SMTA International Conference Proceedings


Authors: Chrys Shea, Greg Wade, Esse Leak, and Ron Tripp
Company: ALPHA - A Cookson Company
Date Published: 9/25/2005   Conference: SMTA International

Abstract: Electronic device footprints continue to shrink, requiring smaller and smaller solder deposits to be consistently produced during the stencil printing process. The transition to lead-free assembly also creates tighter process windows, due to the alloys’ lower spread characteristics. This situation represents a dual challenge for assemblers: not only is development work required to meet miniaturization trends; more is required to understand the behavior of lead-free solder materials.

Stencil printing research over the past four years has aided in demystifying the printing process by understanding the influence of the stencil manufacturing process, providing models to predict actual volumes of fine features, improving stencil-PWB alignment, maintaining stencil aperture libraries, and maximizing lead-free cosmetics and yields. The most recent research has been focused on improving fine feature prints on boards that require thick stencils and modeling transfer efficiencies of modern pastes.

Key words: Stencil printing, transfer efficiency, fine features, aperture design, MicroStep pockets, lead-free

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