Technical panel: Power distribution planes: To split or not to split?

Though the title might suggest that designers have a choice, in today's increasingly dense electronic packaging, we many times do not have the freedom to avoid splitting power distribution planes. Many years ago, splits in planes were rare and were employed primarily to implement some intentional isolation between subcircuits. Such typical scenarios were the splits between analog and digital grounds or isolation between chassis and logic ground. Today the density of trace interconnects drives up layer count in PCBs and packages alike, and the power optimization creates more and more separate power domains. These two factors dictate that we have to reuse power distribution planes by splitting the planes in certain layers to serve multiple circuits. This, however, creates severe routing restrictions if we don't want to cross the splits with signal traces or need to carefully weigh the possible negative consequences in signal distortion, increased crosstalk, mode conversion, and increased radiation and susceptibility. This panel brings together experts from the industry and academia to discuss the various tradeoffs to be considered by package and board designers.