC层在形成和生长过程中应力的解析解.结果表明:IMC层中的扩散应力为压应力,最大值位于Cu/IMC界面处,大小与扩散原子浓度密切相关;随着时效时间的增加,扩散应力增大,但最终趋于稳定并沿IMC厚度方向线性变化.
Intermetallic compound （IMC） layers formed during soldering processes significantly affect the reliability of solder joints. The atomic diffusion effect during reflow and isothermal aging leads to growth and morphological evolution of IMC layers,and stress is developed in the IMC layers. The changed microstructure and the stress in the IMC layer result in degradation of mechanical performance of solder joints. Based on the mechanism of atomic diffusion-reaction,the diffusion-induced stress during the growth of the IMC layer is investigated. An analytic model with two interfaces（Cu/Cu6Sna/Solder）at the early sta- ges of IMC formation is proposed, and then the copper concentration distribution in the IMC layer is calcu- lated using the Laplace transformation method. Diffusion-induced stresses are obtained analytically by transforming atomic diffusion effects into bulk strain. The results show that the diffusion-induced stress is compressive, and it reaches its peak at the Cu/Cu6 Sn5 interface. The diffusion-induced stress increases with the increase of the isothermal aging time, and finally becomes stable and changes linearly along the thick- ness of the IMC layer.
出处
《固体力学学报》
CAS
CSCD
北大核心
2012年第2期162-167,共6页
Chinese Journal of Solid Mechanics
基金
国家自然科学基金(10972012)资助
关键词
金属间化合物
扩散浓度
扩散应力
intermetallic compound （IMC）,atomic diffusion,diffusion-induced stress
