Part average testing (PAT) is a method based on statistical analysis to identify and fail parts that have characteristics significantly outside the normal distribution of other parts in the same lot. The substantial difference of these parts, which might still fall within the test program limits, could indicate the potential for early part failure.

Generally, part average testing collects data from previously tested parts and compares each measurement for the current part to the mean of the previous measurements. If the measurements for the current part are outside a certain number of standard deviations from the mean, the part fails.

Refer to the Guidelines for Part Average Testing document (AEC - Q001 Rev-D version) published by the Automotive Electronics Council for more information about part average testing.

TSM Implementation

TSM does not install a default implementation of part average testing. You must use the TSM PAT plug-in architecture to customize and perform part average testing with TSM. TSM PAT plug-ins include a required PAT callback sequence file and corresponding code modules. The PAT callback sequence file contains PAT entry point sequences that TSM calls during execution to accomplish part average testing. Use the example PAT plug-in, located in the <TestStand Public>\Examples\NI_SemiconductorModule\Part Average Testing\Example Part Average Testing Plug-In directory, as a starting point for custom PAT plug-ins you create.

Use the PAT Algorithm Settings panel of the Test Program Editor to edit settings the PAT callback sequence file defines to customize the behavior of the algorithm execution for each test program.

Use the Part Average Testing tab of the Semiconductor Multi Test step to enable and configure part average testing for individual tests in a test program. The PAT environment settings determine which settings to display in the Part Average Testing tab.

Refer to the Part Average Testing Examples for information about enabling and performing part average testing (PAT) in a test program.

Execution

The first time a PAT-enabled test executes, TSM automatically generates one or more additional PAT tests associated with the original test. After executing all tests in the MainSequence sequence of the test program, TSM calls the PAT entry point sequences to customize and perform the PAT tests. TSM appends PAT test results to the MainSequence sequence test results so that PAT test results appear in the data logs and reports.

Alternatively, you can insert one or more Perform Part Average Testing steps in your test program to perform the PAT tests at specific points during program execution. Use the result from PAT tests performed by these steps to control the execution flow of the program. Tests that are performed by a Perform Part Average Testing step are not performed after the MainSequence sequence of the test program.

Static Limits File

Use the IPartAverageTestingStaticLimitLoader.LoadStaticLimits method in the TSM Application API to load a static limits file that uses the same structure as a TSM test limits file. To read and use limits from a different file format, you must implement a custom file reader and a custom data structure to store the limits.