Reliability of electronic devices containing epoxy resins

Abstract

Epoxy resins, because of their favorable balance of properties including high adhesion and strength, and resistance to heat, chemicals and moisture, along with low shrinkage and dielectric constant, have been widely used in the packaging of electronic circuits containing silicon die, typically IC's, to achieve high reliability. Thus, conductive adhesives have generally replaced solder for die attach. When the more compact flip chip is used, the thermal cycling failure time can be extended by epoxy resin encapsulation. Further, although die coatings have been applied using many types of polymers, which may excel an epoxy resin based coating in any one property, epoxy resin based coatings should provide higher reliability due to their better property balance. In addition, except for extreme conditions (such as very high temperatures), lower cost post-molded epoxy resin based encapsulations are as reliable as hermetic packages. This it shown by many studies of field results as well as by predictions using environmental stress testing. Even lower cost as well as decreased size, while maintaining the reliability comparable to hermetic devices, appear possible through an epoxy resin based upgraded glob top process. It is shown that epoxy resin glob top encapsulations can be formulated to easily exceed 1000 hs. in 85/spl deg/C/85% RH testing. Studies demonstrating the reliability of epoxy resin based surface mount placement and lead bonding adhesives are discussed. Thus lower cost, yet highly reliable, electronic devices can be manufactured through the use of formulations based on epoxy resins.<>