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Purpose ± A study of the influence of megasonic (MS) assisted agitation on Printed Circuit Boards (PCBs) electroplated using copper electrolyte solutions, to improve plating efficiencies through enhanced ion transportation. Design/methodology/approach-The impact of MS assisted agitation on topographical properties of the electroplated surfaces studied, through a Design of Experiments (DOE), by measuring surface roughness, characterised by values of the parameter Ra as measured by white light phase shifting interferometry and high resolution scanning electron microscopy. Findings ± An increase of Ra from 400 nm to 760 nm measured after plating, for an increase to acoustic power from 45 W to 450 W. Roughening increase due to micro-bubble cavitation energy, supported through direct imaging of the cavitation. Current thieving effect by the MS transducer induced low-currents, leading to large Cu grain frosting reducing the board quality. Current thieving was negated in plating trials through specific placement of transducer. Wavy electroplated surfaces, due to surface acoustic waves, also observed reducing the uniformity of the deposit. Research limitations/implications ± The formation of unstable transient cavitation and variation of the topology of the copper surface are unwanted phenomena. Further plating studies using megasonic agitation are needed, along with fundamental simulations, to determine how the effects can be reduced or prevented. Practical implications ± Identify manufacturing settings required for high-quality MS assisted plating and promote areas for further investigation, leading to the development of an MS plating manufacturing technique. Originality/value ± Quantification of the topographical changes to a PCB surface in response to megasonic agitation and evidence for deposited copper artefacts due to acoustic effects.

For numerical simulation of electrodeposition in small features, we have developed a novel method that allows an explicit tracking of the interface between the electrolyte and the deposited metal. The method is implemented in the CFD package PHYSICA and validated by comparing the delivered simulation results with those achieved by real-life measurements and/or obtained by another piece of software, COM SOL Multiphysics using a standard electrodeposition module.