Y.W. Zeng

Development of a novel isotropic conductive adhesive filled with silver nanowires

As an alternative to lead-bearing solder, isotropic conductive adhesives (ICA) have been utilized for many years in microelectronic packaging. ICAs filled with conductive particles generally show high initial contact resistance, unstable contact resistance, and inferior impact strength. In this study, silver nitrate (AgNO3) is used as a precursor, N, N-dimethylformamide (DMF) as a solvent and reducing agent for preparing silver (Ag) nanowires in the nanoporous templates formed by the controlled hydrolysis and condensation of butyl titanate (Ti(OC4H9)4). Fundamental material characterizations including X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) are conducted on these Ag nanowires. A novel ICA is developed by using Ag nanowires as conductive fillers. Electrical and mechanical properties are investigated and compared with that of conventional ICA filled with micrometer-sized Ag particles or nanometer-sized Ag particles, the average diameter of these Ag particles is about 1 mm and 100 nm, respectively. It is found that at a lower filler content, the ICA filled with Ag nanowires exhibited lower bulk resistivity and higher shear strength than ICA filled with micrometer-sized Ag particles or nanometer-sized Ag particles. Possible conductive mechanism of the new ICA is analyzed.

Blue emission of Ge nanocrystals prepared by thermal decomposition

We report here a simple synthesis method for monodisperse Ge nanocrystals by thermal decomposition of precursor TOG at 360 °C, which is obtained by a reaction of GeCl4 with oleylamine at room temperature. The effect of refluxing time on the average dimension of Ge nanocrystals is discussed. Fundamental characterizations including HRTEM and XRD were performed on these Ge nanocrystals. FTIR, DSC and TG were used to explain the mechanism of formation of Ge nanocrystals by thermal decomposition of TOG. Ge nanocrystals with average grain sizes clearly exhibit blue emission, which might result from the hydrocarbon absorbed on the surface Ge nanocrystals, the amorphous oxide layer on the surface of Ge nanocrystals and/or defects in Ge nanocrystals.