The study of the response of solder pastes under sinusoidal vibration

Solder paste is a dense suspension (volume fraction of about 50%) of spherical solder alloy particles in a flux/vehicle system. It is known to exhibit viscoelastic properties and under oscillatory shear, the dynamic viscosity has been shown to decrease as the shear frequency increases. This paper presents experimental results of the effect of sinusoidal vibration on solder paste, and its impact on the performance of the paste printing process. In the first experiment, the solder paste sample was horizontally vibrated inside a cylindrical container. Observations of the sample following vibration showed that a thin liquid rich layer was formed on the surface and at the interface between the container and the paste. In the second experiment the sample was placed on a flat plate and as the plate moved towards a vibration squeegee, the sample was pushed by the squeegee blade to produce a paste roll. In both experiments, the vibration frequency and amplitude were varied to observe their effect.