Published online by Cambridge University Press: 21 February 2011
Polymers used to encapsulate microelectronic devices absorb moisture – it's their nature. But only recently, with the growing use of surface mount technologies, has this phenomenon fostered concern much beyond the traditional chemical (corrosion) issues. The mechanical stability of plastic encapsulated components in use is now affected by moisture and its complex relation to interfacial adhesion and stress distributions within the package under different environmental (test) conditions. Strategies to defend against moisture-associated problems involve control of the application environment (removing moisture), improving package structural designs (increasing robustness), and managing materials choice to reduce moisture sensitivity. Each strategy has limitations, both physical and practical (economic), and all currently are being pursued. This paper will review the technical challenges, with particular emphasis on the state of affairs with regard to material development and application.