电-热耦合作用下Cu/SAC305/Cu中IMC的生长及元素扩散

在一定温度及电流密度下对Cu/SAC305(Sn-3.0Ag-0.5Cu)/Cu焊点进行不同加载时间的电迁移时效试验。分析了电-热耦合作用下,焊点界面IMC的生长机理及界面近区元素扩散特征。结果表明:电-热耦合作用下阳极界面IMC(金属间化合物)层厚度变化与加载时间成抛物线关系;阴极界面IMC层形貌变化显著,其厚度随加载时间的延长呈现先增厚后减薄的变化特征;焊点界面近区元素扩散分为两个阶段:初始阶段由于焊点各部分元素浓度相差悬殊,浓度梯度引起的元素扩散起主导作用,促进两极界面IMC厚度增加;扩散到一定程度后界面近区元素浓度梯度相对减小,电子风力引起的元素扩散占主导部分,促进阴极IMC分解阳极IMC形成,导致阴极IMC层厚度减薄,阳极IMC层厚度逐渐增大。

IMC Growth and Element Diffusion in Cu/SAC305/Cu Interconnect under Electric-thermal Coupling

The electromigration behavior of Cu/SAC305/Cu joints was investigated. Current stressing tests were conducted at a certain temperature and current density for various hours. The diffusion characteristics of the elements near the soldering interface and IMC (intermetallic compound) growth mechanism were studied. Results indicate that the growth of IMC presents a parabola dependence on time under thermal-electrical coupling at the anode. The thickness of IMC increases at first and then decreases. Meanwhile, the morphology of IMC changes obviously at the cathode. The diffusion of the elements at the soldering interface could be divided into two stages. At the initial stage, the high element concentration gradient in the soldering interface plays a leading role to the element diffusion. The IMC shows a similar growth trend at the anode and cathode. At the second stage, the concentration gradient in the soldering interface decreases. The electron-wind force plays a crucial role to the element diffusion. Accordingly, the thickness of IMC decreases at the cathode but increases at the anode.