Analyses of Via-In-Pad Plated Over (VIPPO) and Dogbone in Fanout Routing High-Density Interconnects

The via-in-pad plated over (VIPPO) and the dogbone fanout structures for high-density interconnects are modeled and their high frequency performances are compared. Signal integrity (SI) metrics such as impedance matching, signal loss and crosstalk are analyzed. Compared to the traditional dogbone fanout, the VIPPO fanout features broader impedance matching bandwidth and reduced noise coupling length due to the removal of the parasitics from the dogbone. The SI benefits of the VIPPO vs. the dogbone fanouts are verified further with the eye diagram simulation in channel configurations of a back-to-back module-level channel and a 12dB-loss chip-to-chip system channel. It is shown that the VIPPO structure significantly improves the RMS jitter noise (similar to 40% with the modules at 40Gb/s) and the eye openings (similar to 25% at the system level at 32Gb/s).