This document discusses BGA breakout techniques used on Xilinx® 1 mm pitch BGA devices high-speed interfaces with a data rate of 32 Gb and above. The context includes PCB layout decisions for BGA breakout and what compromises are needed to reduce crosstalk. Traditional designs used a diagonal BGA breakout because it creates the most usable routing area under a BGA device. However, with evermore faster interfaces with data rates at 32 Gb and above, we see a reduction in the usable routing area underneath due to the large keep-out areas required for signal fidelity. This white paper proposes a new BGA breakout style, the Diamond Jog that produces numerous advancements over the traditional Diagonal Jog, with limited drawbacks. To use the Diamond Jog breakout method:
- Convert horizontal solder ball alignment to vertical via alignment, freeing up routing channels
- Switch differential pair routing polarity by jogging to either the top or bottom via from either solder ball
This method avoids high-crosstalk scenarios by providing additional routing flexibility for FPGA breakouts.