Stencil Printing Yield Improvements
The wipe sequence, wipe frequency and wipe solvent and how these interact to provide solder paste printing yield improvement is studied.
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Authored By:
Mike Bixenman, D.B.A
Kyzen, Nashville, TN, USA
Debbie Carboni
Kyzen, Nashville, TN, USA
Jason Chan
Kyzen Asia
Summary
Stencil printing capability is becoming more important as the range of component sizes assembled on a single board increases. Coupled with increased component density, solder paste sticking to the aperture sidewalls and bottom of the stencil can cause insufficient solder paste deposits and solder bridging. Yield improvement requires increased focus on stencil technology, printer capability, solder paste functionality and understencil cleaning.
The wide range of required solder paste volume deposited on mixed technology assemblies is pushing traditional stencil design rules to their limit. There is a need for improved stencil, printing and materials technologies to increase the consistency of the deposit. Cleaning the underside of the stencil is a critical enabler to yield improvement.
The purpose of this research is to study the wipe sequence, wipe frequency and wipe solvent(s) and how these factors interact to provide solder paste printing yield improvement.
Conclusions
Understencil wiping has gained an increase in interest over the last several years. Changes in circuit designs, such as miniaturized components, increased density of components, and new stencil technology need to decrease print defects as well as changes in and increased attention to employee safety and environmental regulations have driven renewed interest.
Initially Published in the SMTA Proceedings
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