Effect of the Deformation State on the Mechanical Degradation of Cu Metal Films on Flexible PI Substrates During Cyclic Sliding Testing

The effect that the deformation state exerts on both the electrical and the mechanical degradation of Cu thin film on a flexible PI substrate was investigated via cyclic sliding test. Two opposite types of deformation (tension and compression) were applied to Cu thin film depending on its outward or inward placement in the cyclic sliding test system. During the cyclic sliding test, the change in electrical resistance of the Cu thin films was monitored using a two-point probe method. Systematic surface observation of deformed Cu thin film under the two opposite types of deformation was performed following specific cycles of sliding motion. Surface observation based on field emission scanning electron microscopy and 3D confocal laser scanning microscopy had been done to quantify the evolution of intrusion extrusions and surface roughness on the deformed Cu thin film. The distribution of microcracks significantly depended on the type of stress/strain applied to the Cu thin film on a flexible PI substrate during the cyclic sliding test. Finite element analysis was performed to explain the deformation behavior of the Cu thin film on a flexible PI substrate during the cyclic sliding test.