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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.
The formation of intermetallic compounds (IMCs) in solder joints during brazing has an important effect on the reliability of solder joints. The growth of the IMC layer during reflow and isothermal aging causes stresses in its interior under the effect of atomic diffusion The microstructure also changes, resulting in the mechanical properties of the IMC layer and the entire solder joints decreased.In this paper, based on the diffusion reaction mechanism, the diffusion stress of IMC layer due to atom diffusion was studied.Firstly, the microstructure characteristics of the IMC layer (Cu / Cu6Sn5 / Solder) model was established. Then, the concentration distribution of Cu atoms in IMC layer was obtained by solving the diffusion equation with Laplace transform method. By changing the atomic diffusion into bulk strain, And the analytical solutions of the stress in the growth process.The results show that the diffusion stress in the IMC layer is compressive stress and the maximum value is located at the Cu / IMC interface, and the size is closely related to the concentration of the diffused atoms. As the aging time increases, the diffusion stress increases , But eventually stabilized and changed linearly along the thickness of the IMC.