OPTIMIZING STENCIL DESIGN FOR LEAD-FREE SMT PROCESSINGAuthors: Chrys Shea and Ranjit S Pandher
Company: Cookson Electronics
Date Published: 9/26/2004 Conference: SMTA International
Because stencil printing has such a large influence on first pass yield, and lead-free alloys have different wetting properties than 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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