Fracture mechanics analysis of low cost solder bumped flip chip assemblieswith imperfect underfills

Solder joint reliability of flip chip on various thickness of printed circu it board with imperfect underfill is presented in this study. Emphasis is p laced on the determination of the temperature-dependent stress and plastic strain at the corner solder joint with different crack (delamination) lengt hs. Also, the strain energy release rate and phase angle at the crack tip o f the interface between the underfill and solder mask are obtained by fract ure mechanics.