Achieving　metal　interconnects　for　printed　circuit　boards　(PCBs)　is　pivotal　for　the　electronics　industry.　Through　electrochemical　analysis　of　Basic　Blue　7　(BB7),　an　excellent　suppressing　effect　was　observed.　Chronopotentiometry　was　used　to　study　the　possible　concentration　range　of　BB7　for　microvia　filling　and　a　BB7　concentration　range　of　50-150　mg　L−1　was　selected　to　achieve　superfilling　electrodeposition.　A　difunctional　mechanism　of　coordination　and　adsorption　of　BB7　during　electrodeposition　is　proposed　based　on　density　functional　theory　(DFT)　calculations　and　in　situ　Raman　spectroscopy　analysis.　The　interaction　among　BB7,　the　copper　substrate　and　Cu2+　leads　to　the　suppression　of　copper　growth.　The　superfilling　electroplating　process　is　optimized　and　high　filling　performance　can　be　achieved　at　100　mg　L−1　with　filling　percentage　(FP)　values　of　80.19%,　84.70%　and　87.90%　for　microvias　with　diameters　of　150　μm,　125　μm　and　100　μm,　respectively.　Besides,　a　differential　diffusion　filling　mechanism　is　proposed　for　the　blind　microvia　filling　process　of　the　newly　proposed　electroplating　system　based　on　the　analyses　of　the　interaction　among　additives　and　diffusion　kinetics.　Furthermore,　the　performance　of　the　copper　interconnect　layer,　including　surface　morphology,　phase　structure　and　signal　transmittance,　is　evaluated.　©　2025　The　Royal　Society　of　Chemistry.