高深宽比微细结构电铸时传质过程数值分析

针对高深宽比微细结构电铸时存在严重传质受限的问题，以微深槽特征为分析对象建立液相传质两种数学模型——维扩散模型和二维对流—扩散模型，并分别用Matlab专用工具箱和Fluent 6.2流体仿真软件进行数值求解，依次分析以扩散、强制对流－扩散、复合对流(强制对流和自然对流)－扩散等为主导传质模式作用下微细电铸时，流场和离子浓度场的空间变化规律及其对液相传质效果的影响，并进行试验验证。结果表明：微细结构电铸时，单一扩散作用仅能用于深宽比小于2且电流密度小于2 A/dm2的液相传质场合；槽外强制对流只能对深宽比小于2的微槽内电解液产生一定搅拌作用；强化槽内自然对流作用并与槽外强制对流协同配合时，槽(深宽比为5)内可形成独特的单个或多个占据整个槽空间的涡流循环胞，涡流流速约为强制对流流速的1/20～1/2，明显改善传质效果，试验结果与此相印证。

Numericall Analysis on Mass Transport in Micro Electroforming of Micro Structures with High-aspect-ratio

Aiming at the problem of mass-transport limitation in the electroforming of microstructures with high-aspect-ratio (HAR), two kinds of numerical models of mass-transport (1-D diffusion model and 2-D diffusion-convection model) are developed. Distribution of flow field and ion-concentration field inside the micro-trench and their effect on mass transport efficiency governed by diffusion, forced convection-diffusion, and complex convection (forced convection and nature convection)-diffusion, respectively, are simulated and analyzed by using Matlab toolbox and Fluent 6.2 fluid simulation software, followed by some experiments to validate the numerical analysis results. The results indicate that diffusion-transport or forced convection transport outside the cavity does well only under the conditions of smaller HAR value (<2) and lower current density (<2 A/dm2); one or more vortex cells that occupy the whole cavity space can be formed in the cavity (aspect ratio = 5) when the natural convection inside the cavity is strengthened and collaborated with the forced convection outside the cavity. The vortex flow rate is about 1/20 ~ 1/2 of the forced convection flow rate, which results in a remarkably better transport efficiency; and experimental results agree well with numerical analysis results.