Fracture properties of molding compound materials for IC plastic packaging

The technique of linear elastic fracture mechanics was employed to characterize the fracture toughness of different molding compound materials. The effect of fast thermal loading rate as in a wave soldering condition was studied by performing the fracture toughness tests at different mechanical loading speeds. The effects of storage conditions and accelerated testing environments were studied by varying the test temperatures from liquid nitrogen temperature to 150°C. Models were built of 208 I/O PQFP devices with cracks in the molding compound at the corner of the die pad. These models were solved to evaluate the effect of CTE mismatches, initial flaw sizes and die pad delamination on molding compound stress intensity factors. Finite element results were then compared with crack growth measurements from PQFP packages which had been subjected to accelerated thermal cycling