Polyurethane-Based Electronic Packaging: The Characterization of Natural Aging over a Decade

Electronic devices with polyurethane electronic packaging have been stored in Chinese tropical marine atmosphere environments for 10 years. The long-term natural aging mechanism was studied by comparing the appearance inspection, molecular structure, elemental content, and chemical functional groups of the surface and interior of polyurethane electronic potting. The results indicated that, despite evident chemical aging and physical changes in the encapsulant material, it continued to effectively protect the internal electronic devices, maintaining their performance within an acceptable range. The interior polyurethane potting of electronic devices was white, but the surface turned yellow with noticeable color change. On the surface, the content of tolylene diisocyanate was greatly decreased. The peak heights of the internal carbamate groups located at 1708 cm^-1 and 1529 cm^-1 were significantly higher than those at the surface. In addition, the internal C element content for the carbamate group at 289.5 eV was higher than that of the surface. It can be inferred that, under ambient temperature and trace oxygen conditions, the urethane groups on the polyurethane electronic potting surface undergo aging reactions. These groups slowly oxidize into the quinoid structure of the chromophore, causing the surface to turn yellow. Despite this discoloration, the potting still protects electronic devices. Therefore, polyurethane electronic potting is ideal for the long-term sealed storage of electronic devices.