STM Network Extraction

Surrogate Thermal Network Builder creates, trains, and exports a Delphi-like Surrogate Thermal Model (STM) that is boundary condition-independent and can be used to emulate the thermal behavior of the integrated circuit (IC) package. The toolkit allows you to select specific geometric features from the Detailed Thermal Model (DTM), including external faces and heat sources. These features have two primary purposes: to inform the DTM simulations for data production and to fully define the STM’s external geometry.

The Surrogate Thermal Network Builder process consists of creating parametric trials for steady-state and transient designs to generate designs containing an STM that feature a network based on the training data. The simplified STM design (geometry and boundary conditions) enables faster, shorter meshing and analysis times. The following image displays a QFN package as a detailed thermal model (left) and surrogate thermal model (right).

The Surrogate Thermal Network Builder workflow consists of three main steps:

1. Geometry extraction: after specifying the package type under Surface Selection, click Extract Geometries to capture geometries and group them.
2. Setup creation: after specifying the parametric origin and associated settings, click Add Setup to add the setup to the Active Setup(s) list. Then, right-click the setup and select Create Setup to initiate a three-step process. Icepak specifies thermal boundary conditions, assigns monitors, and creates a parametric setup. After the process is complete, all of these items appear in the Project Manager.
3. Transient design creation: after running the steady-state to create the training data, click Create Transient Design to generate a transient design based on the selected steady-state design. This includes a consistent set of thermal boundary conditions and monitor assignments, and parametric setups. In addition, the solver settings are automatically updated to enable data generation for a dynamic surrogate model. 

External Faces Editor

In the External Faces Editor, use the External Group Manager to manually create groups of external faces based on geometry selected from the 3D Modeler window or the History tree. Alternatively, you can click Automatic Extraction of Bounding Faces to automatically identify the external faces touching the package's bounding box and categorize them in groups.

Active Setup Options

In the Active Setup(s) list, right-click a setup to display the following options.

• Create Setup: Click Create Setup to generate boundary conditions, monitors, a solution setup, and parametric setup.
• Delete: Click Delete to remove the selected setup.
• Statistics: Click Statistics to display the project variable statistics for the selected setup. The dialog includes data for each variable included in the setup.

  

• Merge: If more than one setup is in the list, click Merge to combine the two setups into one setup.
  Note:

  To merge setups, the setups' variable sets must be identical, though their order can differ. Merging accounts for any duplicates across the different setups in the list.

  

Configure Uniform Sampling Ranges

In the Configure Uniform Sampling Ranges dialog box and specify the Min and Max power and ambient temperature values (if enabled) to be sampled for the analysis. The values used are uniformly sampled between the specified minimum and maximum.

Solve the Steady-State Design for Training Data

After you click Create Setup from the Active Setup(s) options, a new design is created with boundary conditions, monitors, a solution setup, and a parametric setup. To solve for training data, right-click the parametric setup in the Project Manager under Optimetrics and select Analyze.

Create the Steady-State Surrogate Thermal Model

After generating the training data by running the parametric trials, create the STM. In the Project Manager, right-click the design and select Export > Create STM.

From the Parametric Setup drop-down list, select a setup. If you created more than one steady-state design for training data, under Select steady state setup, select a Design and Parametric Setup. Click Create STM to create a new design that includes a network boundary condition that represents the surrogate thermal model based on the package.

Create a Transient Design

After you create an STM based on the steady-state training data, create a transient design to create transient training data. Double-click the newly created steady-state design with the STM to make it the active project. In the Surrogate Thermal Network Builder dialog box, click Create Transient Design.

A new transient design is generated with the same boundary conditions, monitors, solution setup, and parametric trials.

Under Optimetrics, double-click the parametric setup to open the Setup Sweep Analysis dialog box. On the General tab, enable Include next to the parametric analysis.

Click OK to close the dialog box.

Solve the Transient Design for Training Data

To solve for training data for the transient design, right-click the parametric setup in the Project Manager under Optimetrics and select Analyze.

Create the Transient Surrogate Thermal Model

After generating the training data by running the parametric trials, create the STM. In the Project Manager, right-click the design and select Export > Create STM.

From the Parametric Setup drop-down list, select the steady-state setup (if there are multiple). Under Select steady state setup, select the steady-state STM Design and transient Parametric setup. Click Create STM to create a new design that includes a network boundary condition that represents the surrogate thermal model based on the package.