Formation of conductive silver films via inkjet reaction system

A new method is described for conductive silver film formation. An inkjet printing device with two ink channels was used to deposit silver thin films. Two inks, silver ammonia and formaldehyde solutions, were separately ejected, mixed, and reacted on glass slides. The so-called silver mirror reaction created smooth and continuous silver lines of 90 micron in width with an average film thickness of 200 nm. Surface profilometry was used to measure the thicknesses and cross section areas of printed silver lines. The electrical conductivity of the resulting silver lines is 6% of bulk silver at room temperature. After sintering at 150 degrees C for an hour, electrical conductivity was enhanced to 14%. Scanning electron microscopy (SEM) showed that the microstructure of the printed thin films consists of nanoparticle grains of 50 to 200 nanometres. Results of X-ray diffraction (XRD) and Energy-dispersive X-ray spectroscopy (EDS) further confirmed our printed films purely comprised of face-centered cubic (FCC) silver crystalline. The printed conductive lines could be used for various applications, such as embedded printed circuit boards, micro-electromechanical systems (MEMS), and radio frequency identification (RFID) tags.