Solder joint reliability of plastic ball grid array with solder bumped flip chip

A computational parametric study on the solder joint reliability of a plastic ball grid array (PBGA) with solder bumped flip chip (FC) is presented. The basic configuration of the PBGA is 27mm package size and 1.27mm ball-pitch. There were three kinds of bail population: four-row perimeter grid array with/without thermal balls, and full grid array. A total number of 24 cases, involving various chip sizes, chip thicknesses and substrate thicknesses, were studied. The diagonal cross-section of the PBGA-printed circuit board (PCB) assembly was modeled by plane-strain elements and was subjected to uniform thermal loading. Through mismatch of coefficient of thermal expansion (CTE), and lack of structural compliance, the solder joints were stressed to produce inelastic deformation. The accumulated effective plastic strain was evaluated as an index for the reliability of solder joints. The present study revealed the effects of aforementioned design parameters on the solder joint reliability of FC-PBGA assemblies. Some peculiar phenomena were identified.