Polypyrrole conductive film formed by in-situ polymerization as a conductive seed layer for hole metallization of printed circuit boards and blind hole electroplating filling behavior

Abstract

At present, the hole metallization of printed Circuit Boards (PCBs) is achieved through using traditional electroless copper as a conductive seed, accompanied by an electroplating copper filling process. This method has serious environmental issues due to the carcinogenic formaldehyde and recalcitrant chelating agents in the electroless plating solution. To address this issue, a green polymer polypyrrole conductive film is proposed to replace traditional electroless copper as a conductive seed layer for the metallization of PCB. The polypyrrole film is formed via in-situ polymerization of pyrrole monomers on blind-hole walls. The cross-sectional SEM and EDS analysis confirmed that the polypyrrole film was uniformly formed on the walls of blind holes. The polypyrrole conductive layer exhibits a low sheet resistance of 1.45 kΩ/sq. Electrochemical characterizations demonstrate rapid copper electrodeposition on this conductive polymer layer. The contact angle measurements also demonstrate that the polypyrrole conductive film enhances substrate wettability, facilitating electrolyte infiltration into the vias. The filling experiment shows that dense super filling of copper in blind holes can be achieved within about 70 min. Thermal shock experiments confirm excellent adhesion of the plated copper. These results demonstrate that the polypyrrole conductive film represents a highly promising material to replace traditional electroless copper as the conductive seed layer for the metallization of PCB.