Fast Preparation of Printable Highly Conductive Polymer Nanocomposites by Thermal Decomposition of Silver Carboxylate and Sintering of Silver Nanoparticles

We show the fast preparation of printable highly conductive polymer nanocomposites for future low-cost electronics. Highly conductive polymer nanocomposites, consisting of an epoxy resin, silver flakes, and incorporated silver nanoparticles, have been prepared by fast sintering between silver flakes and the incorporated silver nanoparticles. The fast sintering is attributed to: 1) the thermal decomposition of silver carboxylate-which is present on the surface of the incorporated silver flakes to form in situ highly reactive silver nanoparticles: 2) the surface activation of the incorporated silver nanoparticles by the removal of surface residues. As a result, polymer nanocomposites prepared at 230 degrees C for 5 min, at 260 degrees C for 10 min, and using a typical lead-free solder reflow process show electrical resistivities of 8.1 x 10(-5), 6.0 x 10(-6), and 6.3 x 10(-5) Omega cm, respectively. The correlation between the rheological properties of the adhesive paste and the noncontact printing process has been discussed. With the optimal rheological properties, the formulated highly viscous pastes (221 mPa s at 2500 s(-1)) can be non-contact-printed into dot arrays with a radius of 130 mu m. The noncontact printable polymer nanocomposites with superior electrical conductivity and fast processing are promising for the future of printed electronics.