Electronic packages consist of metallic, polymeric, and sometimes ceramic m
aterials as integral entities. Individual physical and mechanical propertie
s of these constituents, and their influence on each other's behavior, affe
ct the overall reliability of the electronic packages. The most common fail
ures in electronic interconnects arise from thermomechanical fatigue of the
solder joints. Mismatches in coefficient of thermal expansion (CTE) that e
xist between these constituent materials are the main cause of such failure
s. Several approaches such as alloying and composite methodology are being
explored to improve the reliability of the solder, which is metallic in nat
ure, by improving its mechanical attributes. Other avenues such as matching
the CTE of the constituent materials are also being considered. In additio
n, the metallization of the electrical components and electrically non-cond
ucting polymeric/ceramic layer to make it solderable has also been a source
of concern regarding the joint reliability. Another concern relates to the
high CTE of polymeric boards. This can cause significant CTE mismatch prob
lems if silicon chips are directly mounted on them. Some of our significant
findings in these respects are presented.