Design for Plastic Ball Grid Array Solder Joint Reliability

Abstract

Computational stress analysis was performed in this study to investigate the solder joint reliability of plastic ball grid array (PBGA) packages with various configurations. The packages under investigation were 27 mm body‐size, 1.27 mm ball‐pitch, perimeter PBGAs with and without thermal balls at the centre. The diagonal cross‐section of the PBGA‐printed circuit board (PCB) assembly was modelled by plane‐strain elements. The model was subjected to a uniform thermal loading and the solder joints were stressed due to the mismatch of coefficient of thermal expansion (CTE). A total number of 24 cases, involving different solder ball populations, chip sizes, and substrate thicknesses, were studied. The accumulated effective plastic strain was evaluated as an index for the reliability of solder joints. The results of this study revealed the effects of the aforementioned parameters on the solder joint reliability of perimeter PBGA assemblies. The findings are very useful for the design of plastic ball grid array packages.