All smart electronics in products such as wrist-wearable computers are on a rigid board under the face of the watch. The roll-to-roll technique enables electronics to be printed on a plastic or elastomeric foil, which has various benefits such as thinness, lightness, elasticity and transparency. In hybrid-integrated systems, separate components are mounted on a printed electronic foil, after which the foil can be overmolded with thermoplastic or thermoplastic elastomer, using the injection-molding process.
"For the wristband demo, we performed all of the key manufacturing stages for printed hybrid systems - the printing of conductors, the assembly of semiconductor LEDs and the overmolding - using the roll-to-roll technique. This enables the mass manufacture of small-sized, easy-to-use, flexible electronics in a cost-effective manner," says Sami Ihme, senior scientist.
In practice, the roll-to-roll overmolding of a printed electronic foil involves feeding a LED foil with a foil-feeder into a mold, in which the overmolding is done. This technique is normally used to decorate plastic for various consumer products. However, the manufacture of flexible electronics -- in place of graphics -- involves feeding electronics with a range of electrical and optical features into a mold.
"The results have been promising. In the first test run for the overmolding of 186 LEDs, we achieved a 100% yield," explains Ihme.
VTT Technical Research Centre of Finland is now seeking product companies interested in trying this new technology to create new product concepts for the market.