A comparison of package thermal resistance using simulation and measurement for two-layer and four-layer PBGA substrate designs

Two Xilinx PBGA packages were evaluated to undergo 4 layer to 2 layer transformation. These packages are the FG256 and FG456. Both packages are full array 1.0mm fine pitch plastic ball grid array (PBGA) packages. Converting from a four-layer package to a two-layer package has the benefit of reducing the substrate cost of the package. However, it is of interest to characterize the impact on the package thermal resistance when the four layer package designs are converted to two layer package designs. The approach of simulations through thermal modeling are utilized to characterize the thermal resistance of the two and four-layer versions of the packages as a means of evaluating the impact to thermal performance. Measurements of the PBGA packages have also been previously available and are used to verify and calibrate the accuracy of the thermal models. The results of the simulations quantifies the difference in thermal performance for the two layer and four layer variations of the substrates.