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

A computational parametric study on the solder joint reliability of a plast ic ball grid array (PBGA) with solder bumped flip chip (FC) is presented. T he basic configuration of the PBGA is 27mm package size and 1.27mm ball-pit ch. There were three kinds of bail population: four-row perimeter grid arra y with/without thermal balls, and full grid array. A total number of 24 cas es, involving various chip sizes, chip thicknesses and substrate thicknesse s, were studied. The diagonal cross-section of the PBGA-printed circuit boa rd (PCB) assembly was modeled by plane-strain elements and was subjected to uniform thermal loading. Through mismatch of coefficient of thermal expans ion (CTE), and lack of structural compliance, the solder joints were stress ed to produce inelastic deformation. The accumulated effective plastic stra in was evaluated as an index for the reliability of solder joints. The pres ent study revealed the effects of aforementioned design parameters on the s older joint reliability of FC-PBGA assemblies. Some peculiar phenomena were identified.