Laser Direct-Write of Metallic Nanoparticle Inks

The combination of nanoparticle inks with laser direct-write allows the laser printing of fine electrically-conductive patterns on substrates requiring extremely low processing temperatures (< 250 degrees C). Silver lines with widths under 20 microns and thicknesses under one micron have been laser printed (using a 355 nm laser direct-write system) on polyimide substrates. These features are equivalent to those seen in typical vapor deposited and lithographically patterned thin films. Electrical resistivities of these lines in the range of 5-10 times bulk silver have been demonstrated. The low processing temperature of the nanoparticle inks also allows the laser-curing of printed silver lines without damage to the sensitive substrate. A cw 532 nm laser was used to cure as deposited silver lines with a resistivity similar to that achieved in oven-curing. This approach is ideally suited for the prototyping and short production runs of interconnects for flexible electronics, RFID antennas and OLED displays. This work will show how these nanoparticle inks are processed using laser direct-write, and will discuss the structure and electrical properties of these printed lines on polyimide substrates.