PCB Modeling with Ansys Icepak

Welcome to another video by Ozen Engineering, Inc. As experts in all things ANSYS, including simulation with fluids, mechanical, electronics, and more, today we will focus on electronics thermal simulation using Ansys Icepak. Our topic is how to model PCBs, import traces and VIAs, or ECAD models into Icepak, and set up and execute different operating conditions like forced or natural convection.

Introduction to PCB Thermal Management

PCBs, with their complex geometry and multiple layers, require careful thermal management. They often have large copper spreads in power and ground planes, along with thermal VIAs that help spread heat from the package. A detailed conductivity map of the PCB is essential for accurate heat transfer simulation, which is possible in Ansys Icepak using the trace import feature.

Importing Trace Layouts

In Icepak, you can import the trace layout of the board and compute the locally varying orthotropic conductivity using a profile mesh size. Supported import formats include:

• ODB++
• EDF
• ANF
• Gerber
• BOL plus Info
• ICP2581

In this tutorial, we will import a typical PCB and solve two sample cases based on the trace layout information. We will also model layers separately for better accuracy.

Setting Up the Model

1. Double-click on the PCB board.
2. Under the geometry tab, import an ECAD file. We will use the NSOF natural neutral ANF format.
3. Reposition the trace object if necessary to align with the coordinate system.
4. Import the object and correct the thickness information on the layers. We will use copper and FR4 as materials.
5. Define the grid density for mesh accuracy. For coarse mesh accuracy, multiply the minimum trace width by four, which comes to about 0.5 mm for this model.
6. Model the layers separately and update the setup.

Conduction Only Model

We will build a conduction-only model by deactivating all components except the board. The cabinet will be auto-scaled to match the board size, and boundary conditions will be defined on the cabinet faces.

1. Set the minimum Z face to a wall with a uniform temperature of 20°C.
2. Set the maximum Z face to a wall with a heat flux of 20,000 W/m².
3. Generate a mesh with a focus on resolving the thickness across the PCB.
4. Set up the problem for conduction only, turning off flow and radiation.
5. Run the solution and post-process the results to analyze temperature and conductivity distribution.

Convection Model

Next, we will activate all components and set up a convection model:

1. Ensure the cabinet size covers all objects.
2. Check and set the correct flow boundary conditions.
3. Remesh the model with a coarser mesh for the convection simulation.
4. Set up the problem to solve for flow using the zero-equation turbulence model.
5. Run the solution, which will take longer due to the higher mesh count and additional equations.
6. Post-process to analyze temperature distribution.

Thank you for watching this tutorial on PCB modeling with Ansys Icepak. We hope you found it informative and helpful.