Jones Thomas D A, Bernassau Anne, Flynn David, Price Dennis, Beadel Matthew, Desmulliez Marc P Y
Institute of Signals, Sensors and Systems, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK; Merlin Circuit Technology Ltd, Deeside, UK; School of Science and Engineering, University of Dundee, Dundee, UK.
Institute of Signals, Sensors and Systems, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK.
Ultrasonics. 2020 May;104:106111. doi: 10.1016/j.ultras.2020.106111. Epub 2020 Feb 25.
The deposition of increased volumes of Cu down an interconnect through-hole via (THV) of a Printed Circuit Board (PCB) is highly desirable for the fabrication of increasing component density and PCB stacks. A quality metric, called micro-throwing power, characterises the volume of Cu that can be deposited within a THV. In this paper, we analyse the influence of 1 ± 0.05 MHz megasonic (MS) assisted agitation applied to copper (Cu) electroplating baths on the micro-throwing ability of a standard, non-filling Cu electroplating solution. Our results indicate that megasonic agitation is shown to increase the Cu deposition volume within a THV by 45% for an increase of MS pressure from 225 W to 450 W, highlighting the significance of acoustic pressure as a key parameter to control MS THV plating volume. Bulk fluid flow rate within a 500 L plating tank is shown to increase by 150% due to Eckhart acoustic streaming mechanisms, compared to existing bath agitation techniques and panel movement. From MS plating experiments and COMSOL finite element acoustic scattering simulations, transducer orientation is shown to influence plating performance, with higher-order acoustic resonant modes forming within THVs identified as the cause. Simulations indicate that higher potential acoustic energy was coupled into a 0.200 mm diameter THV cavity, width-to-length aspect ratio (ar): 8:1, than a larger cavity of diameter 0.475 mm, ar 3.4:1. The maximum acoustic energy coupled into THV cavity is observed for a wavefront propagating along the axis of the cavity entrance, indicating an ideal alignment for the MS plating setup.
通过印刷电路板（PCB）的互连通孔（THV）沉积更多体积的铜对于制造日益增加的组件密度和PCB堆叠非常理想。一种称为微分散能力的质量指标表征了可以沉积在THV内的铜的体积。在本文中，我们分析了施加到铜（Cu）电镀槽的1±0.05 MHz兆声波（MS）辅助搅拌对标准非填充Cu电镀溶液的微分散能力的影响。我们的结果表明，对于MS压力从225 W增加到450 W，兆声波搅拌显示出可使THV内的Cu沉积体积增加45%，突出了声压作为控制MS THV镀覆体积的关键参数的重要性。与现有的镀液搅拌技术和面板移动相比，由于埃克哈特声流机制，500 L镀槽内的整体流体流速增加了150%。从MS镀覆实验和COMSOL有限元声散射模拟可知，换能器方向会影响镀覆性能，已确定THV内形成的高阶声共振模式是其原因。模拟表明，与直径0.475 mm、长宽比（ar）为3.4:1的较大腔体相比，更高的潜在声能耦合到了直径0.200 mm、长宽比（ar）为8:1的THV腔体内。对于沿腔体入口轴线传播的波前，观察到耦合到THV腔内的最大声能，这表明MS镀覆装置的理想对准方式。
