Effects of underfill delamination and chip size on the reliability of solder bumped flip chip on board

The reliability of solder bumped flip chip on printed circuit board (PCB) with a perfect underfill encapsulant has been demonstrated by many researchers. In this study, the effects of delamination crack between the underfill encapsulant and the solder mask on the reliability of solder bumped flip chip on PCB are investigated by a fracture mechanic method. Emphasis is placed on the effects of chip size on the solder joint reliability of flip chip on PCB with perfect and imperfect underfills and without underfill. The energy release rates at the crack tip between the underfill and the solder mask and the inelastic temperature-dependent stress and strains at the corner solder joint for all the cases considered are provided for a better understanding of the thermal-mechanical behavior of the perfect and imperfect underfilled flip chip assemblies.