To investigate how jamming of particles in a solder paste varies as a function of the gap through which the particles flow, and to correlate this with skipping defects during the printing process.
Solder pastes with particle sizes of types 2, 3, 4 and 5 were sheared between the parallel plates of a rheometer. Jamming events that cause the solder particles to be forced against each other were detected by monitoring the electrical current flowing between the plates under a bias of 1.0 V or less. Solder paste printing trials were conducted with the same pastes, and solder paste skipping monitored.
Jamming was detected when the ratio of plate gap to largest particle diameter is reduced to a value between 3.8 and 5.0. Decreasing the gap further results in increased jamming. A strong correlation between levels of skipping and jamming was found.
More extensive printing trials are required before rheometric jamming detection can be used to predict printing performance.
The common rule of thumb used in solder paste printing that the aperture width should be no smaller than 4‐5 particle diameters is justified.
This paper presents a new technique for detecting jamming events which are too brief to be detected using normal rheometric techniques, but which have long been thought to be responsible for stochastic skipping defects during printing. Evidence supporting the link between jamming and this type of defect is presented.
Hillman, S., Mannan, S., Durairaj, R., Seman, A., Ekere, N., Dusek, M. and Hunt, C. (2005), "Correlation between jamming and skipping during solder paste printing", Soldering & Surface Mount Technology, Vol. 17 No. 4, pp. 17-26. https://doi.org/10.1108/09540910510630395Download as .RIS
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