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|Conformal Composite Coatings for Tin Whisker Mitigation|
|Keywords: conformal coatings, tin whiskers, pb-free|
|Pb-free electronics are more prone to exhibit tin whisker growth resulting in electrical failure. In this work, conformal composite coatings comprising moisture-cured polyurethane (PU) reinforced with nanoparticles (nano-silica) were studied to evaluate microstructures and mechanical performance, both of which strongly influence the mitigation of tin whisker growth. In addition, the properties of various UV-cured polyurethane-acrylate (PUA) coatings, due to their advantages in curing time, energy consumption, and environmental impact, were studied with the addition of nanoparticles. The effects of the curing (via moisture and UV light) and the integration of the nanoparticles into the base polymer resin network were systematically investigated. It was attempted to establish the underlying structure-property relationships to correlate enhancements in the coating properties with the nanoparticle addition. Consequently, micro- and macroscale mechanical test data were correlated with structural and chemical analyses of the coatings using SEM, TEM, and Fourier transform infrared spectroscopy. Further, this work explored the interaction of the whisker prone surfaces (i.e. tin-plated leads and surfaces) with various PU and PUA conformal coating layers. For this, the whisker mitigation performance of those coatings was tested under long-term high-temperature, high-humidity testing (85˚C/85% RH). The results will highlight critical microstructural features of the polyurethane composite coatings and the corresponding mechanical properties responsible for mitigating tin whisker growth.|
|Suraj Maganty, Student
binghamton, New York