Journal of SMT Article


Authors: Sung Chul Joo, Daniel F. Baldwin, Ph.D., and Weon
Company: Georgia Institute of Technology and Samsung Techwi
Date Published: 10/30/2008   Volume: 21-4


Abstract: To evaluate the stencil printing performance of a 01005 component whose size is 200x400um, the stencil printing process has been executed using a lead-free solder (Sn3.0Ag0.5Cu). In this paper, a statistical approach was applied to the 01005 component stencil printing evaluation from model validation to inferences to examine the effect of process parameters on the solder paste release efficiency and the process capability (Cp). Through a gage repeatability and reproducibility (GR&R) study, the inspection system is found to be acceptable for measuring solder deposit volume for 01005 components. Electroformed stencil tends to be better than laser cut stencil in terms of solder paste release efficiency by 14-30% of the aperture volume with confidence level of 95%. An aperture size designed as 110% of the pad size can have the mean solder deposit volume as 89-144% with 95% confidence level. There are no differences between 90% and 100% and between 100% and 110% of aperture design in the solder paste release efficiency with at least 95% family confidence level. Based on the fractional factorial design experiment, the low print speed of 10 mm/s and the high release speed of 25 mm/s should be selected within the process levels studied in order to produce the maximum solder release efficiency of 110-129% with 95% confidence level. Finally, the process capabilities are shown to be equal for all the process factor levels considered based on the experiment performed.

Keywords: stencil printing, 01005, electroformed stencil, leadfree solder, DOE, solder paste

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