Fatigue analysis of anisotropic copper-vias in a circuit board

Abstract:
The reliability of a circuit board under thermal loading is restricted by fatigue of plastically deforming copper-vias. Vias consist of electro-deposited copper, which possesses a cubic symmetry as a single crystal – in other words the copper is anisotropic. The grain size of electrodeposited copper is small compared to the geometric size of the via. Hence it is usually assumed that the via behaves isotropically in order to enable a finite element analysis of plasticity with commercial softwares. However, a finite element analysis of anisotropic materials deforming plastically is possible by using research codes. Therefore, we first briefly outline the theory of plasticity for metallic compounds and, second, apply it to a multilayered circuit board by using open-source packages. This computation allows us to perform a fatigue analysis for copper vias in the circuit board and to predict their lifetime.