Electrical Performance Comparison between fcBGA and eWLB Packages

Wafer-level packages, such as embedded-Wafer-Level-Ball-Grid-Array (eWLB) packages, can provide smaller form-factors and thinner profiles, as finer design rules on W/S, and thinner layers (both metal layers and passivation layers) can be applied in such packages. However, a routine conversion from fcBGA to eWLB does not guarantee the electrical performance will be the same. Designer's electrical skills still play important roles to reduce design cycle-time for meeting critical electrical performance. We compare the performance from typical fcBGA and eWLB packages in the following areas: insertion-loss for signal nets, power-ground impedance for P/G nets, and cross-talk for both signal nets and P/G nets. Simulation data for both fcBGA and eWLB, along with some experimental data, is provides in the paper. As metal-layer thickness (4um-12um) in eWLB is typically smaller, and finer design rules are used, the cross-section of a signal trace is smaller, which translates a higher metal-loss in unit- length. In a...