Innovating the Microstructure of Polyurethane Conformal Coatings for Tin Whisker Mitigation
Authors: Junghyun Cho, Suraj Maganty, and Stephan J. Meschter Company: Binghamton University (SUNY) and BAE Systems Date Published: 9/27/2015
Abstract: We have been investigating polyurethane (PU) – based conformal coatings filled with the nanoparticles (nanosilica, nanoalumina) to mitigate tin whisker failure in Pb-free electronics. The added nanoparticles are functionalized with isocyanate, which enable them to be chemically bonded to the PU network. Agglomeration, non-uniform distribution, and defects created during processing limit the maximum nanoparticle concentration that can be added to PU matrix. In this presentation, we will discuss the effect of the matrix formulations, along with the particle concentration, type, and surface functionalization, to evaluate their impact on microstructure developments and conformal coating performance. In particular, UV curing of the coating, in lieu of traditional oven curing of solvent-based systems, not only provides significant energy savings but also impacts on environments. The potential of UV-curable polyurethane acrylate (PUA) resins in terms of microstructure and mechanical properties was thus assessed in comparison with that of PU.
polyurethane, polyurethane acrylate, conformal, coatings, lead-free, tin whisker, nanosilica, nanoalumina