Hygrothermal stress analysis of a plastic ball grid array package during solder reflow

Abstract

This study investigated how the internal temperature and moisture of a plastic ball grid array (PBGA) package affect interfacial hygrothermal stresses (primarily peeling and shear stresses) during solder reflow. Two-dimensional finite element analysis was applied to evaluate temperature distribution, moisture diffusion and hygrothermal stresses inside the PBGA package. A series of popcorn experiments on PBGA packages was carried out to verify the accuracy of the finite element model. The design parameters of the PBGA package were varied to assess their effect on hygrothermal stresses at the interfaces. Moisture absorption and desorption experiments on the PBGA packaging materials were conducted in a hygrothermal chamber and an oven, to obtain moisture diffusivity data and saturated moisture contents of PBGA packaging materials. Results in this study can be applied to optimize the design parameters of the PBGA package and thus reduce interfacial hygrothermal stresses during solder reflow.