Ecad files are imported on to the pcb board. Icepak can read ecad files of various formats such as ODB++,Ansys EDB, Ansoft, Gerber etc. Ansys Icepak reads traces and vias and computes the metal fraction map based on the grid density(rows*column).The model layers seperately option should be turn on to ensure proper mesh connection as shown in figure
Ansys Icepak computes thermal conductivities values based on the grid density. This thermal conductivity values will be used as input for thermal simulation. Grid density cuts the PCB into various rows and columns and assign thermal conductivities values to each grid.
Ansys Icepaks’ HD Mesher generates high-quality mesh even for complex geometries. The process of generating the mesh is extremely easy and less time-consuming. Ansys Icepak generates the fluid domain automatically using the cabinet approach and saves a lot of time spent on pre-processing. The overall time required to perform the simulation reduces drastically. Referring to the current case, the overall time spent on meshing and generating high-quality mesh was ~ 15 mins and within 15 mins, 3 mesh trials were performed to identify and optimize assembly size and slack settings. Icepak automatically finds and generates the fluid domain based on empty spaces inside the cabinet/enclosure (with no solid bodies/hollow bodies). Figure 5 and figure 6 shows the mesh created in Ansys Icepak.
Simulation of the system is done after giving necessary inputs/ boundary conditions required for running the simulation, such as heat sources wattage, ambient temperature, radiation parameters and material properties description, etc.Figure 7 shows the temperature distribution of the pcb assembly.The maximum temperature obtained for the pcb is ~ 92˚C. Figure 8 shows the velocity streamlines starting from the fan. Figure 9 shows the thermal conductivity distribution of the top layer of the pcb.
A second iteration is performed by removing the ECAD from the pcb to know the significance of ecad modelling on the pcb temperature distribution.Figure 10 shows the temperature distribution of the pcb assembly. By removing the ecad from the pcb,thermal conductivity of the pcb became 0.34 W/m- K(Fr4) and this led to a very siginificant rise in the temperature of the heat sources.We can also see due to low conductivity,hot spots are getting formed.The maximum temperature location is also getting changed due to change in thermal conductivity value of board at maximum temperature location for second iteration.Table 1 shows the difference between the maximum temperature obtained from the simulation with the without ECAD pcb.The difference in temperature shows the importance of detailed ECAD PCB modelling and simulaion.
The present work was an attempt to demonstrate Ansys Icepak’s capabilities in reading and simulating ECAD geometry. The temperature obtained for multilayered ECAD PCB is significanlty lower than the temperature obtained for PCB without trace import. Moreover Ansys Icepak ability to model primitive objects such as fans, grills, resistances, openings ,heat sink can help the engineers to change and create these geometries in the Icepak window very fast.
Ansys Icepak not only saves us from the tedious work of creating fluid domain but its HD mesh algorithm generates high-quality mesh effortlessly. Icepak allows us for a great deal of control on meshing. One can mesh assemblies and subassemblies with different mesh sizes while maintaining an overall coarse mesh for the entire system. Moreover, Ansys Icepak has almost all the popular turbulence models / radiations models which can be used according to the simulation requirement. The combination of these features makes Ansys Icepak a great tool.
