NEPCON West - Fiberoptic Expo Conference Proceedings


Authors: Neil Poole, Ph.D. and Brian J. Toleno, Ph.D.
Company: Henkel Loctite
Date Published: 12/3/2002   Conference: NEPCON West - Fiberoptic Expo

Abstract: High-speed placement of components in doubled sided electronics assembly requires high-speed, reproducible, methods of placing surface mount adhesive deposits. Stencil printing these adhesives is a viable option, as long as the user understands the behavior of these materials under a variety of conditions. This paper presents the results of viscosity and stencil printing behavior of three different surface mount adhesives, with different viscosity characteristics.

This investigation was divided into 3 distinct parts: Viscosity characterization, Print characteristics and Deposit analysis. The viscosity profile of each of the materials evaluated was measured in the laboratory to confirm that the material was within specification and to help identify key performance relationships. This data was used to determine the yield point values using the Casson model. Various print performance characteristics were observed during the stencil printing process.

Finally the resulting deposit profiles were measured using acoustic microscopy to determine how the print conditions affect the deposit profile. The correlations between yield point, clean print vs., flood print, and printing speed with respect to deposit height were determined.

Key words: SMA, surface mount adhesive, stencil printing, yield point.

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