SMTA International Conference Proceedings

The Next Big Challenge for Stencil Printing - Sub 0.5 Area Ratio Apertures

Authors: Mark Whitmore and Clive Ashmore
Company: DEK Printing Solutions, ASM Assembly Systems
Date Published: 9/28/2014   Conference: SMTA International

Abstract: Miniaturization has been a hot topic in the electronic assembly industry for a number of years now. Driven predominately by the mobile communications market, components and electronic assemblies have been continually shrinking. From a stencil printing process point of view, printing for smaller components alone is not a major issue; problems arise when trying to accommodate both small and large components on the same assembly (heterogeneous assembly). The underlying roadblock to achieving full heterogeneous assembly with existing printing techniques is todays stencil aperture area ratio capabilities. Stencil apertures with 0.5 area ratios are currently considered to represent the lower limit of the printing process.

This problem however is not exclusive to the mobile communications market. Nearly all major market segments are now experiencing a demand for an increasing range of components – just on a different scale. The underlying issue again falls back to aperture area ratio limitations in the stencil printing process.

If we are to extend the capabilities of the electronic assembly process for the increasing mix of components being experienced in the major markets today, then it is clear that existing stencil printing area ratio rules need to be pushed and broken.

This paper considers the results of two independent experiments conducted to investigate the possibilities of printing with sub 0.5 area ratio stencil apertures. The first experiment concerns a 100 micron (4mil) thick stencil application for the mobile communication market, whilst the second investigates sub 0.5 area ratio capabilities with a 127 micron (5mil) thick stencil aimed at Automotive and Industrial applications.

Key Words: 

Printing, stencil, aperture, area ratio, heterogeneous, fine pitch, transfer efficiency

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