The proposed thesis explores the design of multilayer flex PCB for long distance (up to 2 meters). The flex shall be used instead of a traditional wiring harness among electronic devices for automotive application. The design requires the implementation of both low voltage power supply connections (up to 50A) and high-speed communication (CAN bus 1Mb and ethernet bus 10/100 Mb). The aim of this study is to realize flexible connection systems for electronic control units according to automotive standards.