Finite element analysis (FEM) is a standard technology in product development. Engineering simulation opens up a huge range of possibilities. It is used to understand the physical change in the device. It can be applied to analyze the influence of different parameters (e.g. geometry, material) on the out put signal and furthermore to optimize the design of devices.
According to the transient thermal analysis, a thermal FEM simulation model of chip scale package LED can be set up by using FloEFD, see figure below. After the validation of simulation model, see figure right, the thickness of different layers, even the materials, can be optimized for different applications. Furthermore, different micro-defects models can also be provided based on the validated model and they are utilized to build a reliability model. In addition, a thermo-mechanical simulation using ANSYS is combined with Raman experiment and can be used in reliability analysis.
Short introduction of this Simulation-Project
Aim of this thermal simulation is to investigate the temperature change of junction (where the heat generated in a LED and has the highest temperature in the assembly). As initial step of the simulation a steady state simulation with the thermal load of 2.3W is performed. The calculated temperature distribution from the steady state simulation is taken as initial temperature distribution for the transient simulation of the cooling down phase for which the heat load is switched to zero. The simulated temperature data are post-processed: Tjunction=average temperature of the volume representing the epitaxial layers of the junction and Tcase = maximum temperature of the temperature controlled plate. From the initial steady state simulation the temperature of the junction is calculated. The thermal resistances Rth of the module is defined: Rth = (Tjunction-Tcase)/Pthermal. Finally, the calculated Rth curve is converted into derivative of temperature rise and compared with the experimental results.