Light Emitting Diodes or LEDs are now a days used mostly everywhere whether it’s a car headlight or a light source in home. To make them more efficient and long lasting, one has to consider proper sinking of the heat generated by these LEDs. In this project, the sinking of a LED generated heat has been simulated considering three types of heat sinks; Plate fin, Inline pin fin and Staggered pin fin. Due to symmetry of the model, only 1/4th of the model was considered. The geometries of all LED models were created on Onshape and than imported to SimScale platform. The resulting geometries are shown in the figure below.
These geometries were meshed using tetrahedralization with refinements on SimScale platform. The meshes are shown in the figure below.
For the analysis steady state thermostructural heat transfer was selected since LED temperature was considered static. Since, the LED is normally sitting on a silicon die and transfer equivalent heat on the surface of the die, therefore the LED was omitted from the geometry and a steady heat flux of 694444 W/m² (~1 W) was applied on the die top surface. The Insulate Metal Substrate (IMS) was used as the substrate for the LED attached to the die by a die attach (weld). The IMS consisted of a copper (Cu) plate followed by a dielectric layer beneath it. Beneath dielectric layer was a thick aluminium (Al) plate. The aluminium (Al) plate was connected to an aluminium (Al) heat sink via Thermal Interface Material (TIM) which is used to transfer heat properly to the heat sink.
The adiabatic boundary condition (i.e. zero convective heat flux) was considered for all the upper and symmetry surfaces. The free convection around the heat sink was assumed, therefore a convective heat flux of 10 W/(m² K) was applied on the remaining surfaces of the heat sink with ambient room temperature. The results below shows the comparison of temperature (K) and heat flux (W/m² K) for all the three cases. The heat flux is nearly same in all the cases but important point here is the difference in temperature contour plots in all the three cases. It can be easily observed that the heat sink with plate fin is providing the better sinking compared to inline and staggered pin fin heat sink.
The graph below shows the drop of of temperature in different regions of all the three models. The drop in heat sink clearly shows that the plate fin model is more efficient in this case.
- Ha, Min Seok. “Thermal analysis of high power LED arrays.” (2009).
- Fengze, Hou, Yang Daoguo, and Zhang Guoqi. “Thermal analysis of LED lighting system with different fin heat sinks.” Journal of Semiconductors 32.1 (2011): 014006.