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Copper electroplating of PCB interconnects using megasonic acoustic streaming.
Thomas D A Jones1, Anne Bernassau2, David Flynn2
1Heriot-Watt University, Research Institute of Signals, Sensors and Systems, School of Engineering and Physical Sciences, Edinburgh, UK; Merlin Circuit Technology Ltd, Deeside, UK.
Ultrasonics Sonochemistry
|February 13, 2018
Summary
Megasonic (MS) acoustic-assisted electroplating significantly boosts copper deposition rates for printed circuit board (PCB) interconnects. This advanced technique enhances connectivity and reduces costs in PCB fabrication.
Area of Science:
- Materials Science
- Electrical Engineering
- Surface Science
Background:
- Printed circuit board (PCB) fabrication relies on efficient interconnects like through-hole vias (THVs) and blind vias (BVs).
- Traditional electroplating methods face challenges in achieving uniform and rapid copper deposition, especially in high aspect ratio features.
- Megasonic (MS) technology offers potential for enhanced material processing through acoustic energy.
Purpose of the Study:
- To investigate the impact of megasonic (MS) acoustic-assisted electroplating on the fabrication of THVs and BVs.
- To quantify the improvements in copper plating rate and deposition thickness using MS techniques.
- To explore the underlying mechanisms of plating enhancement through simulation.
Main Methods:
- Experimental electroplating of copper onto THVs and BVs with and without MS assistance (1 ± 0.05 MHz).
- Comparative analysis of plating rates and deposition thickness under various conditions.
- Finite element modeling (FEM) simulations to analyze acoustic scattering and its influence on plating.
Main Results:
- A 700% increase in copper plating rate for THVs (175 µm diameter, aspect ratio 5.7:1) was achieved with MS plating compared to non-agitated conditions.
- A 60% average increase in copper thickness deposition for BVs (150 µm and 200 µm, aspect ratio 1:1) was observed with MS plating versus standard agitation.
- FEM simulations indicated that the 1st harmonic of the acoustic field significantly influences the plating rate enhancement.
Conclusions:
- Megasonic acoustic-assisted electroplating provides substantial benefits for fabricating PCB interconnects.
- The technique leads to increased copper deposition rates and improved thickness uniformity, enhancing PCB connectivity and potentially reducing manufacturing costs.
- Acoustic field dynamics, particularly the 1st harmonic, play a crucial role in the observed plating enhancements.
Keywords:
Acoustic streamingCopper platingElectroplatingMegasonic agitationPrinted circuit boardStanding waveMore Related Videos
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