Predicting printability of WSPs through rheological characterization

Abstract

Water soluble fluxes and pastes contain a high percentage of free acids that increase the activation level and subsequently enhance solderability, but do not contain resins. A method was developed that can be used to predict the printability of a water soluble solder paste. Since a solder paste shear thins and exhibits a yield point during actual printing (paste flow) these two parameters were measured and then correlated to the resultant paste print performance on more than 40 different lots of paste. The measurement techniques used for the in-depth rheological characterization as well as the viscometers employed are discussed in detail.<>