Effects of surfactant treatment of silver powder on the rheology of its thick-film paste

The effects of surfactant treatment and surface area of silver powder on the screen printability of the conducting silver pastes were investigated in the present study. The silver powders treated with both caprylic acid and triethanolamine (lots S10T2, S8T2 and S7T3) were observed to be more appropriate for thick-film paste as compared to the powders treated with a single surfactant (lots C and A) or none (lot O). The pastes prepared from lots S10T2, S8T2 and S7T3 exhibited a pseudoplastic flow and also demonstrated good screenability. The surface area (SA), rather than the tap density (TD), was observed to play a dominant role in determining the paste rheology for powders treated with the same surfactants. The pastes prepared from powders having a greater SA (5-10 x 10(3) m(2) kg(-1)) demonstrated better printability than those having a smaller SA (<5 x 10(3) m(2) kg(-1)). The influence of TD (1.7-3.5 Mg m(-3)) on paste rheology was observed to be almost negligible. Furthermore, a paste containing silver powder treated with both caprylic acid and triethanolamine as well as having a higher SA was observed to stabilize readily as far as the settling stability is concerned.