SU-8-Induced Strong Bonding of Polymer Ligands to Flexible Substrates via in Situ Cross-Linked Reaction for Improved Surface Metallization and Fast Fabrication of High-Quality Flexible Circuits

On account of in situ cross-linked reaction of epoxy SU-8 with poly(4-vinylpyridine) (P4VP) and its strong reactive bonding ability with different pretreated substrates, we developed a simple universal one-step solution-based coating method for fast surface modification of various objects. Through this method, a layer of P4VP molecules with controllable thickness can be tethered tightly onto substrates with the assistance of SU-8. P4VP molecules possess a lot of pyridine ligands to immobilize transitional metal ions that can behave as the catalyst of electroless copper plating for surface metallization while functioning as the adhesion-promoting layer between the substrate and deposited metal. Attributed to interpenetrated entanglement of P4VP molecules and as-deposited metal, ultrathick (>7 μm) strongly adhesive high-quality copper layer can be formed on flexible substrates without any delamination. Then through laser printer to print toner mask, a variety of designed circuits can be easily fabricated on modified flexible PET substrate.