Engineering news
The technique could improve smart packaging and enhance wearable and flexible electronics.
Bonded circuit chips, called surface mounted devices (SMD), are electrical components that are placed directly on top of printed circuit boards. These are used in complex electrical systems such as computers and mobile phones to enable specific functions and deliver high performance.
The researchers used silver nanoparticle ink as the bonding agent, since the metal is easy to come by and the process only requires a small amount, keeping the cost low.
The silver droplets were deposited between the thin interface of the SMD chips and the circuit board, printed by an inkjet printer, flowing through a capillary in the space between. The interface behaves like the voids in a sponge, absorbing liquid into the crevice.
Creating devices at a nanoscale – smaller than 100 nanometres – can exploit surface energies for more efficient electrical conductivity. In addition, the ink allows thermal processing at lower temperatures, say the scientists.
A challenge the team faced was attempting to "do everything with the same equipment," says Javier Arrese, a professor at the department of electronics at the university.
"Our approach was to use the same machine for bonding that was used for the printed circuit. We developed several electronics circuits with inkjet printing,” Arrese added.
The technique was born out of the need for reliable and fast manufacturing methods for bonding chips, with minimum environmental impact, say the scientists. Traditionally, chips have been bonded to circuit boards using wire bonding, where a small piece of wire connects the electrical component and the circuit substrate.
The study was published in the
Journal of Applied Physics.