Rheological characterization of solder pastes

Solder paste is the strategic material for the electronic card assembly process, based on the surface mounting technology. The paste is a concentrated suspension (50% of volume) of metallic powder in an organic continuous phase and its screening on the printed circuit board is the first operation of the assembly. The result of the screening depends strongly on the rheological characteristics of the solder paste but, nevertheless the research activity on this material is so far very poor. In this paper, an analytical procedure for the rheological characterization is given and the most important rheological parameters, affecting the screening performance, are shown.