ICSR (Soldering and Reliability) Conference Proceedings

Characterization Of Hybrid Conformal Coatings Used For Mitigating Tin Whisker Growth

Authors: Junghyun Cho, Stephan J. Meschter, Suraj Maganty, Dale Starkey, Mario Gomez, David G. Edwards, Abdullah Ekin, Kevin Elsken, Jason Keeping, Polina Snugovsky, and Jeff Kennedy
Company: Binghamton University (SUNY), BAE Systems, Henkel Electronic Materials LLC, Bayer MaterialScience LLC, Celestica Inc.
Date Published: 5/14/2013   Conference: ICSR (Soldering and Reliability)

Abstract: A conformal coating of polyurethane (PU) consisting of hard and soft segments is being studied in an effort to prevent tin whisker penetration. For this, the coating needs to possess optimum mechanical properties by providing sufficient strength, modulus, and hardness while maintaining good ductility and toughness. Typical monolithic PU films, however, do not possess all these required properties, so silica nanoparticles are incorporated into a PU film to improve its whisker mitigation effectiveness. In the present work, nanoparticles were functionalized to bind them to the polymer structure while avoiding the agglomeration among the particles. Selection of the ideal concentration of nanoparticles is determined by establishing microstructure–property relations. Structural features at different length scales are characterized by various instruments including atomic force microscope (AFM) and scanning electron microscope (SEM) while mechanical properties are evaluated via macroscopic tensile testing as well as nanoindentation. In particular, the nanoindentation testing emulates the whisker penetration behavior by producing local deformation of PU around an indenter tip.

Key Words: 

Pb-free, tin whisker, conformal coatings, nanoparticles, polyurethane, nanoindentation

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