Thermal aging of laminate materials and the maximum use temperature of organic packages

The assessment of package reliability is often based on finite element models which typically use properties of materials that have undergone only a standard cure treatment which often amounts to exposure to elevated temperatures for a few hours. Today's applications however often require packaging materials to be exposed to use temperatures for thousands up to 100, 000 power on hours (POH). Yet, the reliability of components for such applications is evaluated after exposure to use temperatures for only a few hundred to a few thousand hours. The change in material properties during prolonged exposure to power-on conditions is generally neglected. In this paper we discuss the changes in the mechanical behavior upon thermal aging of typical packaging materials such as solder masks and build up materials. We also describe methods that allow an assessment of the maximum continuing use temperature of packages containing such materials.