Electrical failure and damage analysis of multi-layer metal films on flexible substrate during cyclic bending deformation

The electrical resistance Cu film on flexible substrate was investigated in cyclic bending deformation. The electrical resistance of 1 μm thick Cu film on flexible substrate increased up to 120% after 500,000 cycles in 1.1% tensile bending strain. Crack and extrusion were observed due to the fatigue damage of metal film. Low bending strain did not cause any damage on metal film but higher bending strain resulted in severe electrical and mechanical damage. Thinner film showed higher fatigue resistance because of the better mechanical property of thin film. Cu film with NiCr under-layer showed poorer fatigue resistance in tensile bending mode. Ni capping layer did not improve the fatigue resistance of Cu film, but Al capping layer suppressed crack formation and lowered electrical resistance change. The NiCr under layer, Ni capping layer, and Al capping layer effect on electrical resistance change of Cu film was compared with Cu only sample.