Squeegee deformation study in the stencil printing of solder pastes

We report on the results of an experimental comparison of different types of squeegee blade used in the stencil printing of solder pastes for reflow soldering in SMT, concentrating on paste heights (scooping) and printing defects. We show how our experimental results for squeegee deformation into stencil apertures lead to the construction of a model for squeegee deformation. The model takes into account the force on the squeegee due to solder paste flow and some of the non-Newtonian properties of the solder paste. An explanation is proposed for the differences in paste heights between apertures of different orientations.<
>