Apply Restraints

Apply restraints to constrain the printed circuit board (PCB) so that it cannot move during the simulation.

You use clamp restraints to completely define the response of a surface during simulation, ensuring it will not move. You use fixed displacement restraints to restrict specific degrees of freedom for portions of the model. Ensuring adequate restraints on the model avoids rigid body motion during the simulation.

In this example, a small part of the PCB surface in each corner has predefined kinematic couplings to a single main node, representing a bolted connection. Before the first frequency step, you create clamp restraints to restrain the PCB in all four corners with respect to all mechanical degrees of freedom. You then create clamp restraints to restrain the PCB on one side (near the heat sink) while loading the other side. To avoid twisting in the unclamped corners of the PCB during loading, you create fixed displacements constrained in the rotation degrees of freedom.

This task shows you how to:

Restrain the PCB

  1. From the context selector, select the preloading frequency step.
  2. From the Restraints section of the action bar, click Clamp .
  3. From the Support options, select Connection as the selection method.
  4. From the selection tree, select Free.17 > Coupling-Support-chipB, and click OK.
  5. Click OK.
  6. Similarly, create clamps for Free.18 > Coupling-Support-chipA, Free.19 > Coupling-Support-heatsinkA, and Free.20 > Coupling-Support-heatsinkB.

    Tip: The clamps appear in the Scenario > Structural Analysis Case.1 > Frequency_step category of the tree. Press F3 to display the tree if it is not visible.

  7. From the context selector, select the static loading step.
  8. Similarly, create clamps for Free.19 > Coupling-Support-heatsinkA and Free.20 > Coupling-Support-heatsinkB.
    The clamps appear in the Scenario > Structural Analysis Case.1 > Static_Step_Loading category of the tree.

Define Fixed Displacements

  1. Confirm the static loading step is selected.
  2. From the Restraints section of the action bar, click Fixed Displacement .
  3. From the Support options, select Connection as the selection method.
  4. From the selection tree, select Free.17 > Coupling-Support-chipB, and click OK.
  5. Constrain all rotation degrees of freedom.
  6. Click OK.
  7. Similarly, create a fixed displacement for Free.18 > Coupling-Support-chipA.