Influence of Flexibility of the Interconnects on the Dynamic Bending Reliability of Flexible Hybrid Electronics
The growing interest towards thinner and conformable electronic systems has attracted significant attention towards flexible hybrid electronics (FHE). Thin chip-foil packages fabricated by integrating ultra-thin monocrystalline silicon integrated circuits (ICs) on/in flexible foils have the potential to deliver high performance electrical functionalities at very low power requirements while being mechanically flexible. However, only very limited information is available regarding the fatigue or dynamic bending reliability of such chip-foil packages. This paper reports a series of experiments where the influence of the type of metal constituting the interconnects on the foil substrates on their dynamic bending reliability has been analyzed. The test results show that chip-foil packages with interconnects fabricated from a highly flexible metal like gold endure the repeated bending tests better than chip-foil packages with stiffer interconnects fabricated from copper or aluminum. We conclude that further analysis work in this field will lead to new technical concepts and designs for reliable foil based electronics.