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.

 

Fig.: The figure shows the stable temperature distribution of a chip scale package (CSP) LED, which is mounted on a heat sink and switched on after a long time. The diagram on the right side demonstrate the derivative of temperature change after switching off the LED. The different color represent LED with phosphor and Side coating (ps) (in blue), LED with phosphor without Side coating (pos) (in green) and LED without phosphor or Side coating (opos) (in red). The Simulation results (dash line) are evaluated and fitted on the measurement results (full line) quantitative well.
Fig.: The figure shows the stable temperature distribution of a chip scale package (CSP) LED, which is mounted on a heat sink and switched on after a long time. The diagram on the right side demonstrate the derivative of temperature change after switching off the LED. The different color represent LED with phosphor and Side coating (ps) (in blue), LED with phosphor without Side coating (pos) (in green) and LED without phosphor or Side coating (opos) (in red). The Simulation results (dash line) are evaluated and fitted on the measurement results (full line) quantitative well.

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.

 

Open positions

If you are interested in vacancies for student work within the research group, please send an email with CV to assistenz-iimo-elger.de.