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.