Dave Savastano11.01.12
Researchers from Holst Centre and TNO Eindhoven have taken a new step towards cost-effective high-volume production of flexible electronics. The team used laser-induced forward transfer (LIFT) to create well-defined 6 µm copper lines with good conductivity – bringing this flexible emerging technology for patterning plastic electronics closer to production.
LIFT is an additive, roll-to-roll-compatible patterning technology for creating structures of functional materials such as metals, inks and pastes. It is highly versatile and could expand the range of materials that can be used within roll-to-roll production. For example, it can pattern many materials that aren’t suitable for printing techniques or wouldn’t withstand the etch step required in photolithography. Moreover, it wastes less of the functional material than subtractive techniques like photolithography, improving manufacturing costs.
In a LIFT process, a donor substrate is coated with the appropriate functional material, and placed in close proximity to an acceptor substrate. A laser is focused on the donor, heating it and forming droplets of the functional material that are transferred in the desired pattern. The droplet size can be varied to control the resolution of the structures formed.
The Holst Centre / TNO team used a glass donor coated with copper to create well-defined copper droplets with a diameter of 2 µm. These formed a clean, well-defined copper line 6 µm wide on the acceptor. “This is the first time a LIFT process has been used to create such a clean copper line with good conductivity. It shows that LIFT processes have the potential for high yields in volume manufacturing,” said An Prenen, a researcher in Holst Centre’s Patterning techniques for flexible systems program.
The copper-LIFT process could be used to manufacture backplanes for thin-film transistor displays. It could also be used to repair backplanes that suffered from defects during the production process, helping manufacturers further reduce costs. The team now plans to develop the technique further to improve line width to around 3 µm and conductivity to levels comparable with bulk copper.
LIFT is an additive, roll-to-roll-compatible patterning technology for creating structures of functional materials such as metals, inks and pastes. It is highly versatile and could expand the range of materials that can be used within roll-to-roll production. For example, it can pattern many materials that aren’t suitable for printing techniques or wouldn’t withstand the etch step required in photolithography. Moreover, it wastes less of the functional material than subtractive techniques like photolithography, improving manufacturing costs.
In a LIFT process, a donor substrate is coated with the appropriate functional material, and placed in close proximity to an acceptor substrate. A laser is focused on the donor, heating it and forming droplets of the functional material that are transferred in the desired pattern. The droplet size can be varied to control the resolution of the structures formed.
The Holst Centre / TNO team used a glass donor coated with copper to create well-defined copper droplets with a diameter of 2 µm. These formed a clean, well-defined copper line 6 µm wide on the acceptor. “This is the first time a LIFT process has been used to create such a clean copper line with good conductivity. It shows that LIFT processes have the potential for high yields in volume manufacturing,” said An Prenen, a researcher in Holst Centre’s Patterning techniques for flexible systems program.
The copper-LIFT process could be used to manufacture backplanes for thin-film transistor displays. It could also be used to repair backplanes that suffered from defects during the production process, helping manufacturers further reduce costs. The team now plans to develop the technique further to improve line width to around 3 µm and conductivity to levels comparable with bulk copper.