A study on the creep damage of epoxy molding compound in IC package

Abstract

The thermo-mechanical reliability of epoxy molding compound (EMC) is a main concern for the electronic industry. In order to investigate creep-induced damage in packaging polymers, creep tests of EMC were carried out. The fracture surfaces of the specimens were analyzed by scanning electron microscopy to investigate the creep failure microcosmic mechanism. A modified Lermaitre creep damage model was used in a first attempt to describe creep damage of the EMC. The effect of multiaxial stress state was considered by the triaxial parameter R/sub v/. Finally, an FEM model of a QFP package was set up, and the creep damage model was used to analyze the creep damage of the EMC in the IC package. The results show that the EMC creep behavior can be characterized as primary, secondary, and tertiary creep, and volume damage is done before the cracks propagate by void coalescence which involves further ductile matrix deformation (micro-banding), and this mechanism leads to a rough zone of sub-critical crack growth. The creep lifetime obtained by the creep damage model agrees with the experimental results well at relatively low stress levels, but at higher stress levels, it does not do well.