Fatigue life and plastic deformation behavior of electrodeposited copper thin films

Using a commercial, electrodeposited copper film of 12 μm thickness, tensile tests, fatigue tests and static loading tests were performed. The elastic modulus, two types of yield strengths, tensile strength and strain-hardening exponent were obtained. Fatigue tests were performed at four levels of mean stresses and cyclic plastic strain and ratcheting strain (monotonic plastic strain) were measured continuously during the tests. Irrespective of mean stress, fatigue life can be well represented by the maximum stress. The monotonic plastic strain at fracture is nearly constant, irrespective of fatigue life or mean stress. Based on the results obtained, the reason why fatigue life can be well represented by the maximum stress is discussed.