Fluid Mechanics and Mass Transfer of the Rotating Screw Electrode Process for Plating Through-Holes in Multilayered Printed Circuit Boards

多层印刷电路板电镀通孔旋转螺杆电极工艺的流体力学和传质

• 批准号: 9422770
• 负责人: Arne Pearlstein
• 金额: $ 13.25万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-15 至 1998-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9422770&HistoricalAwards=false
• 关键词: Fluid; Mechanics; Mass; Transfer; Rotating

ABSTRACT CTS-9422770 PEARLSTEIN UNIVERSIRTY OF ILLINOIS A key problem in manufacture of multi-layered printed circuit boards is rapid and uniform deposition of copper on inner surfaces of plated "through-holes." For conventional boards (in which all interconnects are by means of through- holes) as well as boards also using surface-mount technology, the trade-off between plating speed, uniformity, and deposit ductility is such that acceptable yields are achievable only at the cost of reduced speed, requiring large capital investment and in-process inventory costs. For holes of higher aspect ratio in future boards, incremental modification of the existing process will be incapable of providing the desired uniformity at acceptable processing rates. This project consists of a fundamental study of the fluid mechanics and mass transfer of a radically new approach to plating high aspect ratio holes. The key idea is to operate rotating screw electrodes (RSEs) in through-holes of submerged boards. The RSE generates radial, azimuthal, and axial flow, leading to much more effective mass transfer into and within the hole than is possible using conventional technology. Experiment shows the thickness of the resulting copper deposit has much greater axial uniformity than is achieved using the popular oscillating board technique, which establishes time-periodic Poiseuille flow in the hole. Flow modification by an axial pressure gradient, whose magnitude will be chosen to give flow reversal, will also be considered. This will provide countercurrent mass transfer between oppositely directed portions of the flow and suppress formation of cation-depleted boundary layers in the central section of the hole. This approach will lay the foundation for industrial evaluation and development of an improved plating process for high aspect ratio through-holes currently being developed. The results will also have implications for enhancing heat and mass transfe r in other applications.

多层印刷电路板制造的关键问题是在镀“通孔”的内表面快速均匀地沉积铜。对于传统的电路板（其中所有的互连都是通过通孔的方式）以及使用表面贴装技术的电路板，在电镀速度、均匀性和镀层延展性之间的权衡是这样的，只有以降低速度为代价才能实现可接受的产量，这需要大量的资本投资和过程中的库存成本。对于未来电路板中更高纵横比的孔，现有工艺的增量修改将无法在可接受的加工速率下提供所需的均匀性。该项目包括流体力学的基础研究和一种全新的镀高纵横比孔的传质方法。关键思想是在浸没板的通孔中操作旋转螺旋电极（RSEs）。RSE可以产生径向、方位和轴向流动，从而比传统技术更有效地将质量传递到井内。实验表明，与常用的振荡板技术相比，所得到的铜矿厚度具有更大的轴向均匀性，从而在孔中建立了时间周期的泊泽维尔流。还将考虑轴向压力梯度对流动的修正，其大小将被选择以使流动逆转。这将在流动的相反方向部分之间提供逆流传质，并抑制孔中央部分阳离子耗尽边界层的形成。该方法将为目前正在开发的高纵横比通孔的改进电镀工艺的工业评价和开发奠定基础。研究结果也将对其他应用中加强传热传质具有启示意义。