Electroless copper deposition is more uniform than the electroplating, but its uniformity is decreased with increasing aspect ratio of through holes on the printed circuit boad.
To improve the uniformity, we investigated concomitant application of current during the electroless copper plating process.
The studies showed that the uniformity, physical properties and plating rate were greatly improved when PR and pulse current were applied simultaneously. To investigate the effect of current, galvanostatic electroplating was carried out in an electroless copper bath containing no formaldehyde. The surface morphology was found to be similar to that of the electroless copper deposition with improved the uniformity and the physical properties.
From the potential-time curves, we also found that the transient phenomena of the potential are closely related to the plating morphology and specifically to the faradic region of the cathode process.
Thus it is confirmed that the uniformity and the physical properties of electroless copper plating are also greatly influenced by the faradic region of the applied cathodic current.