Mechanical Failure Analysis For High Power LED

High power LEDs are regarded as the next generation of lighting source for its high-light efficiency and environmental friendly features. However, LED may fail during assembling and application process because of sustaining mechanical loads, which would be obstacle to extend its application. Based on the packaging process of LED, this paper focuses on the difference of failure modes and mechanisms of LED when LED is under the mechanical loads, and improving the mechanical strength of LED through optimizing its structure. At the same time, finite element analysis(FEA) is used to explore the deformation process of the weak part of LED such as the bonding wire. The main research contents are as followings:(1) Based on different bonding modes of LED, we figure out the corresponding failure modes of LED when they sustain various loads and confirm the best kind of bonding wire. Based on mechanical model of bonding process, the residual bonding stress is analyzed and the severe stress concentrate is found at fist and second bonding. The large scale lattice is assured in the first bonding and ensured with high strength under shear stress. But the work hardening happens in the second bonding, which leads the worse ductility.(2) Study packaging structural parameters effect on the mechanical strength of LED. Explore the influence of process parameters of first bonding for bonding strength and assure the failure forces of LED with different bonding height through experiments. The influence of lens structure parameters including the height and radius on LED strength is also figured out. Investigate the LED failure mechanisms through various detection methods and the light distribution of LED is also assured.(3) Use finite element analysis(FEA) to study the influence of package structure parameters including bonding wire span, bonding wire height, lens radius and lens height, on LED mechanical strength. The deformation process of bonding wire and lens are analyzed when LED is under pressure loads. The stress distribution of bonding wire is focused, and optimization to improve LED strength is present based on bonding wire’s deformation.