Reliability prediction of LED packaging by fatigue behavior of bonding wire in power cycling accelerated test

An economical accelerated testing method called power cycling is presented in this paper to evaluate the reliability of LED packages. The LED samples are implied different heavy pulse current, on-line voltage monitor will find out the exact number of power cycle when failure occurs. Samples used in experiment are divided into two types, one is filled with pure silicone, and the other is filled with silicone/phosphor composite. After the experiment of power cycling, gold wires crack just above the first bonding region are founded. Finite element method is introduced to extract the temperature distribution, elastic and plastic amplitude during experiment of power cycling. Pattern of wire is taken by stereomicroscope, spline curve then used to fit these data points which extracted from the picture. Temperature variation trends of LED samples are observed by infrared thermal imager to correct its boundary condition. The errors of temperature between simulation and observation are controlled within 10%.