Defining the Setup

Set up the solution physics and materials for the solid components and the flow domain. For the length dimension, change the default unit.

To define the solution physics:
  1. Right-click the Setup > Physics node and select Edit.
    An additional Edit tab opens that displays the default ambient conditions, solution physics, and materials.
  2. Within the Solution Physics group box, make sure that Solve is set to Natural Convection.
When solving for a natural convection problem, the Electronics Cooling Module by default solves for flow and energy in a turbulent flow regime including gravity and radiation effects. For the given geometry and temperature differences in this tutorial, you can expect a laminar flow:
  1. Set Flow Regime to Laminar.
Within the Materials group box, define the materials of the chip package and the test device:
  • Silicon for the integrated circuit, an alloy of tin (Sn) and lead (Pb) for the solder balls, and an epoxy molding compound for the case of the BGA package
  • A material of low thermal conductivity for the table and support fixture, here polypropylene.

To specify the various solid materials:

  1. Next to the Solid Sim Materials box, click Select.
  2. In the Select Materials dialog, click Add Material.
  3. From the database of standard solid materials, select Si (Silicon) and click OK.
  4. In the list of Solid Simulation Materials, select Si and click Duplicate Material.
  5. Select the additional material and set the following properties:
    Property Setting
    Material Name SnPb
    Thermal Conductivity 51 W/m-K
    Specific Heat 180 J/kg-K
    Density 9250 kg/m^3
  6. Repeat steps 7 and 8 to create the remaining solid materials using the following properties:
    Property Setting
    Material Name Epoxy
    Thermal Conductivity 0.4 W/m-K
    Specific Heat 1100 J/kg-K
    Density 1250 kg/m^3
    Property Setting
    Material Name Polypropylene
    Thermal Conductivity 0.23 W/m-K
    Specific Heat 1920 J/kg-K
    Density 950 kg/m^3
  7. Click Apply and Close.
To set polypropylene as the default material for a new solid component in the simulation:
  1. Click the Default Solid box and select Polypropylene.
  2. Finish the physics setup by clicking Close at the bottom of the tab.
To simplify geometry creation, set the default length unit to mm:
  1. Right-click Setup > Units and select Edit.
  2. For the Length dimension, set Preferred Units to mm.
  3. Click Close.
    The physics and default units for the natural convection JEDEC simulation are now complete.
Save the simulation:
  1. In the System toolbar (see Toolbar Reference), click (Save).