Copper electroplating of PCB interconnects using megasonic acoustic streaming

Thomas D A Jones; Anne Bernassau; David Flynn; Dennis Price; Matthew Beadel; Marc P Y Desmulliez

doi:10.1016/j.ultsonch.2017.12.004

Copper electroplating of PCB interconnects using megasonic acoustic streaming

Ultrason Sonochem. 2018 Apr:42:434-444. doi: 10.1016/j.ultsonch.2017.12.004. Epub 2017 Dec 5.

Authors

Thomas D A Jones¹, Anne Bernassau², David Flynn², Dennis Price³, Matthew Beadel³, Marc P Y Desmulliez²

Affiliations

¹ Heriot-Watt University, Research Institute of Signals, Sensors and Systems, School of Engineering and Physical Sciences, Edinburgh, UK; Merlin Circuit Technology Ltd, Deeside, UK. Electronic address: t.jones@hw.ac.uk.
² Heriot-Watt University, Research Institute of Signals, Sensors and Systems, School of Engineering and Physical Sciences, Edinburgh, UK.
³ Merlin Circuit Technology Ltd, Deeside, UK.

PMID: 29429689
DOI: 10.1016/j.ultsonch.2017.12.004

Abstract

In this research experimental and simulated analysis investigates the influence of megasonic (MS; 1 ± 0.05 MHz) acoustic-assisted electroplating techniques, with respect to the fabrication of through-hole via (THV) and blind-via (BV) interconnects for the Printed Circuit Board (PCB) industry. MS plating of copper down THV and BV interconnects was shown to produce measurable benefits such as increased connectivity throughout a PCB and cost savings. More specifically, a 700% increase of copper plating rate was demonstrated for THVs of 175 µm diameter and depth-to-width aspect ratio (ar) of 5.7:1, compared with electrodeposition under no-agitation conditions. For BVs, a 60% average increase in copper thickness deposition in 150 µm and 200 µm, ar 1:1, was demonstrated against plating under standard manufacturing conditions including bubble agitation and panel movement. Finite element modelling simulations of acoustic scattering revealed 1st harmonic influence for plating rate enhancement.

Keywords: Acoustic streaming; Copper plating; Electroplating; Megasonic agitation; Printed circuit board; Standing wave.