Done in a Flash! Photonic sintering for printed electronics Guy Bex, TNO/Holst Centre 1
Introduction Presentation overview Sintering principle Photonic flash sintering Way of working Curing Summary and acknowledgement Introduction Holst Centre High Tech Campus Eindhoven TNO (NL) & imec (BE) Shared innovation & knowledge Flexible electronics Wireless Autonomous Sensor Technologies System demonstrators Technologies 2
Flexible electronics Printed electronics Research objective Develop R2R compatible printing and sintering technology for functional structures on flexible substrates Base program, used for many applications General requirements High conductivity: 5 X bulk silver resistivity Low sintering temperature: 130ºC, foil compatible Short sintering time: <(<) 1 min, R2R compatible Compatible with device stack Investigated topics Conductive materials (Ag, Cu) Printing methods (Inkjet printing, flatbed- and rotaryscreenprinting) Sintering/curing technologies (thermal, (N)IR, photonic) Integration in applications/devices (OLED, OPV, printed electronics) Sintering principle Solvent evaporation Agglomeration of metallic particles Percolation path (initial conductivity) Proper sintering (high conductivity) Conventional: Thermal (oven) Presented: Photonic unsintered sintered 3
Photonic flash sintering Principal of photonic drying/sintering Light is absorbed in the printed structures, not substrate Elliptical reflectors focus the light in narrow lines High frequency flashing Top and bottom illumination Off the shelf lamps and electronics > inexpensive Ink Substrate Simulation of photonic sintering Curing: Thermal vs. Photonic Thermal Simple process Well understood Slow Unspecific Energy inefficient R2R in-compatible Photonic Many variables Still researched Fast Specific Energy efficient R2R compatible 4
Way of working - Systems Different systems Sheet-2-sheet ink benchmarking Sheet-2-sheet process optimization Roll-2-roll research tool Way of working Sheet-2-sheet inline temp/res measurement Holst made setup 2 4-point resistance measurements Temperature & Resistance 4-point resistance probe Standalone photonic sintering unit 5
Way of working - Sample analysis Microscope Visual observation of printed structure Proper line definition Homogeneous line Profilometer Cross-section to determine resistivity Compare to bulk Ag resistivity Goal: <5x bulk Ag State of the art: Roll-2-roll rotary-screenprinting conductive silver Rotary screen printing in combination with photonic curing 6
State of the art - Roll-2-roll inkjet printing conductive silver Nanoparticle silver ink inkjet printed @ 10m/min Summary & Conclusion An efficient route from batch to roll-to-roll production was shown Small scale material testing and evaluation using Holst photonic flash setup Up-scaling to S2S processing using PulseForge 1300 R2R printing using Holst (N)IR & Photonic flash setup Dedicated photonic sinter equipment for each stage Inline temperature and resistance measurement reveal best sinter settings Photonic sintering gives better conductivity compared to oven sintering R2R inkjet printing and sintering at 10 m/min was demonstrated 45µm resolution on PEN No foil deformation Resistivity of 8.5x bulk Silver 7
Team members: Robert Abbel, Tim van Lammeren, Eric Rubingh, Linda van de Peppel, Pit Teunissen, Ruben Lelieveld, Rob Hendriks, Erica Coenen, Cornelis de Mooij, Pim Groen Industrial partners Academic partners 8