SMTA International Conference Proceedings


Authors: Michael Rösch, Prof. Dr.-Ing. Jörg Franke; Carmina Läntzsch, Georg Kleemann
Company: Institute FAPS, University of Erlangen-Nuremberg; LaserJob GmbH
Date Published: 10/24/2010   Conference: SMTA International

Abstract: The stencil printing process in electronics production asks for permanent optimization because of its sensitivity to process defects like solder paste bridges, insufficient or even missing solder paste. The performance of the stencil technology within the printing process contributes significantly to the productivity and the quality of this important and complex process.

The paper presents the new and innovative technology of nano-coated stencils. This includes the coating process and the coating material as well as the resulting stencil characteristics and the potentials of the nano-coated stencil for the printing process. The nano-coating is an innovative finishing technology to improve the stencil performance. The production takes place by a so called sol-gel process, a unique process with an economical possibility to realize a permanent and functional coating on the stencil surface. The nano-coating that covers the aperture walls and the stencil bottom side provides a hydrophobic characteristic with the consequence of a reduced adhesion between stencil surface and solder paste. The potentials of nano-coated stencils are illustrated on the basis of extensive printing experiments. On the one hand nano-coated stencils show less paste residues on the stencil bottom side with the consequence of significantly decreased stencil cleaning intervals. This leads to higher line efficiency and a reduced consumption of cleaning material. On the other hand the improved release behavior results in higher transfer efficiencies, especially for apertures with a critical area ratio. With regard to the stencil design, the area ratio of nano-coated stencils can be reduced down to a value of approximately 0.4. Both effects of nano-coated stencils contribute to a very robust and economical printing process.

Key words: Stencil Printing, Nano-Coated Stencil, Area Ratio, Transfer Efficiency.

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