The effect of wall-slip formation on the rheological behaviour of lead-free solder pastes

Durairaj, R., Man, Lam Wai, Ekere, N.N. and Mallik, S. (2010) The effect of wall-slip formation on the rheological behaviour of lead-free solder pastes. Materials and Design, 31 (3). pp. 1056-1062. ISSN 0261-3069

Abstract

Wall-slip plays an important role in the flow behaviour of solder paste materials. The wall-slip arises due to the various attractive and repulsive forces acting between the solder particles and the walls of the measuring geometry. These interactions could lead to the presence of a thin liquid layer adjacent to the wall, which causes slippage. The aim of this study is to investigate the influence of the solder paste formulation on wall-slip formation and its effect on the printability of these pastes material. A wall slip model is utilised to calculate the true viscosity and slip velocity for the lead-free solder pastes samples used in this study. The difference in the measured viscosity and the true viscosity could indicate wall-slip formation between the solder pastes and the parallel plate. Sample P1 showed a higher slip velocity compared to sample P2. The slip velocity calculated for the solder pastes could be used as a performance indicator to understand the paste release characteristics in the stencil printing process.

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