Electroless (ELS) copper plating process has been commonly used for PCB metallization. However, the ELS copper process is not environment-friendly because it contains precious metal (i.e., Pd catalyst), formaldehyde and chelating agents. Also, ELS copper plating process gives rise to several problems on the metallization of through holes (THs) and microvias.

In this work, ELS copper deposition process was replaced by a reduced graphene oxide (rGO) process to form a conducting layer on the sidewalls of THs and microvias of a PCB for subsequent copper electroplating. rGO has an excellent conductivity and metal barrier capability. Also, the rGO process has more advantages such as environment-friendly, short process steps, no toxic chemicals and organic solvent. A high copper throwing power (> 90 %) in the THs with a high aspect ratio can be obtained using rGO as a conducting layer, even better than ELS copper plating. Moreover, the rGO process could result in good copper filling performance in the microvias without seam or void in the via center. After thermal reliability test, the rGO grafted on the sidewall of the through holes and microvias could pass critical thermal reliability criterion due to its excellent thermal stability. Therefore, brand-new and promising rGO process is hopeful to play a significant role in the future PCB fabrication.