The evolution of paste pressure during stencil printing

Author: Clements David J.   Desmulliez Marc P.Y.   Abraham Eitan  

Publisher: Emerald Group Publishing Ltd

ISSN: 0954-0911

Source: Soldering & Surface Mount Technology, Vol.19, Iss.3, 2007-07, pp. : 9-14

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Abstract

Purpose ‐ The objective of this investigation is the derivation of a mathematical model that describes the pressure characteristics of paste during the stencil printing process. This model is intended to generalise a qualitative understanding of these effects using squeegees that can be curved but otherwise are standard in design. Design/methodology/approach ‐ This is an analytical treatment of the paste behaviour from the foundations of continuity of fluid flow and shear stresses that are imparted by the squeegee blade movement. Findings ‐ An equation is obtained that profiles the pressure generated by the squeegee movement which, for the case of a linear squeegee, shows very good agreement with predicted pressure profiles using experimental data. Practical implications ‐ This model provides a theoretical framework for a better understanding of how to overcome the failure modes inherent in stencil printing, such as over- or under-filled stencil cavities. Originality/value ‐ This is a generalisation of a previously developed mesh printing model. It goes beyond flat squeegee designs to describe the printing process when the blade and stencil are in contact. In addition, it encompasses non-Newtonian fluid behaviour.