This article provides a review of the attitude of the scientific community
towards reliability in electronic packages, with emphasis on the prevailing
mechanisms for package failure under highly stressed environmental conditi
oning. Once this failure mechanism is fully developed, approaches to the re
solution can be more rigorously applied. Overall, the predominant evidence
points to moisture, both diffusivity and equilibrium weight gain, as the ke
y factor in reduced reliability performance. Other fundamental polymer prop
erties are important, but generally, methods are well established for adjus
ting these parameters. Moisture uptake is somewhat inherent to a particular
chemistry type and this can direct the use of resin systems that are more
suited to particularly moist Epoxy resin systems, while pervasive in the el
ectronics industry, environments. do have limitations under humid environme
ntal test conditions. Cyanate ester resin chemistry is claimed to have low
moisture uptake by virtue of a non-hydrophilic cure mechanism. However, cer
tain aspects of the cure chemistry and side reactions with water can result
in misleading predictions on humid environment performance. Siloxane-based
materials present an attractive solution to many moisture related issues.
Traditional condensation and addition cure silicone systems have, thus, fou
nd widespread use as packaging adhesives and encapsulants. Siloxane-functio
nal polyimides have also been successfully utilized in a number of applicat
ion areas. Relatively new siloxane/hydrocarbon resins, developed specifical
ly for electronics applications, further address the shortcomings of classi
c silicone adhesives and coatings.