Characterization of warpage of flip-chip PBGA package and its effect on solder joint reliability

Far infrared Fizeau interferometry is employed to characterize thermally-induced warpage behavior of a FC-PBGA package and its assembly. A whole field warpage information including the chip and substrate are documented while the package and the assembly are cooled to -40 degrees C. The results delineate the effect of the constraints from the chip and the PCB on the global behavior of the substrate after the package is mounted on the PCB. An experimentally verified 3-D non-linear FEM analysis proceeds (1) to quantify the effect of the substrate deformation on the solder ball strains and (2) to conduct a parametric study to identify the most critical design parameter for optimum solder ball reliability.