System integration technology requires multifunctionality and in many cases energy autarkic systems, very cost-efficient or open form factor solutions. Integration in plastic or foil substrates by a flex-to-flex integration concept shows the potentially free form factor which allows placing of film based systems on curved surfaces or in housings of very low thickness. Such technologies are not limited to flexible applications. They are available for optimized rigid modules and improve the heat sink by thinning and foil handling of transceiver chips or power devices. Thin semiconductor technologies are not limited to silicon, enabling also heterointegration with compound semiconductors. Meanwhile it is possible to integrate high frequency interconnects and printed passives in plastic foil and thin silicon interposer. Possible application scenarios are large area electronics in ceilings panels of cars or mobile communication systems for the "internet of things and humans".