Solder joint reliability of cavity‐down plastic ball grid array assemblies

Abstract

A computational model was established in this study to simulate cavity‐down plastic ball grid array (PBGA) assemblies. Stress analysis was performed to investigate the solder joint reliability of a PBGA‐PCB (printed circuit board) assembly. The packages under investigation had two different body sizes and two kinds of ball population. The diagonal cross‐section of the assembly was modeled by plane‐strain elements and was subjected to a uniform thermal loading. The solder joints were stressed due to the mismatch of the assembly’s coefficient of thermal expansion (CTE). The accumulated effective plastic strain was evaluated as an index for the reliability of solder joints. Effects on solder joint reliability such as package size and ball population were identified. Furthermore, it was found that, unlike conventional PBGA assemblies, the outermost solder ball has the highest plastic strain for all cases in the present study. This peculiar phenomenon was further discussed with the consideration of package deformation.