Research and Application of Copper Electroplating in Interconnection of Printed Circuit Board
- 2021年第27卷 
电镀铜技术是制造印制电路板、封装载板等电子互连器件的核心技术。本文介绍了印制电路中电镀铜技术及其发展概况,主要总结了电子科技大学印制电路与印制电子团队在印制电路电镀铜技术基础研究和产业化应用等方面的工作。首先,以三次电流分布理论为基础,采用多物理场耦合方法构建阴极表面轮廓线随时间变化的镀层生长过程模型。该模型描述了铜沉积与微纳孔结构、添加剂特性、输入电流、对流强度等相关影响因素的函数关系。通过引入添加剂相关函数,该模型能够较好应用到整平剂筛选和性能评价、电镀铜需求和镀液配方匹配、电镀参数优化等技术开发和应用领域。然后,介绍了添加剂竞争吸附过程的电化学研究以及利用传质调控添加剂局域浓度实现快速微盲孔、微沟槽填充的工业技术。之后,介绍了氮杂环低聚物系列整平剂结构-电化学构效关系研究和应用。最后展示了氧化还原型添加剂的开发情况,并对印制电路中电镀铜技术的研究和应用发展进行了预测。Copper electroplating is the key technology for manufacturing of integrated circuit, packaging substrate, printed circuit board, and other electronic interconnection components. However, the electrochemistry and mechanism of deposition growth have not been fully elucidated, and the development of additives and bath maintenance are inseparable from a large number of experiments. This article reviews recent fundamental research and application progress in copper electroplating for printed circuit board industry, and these works are mainly dedicated by the research group of Printed Circuit and Printed Electronics from University of Electronic Science and Technology of China. First of all, a brief history of copper plating in printed circuit board is given. Then, modeling and simulation studies are introduced. A multi-physics coupling model is built on the basis of an electroplating bath, and an additive related parameter is introduced into the model to connect the convection intensity and the voltammetric response of the electrolyte. Base on tertiary current distribution, a relational model with the growth process of cathode surface related to micro-scale hole structure, plating current, convection intensity, additives etc., is obtained. Some applications using the above model are presented successively. By simplifying this model, a fast electrochemical evaluation method is developed to screen leveler candidates. Two dependent indicators, polarization overpotential of leveler injection (Δη) and deposition potential difference with low and high convection (ΔEr), are introduced, and the chemical having both high Δη and Δ Er may be an appropriate leveler. Fix the parameters of plating conditions and set TP as the index, the additive related parameter, size and structure of micro-scale hole are varied. It is feasible for a specific copper electroplating application couple to an appropriate additives’ pack. Then, a multi-physics modeling helping to optimize plating parameters of fine circuit pattern plating to meet the requirement of high thickness uniformity over the whole board has been demonstrated. Secondly, the mechanism of competitive adsorption of the organic additives has been discussed from the electrochemical results. The adsorption amount of the accelerator is independent of solution convection, but it shows dependency on the suppressor, and the adsorption strength of the accelerator is weaker than that of the suppressor. From that, a fast via-filling process is developed. Molecules of accelerator are selectively replaced from board surface but remained on via bottom by a mass-transport controlled pre-dip step of oxidant or suppressor, and the plating time of via filling is significantly shortened. Thirdly, the structure-electrochemistry relationship of series nitrogen heterocyclic oligomers is studied, and applications of the levelers and redox additive are discussed. Finally, a prospect on the research and application of copper electroplating has been made.