Influence of surfactants treatment on silver powder and its thick films

Thick film pastes have very high viscosities to retain the particles in suspension. The effects of surfactant treatment and the particle size of the silver powder on the screen printability (i.e. rheology, thixotropy, etc) and sintering of silver conductor paste have been investigated in this study. The variation in the rheology and sintering microstructure has been found to depend upon the type of surfactant treatment of the powders and their particle size. The paste prepared from silver powder treated with triethanolamine and caprylic acid exhibited a pseudoplastic flow and also demonstrated good screenability and better densification in both dried films as well as fired films as compared to those not treated with surfactants. The prepared powders consist of either separated particles or loose agglomerates, which get wetted and dispersed by the organic vehicle, forming a suspension displaying pseudoplastic behaviour. The powders with nanoscale size (100-200 nm) can be considered appropriate for effective thick film applications. Microstructure evolution after firing at 850 degreesC has been studied by examining the morphology and sheet resistance of the thick films. (C) 2003 Elsevier Science B.V. All rights reserved.