New electronic packaging technologies, such as the use of ultra-fine pitch components and especially the introduction of chip-scale packaging(CSP) technology, are pushing the industry toward 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 shape design and the stencil manufacturing process.
A better understanding of how these parameters affect the printing process may be achieved through set of controlled experiments using different conditions.
This paper describes a methodology used to evaluate aperture shape and sizes, squeegee speed, deposit times, pattern array type. Data collected included printing defects and solder paste volume.
Printing method using air pressure difference is devised to ensure high transfer efficiency and low standard deviation of transfered paste. It is shown that printing method using air pressure difference is very successful in fine pitch printing as well as conventional printing.
Ball shear test was conducted. Ball shear test parameter including stylus speed and height was characterized and correlated to the corresponding shear loading curves.
