Model an electronic package with a compact thermal model

Use a compact thermal model (CTM) when you have junction-to-face thermal resistances for a package and do not want to mesh its internal construction.

Use implicit coupling

Set the coupling formulation at the top level of the request:

"ctm_coupling": "implicit"

With implicit coupling, omit relaxation_factor from each CTM because it has no effect. See Compact thermal models for how the two coupling formulations differ.

Add the package

1. Add an axis-aligned package to cuboid_components.
2. Set case_side to the face away from the board. The opposite face is used as the board side.
3. Make the inferred board face touch the conducting board and the complete case face touch fluid or another conducting region.
4. Set power in W and the junction-to-board and junction-to-case resistances in K/W.

{
  "tag": "processor",
  "bbox": {
    "origin": [0.045, 0.002, 0.04],
    "size": [0.01, 0.002, 0.01]
  },
  "thermal_model": {
    "two_resistor_ctm": {
      "case_side": "y_max",
      "power": 5.0,
      "resistance_jb": 8.0,
      "resistance_jc": 0.35
    }
  }
}

power must be non-negative, and both resistances must be positive.

Include heat transfer through the sides

If you have a junction-to-side resistance, use star_resistor_ctm and add resistance_js in K/W:

"thermal_model": {
  "star_resistor_ctm": {
    "case_side": "y_max",
    "power": 5.0,
    "resistance_jb": 8.0,
    "resistance_jc": 0.35,
    "resistance_js": 12.0
  }
}

Ensure all six package faces touch the thermal domain: fluid or a conducting solid. No active face can partly touch an insulating component or the exterior of the computational domain. The same resistance_js is applied separately to each of the four side faces.

See also

• Monitor a result and stop when it settles configures junction-temperature convergence.
• Compact thermal models explains the resistor networks and coupling formulations.
• Monitors and derived quantities explains recorded junction temperatures.
• API reference lists all CTM fields.