Journal of SMT Article
OPTIMIZING STENCIL DESIGN FOR LEAD-FREE SMT PROCESSING
Company: Cookson Electronics
Date Published: 1/1/2005 Volume: 18-1
Because stencil printing has such a large influence on first pass yield, and lead-free alloys exhibit different wetting properties from their lead-bearing counterparts, the authors have undertaken a study to identify stencil aperture geometries that optimize desired SMT characteristics. The concern of the lower spread of lead-free alloys on some alternate surface finishes is explored. Aperture designs that maximize pad coverage while minimizing defects like midchip solder balls are offered. In addition to aperture design guidelines, methods of optimizing the overall stencil design will be reviewed.
Key words: lead-free, stencil printing, aperture design, process control.
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