8 Libraries Section 8.4

8.4 The Failure Mechanisms Library

8.4.1 Purpose of Failure Mechanisms Library

The Failure Mechanisms Library contains failure mechanisms/models and supporting information. The Library can be used to create, edit, and access information and algorithms pertaining to potential microelectronic failure mechanisms. The Failure Mechanisms Library contains:

algorithms for microelectronic reliability assessment;
models for device failure mechanisms;
descriptions of the parameters used in failure models;
assumptions and limitations of failure models;
validation histories with references.

8.4.2 The Failure Mechanisms Library Screen

In the CADMP Manager, go to the Libraries header and select Failure Mechanisms (see Figure 48). The Failure Mechanism Library screen appears.

Figure 48. Selecting the Failure Mechanism Library

The screen contains four options (see Figure 49):

Figure 49. The Failure Mechanism Library screen.

Failure Mechanism enables you to load, add, and delete failure mechanisms.
Model Builder enables you to create, modify, delete, and copy a model, sub-model, or model factor.
Constants enables you to add, modify, and delete constants.
Model Factors enables you to add, modify, and delete typical model factors.

8.4.3 The Failure Mechanism Option

The Failure Mechanism option has three commands:

Load enables you to load a failure mechanism.
Add enables you to add failure mechanisms.
Delete enables you to delete failure mechanisms.
Save enables you to save a failure mechanism after changes have been made.

8.4.3.1 The Load Command

Select the Load command from the Failure Mechanisms menu. The window in Figure 50 appears.

Figure 50. The Failure Mechanism list

Select the failure mechanism you want to use. (You can activate only one failure mechanism at a time.) You return to the Failure Mechanism Library screen. The failure mechanism name appears in the menu bar.

Figure 51. The Help window.

8.4.3.2 The Add Command

Select the Add command from the Failure Mechanism menu. A window requesting the name of the new failure mechanism appears.
Type the name of the new failure mechanism and press Enter. The name appears in the menu bar. Use the Model Builder option to complete it.

8.4.3.3 The Delete Command

Select the Delete command from the Failure Mechanism menu. A failure mechanisms list appears.
Select the failure mechanism you want to delete. A window appears asking you to confirm the deletion.
Select Yes to confirm, No to cancel. You return to the Failure Mechanism Library screen.

8.4.4 The Model Builder Option

You must load a failure model before invoking the Model Builder option, which contains four commands (see Figure 52):

Figure 52. The Model Builder menu

New enables you to create new models, submodels, and model factors.
Edit enables you to change existing models, submodels, and factors.
Delete enables you to erase models, submodels, and factors.
Copy enables you to copy existing models, submodels, and factors.

8.4.4.1 The New Command

Select the New command from the Model Builder menu. A window appears, asking what you want to create: a model, a submodel, or a factor.
Select Model. The window shown in Figure 53 will appear. Type in the name and units for the new model.

Figure 53. Adding a New Model

Press Enter at the Failure Modes field. An empty list window will appear. There are two hot keys: Insert and Delete. When you use Insert the window shown in Figure 54 will appear. Highlight the Mode you want to add and press Enter. Repeat until you have selected all relevant failure modes. This procedure can be followed for adding Stress Types as well.

Figure 54. Inserting a Failure Mode

Select the Model Type, either Wearout or Overstress, by toggling the field with the Space Bar. In the wearout model, a stress is repeatedly applied to the device, causing it to fail after a period of time. CADMP-II typically reports the number of hours to failure. In the overstress model, device failure is caused by subjecting it to stress that exceeds the strength of the device.
Move to the Expression field and press Enter. The window shown in Figure 55 appears. You are now ready to build the model. You will now construct the right-hand part of the failure model equation. The failure model equation is written using the Mathematical Functions, User-defined models, Attributes, and Constants hot keys at the bottom of the window. There is also a help command, F1, used to examine your equation.

Figure 55. The Display Model window

Select the Mathematical Functions hot key. The window in Figure 56 appears.

Figure 56. The Mathematical functions window

Select an intrinsic function to include in the failure model equation. You will be returned to the Expressions window. Repeat until all relevant functions are included.
Select the Attributes hot key. A window appears which lists all of the parts and the environment.
Select a package part. The Attributes window in Figure 57 appears.

Figure 57. The Package Attributes window

Select an attribute. You will be returned to the Expressions window. Repeat until all relevant parts are included.
Select the Constants hot key. A list of constants appears.
Select a constant to include in the failure model equation. You return to the Expressions window. Repeat until all relevant constants are included.
Select the User Defined Models hot key. A list of user-defined models appears, including the various models/sub-models used by the loaded failure mechanism. The user-defined models are provided in case a sub-model is used by more than one model.
Select a model to include in the failure model equation. You will be returned to the Expressions window. Repeat until all relevant models are included.
Hit F1 to examine the equation. A list of the variables contained in your model will appear. Make sure all of your variables can be identified by CADMP-II.

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