Integrated flow-thermomechanical and reliability analysis of a low air cooled flip chip-PBGA package

This paper presents an integrated flow-thermomechanical and reliability analysis of a flip chip plastic ball grid array (PBGA) package under power cycling. A low air flow condition in a mixed convection environment was simulated. A cyclic chip power load of 0-3 watts with a frequency of 2 cycles per hour was applied to a 119-ball PBGA package at various air flow velocities ranging between 0.1 and 0.5 m/s. A computational fluid dynamics (CFD) model was used to determine the local heat transfer coefficients as the thermal boundary condition for finite element analysis of this power-cycled package. In reliability analysis, deformation based lifetime analysis method in conjunction with a 2-parameter Weibull statistical model was applied to estimate the thermal fatigue life and failure rate for the PBGA solder joint in the modeled package. The power-cycled PBGA has an earlier fatigue failure at the center solder joint that is contrary to the classical DNP theory. The predicted power cycling fatigue life is 1.07x to 4.87x that of temperature cycling.