Characterization of Particle Morphology and Rheological Behavior in Solder Paste

Solder paste is an integral part of surface mount technology. An adequate understanding of its behavior and properties is essential to comprehend the relationship solder paste has to the overall manufacturing process. Techniques to characterize solder paste behavior adequately were explored. Particular emphasis was placed on characterizing solder particle size and shape as well as the viscous behavior of pastes. In all, 24 samples were characterized. Size and shape were effectively measured utilizing an image analysis technique which employs Fourier shape descriptors. The Shape Analyzer^TMwas the instrument employed. Viscous behavior was characterized over a range of shear rates. The behavior of the paste was found to fit a power law model. In addition, paste viscous behavior was found to he very complex. Metal loading and particle size affect the solder paste. The characterization schemes discussed could be adapted to the specification of solder paste parameters.