'Changing the Rules of Stencil Design' at SMTAI

Do nano coatings applied to solder paste stencils really make a noticeable improvement on the solder paste printing process? The effect of nano coatings on solder paste print performance was investigated for the presentation, with transfer efficiencies being studied across aperture sizes ranging from 0.300 to 0.800 area ratio. The effects of nano coatings on transfer efficiencies of tin-lead, lead-free, water soluble, no-clean and type 3, 4 and 5 solder pastes was also studied. For each nano coating, solder paste print performance has been summarised with respect to all of these variables.

For acceptable transfer efficiency, industry standards for stencil aperture design indicate that area ratios be kept above 0.66. This is designed to ensure that solder paste volume is adequate for an acceptable process window. However, nano coatings are changing this rule: based on the performance of nano coatings, guidelines for stencil design are recommended.

A 20 year electronics industry veteran, Lentz has extensive experience performing research and development, quality control, and technical service with products used to manufacture and assemble PCBs. He holds B.S. and M.B.S. degrees in chemistry.