Intelligent packaging can do more than just wrap a product. They help in the identification and logistics of the products, they protect against theft or product piracy. The core of the intelligent system are small chips, RFID labels or generally printed electronics. For this purpose, a metallic ink is printed and then made conductive by sintering. Sintering of low-cost copper inks works particularly well with flash lamps, since they sinter more rapidly than the copper could oxidize.
Heraeus Flash systems make it possible to sinter copper ink for smart packaging in milliseconds without damaging the paper
Copper inks are a cost-effective alternative to silver inks when it comes to printed electronics for RFID or smart packaging. However, the sintering of copper ink on paper poses a genuine challenge. A co-operation between three companies: Promethean Particles, Dycotec Materials and Heraeus Noblelight, showed how copper nanoparticles in printed ink are easily and quickly fused by xenon flash lamps and thus form highly conductive and stable electronic circuits.
Unlike silver, copper rapidly forms oxides in the air, which makes sintering more difficult or even impossible. So far, copper ink is often sintered in an oven under inert gas, which requires specialized environment not suited for every process line and is relatively slow. Xenon flash systems on the other hand, transfer a great deal of energy into the ink within milliseconds. This causes the ink to sinter so rapidly that no oxidation process takes place. In addition, the substrate, e.g. foil or paper, is hardly heated with this rapid energy transfer and is thus not damaged.
Co-operations for the sintering of metallic inks
- Promethean Particles from Nottingham, UK: manufacture of nanomaterials
- Dycotec Materials from Swindon: producer of inks and coatings
- Heraeus Noblelight from Cambridge, UK: development of a Xenon flash lamp system for the sintering of metallic inks in Cambridge.
“From discussions with our customer base, there is a clear need for digital additive processing with low cost ink systems. Our new high volume manufacturing facility has enabled us to demonstrate our capability to produce high quality nanoparticles at quantities in excess of 1,000 tonnes per annum”, commented Laurie Geldenhuys, CEO of Promethean Particles. Dr. Richard Dixon, Managing Director of Dycotec Materials added, “using the Promethean Particles’ nanomaterials we were able to produce high solids loading inks with demonstrable stability that can be processed using inkjet heads operating at high frequencies, ensuring compatibility with high volume production. Processing our inks with the Heraeus flashlamp system enabled excellent electrical conductivity to be achieved of ~3 mΩ/□/mil.”
Martin Brown, Applications Manager of Heraeus Noblelight commented that “photonic sintering of inks offers significant benefit over conventional oven processing that requires substantially larger footprints, higher operating costs and longer processing times. For copper inks, our Heraeus Xenon Flash technology is particularly well suited as the fast processing speeds overcome the copper oxidation issues.
Click here to find out more about the sintering of metallic inks.