FPC design and testing for the High-Granularity Timing Detector for the Phase II upgrade of the ATLAS calorimeter system

The High-Granularity Timing Detector (HGTD) will improve the performance of the ATLAS detector for the Phase II upgrade of the HL-LHC by providing precise timing information. The detector base unit consists of a hybrid module of a 2x4 cm2 Low Gain Avalanche Detector (LGAD) bump-bonded to two ASICs and wire-bonded to a Flexible Printed Circuit (FLEX cable). The latter transmits high-speed signals (1.28 Gbps) for data readout while providing power and HV to the module. Its design must fulfil the HGTD requirements both mechanically and electrically, combining different signal types. Test results of our initial prototype are presented.