What is the fastest and cheapest way for conductive inks to be sintered without using the conventional thermal sintering procedure? This question constitutes the starting point for employeneur Guy Bex’ work. For his bachelor’s degree graduation project, Guy worked on chemical-assisted sintering of silver nanoparticle inkjet inks at Holst Centre. Shortly after he graduated, Holst Centre contacted Guy for a job as a Process Engineer for another sintering project, seconded by TMC.
“Together with a technical program team, I’m focusing on a method called photonic sintering, which is an alternative method for sintering conductive inks,” Guy explains. “Conventional thermal sintering requires full substrate heating, but this technique uses high intensity Xenon lamps to selectively heat up printed structures. The method makes it possible to use substrates, which have a thermal stability, for instance which deforms easily upon heating because of the very local and short-timed, high peak temperatures. Because sintering generally occurs at temperatures above the substrates Tg, it’s impossible to use thermal sintering. Another benefit of photonic sintering is the selectivity of the method by applying filters to the light, so specific materials can be cured without interfering with others.”
Photonic sintering can be applied to a wide variety of printed electronics applications, such as credit cards, OV-chip cards, solar cells, OLED's and displays. The goal for the technical program team is to search for the highest electrical conductivity for structures, with minimal foil deformation in the shortest amount of time. “We use three different lamp systems for our research,” Guy says. “The first system is a custom-made setup for research and laboratorial purposes. The second setup is a commercial tool from NovaCentrix and used for sheet-to-sheet processing. The last sintering system is built into the roll-to-roll (R2R) line. This is the final research stage within the Holst Centre regarding this topic. Holst Centre has developed the complete photonic sintering setup within the R2R setup. Currently, the R2R setup has a speed of 10 meter per minute and is limited by the photonic curing setup. The goal is to upgrade the setup to enable higher processing speeds; 20 meters per minute with the same quality is the goal!”
Working in the lab, Guy spent most of his time on executive work. “I like to have a job which includes various activities,” Guy states. “Together with another technical program, I’m working on the selective sintering of top electrodes on an OPV-stack. I expect to be working on the photonic sintering technique for quite some time still. TMC and Holst Centre offer me the two most important things for a job: contributing in making something new and working on innovative projects!”