FlexTech Project to Scale Up, Print Functional Devices on a Commercial Press Completed by Clemson University and PARC

Among the principal challenges facing developers is transitioning printed electronics research conducted in a laboratory to meet the demands of large-scale production.

To better understand and address these issues, Clemson University and PARC, a Xerox company, collaborated and recently completed a FlexTech Alliance–funded project to investigate the scaling up and printing of functional devices on a commercial printing press. This project focused on the gravure printing process.

PARC provided an extensive library of device designs from prior research utilizing inkjet printing, which offers many advantages for design purposes. While it provides tremendous versatility and speed for prototyping designs, inkjet does not lend itself to the high-speed, roll-to-roll throughput. So, for this project, PARC deployed its lab-scale gravure printing press developed by Ohio Gravure Technologies.

Clemson University represented the commercial-scale printing aspect of this collaboration with its seven-station Omet printing press, a modular platform. Consequently, all multi-layer device printing in this study involved a gravure/flexo hybrid approach.

Among the team’s accomplishments were:
• Engineering a chambered doctor blade system on the Omet press. Whereas a typical gravure press configuration can uses a large amount of ink to fill a pan, the chamber allows one to seal a small volume (< 50 ml can be used) of ink against the cylinder. This technique greatly reduces the ink volume required, providing substantial cost and material savings.
• Testing a variety of inks, including graphics inks, conductors, dielectrics and semiconductors at both the lab and commercial scale.
• Printing numerous functional multilayer devices such as capacitors and diodes, as well as thin film field effect transistors (TFTs) having mobilities up to 1.4 cm2/Vs.
• Using multiple cylinder engraving techniques to optimize printed line edges.
• Optimizing device parameters by using high speed optical metrology to make ~250K measurements.
• Achieving resistivity of ~4X bulk silver for features ~50 nm thick at speeds of ~200 ft./min with very high yield.

“This project provided critical information for the scale-up of printed electronic processes using gravure printing, as well as thorough information on process capabilities and limitations,” said Dr. Bruce Kahn, adjunct professor at Clemson University.