SMTA International Conference Proceedings


Author: Jeff Kennedy
Company: Manufacturers' Services
Date Published: 9/12/1999   Conference: SMTA International

Abstract: New technologies, such as the use of ultra-fine pitch components and especially the introduction of chip-scale packaging (CSP) technology, are pushing towards smaller aperture sizes and the use of thinner stencils for the solder paste printing process. Understanding of solder paste print performance is vital to achieving an appropriate solder paste volume with high repeatability.

Solder paste print performance is affected by many parameters, including stencil thickness, stencil area ratio, solder paste particle size, aperture shapes design and the stencil manufacturing process.

A better understanding of how these parameters affect the printing process may be achieved through a controlled experiment using different stencil designs and different solder pastes.

This paper describes the methodology used to evaluate several different stencil fabrication methods, aperture sizes and thickness and different solder pastes. Data collected included the number of defects and measurement of solder paste volume and height. Statistics have been used for the analysis of quantitative data.

Results from this evaluation have been critical in the success of a new process for CSP assembly in a standard SMT environment. Also, stencil design and solder paste selection for other applications have benefited from the conclusions of this study.

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