Conference Program - LOPE-C 2011

SCIENTIFIC CONF. | THURSDAY-JUNE 30, 2011
Track 4
Systems and Implementation Issues (02:30 pm - 04:00 pm) | LOCATION HARMONIE D / LEVEL C2
03:40 pm Binary clock with interactive function on flexible paper substrate
Dr Thomas Knieling,
Fraunhofer ISIT, Scientist, Germany
In this paper we present a binary clock demonstrator on flexible paper substrate whose conductive lines where printed in a low invest inkjet printing process (Fig. 1 left).
The low voltage (5V DC) driven clock is adjustable by simply touching printed electrodes on the carrier surface. The binary encoded time is shown by a LED display.
For printing a common EPSON Inkjet printer C88+ was used. The used ink consists of silver particles with average diameters of about 55 nm disperged in an ethylene
glykol based solution. The silver lines where printed at room temperature on photo paper substrates and afterwards cured at 100 °C for 2 h, where solvent residues were
brought out and silver particles were sintered. The obtained conductivity was then 2,9 ± 0,2 Sm/mm². For fixing common SMD electronic parts a conductive epoxy adhesive
containing silver particles was used and cured at 80 °C for 3 h after deposition. Thus the whole production process is limited to low temperatures suited for cheap subtrate
materials like paper, PET or PEN.
The printed lines withstand about 64000 bending cycles with bending radii of 1 cm. Afterwards small cracks with resistances increased from 100 Ohm to about 20 MOhm
are observed (Fig. 1 right). Glue connections between components and silver surfaces should be covered by protection layers.
Since only office printing equipment is used the invest is at least two magnitudes lower than for industrial print head systems. However, printing resolution is limitied to
about 0,2 mm. This is sufficient for fast evaluation of simple systems but will hardly be usable for printing highly integrated circuits or electronics parts like resistors or
capacitors where exact geometric features are demanded. Thus main advantages of this technique lie in its low price, simple installation and in its layout flexibility. Low
invest rapid prototyping of low or medium standard electronic devices will be the main application area of this process.
04:00 pm COFFEE BREAK
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