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

Abstract

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.

Epoxy Resin-Assisted Cu Catalytic Printing for Flexible Cu Conductors on Smooth and Rough Substrates

“…However, these methods have high manufacturing costs and result in the wastage of a considerable amount of material . In recent years, printing techniques such as screen, transfer, inkjet, and 3D printing have attracted increasing attention owing to their low cost. Compared with other printing techniques, screen printing is inexpensive and exhibits a high processing efficiency …”

“…The prepared catalyst ink is compatible with a variety of substrates, including rough/porous and smooth/dense substrates. When the ink is applied to a PET surface, the epoxy groups in the resin form covalent bonds with the carbonyl and hydroxyl groups in the PET, 19 which ensures robust bonding between the metal and substrate. Conversely, when the ink is applied to a rough porous substrate, such as filter paper, it can easily penetrate the substrate to create a mechanical locking relationship, which produces a strong bond.…”

Photocatalytic activation of TiO2-functionalized anodic aluminium oxide for electroless copper deposition

“…Some approaches for spatially controlled activation of the dielectric surface are investigated, e.g. , through inkjet printing, 26 laser-induced deposition, 27 or even by the use of a magnetic catalyst colloid and patterned magnetic fields. 20 However, in the typical case the dielectric is initially completely plated in the Cu-ELD bath and the desired conductive pattern is subsequently formed, subtractively, by means of photolithography and etching, thus increasing both the number of technological steps and the waste generated.…”