Fabrication of conductive copper patterns using reactive inkjet printing followed by two-step electroless plating

•Copper patterns were fabricated by reactive inkjet printing and two-step electroless plating.•Cu particles produced via reactive inkjet printing act as catalyst for copper electroless plating.•High conductivity can be obtained without many printing passes and high temperature sintering.•This approach can largely avoid nozzle-clogging problems.•This approach presents a potential way in the flexible printed electronics with simple process.

A simple and low-cost process for fabricating conductive copper patterns on flexible polyimide substrates was demonstrated. Copper catalyst patterns were first produced on polyimide substrates using reactive inkjet printing of Cu (II)-bearing ink and reducing ink, and then the conductive copper patterns were generated after a two-step electroless plating procedure. The copper layers were characterized by optical microscope, SEM, XRD and EDS. Homogeneously distributed copper nanoclusters were found in the catalyst patterns. A thin copper layer with uniform particle size was formed after first-step electroless plating, and a thick copper layer of about 14.3 μm with closely packed structure and fine crystallinity was produced after second-step electroless plating. This resulting copper layer had good solderability, reliable adhesion strength and a low resistivity of 5.68 μΩ cm without any sintering process.