Numerical investigation on the effect of solder paste rheological behaviour and printing speed on stencil printing

Krammer, Olivér and Al-Ma’aiteh, Tareq Ibrahim and Illés, Balázs and Bušek, David and Dušek, Karel (2020) Numerical investigation on the effect of solder paste rheological behaviour and printing speed on stencil printing. Soldering & Surface Mount Technology, 32 (4). pp. 219-223. ISSN 0954-0911

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Abstract

Purpose of this paper was to investigate the effect of different viscosity models (Cross and Al-Ma’aiteh) and different printing speeds on the numerical results (e.g., pressure over stencil) of a numerical model regarding stencil printing. A finite volume model was established for describing the printing process. Two types of viscosity models for non-Newtonian fluid properties were compared. The Cross model was fitted to the measurement results in the initial state of a lead-free solder paste, and the parameters of a Al-Ma’aiteh material model were fitted in the stabilised state of the same paste. Four different printing speeds were also investigated from 20 to 200 mm/s. Noteworthy differences were found in the pressure between utilising the Cross model and the Al-Ma’aiteh viscosity model. The difference in pressure reached 33–34% for both printing speeds of 20 and 70 mm/s, and reached 31% and 27% for the printing speed of 120 and 200 mm/s. The variation in the difference was explained by the increase in the rates of shear by increasing printing speeds. Parameters of viscosity model should be determined for the stabilised state of the solder paste. Neglecting the thixotropic paste nature in the modelling of printing can cause a calculation error of even ~30%. By using the Al-Ma’aiteh viscosity model over the stabilised state of solder pastes can provide more accurate results in the modelling of printing, which is necessary for the effective optimisation of this process, and for eliminating soldering failures in highly integrated electronic devices.

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