A novel low cost roll-to-roll manufacturing compatible ultra-thin chip integration and direct metal interconnection process for flexible hybrid electronics

The emerging Internet-of-Everything (IoE) framework aims to revolutionise human-machine interaction where billions of sensors and actuators placed on almost every physical object will be tasked to communicate with each other. A substantial fraction of these devices will be placed on locations that would undergo repeated bending deformation (such as sensors for prosthetics, human body and robots) or on curved surfaces (like interior as well as exterior of automobiles, buildings and industrial equipment). Therefore, flexible sensors and actuators delivering high performance at low power requirements and manufactured at low cost will be the key for successful implementation of IoE. Though massive developments achieved in printed and organic electronics have enabled them to fulfil the required flexibility and low cost demands of IoE applications, printed and organic electronics often fall short of the high performance and low power requirements demonstrated by silicon ICs. Flexible chip foil packages fabricated by integrating ultra-thin bare silicon ICs fulfil the aforementioned demands posed by IoE applications and therefore, they are often considered as potential enablers of IoE. Here, we present an innovative roll-to-roll manufacturing compatible low cost approach for direct metal interconnection and integration of ultra-thin silicon ICs. The thickness of the fabricated flexible packages with the integrated and interconnected ultra-thin ICs were as thin as 100 μm. Electrical measurements conducted on the 60 fabricated samples with interconnected flexible ultra-thin ICs revealed a very promising yield of 94%.