Reliability model of LED package regarding the fatigue behavior of gold wires

In this study the mechanical properties and fatigue behavior of ultra-fine gold wires are investigated by experimental tension fatigue tests and finite element (FE) simulation. Hardening behavior, yield criterion and yield surface of gold wire are determined by tensile tests and force controlled tension fatigue tests. The relationship between plastic strain and loading stress amplitude is determined and the cyclic strain hardening coefficient is calculated. The fatigue data are used to develop a predictive crack model for gold wires bonded in LED packages, based on finite element (FE) stress simulation at temperature cycles (TC). The computer model of the gold wire in the LED package used in the simulation is reconstructed from computer tomography (CT) analysis. The predictive crack model is calibrated using on-line monitoring of LED wire cracks during TC tests. Finally, using the reliability model, the impact of LED package design and material on the wire lifetime is investigated.