SMTA International Conference Proceedings

Fundamental Study on a Secure Printing Process Using Nanowork Stencils for 01005 Components

Authors: Stefan Härter, Jörg Franke, and Carmina Läntzsch
Company: Friedrich-Alexander University Erlangen-Nürnberg (FAU) and LaserJob GmbH
Date Published: 9/28/2014   Conference: SMTA International

Abstract: The ongoing trend of miniaturization has induced many developments towards size reduction of electronic components for highly integrated electronic products. To meet the increasing requirements on the surface mount technology each step of the process chain has to be considered as well as cross-process observations. The process of solder paste printing occupies a key position in electronics production and will be focused in this study. Based on literature, about 50 % to 80 % of all process defects originate in the stencil printing process [1–5]. Despite the exact percentage of failures the process of stencil printing needs to be characterized for miniaturized printed structures as the complexity of this process step increases using materials for high integration like fine-grained solder paste materials and stencils with small openings of the apertures.

For this study, a double-sided FR4 printed circuit board was developed that allows numerous variations within the entire process chain of assembly and interconnection technology. In previous investigations on the printing process, the solder paste types were identified as a major effect, therefore different solder paste materials will be evaluated. Various stencil foil thicknesses and aperture geometries are employed and studied. The alloy of the solder paste is a lead-free tin/silver/copper (SAC305) of type 4 as well as type 5. The stencils for the study are laser-cutted, nano-coated and optimized for small aperture geometries and aspect ratios. Aims of the experiments are findings on process windows for components of the size 01005 for a secure printing process. To give an outlook the results will be adapted for even smaller passive components as the component size of 03015mm and 008004, respectively.

Key Words: 

stencil printing, nano-coating, nanowork, transfer efficiency, area ratio, 01005, 03015mm, solder paste inspection, SPI

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