LIFT or laser induced forward transfer is a process enabling digital non-contact deposition of highly viscous conductive pastes and even adhesives and solder. This is in contract to inkjet which digital prints low viscousity inks.
The principle of operation is demonstrated in the first slide. A transparent film is coated uniformly with a thin layer of paste. When laser pulses hit a spot on the film, if the paste is correctly formulated, it will detach and land on the substrate. As such, this technique opens to way to print without mask or nozzles pattens of various viscous materials on any substrates.
The second slide shows the various materials that could be printed. The table is from IO Tech, suggesting that a wide range of off-the-shelf materials can be LIFT printed. It is of course not as straighforward as this since many parameters need to optimized, e.g., laser fluence, pulse rate, distance of film to substrate, print speed, coated film thickness, shear thinning properties of the paste, target substrate, etc, etc
I include some printed patterns from literature. These are printed straightlines using PV metallization pastes, showing that narrow linewidths as well as very high aspect ratios can be achieved. In one example, a linewidth of 65um is achieved. Note that this is below the state of production in screen printing of PV pastes (34um).
In subsequent slides, you can see various demonstrations. In these examples, solder paste is LIFT printed, adhesives are deposited, or packaging interconnects are fomed (in this example a linewidth of 20um is claimed, although we have not seen verification yet). Finally, you can see that also Ag and Cu nanoparticle inks can be formulated to be compatible with LIFT.
In general, LIFT is a intersting technology. The production is not yet fully commercialized despite the principle of LIFT being well established for some years. The latest efforts aimed at creating industrial-scale R2R machine able to print multi-materials. It will be an interesting space watch, especially if it indeed succeeds in printing ultrafine linwidths using viscous pastes digitally but at R2R speeds.
Join the TechBlick Innovations Festival (24 June 2022 | FREE | Online) to hear from Keiron Printing Technologies, a start-up in Eindhoven developing and commercialising a novel LIFT machine.
