Flexible Copper Metal Circuits via Desktop Laser Printed Masks

Abstract

A novel process is demonstrated that produces patterns of electrically conductive copper on a flexible polyimide film substrate using standard desktop laser printed toner and near room temperature aqueous chemistry. The laser toner acts as a mask to selectively block the ion exchange self‐metallization (IESM) reduction reaction that forms nanoscale silver or palladium coatings at the polyimide surface. The silver or palladium IESM coating is then used as a catalyst for electroless deposition of copper. Under appropriate conditions, the copper is deposited selectively on top of the catalyst layer. The resulting copper layer has a measured sheet resistance as low as 0.3 Ohms/sq. Electrical isolation is measured between copper traces spaced as close as 300 microns, and high conductivity is measured along traces with widths as low as 200 microns. The minimum pattern size appears to be limited primarily by the resolution of the laser toner pattern, as the IESM metal layer is observed to follow the contours of individual toner particles. The process avoids the use of high temperature, vacuum, and organic solvents and is thus suitable for very low cost prototyping or distributed manufacturing of simple electronic devices.

Hybrid Transfer Printing of Liquid Metals and Allied Inks for Rapid Fabrication of Multifunctional Soft Electronics

“…Later researchers adopted toner as a positive mask to prepare copper electrodes and adopted them for sensor applications. , Toner masks can also be used as negative masks for the deposition of materials for the preparation of patterns, e.g. silver, copper, , gold, MoS 2 , etc. However, the methods and materials for the fabrication of stretchable electronics still need further research to avoid the limitations of nonstretchable substrates and harmful organic solvents.…”

The Synthesis of Copper Nanoparticles for Printed Electronic Materials Using Liquid Phase Reduction Method

“…After printing into circuits and curing at 150 °C for 60 min, the resulting printed silver circuit had a resistivity of approximately 5 × 10 −5 Ω•cm [16]. In contrast, copper nanoparticles have become a research hotspot, due to their low cost and good electrical conductivity [17][18][19][20]. Bong Kyun Park and colleagues used copper sulfate as a precursor, polyvinylpyrrolidone (PVP) as a capping agent, sodium hypophosphite as a reducing agent, and diethylene glycol (DEG) as a solvent to prepare copper particles with an average size of 45 ± 8 nm at 140 °C.…”