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74 The PCB Magazine • June 2017 By Thomas Jones, Dr. David Flynn, Marc P.Y. Desmulliez and Dennis Price Introduction A printed circuit board is populated with a multitude of electro-mechanical components plus various active and passive devices such as transistors, capacitors, inductors and resistors, which enable the functionality and assembly of the PCB. Increasing the density of the compo- nents on the surface of a board enables greater functionality and use. A high-density (HD) de- sign is desirable for technology high end appli- cations, which include automotive, aerospace, space, defense, mobile phones, medical, net- working, communications, and computer stor- age [1] . The current trend in PCB markets is low- technology, high-volume demand and is typi- cally supplied by low-cost, large-scale facilities in Southeast Asia, such as China, India and Thailand. High-value, low-volume PCB markets are typically supplied by smaller-sized facilities in western regions such as North America and Europe, but also economically developed east- ern locations such as Japan, South Korea and Taiwan [2] . The UK PCB demand typically focuses on this latter market. Manufacturing develop- ments bringing increased capability and cost savings to a factory in the UK would be highly desirable and enable increased market competi- tiveness. For more than four years, Merlin Circuit Technology Ltd (MCT), in Deeside, North Wales, has been working in collaboration with Heriot-Watt University (HWU) in Edinburgh, Scotland, on a UK government project funded by the Engineering and Physical Sciences Re- search Council (EPSRC), looking to improve HD PCB manufacturing capability through en- hancements to the electrodeposition of copper using high frequency acoustic, applied within a copper plating bath [3,4,5] . This article outlines some of the key findings from this project. High-Frequency Acoustics Applied within Manufacture The introduction of high frequency acous- tics—greater than the human hearing range which is typically over 20 kHz—has been used Megasonic Acoustic Surface Treatment Process for Enhanced Copper Electrodeposition in Via Interconnects ARTICLE