PET Surface Modification with Inkjet-Printing Pd²⁺/Epoxy Resin Solution for Selective Electroless Copper Plating

This article introduces a simple method to selectively fabricate conductive lines with good adhesion and outstanding electrical properties on the surface of the polyethylene terephthalate (PET) film with simple pre-treatment. The synthetic Pd2+ complex solution is selectively coated on the surface of PET to establish a bridging layer by an inkjet printing instrument. The bridging layer then catalyzes the electroless deposition of copper after plasma activation. The deposited copper coating and the bridging layer are characterized by X-ray photoelectron spectroscopy, atomic force microscopy, contact angle, and scanning electron microscopy. The results indicate that the bridging layer is activated and reformed into a network structure after air plasma treatment. The activated bridging layer effectively catalyzes the electroless deposition of copper. An even and compact surface is achieved in the as-prepared copper plating layer with 5B-level adhesion. In addition, the electrical resistivity of selectively deposited copper circuit is 2.26 μΩ/cm, which is equivalent to 1.3 times of the bulk copper.