PCBs DCIR and thermal analysis using 3D Layout and Icepak

In this tutorial, you will learn how to perform DCIR using 3D Layout, and then use the power loss data to perform a thermal analysis. The thermal analysis will be conducted using the electronic desktop Icepak. SIwave and its embedded icepak can be used to perform the same analysis, with one exception. Electronic desktop Icepak is a full-featured 3D tool. The user may add 3D objects, fans, heat sinks, and many other items to do a complete and thorough analysis.

Data can be generated for Icepak using 3D Layout, HFSS, or Q3D. DC analysis cannot be performed by HFSS, only by 3D Layout. For low frequency applications, Q3D is used, and for High power high frequency applications, HFSS is used.

This blog focuses on using 3D Layout in conjunction with Icepak. For those who are familiar with SIwave, 3D Layout is similar to that program. You can view the nets and layers in 3D Layout. All of the elements you add are in 2D, whether they be rectangles, circles, or polygons. When you enter a shape, it is automatically converted into a 3D model.

It is possible to import standard ECAD files, IPC2581 files, and ODB++ files into 3D Layout.

Additionally, the user can specify which solver to use: HFSS, Planar, or SIwave. Change the Cosim setup to select which one to use.

A DCIR analysis of the board is required. We would like to use SIwave for this purpose. Go to Cosim, and change the automatic solution selection to SIwave.

Select the powerplanes that you wish to include in the simulation. The user is required to specify the voltage source location and value for each powerplane, as well as the current sink location and value for each powerplane.

For example we choose PowerPlane 1.2V, and we put the voltage source at the output of the VMR, to be 1.2V source.

Look at the sources in the project manager, to see the newly added voltage source.

Double click on the Voltage, and set the voltage to 1.2Volt.

At the CPU, we add a current sink of approximately 2.4A. If the load has many pins, we need to combine them into one group. Select the pin group by clicking on it.

Select the part name, the reference designator, then select the nets connected to this component. Click Create pin groups.

Go back and select to add a current source. The current source between any two pins will do the job. Double click on the current and enter 2.4A.

In the project manager panel, right-click Anslysis, select SIwave bundle, then DCIR.

Give the analysis a name. Select the sources defined in the project for the excitations. For Ansys Icepak Options, we activate exporting power dissipation for use in Ansys Icepak and mechanical. In the table, the user needs to confirm that for the current sink, select neither, and for the voltage source select negative. Negative simply means that the negative column is the reference.

Select other solver options

Choose the level of accuracy for your solver. You may choose to use the advanced settings in the next panel if you wish.

For now, we will keep everything as is. Press OK.

Right-click on the model name in the project manager panel, and select to set the temperature. Activate include temperature dependence and enable feedback for thermal analysis, and set the current temperature to 22 cel. Now the model is ready.

Press OK.

Right-click on the copper material and select properties to open the material panel. Click on the Edit material button:

In the View/Edit modifier for, select the Thermal Modifier option:

In other words, you are allowing the copper conductivity to change. The thermal formula for conductivity should be edited as follows:

The formula can be modified here in accordance with the supplier's instructions. In accordance with the default formula, the conductivity remains nominal if the temperature is between -25 and 1000 degrees Celsius. We change that to formula provided by google.

Once you have clicked OK, click OK again, and start solving the for DCIR.

To see the results, go to the Field Overlays, and select the DC results.

You can plot the current magnitude, the current arrows, the voltage and the power density. Select the mag_VolumeJc, you can now specify on which layer, we select the VCC layer.

Press done.

This is the DCIR at 22 Cel. To change the copper conductivity, we need to know the temperature distribution and we would like the Icepak to calculate that for us. This is an iteration process. Both DCIR and thermal analysis should be carried out until saturation is reached.

Add a fresh Icepak model.

Right-click 3D Components, select Create, then PCB

Select a name:

Press Next:

Select setup a link:

Enable Use this project, and select the DCIR model and the DCIR solution

Enable Simulate source design as needed, and also enable Preserve source design solution. Press OK.

Go Next:

Select use From Linked source, and press next.

Change the resolution if you want, and press Next,

Press finish, and now we have a copy of the PCB inside the Icepak model. The PCB in Icepak is linked to the 3D Layout model.

You can add an air region or and a component related to thermal analysis. Check the Component Libraries panel. If you do not see this panel, View, select Component Libraries.

In our case here, we add an air region.

After adding the air region, you need to tell the system the boundary conditions at the outer surface of the air region. Switch to faces, and select all the faces of the air region.

Right click the mouse anywhere on the display, select thermal, opening, and free. After selecting free

Make sure to leave the temperature field empty, if you do not know the temperature of the outer surfaces of the air region.

Press OK.

At this step, you can add any other component you want, like a fan, a heat spreader, other PCBs, enclosure, ...etc

Last step is adding a solution setup

What we have here is a traditional setup:

• The name of the setup,
• Number of iterations to reach a solution for convergence
• Problem type: temperature mainly, there is no fluid here
• Flow regime, not applicable for our case.
• Radiation model: off.
• Include gravity, not applicable.
• Solve flow and energy, and the answer is no.

The other panels are for more accuracy. The user can modify them if there are complicated structures, with many small features.

Press OK.

Right click on Setup1, and select 2-Way coupling

Enter the number of iterations, let us say 5, and the Max icepak iterations per coupling to be 20.

Now the 2-Way coupling is added to the setup.

Then analyze.

To see the results, select the PCB first, use the Field Overlays to display the results. We can display the temperature as a contour plot by selecting Temperature, or as a solid plot by selecting the SurfTemperature.

You can also display the temperature in contours.

You can also go back to DCIR model, and display the temperatures

Select the layer you want to see the temperature on it

This concludes the blog.