On the design parameters of flip-chip PBGA package assembly for optimum solder ball reliability

An experimental investigation of the warpage of a flip-chip plastic ball grid array package assembly is presented and a critical deformation mode is identified. The experimental data, documented while cooling the assembly from the underfill curing temperature to -40/spl deg/C, clearly reveal the effect of the constraints from the chip and the PCB on the global behavior of the substrate. The constraints produce an inflection point of the substrate at the edge of the chip. An experimentally verified three-dimensional (3-D) nonlinear finite element analysis proceeds to quantify the effect of the substrate behavior on the second-level solder ball strains. An extensive parametric study is conducted to identify the most critical design parameter for optimum solder ball reliability.