Abstract:
The Flexible Hybrid Electronics (FHE) concept requires a change in the way we perceive flexible electronics. Stating the obvious, FHE is not conventional electronics with thin chips neither printed electronics with conventional chips. In a truly flexible FHE device everything must be flexible, the substrates as well as all the components assembled on it, including the ICs. The use of the conventional ICs provides the lowest cost and shortest time to market for the FHE devices. However, the relatively thick silicon chips must be thinned to less than 30-40 microns to acquire the flexibility and conformity essential for the reliable operations of the FHE device.
Methods for creating, placing, and interconnecting ultra-thin ICs are not commercially available today as the methods used for conventional ICs are not directly applicable. Each step in the FHE packaging process must be re-engineered in a holistic manner to accommodate the new challenges present when wafers and dies become ultra-thin and flexible. Fundamental decisions in the packaging process are re-evaluated, starting with the applicability of today’s IC packaging platforms for FHE applications, the position of the ultra-thin chips on the flexible circuit board and the related methods for interconnection. One significant problem, which is closely related to the IC packaging solutions, is how to address the widening interconnect gap between the ICs and the flexible printed circuit boards while maintaining flexibility and performance.