Study on the effect of addition of spherical silver nanoparticles into electrically conductive adhesives

Electrical resistance and nonlinearity of current vs. voltage characteristic of joints formed of electrically conductive adhesives modified with addition of spherical silver nanoparticles are investigated. The resistance of adhesive joints is measured using a four point method, the nonlinearity of the current vs. voltage charactristic using a modulation technique. Measurement of nonlinearity using powering of joints with the very pure sinusoidal current is discussed, too. The samples are prepared by adhesive assembly of jumpers (resistors with the “zero” resistance) of the type 1206 on a test board of FR4 covered with a copper foil with the thickness of 40 mm. Contact leads of jumpers have surface finish proper for adhesive assembly. No special surface finish of pads is used. Adhesive is applied by dispensing, jumpers are placed using a semi-automatic pick and place machine. The results of the measurement show that addition of spherical silver nanoparticles into standard adhesive does not improve neither electrical conductivity of adhesive, nor nonlinearity of a current vs. voltage characteristic of adhesive joints. The reason is increase of number of contacts in conductive net in adhesive caused by added nanoparticles