Bonding SMT components via inkjet printing

March 16, 2017 // By Julien Happich
Noting that today's additive manufacturing and roll-to-roll processes for flexible electronics still lack the adequate materials and level of precision to do without discrete surface mount devices (SMD), researchers from the University of Barcelona have investigated the possibility to replace the screen-printing of reflow solder pastes, epoxies or other conductive adhesives with direct inkjet printing of a silver-based ink.

They describe their recently patented approach in the AIP Journal of Applied Physics in a paper titled "Flexible hybrid circuit fully inkjet-printed: Surface mount devices assembled by silver nanoparticles-based inkjet ink". With a 40% silver weight concentration, the AgNP ink was first used to print conductive patterns based on tracks and pads (with an average thickness of about 250nm) on different substrates, before being thermally cured in a convection oven at 150°C to evaporate the organic ink solvents and to sinter the silvernanoparticles.

Then, surface mount devices of various sizes were placed on their corresponding pads of the circuit and their SMD metallic pads were bonded with the printed pads through the non-contact deposition of an appropriate AgNP ink pattern using a high resolution drop jetting printer.