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 gr id array package assembly is presented and a critical deformation mode is i dentified. The experimental data, documented white cooling the assembly fro m the underfill curing temperature to -40 degreesC, clearly reveal the effe ct of the constraints from the chip and the PCB on the global behavior of t he 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 s ubstrate behavior on the second-level solder ball strains, An extensive par ametric study is conducted to identify the most critical design parameter f or optimum solder ball reliability.