Highly Elastic Gold Passivated Mechanically Flexible Interconnects

A wafer-level batch fabricated mechanically flexible interconnect (MFI) technology with 65- μm vertical elastic range of motion is experimentally demonstrated. A metal alloy (NiW) with ultrahigh yield strength and enhanced geometrical design is adopted to enable elastic deformation over the entire vertical range of motion. The enhanced geometrical design of the MFIs ensures that the stress is distributed uniformly during deformation, and simultaneously maintains an inner stress that is lower than the yield strength of NiW during vertical deformation. In addition, the MFIs are passivated with gold, which is experimentally verified to not only lower the electrical resistance, but also significantly extends the lifetime of the MFIs as it eliminates oxidation of NiW. For 10- μm-thick Au-NiW MFIs, the contact force is up to 10 mN at 50- μm elastic vertical deformation (i.e., compliance of 5 mm/N).