Design and prototyping of large-scale flex circuits for the ATLAS ITk Pixel detector

The tight space constraints of the ATLAS ITk Pixel system motivate the design of large-scale flex circuits for carrying low-voltage power, high-voltage sensor bias, and command/data transmission. These circuits extend over long distances in the barrel or large areas in the endcap rings, and they pose unique design challenges. We report on the design and prototyping of large-scale flex cir- cuits for the ATLAS ITk Pixel system, with a focus on technical issues encountered and lessons learned.