Elastoplastic and fatigue properties of copper in printed circuit boards: from experimental characterization to numerical simulations

In operation, a Printed Circuit Board (PCB) will face various and repeated thermomechanical loadings that may lead to the failure of the copper, and thus to the malfunction of the PCB itself. In order to simulate and better predict the reliability of PCBs, the constitutive behavior of copper has to be defined. Therefore, a $17 \mu \mathrm{m}$ rolled annealed copper film frequently used in the flexible PCB industry has been tested under a cyclic tensile-compressive loading. The copper has a low elastic limit and plastic deformation plays thus an important role in its mechanical behavior. Under cyclic loadings, a predominant kinematic hardening has been observed. The plastic behavior of the studied copper film has been identified with a Lemaitre-Chaboche hardening model. Next, an original experimental setup has been developed, allowing to measure the fatigue behavior of thin copper films under cyclic loadings. Tests with various loading amplitudes are carried out. A Coffin-Manson model has been adopted to reproduce the experimental data.