High Performances PPR Copper Plating for High Aspect Ratio Boards

Multilayer boards, which are widely used in professional electronics such as sever, communication, medical and military equipments, trend to increase layer counts (up to more than 56 layers) and aspect ratio (up to more than 25: 1). Accordingly, it becomes more and more difficult to plate copper into the through holes with an acceptable deposit. To meet these demands, a new generation of high performances periodic pulse reverse (PPR) copper plating process has been developed. It is designed for use with soluble anodes and simple rectangle waveforms in vertical application. The new PPR chemistry demonstrates an excellent and stable throwing power up to a tested bath life of more than 200 AH/L. Neither a continuous carbon polish nor the frequent carbon treatment is required during operation. Meanwhile, it is easy to restart after idling with no need for a long dummy process. Effects of substrate, waveform on throwing power performance, the process capability to pattern and blind vias plating are also discussed in this article.