Use inkjet printing components instead of solder paste printing + SMT form

[Chinese Packaging Network News] Spanish researchers use silver ink-based inkjet printing instead of reflow solder paste, epoxy resin or other conductive adhesive stencil printing, bonding SMD components...

Researchers at the University of Barcelona in Spain pointed out that the current manufacturing and roll-to-roll (R2R) processes used in flexible circuit manufacturing still lack adequate materials and precision, making it impossible to install components without separate surfaces ( SMD). Researchers continue to explore various possibilities and expect to use silver ink-based inkjet printing instead of stencil printing that must use reflow solder paste, epoxy or other conductive adhesives...

The researchers published in the "Applied Physics" journal "Flexible Hybrid Circuit Complete Inkjet Printing: Surface Mount Devices assembled with silver nanoparticles". The patented approach is described in silver nanoparticles-based inkjet ink. Firstly, silver nanoparticles (AgNP) are mixed with silver at a concentration of 40%, conductive patterns are printed on different substrates according to the track and the pad, then thermally cured in a convection oven at 150° C., and the organic ink solvent is evaporated, and sintered. Silver nanoparticles.

Then, various sizes of surface mount components are placed on the corresponding pads of the circuit, and the SMD metal pad and the printed solder are bonded via a non-contact deposition of the AnNP ink pattern using a high-resolution droplet jet printer. plate.

This printing technique can selectively deposit a few litres of ink in a non-contact process without the need for masks and vacuum systems. This selective deposition uses capillary action (wetting ink water between the SMD and the pad) and prevents material waste.

Using solder paste or epoxy instead of screen printing, the researchers stated that this method uses much less material, even though it is based on silver ink, but it is more cost-effective. After a low-temperature heat treatment at 150°C, the agglomerated silver nanoparticles can interconnect with silver to achieve a strong bonding force of 98%.

According to the research report, the AgNP bonding method using ink jet printing has the electrical and mechanical properties equivalent to that of assembling materials to several ink printing flexible substrates, including paper, polyimide Kapton and rigid glass, in SMD and printing welding. A uniform and undetectable contact is formed between the pads.

This bonding approach is compatible with the roll-to-roll process and is particularly well-suited for manufacturing flexible hybrid electronic circuits with high densities and requires rapid assembly up to 6m/s.